Invited talk given at the Workshop on Fundamentals of Atomic Layer Deposition (ALD): Modelling and ValidationTU Delft, The Netherlands, July 3, 2019. Talk was recorded by TU Delft staff and is to be shared later. Website: https://www.tudelft.nl/en/faculty-of-applied-sciences/about-faculty/departments/chemical-engineering/scientific-staff/van-ommen-group/workshop-fundamentals-of-ald/. Twitter hashtag: #ALDfun
Introduction to atomic layer deposition (ALD): principles, applications, futureRiikka Puurunen
<erratum at the bottom / update 3.5.2019> Introductory lecture on Atomic Layer Deposition (ALD) by Prof. Riikka Puurunen, given at Aalto University School of Chemical Engineering on November 8, 2018. Lecture contents: Principles and concepts of ALD; Some history; Applications of ALD; Words on future. In addition to the core lecture contents, discusses where we have ALD layers in our smart mobile phones; mentions (some) faces of ALD in Finland; STG podcasts; Virtual Project on the History of ALD.
Corresponding lecture capture by Panopto available at: https://aalto.cloud.panopto.eu/Panopto/Pages/Viewer.aspx?id=bd0aee67-7ca5-4973-8216-a99200e888b1
Erratum! Small errors spotted in the slides are described below. Updated 3.5.2019.
* slide 44 Luminescent: ZnS:Mg —> not Mg but Mn! --> ZnS:Mn
* slide 54 high-k solution: article not from 2017 but 2007
Slides of invited "ALD 101" tutorial by Puurunen at ALD 2021 Riikka Puurunen
(INVITED) Fundamentals of atomic layer deposition: an introduction (“ALD 101”)
Riikka L. Puurunen, Aalto University School of Chemical Engineering, Department of Chemical and Metallurgical Engineering, AVS 21st International Conference on Atomic Layer Deposition (ALD 2021), Virtual Meeting 27.6.-30.6.2021. Tutorial Session 27.6.2021
ABSTRACT: Atomic layer deposition (ALD) has become of global importance as a processing technology for example in semiconductor device fabrication, and its application areas are continuously expanding. The significance of ALD was highlighted e.g. by the recent (2018) Millennium Technology Prize. Tens of companies are offering ALD tools, and thousands of people are involved in ALD R&D globally. A continuous need exists to educate new people on the fundamentals of ALD.
While ALD for manufacturing may be regarded mature, as a scientific field, ALD—in the author’s view—is developing. For example, understanding of the early history of ALD is evolving, related to the two independent inventions of ALD under the names Atomic Layer Epitaxy in the 1970s and Molecular Layering in the 1960s [1-4]. Also, significantly varying views exist in the field related to the description and meaningfulness of even some core ALD concepts [5].
The purpose of this invited “ALD 101” tutorial is to familiarize a newcomer with fundamentals of ALD. The presentation largely follows the organization of a recent encyclopedia chapter on ALD [6]. Surface chemistry concepts will be introduced, such as ideal ALD from repeated, separate self-terminating (saturating and irreversible) reactions; growth per cycle in ALD; various monolayer concepts relevant to ALD; typical classes of surface reaction mechanisms and saturation-determining factors; growth modes; and ways to describe growth kinetics. Concepts, where differing views exist in the field and which thus need special attention, are pointed out. Typical deviations from the presented ideality are discussed.
For continuous education, a collaborative OpenLearning website on ALD is under construction [7]. Many of the images used in this tutorial—and in Refs. 6 and 7—are available in Wikimedia Commons [8] for easy and free reuse. To contribute to collective learning of the early history of ALD, the open-science effort Virtual Project on the History of ALD [4] still welcomes new volunteer participants.
[1] E. Ahvenniemi et al., J. Vac. Sci. Technol. A 35 (2017) 010801 (2017).[2] R.L. Puurunen, ECS Transactions 86 (6) (2018) 3-17; OA: DOI:10.1149/osf.io/exyv3[3] G.N. Parsons et al., J. Vac. Sci. Technol. A 38 (2020) 037001.[4] http://vph-ald.com[5] J.R. van Ommen, R.L. Puurunen, ALD 2020, https://youtu.be/jqm_wf49WwM[6] J.R. van Ommen, A. Goulas, R.L. Puurunen, Kirk-Othmer Encyclopedia on Chemical Technology, submitted. [7] http://openlearning.aalto.fi, ALD [8] https://commons.wikimedia.org/wiki/Category:Atomic_layer_deposition
Roll-to-Roll ALD Coatings for Battery Cell Interfaces at Production ScaleBeneq
ALD/AVS 2022
Presented by D.Sc. Andrew Cook
ALD is an enabling technology for future batteries. ALD technology introduction has been hindered by lack of production scale equipment, but now Beneq R2R ALD technology offers a straightforward scale-up path to mass-production. Beneq has a long experience with R2R ALD on other application areas, and is now applying that know-how to offer R2R ALD solutions for battery manufacturing.
ALD for Industry 2019: Slides of invited tutorial by Prof. Riikka PuurunenRiikka Puurunen
Invited tutorial given by Prof. Riikka Puurunen at the ALD for Industry event, Berlin, 19.3.2019.
Video record taken with Panopto, (to be) shared in Youtube, you find the links e.g. through the blog post: https://blogs.aalto.fi/catprofopen/2019/03/19/prof-puurunen-invited-tutorial-at-ald-for-industry-berlin/
Title: ALD Technology – Introduction, History & Principles
Abstract: This tutorial keynote will introduce atomic layer deposition (ALD) – a variant of chemical vapor deposition - and fundamental principles and concepts related it from a generic viewpoint applicable to any ALD process and reactor. The early history and current usage of ALD are briefly overviewed: who made the first experiments, when, and why? How has the view on the history of ALD evolved? Where is ALD now used, by whom, and why? ALD relies on repeated chemical adsorption steps from gas phase to surface. The status of understanding the adsorption steps of ALD films will be presented and discussed using mainly the archetype trimethylaluminium-water ALD process as example and 3D conformality modelling as additional vehicle. Plenty of links to further sources of information will be included in this keynote presentation.
A related SlideShare: placeholder, where I meant to update the slides afterwards, but this did not succeed as the reupload function has been removed: https://www.slideshare.net/RiikkaPuurunen/ald-for-industry-2019-invited-tutorial-by-prof-riikka-puurunen/RiikkaPuurunen/ald-for-industry-2019-invited-tutorial-by-prof-riikka-puurunen. The update was waiting for the publication of the following review article, which was still in press when giving the presentation: Cremers, Puurunen, Dendooven, Appl. Phys. Rev. (2019), https://doi.org/10.1063/1.5060967. Article published 4.4.2019: Applied Physics Reviews 6, 021302 (2019)
Introduction to atomic layer deposition (ALD): principles, applications, futureRiikka Puurunen
<erratum at the bottom / update 3.5.2019> Introductory lecture on Atomic Layer Deposition (ALD) by Prof. Riikka Puurunen, given at Aalto University School of Chemical Engineering on November 8, 2018. Lecture contents: Principles and concepts of ALD; Some history; Applications of ALD; Words on future. In addition to the core lecture contents, discusses where we have ALD layers in our smart mobile phones; mentions (some) faces of ALD in Finland; STG podcasts; Virtual Project on the History of ALD.
Corresponding lecture capture by Panopto available at: https://aalto.cloud.panopto.eu/Panopto/Pages/Viewer.aspx?id=bd0aee67-7ca5-4973-8216-a99200e888b1
Erratum! Small errors spotted in the slides are described below. Updated 3.5.2019.
* slide 44 Luminescent: ZnS:Mg —> not Mg but Mn! --> ZnS:Mn
* slide 54 high-k solution: article not from 2017 but 2007
Slides of invited "ALD 101" tutorial by Puurunen at ALD 2021 Riikka Puurunen
(INVITED) Fundamentals of atomic layer deposition: an introduction (“ALD 101”)
Riikka L. Puurunen, Aalto University School of Chemical Engineering, Department of Chemical and Metallurgical Engineering, AVS 21st International Conference on Atomic Layer Deposition (ALD 2021), Virtual Meeting 27.6.-30.6.2021. Tutorial Session 27.6.2021
ABSTRACT: Atomic layer deposition (ALD) has become of global importance as a processing technology for example in semiconductor device fabrication, and its application areas are continuously expanding. The significance of ALD was highlighted e.g. by the recent (2018) Millennium Technology Prize. Tens of companies are offering ALD tools, and thousands of people are involved in ALD R&D globally. A continuous need exists to educate new people on the fundamentals of ALD.
While ALD for manufacturing may be regarded mature, as a scientific field, ALD—in the author’s view—is developing. For example, understanding of the early history of ALD is evolving, related to the two independent inventions of ALD under the names Atomic Layer Epitaxy in the 1970s and Molecular Layering in the 1960s [1-4]. Also, significantly varying views exist in the field related to the description and meaningfulness of even some core ALD concepts [5].
The purpose of this invited “ALD 101” tutorial is to familiarize a newcomer with fundamentals of ALD. The presentation largely follows the organization of a recent encyclopedia chapter on ALD [6]. Surface chemistry concepts will be introduced, such as ideal ALD from repeated, separate self-terminating (saturating and irreversible) reactions; growth per cycle in ALD; various monolayer concepts relevant to ALD; typical classes of surface reaction mechanisms and saturation-determining factors; growth modes; and ways to describe growth kinetics. Concepts, where differing views exist in the field and which thus need special attention, are pointed out. Typical deviations from the presented ideality are discussed.
For continuous education, a collaborative OpenLearning website on ALD is under construction [7]. Many of the images used in this tutorial—and in Refs. 6 and 7—are available in Wikimedia Commons [8] for easy and free reuse. To contribute to collective learning of the early history of ALD, the open-science effort Virtual Project on the History of ALD [4] still welcomes new volunteer participants.
[1] E. Ahvenniemi et al., J. Vac. Sci. Technol. A 35 (2017) 010801 (2017).[2] R.L. Puurunen, ECS Transactions 86 (6) (2018) 3-17; OA: DOI:10.1149/osf.io/exyv3[3] G.N. Parsons et al., J. Vac. Sci. Technol. A 38 (2020) 037001.[4] http://vph-ald.com[5] J.R. van Ommen, R.L. Puurunen, ALD 2020, https://youtu.be/jqm_wf49WwM[6] J.R. van Ommen, A. Goulas, R.L. Puurunen, Kirk-Othmer Encyclopedia on Chemical Technology, submitted. [7] http://openlearning.aalto.fi, ALD [8] https://commons.wikimedia.org/wiki/Category:Atomic_layer_deposition
Roll-to-Roll ALD Coatings for Battery Cell Interfaces at Production ScaleBeneq
ALD/AVS 2022
Presented by D.Sc. Andrew Cook
ALD is an enabling technology for future batteries. ALD technology introduction has been hindered by lack of production scale equipment, but now Beneq R2R ALD technology offers a straightforward scale-up path to mass-production. Beneq has a long experience with R2R ALD on other application areas, and is now applying that know-how to offer R2R ALD solutions for battery manufacturing.
ALD for Industry 2019: Slides of invited tutorial by Prof. Riikka PuurunenRiikka Puurunen
Invited tutorial given by Prof. Riikka Puurunen at the ALD for Industry event, Berlin, 19.3.2019.
Video record taken with Panopto, (to be) shared in Youtube, you find the links e.g. through the blog post: https://blogs.aalto.fi/catprofopen/2019/03/19/prof-puurunen-invited-tutorial-at-ald-for-industry-berlin/
Title: ALD Technology – Introduction, History & Principles
Abstract: This tutorial keynote will introduce atomic layer deposition (ALD) – a variant of chemical vapor deposition - and fundamental principles and concepts related it from a generic viewpoint applicable to any ALD process and reactor. The early history and current usage of ALD are briefly overviewed: who made the first experiments, when, and why? How has the view on the history of ALD evolved? Where is ALD now used, by whom, and why? ALD relies on repeated chemical adsorption steps from gas phase to surface. The status of understanding the adsorption steps of ALD films will be presented and discussed using mainly the archetype trimethylaluminium-water ALD process as example and 3D conformality modelling as additional vehicle. Plenty of links to further sources of information will be included in this keynote presentation.
A related SlideShare: placeholder, where I meant to update the slides afterwards, but this did not succeed as the reupload function has been removed: https://www.slideshare.net/RiikkaPuurunen/ald-for-industry-2019-invited-tutorial-by-prof-riikka-puurunen/RiikkaPuurunen/ald-for-industry-2019-invited-tutorial-by-prof-riikka-puurunen. The update was waiting for the publication of the following review article, which was still in press when giving the presentation: Cremers, Puurunen, Dendooven, Appl. Phys. Rev. (2019), https://doi.org/10.1063/1.5060967. Article published 4.4.2019: Applied Physics Reviews 6, 021302 (2019)
Battery Show Europe 2022
Presented by D.Sc. Andrew Cook
ALD is an enabling technology for future batteries. ALD technology introduction has been hindered by lack of production scale equipment, but now Beneq R2R ALD technology offers a straightforward scale-up path to mass-production. Beneq has a long experience with R2R ALD on other application areas, and is now applying that know-how to offer R2R ALD solutions for battery manufacturing.
Invited talk at 98th CSC: Surface chemistry of ALD: mechanisms and conformality Riikka Puurunen
Abstract of the presentation:
Atomic layer deposition (ALD) is a thin film growth method generally applicable for the growth of conformal, highquality
inorganic material layers down to the nanometer thickness range. ALD is indifferent to the morphology of the
underlying substrate and covers even most complex 3-D shapes with a uniform film; as a consequence, ALD is used
in an ever-increasing field of applications from catalysts to photovoltaics to microelectronics and beyond. ALD
belongs to the general class of chemical vapour deposition (CVD) techniques. The speciality of ALD is the use of
repeated self-terminating (saturating, irreversible) gassolid reactions of at least two reactants for the film growth; ALD
is therefore non-continuous in nature, as opposed to the continuous CVD processes. In this presentation, I will
discuss some challenges related to understanding the surface chemistry of ALD. The commonly-used
trimethylaluminium-water ALD process to deposit Al2O3 is used as case example, as it is often presented as model
case for ALD. I will also discuss the characteristics of ALD film conformality, as detected by using microscopic lateral
high-aspect-ratio structures ("VTT μLHAR") [J. Vac. Sci. Technol. A 33, 010601 (2015)]. Here, the gap height is in
the range of 100 nm's and the aspect ratio (AR) can be extremely challenging, e.g. up to 25 000:1. Finally, I will
briefly introduce the on-going international volunteer-based Virtual Project on the History of ALD (http://vph-ald.com),
where new participants are still welcome.
Acknowledgement: The author thanks Finnish Centre of Excellence in Atomic Layer Deposition for funding.
Perovskites-based Solar Cells: The challenge of material choice for p-i-n per...Akinola Oyedele
Perovskite-based PV have triggered widespread interest in the scientific community because these materials offer the attractive combinations of low cost and theoretically high efficiency. However, several challenges must be overcome for these relatively new PV materials. Among the many important challenges, one is the choice of materials to be used in thin film PV devices..
Based on fundamental principles of solar photovoltaics, this problem focuses on two aspects of the perovskite system:
1) Based on a planar p-i-n device structure, a potential list of p- and n-type charge collecting layers as well as the conductive contacts that could be used with a promising perovskite absorber material was identified, and a proper justification for the selection of each material in the device was given.
2) Three theoretical p-i-n type solar cells were made with the chosen materials and appropriate conductive contacts.
ALD for energy application - Lithium ion battery and fuel cellsLaurent Lecordier
This presentation offers a review of latest works done on Ultratech Cambridge Nanotech ALD tools related to atomic layer deposition of Li2O and other lithium-based thin films for lithium-ion battery applications. It illustrates the benefits of ALD for deposition in 3D nanostructure.
Perovskite Solar Cells
a short general overview presentation
hadi maghsoudi
device structure
crystal structure
preparation synthesis method
review papers
Film Properties of ALD SiNx Deposited by Trisilylamine and N2 PlasmaBeneq
Presented by Dr. Markus Bosund
Silicon nitride is a widely used material in semiconductor applications‚ such as gate dielectrics‚ III/V surface passivation and etch stop layer.
PEALD SiNx films have been previously grown using aminosilanes like BTBAS with N2 plasma [1]. These processes generally have a relatively low growth rate of 0.15 - 0.21 Å/cycle and high film quality can only be reached at above 300 °C deposition temperatures. Trisilylamine (TSA) has been previously combined with N2/H2 plasma at 300–400 °C [2]‚ NH3 plasma at 50–400 °C [3] and N2 plasma at 250 – 350 °C [4] to grow PEALD SiNx films. However‚ in these works the low temperature range has remained either inaccessible or uncharted.
In this work we explored the PEALD TSA-N2 plasma process with a wide deposition temperature range from 50 to 350 °C. Focus was given to the electrical and optical properties of the films. A Beneq TFS 200 capacitively coupled hot wall plasma ALD reactor was used at direct plasma mode. It was found that reactor temperature‚ and plasma power and time had the highest impact on the film properties. Film deposition was observed at temperatures as low as 50 °C. Metal insulator semiconductor (MIS) structures were used to determine the breakdown field and leakage current at different temperatures. Films were dipped in 1 % HF solution for etch rate determination.
This presentation summarizes history and recent development of perovskite solar cells. If you have any questions or comments, you can reach me at agassifeng@gmail.com
Catalysis Connected, Utrecht - slides of invited talk by Prof. Riikka PuurunenRiikka Puurunen
Talk given in Utrecht, The Netherlands, August 24, 2019
Title: Atomic layer deposition: Bridging semiconductors to catalysis and beyond
Abstract: This talk will briefly explain the fundamentals of atomic layer deposition (ALD), view key historical turning points of the technique, and attempt to look into the future of ALD in the field of catalysis. ALD, a thin film growth method based on repeated self-terminating gas-solid reactions of compatible compounds, has become known as an enabler of Moore’s law and is today commonplace in the manufacturing of semiconductor devices. Currently, ALD is seen as highly promising for the controlled preparation of heterogeneous catalysts, testified e.g. from the number of reviews that appear on the topic. ALD can be used to grow films or nanoparticles and even single sites, and it can be similarly applied on powders, engineered 3D structures, and flat model catalysts.
Adsorption-controlled catalyst preparation by ALDRiikka Puurunen
Lecture slides of Prof. Riikka Puurunen at Aalto University School of Chemical Engineering, CHEM-E1130 Catalysis, 25.2.2019, on the preparation of catalysts by atomic layer deposition.
Battery Show Europe 2022
Presented by D.Sc. Andrew Cook
ALD is an enabling technology for future batteries. ALD technology introduction has been hindered by lack of production scale equipment, but now Beneq R2R ALD technology offers a straightforward scale-up path to mass-production. Beneq has a long experience with R2R ALD on other application areas, and is now applying that know-how to offer R2R ALD solutions for battery manufacturing.
Invited talk at 98th CSC: Surface chemistry of ALD: mechanisms and conformality Riikka Puurunen
Abstract of the presentation:
Atomic layer deposition (ALD) is a thin film growth method generally applicable for the growth of conformal, highquality
inorganic material layers down to the nanometer thickness range. ALD is indifferent to the morphology of the
underlying substrate and covers even most complex 3-D shapes with a uniform film; as a consequence, ALD is used
in an ever-increasing field of applications from catalysts to photovoltaics to microelectronics and beyond. ALD
belongs to the general class of chemical vapour deposition (CVD) techniques. The speciality of ALD is the use of
repeated self-terminating (saturating, irreversible) gassolid reactions of at least two reactants for the film growth; ALD
is therefore non-continuous in nature, as opposed to the continuous CVD processes. In this presentation, I will
discuss some challenges related to understanding the surface chemistry of ALD. The commonly-used
trimethylaluminium-water ALD process to deposit Al2O3 is used as case example, as it is often presented as model
case for ALD. I will also discuss the characteristics of ALD film conformality, as detected by using microscopic lateral
high-aspect-ratio structures ("VTT μLHAR") [J. Vac. Sci. Technol. A 33, 010601 (2015)]. Here, the gap height is in
the range of 100 nm's and the aspect ratio (AR) can be extremely challenging, e.g. up to 25 000:1. Finally, I will
briefly introduce the on-going international volunteer-based Virtual Project on the History of ALD (http://vph-ald.com),
where new participants are still welcome.
Acknowledgement: The author thanks Finnish Centre of Excellence in Atomic Layer Deposition for funding.
Perovskites-based Solar Cells: The challenge of material choice for p-i-n per...Akinola Oyedele
Perovskite-based PV have triggered widespread interest in the scientific community because these materials offer the attractive combinations of low cost and theoretically high efficiency. However, several challenges must be overcome for these relatively new PV materials. Among the many important challenges, one is the choice of materials to be used in thin film PV devices..
Based on fundamental principles of solar photovoltaics, this problem focuses on two aspects of the perovskite system:
1) Based on a planar p-i-n device structure, a potential list of p- and n-type charge collecting layers as well as the conductive contacts that could be used with a promising perovskite absorber material was identified, and a proper justification for the selection of each material in the device was given.
2) Three theoretical p-i-n type solar cells were made with the chosen materials and appropriate conductive contacts.
ALD for energy application - Lithium ion battery and fuel cellsLaurent Lecordier
This presentation offers a review of latest works done on Ultratech Cambridge Nanotech ALD tools related to atomic layer deposition of Li2O and other lithium-based thin films for lithium-ion battery applications. It illustrates the benefits of ALD for deposition in 3D nanostructure.
Perovskite Solar Cells
a short general overview presentation
hadi maghsoudi
device structure
crystal structure
preparation synthesis method
review papers
Film Properties of ALD SiNx Deposited by Trisilylamine and N2 PlasmaBeneq
Presented by Dr. Markus Bosund
Silicon nitride is a widely used material in semiconductor applications‚ such as gate dielectrics‚ III/V surface passivation and etch stop layer.
PEALD SiNx films have been previously grown using aminosilanes like BTBAS with N2 plasma [1]. These processes generally have a relatively low growth rate of 0.15 - 0.21 Å/cycle and high film quality can only be reached at above 300 °C deposition temperatures. Trisilylamine (TSA) has been previously combined with N2/H2 plasma at 300–400 °C [2]‚ NH3 plasma at 50–400 °C [3] and N2 plasma at 250 – 350 °C [4] to grow PEALD SiNx films. However‚ in these works the low temperature range has remained either inaccessible or uncharted.
In this work we explored the PEALD TSA-N2 plasma process with a wide deposition temperature range from 50 to 350 °C. Focus was given to the electrical and optical properties of the films. A Beneq TFS 200 capacitively coupled hot wall plasma ALD reactor was used at direct plasma mode. It was found that reactor temperature‚ and plasma power and time had the highest impact on the film properties. Film deposition was observed at temperatures as low as 50 °C. Metal insulator semiconductor (MIS) structures were used to determine the breakdown field and leakage current at different temperatures. Films were dipped in 1 % HF solution for etch rate determination.
This presentation summarizes history and recent development of perovskite solar cells. If you have any questions or comments, you can reach me at agassifeng@gmail.com
Catalysis Connected, Utrecht - slides of invited talk by Prof. Riikka PuurunenRiikka Puurunen
Talk given in Utrecht, The Netherlands, August 24, 2019
Title: Atomic layer deposition: Bridging semiconductors to catalysis and beyond
Abstract: This talk will briefly explain the fundamentals of atomic layer deposition (ALD), view key historical turning points of the technique, and attempt to look into the future of ALD in the field of catalysis. ALD, a thin film growth method based on repeated self-terminating gas-solid reactions of compatible compounds, has become known as an enabler of Moore’s law and is today commonplace in the manufacturing of semiconductor devices. Currently, ALD is seen as highly promising for the controlled preparation of heterogeneous catalysts, testified e.g. from the number of reviews that appear on the topic. ALD can be used to grow films or nanoparticles and even single sites, and it can be similarly applied on powders, engineered 3D structures, and flat model catalysts.
Adsorption-controlled catalyst preparation by ALDRiikka Puurunen
Lecture slides of Prof. Riikka Puurunen at Aalto University School of Chemical Engineering, CHEM-E1130 Catalysis, 25.2.2019, on the preparation of catalysts by atomic layer deposition.
Photocatalysis has now become an emerging scientific discipline due to its interdisciplinary nature. The wide range of research groups is now working on different aspects of photocatalysis worldwide. It is one of the technology the world looking forward to address environmental as well as energy related issues. Hence we can call it as a technology for the future or a dream technology! We need to overcome too many hurdles to implement this technology in real life. Like any other discipline there is a lot of misunderstanding/ misconceptions in photocatalysis.
Most frequently cited article in the field of photocatalysis is by Fujishima and Honda published in 1972 in nature and it has been cited by the photocatalytic community as an origin of photocatalysis. This aspect is not true at all. This article cannot be the origin of photocatalysis. This article only promoted photocatalytic studies. The author itself, actually, started a research career in the “boom” of photocatalytic studies initiated by this article.
This small presentation aims to deliver some misconceptions like above in photocatalysis. The entire presentation is based on different personal commentaries written by Jean Mary Hermann and Bunsho Ohtani. Some recent articles relevant to the topic are collected by the speaker itself and put it in one platform.
Invited talk by R.L. Puurunen "Recent Progress in Analysis of the Conformality of Films by Atomic Layer Deposition" at AVS69, Portland, Oregon, Nov 5-10, 2023, https://avs69.avs.org/.
ABSTRACT. Conformality is a fundamental characteristic of atomic layer deposition (ALD) thin film growth technique. “Conformal” film refers to a film that covers all surfaces of a complex three-dimensional substrate with everywhere the same thickness and properties. ALD - invented independently by two groups in 1960s and 1970s - has since late 1990s been transformational in semiconductor technology. Apart from semiconductors, conformal ALD films find applications and interest in widely varied fields such as microelectromechanical systems, pharmaceutical powder processing, optical coatings, battery technologies and heterogeneous catalysts.
Conformality follows directly from the “ideal ALD” principles: growth of material through the use of repeated separate self-terminating (i.e., saturating and irreversible) gas-solid reactions of at least two compatible reactants on a solid surface. Obtaining conformality in practice is not self-evident, however. Reasons for deviation from conformality are multiple, ranging from mass transport limitations to slow reaction kinetics and various deviations from ideal ALD (e.g., by-product reactivity or a continuous chemical vapor deposition (CVD) component through reactant decomposition or insufficient purging). Incomplete conformality can also be intentional: a saturation profile inside a feature can be exposed, to enable an analysis of kinetic parameters of the reactions.
This invited talk will explore recent progress especially by the author and collaborators in understanding ALD conformality and kinetics, obtained via experiments and simulations. Experiments have been made with the recently commercialized (chipmetrics.com) silicon-based PillarHallTM lateral HAR test chips (channel height ~500 nm) and spherical mesoporous high-surface-area materials (average pore diameter ~10 nm, sphere diameter ~1 mm). Simulations are presented for 1d feature-scale models and optionally a recently developed 3d code for spheres. Two codes are available on GitHub: DReaM-ALD (diffusion-reaction model, DRM) and Machball (ballistic transport-reaction model, BTRM). Often it is assumed that diffusion during an ALD process in HAR features is by Knudsen diffusion and free molecular flow conditions prevail (Kn >>1). If so, a characteristic “fingerprint saturation profile” can be obtained, and the slope method (derived for DRM-ALD-Arts, GitHub) can be used to back-extract the lumped sticking coefficient. When diffusion is in the transition flow (Kn ~1) or continuum flow (Kn<<1), the shape of the saturation profile depends on process conditions and the slope method is not applicable.
"On the fundamentals of ALD: the importance of getting the picture right" by ...Riikka Puurunen
Presentation at the AVS 20th International Conference on Atomic Layer Deposition (ALD 2020) featuring the 7th International Atomic Layer Etching Workshop (ALE 2020), online, 29.6.-1.7.2020.
Authors: Riikka L. Puurunen and J. Ruud van Ommen
Abstract text:
Atomic layer deposition (ALD) has become of global importance as a fundamental building block for example in semiconductor device fabrication, and also gained more visibility (e.g., the Millennium Technology Prize 2018). In recent years, the number of ALD processes has increased, new groups have entered the field, and fundamental insights have been gained. At the same time, significantly varying views exist in the field related to the description and meaningfulness of some core ALD concepts. Open, respectful but critical scientific discussion would be needed around these concepts - for example at this AVS ALD/ALE conference, the world’s largest conference on ALD.
The discussion on terminology of ALD that started in the 2005 surface chemistry review [1] is continued in this contribution, taking into account recent progress reported in leading reviews such as Ref. 2. We start by considering the concept of “ideal ALD”. How should it be defined so that the well-recognized practical benefits of ALD are maintained, while no unnecessary utopian requirements are created? We propose that the repetition of well-separated saturating, irreversible chemisorption reactions (which by definition saturate at a monolayer of the chemisorbed species) is sufficient to reproduce the benefits of ALD. A requirement of “full monolayer growth” (of the ALD-grown material), progressed e.g. in numerous cartoons of ALD, is not needed. There should also be no reason to expect a constant growth per cycle (GPC) within the ALD window (the saturating chemistry is typically weakly temperature dependent), although such a scheme is repeatedly reproduced in the literature.
Other fundamental concepts will be pointed out, where mix-ups have been created. For example, although the GPC (or etch per cycle in Atomic Layer Etching) is a saturation-related concept and not a time-related kinetic parameter, Arrhenius plots have been sometimes created to extract “activation energies” of some process from these “growth/etch rates (per cycle)”. Also, “Langmuir adsorption” has been adopted as a way to model ALD in a simplified, lumped way. Notably, Langmuir adsorption assumes no interaction between adsorbed species, contrasting some recent discussions of “cooperative effects” in ALD. Also, concepts of “adsorption isotherm” and amount adsorbed vs. time (“saturation curve”), although fundamentally different, have been mixed.
We hope that the discussion on the fundamentals of ALD will be intensified, and that the discussion will help the field progress and flourish in the future.
[1] Puurunen, J. Appl. Phys. 97 (2005) 121301.
[2] Richey, de Paula, Bent, J. Chem. Phys. 152 (2020) 040902.
The Effects of Nitrogen and Oxygen Atmosphere on the Photoconductivity of Tri...journalBEEI
Organic materials were previously used as insulators in electrical technology. These materials, however, are currently used as conductors once their photoconductivity is confirmed and studied. From the literature, it has shown that the photoconductivity of trimethyl phenyl diamine (TPD) increases in the air and decreased in the atmosphere of the vacuum. To the best of our knowledge, there is no detailed study of the effects of gas in the air that affect TPD photoconductivity. In this study we investigate the effects of nitrogen (N2) and oxygen (O2) gases on photoconductivity, degradation and residual decay of photoconductivity for thin film TPD. The results of the study show that in the atmosphere of O2, TPD produces about seven times higher photoconductivity compared to N2 conditions. It also shows that, N2 and O2 provide more effective response time during photoconductivity residual decay. Photoconductivity degradation occurs in all conditions and its recovery takes more than 65 hours.
Puurunen (on behalf of Järvilehto) oral presentation at ALD 2023 conferenceRiikka Puurunen
ALD 2023, Bellevue, Washington, July 2023
AUDIO: (see 1st page)
Title: Simulated Conformality of ALD Growth Inside Lateral HAR Channels: Comparison Between a Diffusion–Reaction Model and a Ballistic Transport–Reaction Model
Authors: Jänis Järvilehto,1 Jorge A. Velasco,1 Jihong Yim,1 Christine Gonsalves1 and Riikka L. Puurunen1
1Aalto University, School of Chemical Engineering, Department of Chemical and Metallurgical Engineering
Atomic layer deposition (ALD) is known for its ability to produce films of controllable thickness, even in narrow, high-aspect-ratio (HAR) structures [1]. These films can be highly conformal, meaning that the structure is covered by a film of uniform thickness [1,2]. However, when the structure’s aspect ratio is increased sufficiently, deposition becomes limited by the diffusion of the reactants into the deep end of the structure, potentially resulting in the formation of an adsorption front, followed by a region of lower coverage [3]. Theoretical models have been developed to predict film conformality in HAR structures, as reviewed in [2].
This work presents a comparison of a diffusion–reaction model (DRM) developed by Ylilammi et al. [4,5] (Model A) and a ballistic transport–reaction model (BTRM) by Yanguas-Gil and Elam [6,7] (Model B). For the comparison, saturation profiles were generated using both models with similar simulation parameters (Knudsen number Kn >> 1).
Qualitatively, both models produced similar trends in terms of half-coverage penetration depth and slope at half-coverage penetration depth. The saturation profiles were similar in shape, except for the film growth observed at the channel end in Model B. Quantitative examination yielded consistently higher half-coverage penetration depths in Model B. Model A produced steeper slopes at half-coverage penetration depth. In Model B, the discretization resolution was found to affect the penetration depth.
While the models gave qualitatively similar results, quantitatively extracted parameters differed. This finding is consistent with a previous comparison of a DRM and BTRM in the context of low pressure chemical vapor deposition [8]. The quantitative differences are relevant, for example, when the models are fitted to experimental data for the extraction of kinetic parameters, such as the sticking coefficient.
[1] J.R. van Ommen, A. Goulas, and R.L. Puurunen, “Atomic layer deposition,” in Kirk Othmer Encyclopedia of
Chemical Technology, John Wiley & Sons, Inc., 42 p, (2021).
[2] V. Cremers et al., Appl. Phys. Rev. 6 (2019) 021302.
[3] J. Yim and O.M.E. Ylivaara et al., Phys. Chem. Chem. Phys. 22 (2020) 23107-23120.
[4] M. Ylilammi et al., J. Appl. Phys. 123 (2018) 205301.
[5] J. Yim and E. Verkama et al., Phys. Chem. Chem. Phys. 24 (2022) 8645–8660.
[6] A. Yanguas-Gil and J.W. Elam, Theor. Chem. Acc. 133 (2014) 1465.
[7] A. Yanguas-Gil and J.W. Elam, (2013) ...
OLED Device Review and A Summary of the Plasmonic Enhancement thereofAI Publications
Within this work the major breakthroughs in the development of OLED technologies are described. There is a strong emphasis placed upon materials discovery. The basic OLED structure is shown and the plasmonic effect is detailed in the context of OLED technologies.
Puurunen invited talk at IUPAC|Chains2023, The Hague, Netherlands, Aug 20-25,...Riikka Puurunen
Title: Atomic layer deposition: Introduction and progress examples
RECORDED AUDIO: https://aalto.cloud.panopto.eu/Panopto/Pages/Viewer.aspx?id=835b50be-f687-463a-b0dc-b06900e0b47b
IUPAC|CHAINS2023 August 20-25, 2023. ‘Connecting Chemical Worlds’
Invited talk in parallel session 62: Advanced Thin Film Technology of Energy and Smart Materials
ABSTRACT
Atomic layer deposition (ALD), a thin film growth method based on self-terminating gas-solid reactions, has enabled the miniaturization of semiconductor devices in 2000s and finds commercial and emerging applications in varied other fields [1]. ALD has been invented independently twice [2,3]; in 1998, the Finnish inventor of ALD Tuomo Suntola received the Millennium Technology Prize for his pioneering work. This invited talk will first introduce the chemical principles of ALD. The ideally self-terminating (saturating, irreversible) reactions lead to almost unparalleled uniformity and conformality of the films, and to expanding interest in the ALD technique. Second, case examples will be shared of recent research in Puurunen’s group at Aalto University related to preparation of heterogeneous catalysts by ALD and conformality investigations by experiments and modelling. As the speaker is interested in bringing more openness to science and education in a sustainable way, recent progress in Open Science in the field of ALD will be also briefly touched upon.
References:
[1] J.R. van Ommen, A. Goulas, R.L. Puurunen, “Atomic layer deposition”, in Kirk-Othmer Encyclopedia of Chemical Technology, 2021, https://doi.org/10.1002/0471238961.koe00059.
[2] R.L. Puurunen, “A Short History of Atomic Layer Deposition: Tuomo Suntola's Atomic Layer Epitaxy”, Chem. Vap. Deposition 20 (2014) 332-344. https://doi.org/10.1002/cvde.201402012
[3] A.A. Malygin, V.E. Drozd, A.A. Malkov, V.M. Smirnov, “From V. B. Aleskovskii's “Framework” Hypothesis to the Method of Molecular Layering/Atomic Layer Deposition”, Chem. Vap. Deposition 21 (2015) 216-240. https://doi.org/10.1002/cvde.201502013
ALD for Industry 2019: Invited tutorial by Prof. Riikka Puurunen Riikka Puurunen
Oops! Could not update this placeholder with the final presentation as planned: The reupload function that I planned to use, has been removed from SlideShare, see: https://www.slideshare.net/dolaneconslide/bring-back-reupload
Slides uploaded separately: https://www.slideshare.net/RiikkaPuurunen/ald-for-industry-2019-slides-of-invited-tutorial-by-prof-riikka-puurunen
Originally, this update was waiting for the publication of a review article to be published on ALD conformality: Cremers, Puurunen, Dendooven, Appl. Phys. Rev. (2019), https://doi.org/10.1063/1.5060967. Article published 4.4.2019: Applied Physics Reviews 6, 021302 (2019)
Related post in Catalysis Professor's Open: https://blogs.aalto.fi/catprofopen/2019/03/19/prof-puurunen-invited-tutorial-at-ald-for-industry-berlin/
On the history and future of ALD: VPHA, conformality analysis, mechanismsRiikka Puurunen
Invited presentation at the HERALD COST MP1402 event in Riga (Riika), Latvia, May 22-23, 2017.
Topics:
1) History of atomic layer deposition (ALD)
2) Conformality analysis of ALD and other thin films
3) Surface chemistry questions in ALD
Presentation dedicated to the memory of Mr. Sven Lindfors, pioneer in building ALD reactors, close collaborator of Dr. Tuomo Suntola from 1975.
Slides of my first invited talk at a conference, the ALD 2005 conference in San Jose 2005, about ALD modelling. ALD is fantastic, but fantastic is not perfect :)
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R. L. Puurunen, Atomic-scale modelling of atomic layer deposition processes, American Vacuum Society Topical Conference on Atomic Layer Deposition (ALD 2005), San Jose, California, August 8-10, 2005. Invited talk.
Slides of invited talk on ALD for MEMS at the AVS-ALD conference ALD 2009 Monterey, California, USA
---
Full reference:
R. L. Puurunen, M. Blomberg, H. Kattelus, ALD layer in MEMS fabrication, 9th International Conference on Atomic Layer Deposition “ALD 2009”, Monterey, California, July 19-22, 2009. Invited talk.
Slides of an invited talk, given at EuroCVD in 2007
R. L. Puurunen, Understanding the surface chemistry of atomic layer deposition: achievements and challenges, Sixteenth European Conference on Chemical Vapor Deposition, EuroCVD-16. Den Haag, The Netherlands, 16 - 21 Sept. 2007. Book of Extended Abstracts. Klein, C.R. (Ed.). Delft University of Technology (2007), 11. Invited talk.
History of ald riikka puurunen 15.11.2013 finalRiikka Puurunen
Invited seminar talk by R. L. Puurunen, November 15, 2013, Beneq and ETU (LETI) joint ALD laboratory opening seminar, St. Petersburg, Russia, title: History of ALD: from lab research to industrial applications
ALD ATO nanolaminates with adjustable electrical properties, poster published...Riikka Puurunen
R. L. Puurunen, H. Kattelus, ALD ATO nanolaminates with adjustable electrical properties, 9th International Conference on Atomic Layer Deposition “ALD 2009”, Monterey, California, July 19-22, 2009. Poster presentation.
Acknowledgement (from the Abstract):
Acknowledgements: The authors are grateful to Ari Häärä for making the electrical measurements and to Sari Sirviö for supervising part of the sample fabrication and for initial interpretations of the results of the electrical measurements. This work was performed within the “ALDKOMP” project funded by Tekes (Finnish Funding Agency for Technology and Innovation).
Poster presented at the AVS ALD 2005 conference. This contains Al2O3 solubility data in deionized water and a report on the "bubbles" which form on ALD Al2O3 when heated. This work has been cited sometimes especially for the bubble formation, and now I want to make it easily accessible for all.
---
Controlling the Solubility of ALD Aluminium Oxide in Deionised Water
Riikka L. Puurunen, Jyrki Kiihamäki and Hannu Kattelus
VTT Technical Research Centre of Finland
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Surface coverage in atomic layer deposition - slides related to invited talk by Prof. Riikka Puurunen
1. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Surface coverage
in ALD
Prof. Riikka Puurunen,
Aalto University, Finland
Workshop on Fundamentals of Atomic Layer
Deposition (ALD): Modelling and Validation
TU Delft, The Netherlands, July 3, 2019
aalto.fi/cmet/catalysis; @rlpuu
2. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
EuroCVD 22 - Baltic ALD
16, in Luxembourg,
June 24-28,
2019. Abstract. Poster.
2002 Doctoral thesis, Helsinki
University of Technology, 2002
Cartoon model of ALD GPC,
Chem. Vap. Deposition
2005 ALD review: history, processes &
Me3Al-H2O surface chemistry case study,
J. Appl. Phys. (Appl. Phys. Rev.)
>1400 time cited
2015 Microscopic conformality test structures
pillarhall.com;
2019 ALD conformality review App. Phys. Rev.
2013 ALD review, process update + crystallinity,
J. Appl. Phys. (Appl. Phys. Rev.)
2013 Virtual Project on the History of ALD
(VPHA), vph-ald.com; review 2016
2018 Millennium Technology Prize
1974 Suntola ALE
http://vph-ald.com
Aldhistory.blogspot.fi
2
3. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Outline
1. ALD introduction
+ Why TMA + Al2O3?
2. Surface coverage
-- (so) many definitions
3. Growth-Per-Cycle (GPC) in ALD:
Cartoon model(s)
4. GPC in ALD: Model validation
5. Some terminology discussion
6. Conclusion
Contains
“Twitter portals”
to click!
3
5. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Atomic layer deposition (ALD)
ALD cycle
Reactant A
Reactant B
By-product
Substrate
before ALD
Step 2 /4
purge
Step 4 /4
purge
Step 1 /4
Reactant A
Step 3 /4
Reactant B
Reactant A
Reactant B
By-product
(Scheme: Puurunen)
George, Chem. Rev. 110 (2010) 111–131.
DOI: 10.1021/cr900056b
Time
Most cited ALD
review of all times
5
6. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
ALD
materials
by two-
reactant
processes
> 700 processes
”Periodic table of ALD processes”: 1st ed.: Puurunen, J. Appl. Phys. 97 (2005) 121301. DOI: 10.1063/1.1940727
2nd ed.: Miikkulainen, Leskelä, Ritala, Puurunen, J. Appl. Phys. 113 (2013) 021301. DOI: 10.1063/1.4757907.
Web-based voluntary updating in TU Eindhoven-led initiative in: https://www.atomiclimits.com/alddatabase/
https://www.atomiclimits.com/alddatabase/,
62005 Puurunen review2013 update+crystallinity
7. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
>700 ALD reactant - co-reactant pairs
7
H2O
NH3
H2S
Non-metal co-reactants, “thermal” ALD
Energy-enhanced ALD
O2
N2
H2
Metal precursor type
Elements
Halides
Alkyls
Cyclopentadienyls
Alkoxides
b-diketonates
Alkylamides and
silylamides
Amidinates
InorganicMetal-organic
Organo-
metallic
Class
N
NM
N
M
O
M
O
O
M
M
M
M
Cl
M
etc
etc
Puurunen, Appl. Phys. 97 (2005) 121301. https://doi.org/10.1063/1.1940727
Miikkulainen, Leskelä, Ritala, Puurunen, J. Appl. Phys. 113 (2013) 021301. http://doi.org/10.1063/1.4757907.
O3
…
Metal reactant type
2005 Puurunen review2013 update+crystallinity
8. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
In ALD, gas-solid reactions ideally:
saturating & irreversible*
amount adsorbed saturates
amount adsorbed stays
pulse purge
Definition of ”ideal ALD”, especially for modelling purposes:
Puurunen, J. Appl. Phys. 97 (2005) 121301. DOI:10.1063/1.1940727
*chemisorption
non-saturationunsaturationdesorption
NO:
YES:
?
partial reversibility?
82005 Puurunen review
9. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Concept of “ALD window”:
where ALD conditions fulfilled
92005 Puurunen review
Simplified
George, Chem. Rev. 110 (2010) 111; DOI: 10.1021/cr900056b. Adapted
from: Suntola, Atomic Layer Epitaxy. In Handbook of Crystal Growth, Vol.
3, Part B, Hurle, D. T. J., Ed.; Elsevier: Amsterdam, 1994; Chapter 14.
15. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Adsorption
Physisorption
• non-specific
• minimal electronic interaction
• chemical nature of the adsorbate not
altered
• adsorption energy similar to the energy
of condensation (exothermic)
• non-activated
• equilibrium is established
• multilayers may form
Chemisorption
• chemical specificity
• changes in electronic state
• reversible/irreversible
• chemisorption energy as for a chemical
reaction (exothermic/endothermic)
• often involves an activation energy
• for “large” activation energies (“activated
adsorption”), true equilibrium may be
achieved slowly
• monolayer adsorption
http://old.iupac.org/reports/2001/colloid_2001/manual_of_s_and_t/node16.html, accessed 2.7.2019
Ideal ALD: sequential use of self-terminating
gas–solid reactions (i.e., chemisorption)
152005 Puurunen review
16. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Coverage & monolayer:
so many definitions!
Chemisorbed ML, Q
Physisorbed ML,
ML of the ALD-grown
material,
*, , Q, …
* units? none; nm-2
162005 Puurunen review
17. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Different uses for the definitions
Chemisorption: coverage Q
at saturation unity by definition
Physisorption: Estimate steric hindrance
Material monolayer:
ALD sanity check
(GPC < 1 ML);
process throughput
172005 Puurunen review
Ideal ALD: irreversible chemisorption
(Model III)
18. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Coverage - one more definition:
GPC in saturation profile modelling
• Rose & Bartha 2009 “The density of reactive sites
equals the density of deposited <metal> atoms
divided by the number of deposition cycles.”
• Ylilammi et al. 2018 Adsorption density q defined
via gpcsat
• Arts et al. 2019: “… the surface coverage θ is defined
as the reacted fraction of available reaction sites, in
such a way that θ = 1 in saturation”… “… average
area … of an adsorption site … can be calculated
from the growth per cycle.”
Rose & Bartha, Appl. Surf. Sci. 255 (2009) 6620; DOI:10.1016/j.apsusc.2009.02.055
Ylilammi et al. J. Appl. Phys. 123 (2018) 205301; DOI:10.1063/1.5028178
Arts et al. J. Vac. Sci. Technol. A 37 (2019) 030908; DOI:10.1116/1.5093620
18
pillarhall.com
19. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Saturation profile modelling:
lumped sticking probability
19
https://en.wikipedia.org/wiki/Langmuir_adsorption_
model#/media/File:Langmuir_Adsorption_Model.jpg
Ylilammi, Ylivaara, Puurunen, J. Appl. Phys. 123, 205301 (2018); DOI: 10.1063/1.5028178
Arts et al. J. Vac. Sci. Technol. A 37 (2019) 030908; DOI:10.1116/1.5093620
https://en.wikipedia.org/wiki/Langmuir_adsorption_model, accessed 13.9.2018
• Flat surface & isothermal conditions
• Surface sites are equal
• Adsorbed species do not interact
• Adsorption & desorption are elementary processes
Cremers, Puurunen, Dendooven, Appl. Phys. Rev. (2019) in press, DOI: 10.1063/1.5060967
AssociationAssumed: Langmuir adsorption
20. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Chemisorbed ML
Physisorbed ML
ML of the ALD-
grown material
(d) “Sticking coefficient and
GPC-related monolayer
& coverage” NEW!
Coverage & monolayer:
so many definitions!
… and there are more …
20(a)-(c): 2005 Puurunen review
22. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
ALD GPC cartoons
FIG. 13. Schematic illustration for analyzing
sterically hindered chemisorption
• on the basis of the size of the MLn
reactant Model I by Ritala et al. Refs. 462
and 468 and Morozov et al. Ref. 133,
• the size and geometry of the chemisorbed
MLz species Model II by Ylilammi Ref.
1127, and
• the size and number of ligands L Model III
by Siimon and Aarik Ref. 432 and
Puurunen Ref. 1128.
Left: side view, right: top view.
222005 Puurunen review
Model III: Ligands L
23. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
The ALD Model:
background
Fig. 11, Puurunen, J. Appl.
Phys. 97 (2005) 121301.
https://doi.org/10.1063/1.19
40727 open access pdf
Dissociation
L
Reaction:
MLn + surface
L/M < n
L/M = n
L/M = n
2005 Puurunen reviewPuurunen, CVD 9 (2003) 249; DOI:10.1002/cvde.200306265
24. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
The ALD Model (part 1 of 2)
1. Mass balance for L for MLn
chemisorption
• ligands can be lost via ligand
exchange with “-a”:
24
2. Ligand size (nm2)
• Maximum packing density
Puurunen, Chem. Vap. Deposition 9 (2003) 249; DOI:10.1002/cvde.200306265
max
25. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
3. Know / assume the
reaction mechanism / cause of
saturation
• Fixed or flexible L/M ratio?
• Ligand exchange /
association-dissociation?
4. Know / assume
number of “-a” sites (nm-2)
• Which fraction reacts?
The ALD model (part 2 of 2)
Puurunen, CVD 2003; https://doi.org/10.1002/cvde.200306265
25
26. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Example 1: ML4 + –a -ML3 + gas (L/M = 3)
• Ligand
exchange
with one -a
• Steric
hindrance
or –a
concentrati
on limits
Puurunen, Chem. Vap. Deposition 9 (2003) 249; https://doi.org/10.1002/cvde.200306265
GPC in ML
26
27. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Example 4: ML4 + –a -MLx + gas (L/M varies)
• All –a
consumed
in ligand
exchange
• Further
association/
dissociation
• Steric
hindrance
limits
Puurunen, Chem. Vap. Deposition 9 (2003) 249; https://doi.org/10.1002/cvde.200306265
GPC in ML
27
32. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Some “ALD window” discussion
• Barry, 2018: “I belive that some processes show an
#ALDep window, I just don't believe it is a necessary
condition for #ALDep to occur”
• Yanguas-Gil, 2018: “I object to the idea that
stability with temperature of the growth per cycle
is a property of self-limiting processes.”
• Elliott, 2018: “… the max coverage is 100%, so above
a sufficiently high temperature, GPC=const... ignoring
non-ALD reactions of course.”
• Puurunen, 2019: “... The sources … which presented
#ALDwindow as a region of constant GPC, pointed as
reference to https://doi.org/10.1021/cr900056b … -
now the most cited #ALDep review of all times …
George 2010, Chem. Rev., DOI:10.1021/cr900056b2010
Over-
simplified?
32
34. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Surface chemistry of TMA-water process
Puurunen:
• Different works/reviews present substantially different conclusions on the surface
chemistry. See e.g. TSF 2014, DOI:10.1016/j.tsf.2013.11.112 98th CCC 2015,
SlideShare
Vandalon & Kessels, JVSTA 2017, DOI:10.1116/1.4993597:
• ” … the self-limiting behavior in the TMA half-cycle cannot be caused by steric
hindrance.” “The absolute –CH3 densities reached after the TMA half-cycle, <6 nm-2
…, are not high enough for steric hindrance””
Adomaitis, at EuroCVD-BalticALD (#CVDALD2019), unpublished:
34
35. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Saturation profile (TMA-water)
“ALD measurable” (Yanguas-Gil, 2017)
Fingerprint saturation profile (?)
* Contains maximum information
Ylivaara, Yim, Ylilammi, Utriainen,
Puurunen, unpublished material,
manuscript in preparation
Example image: Arts et al. J. Vac. Sci. Technol. A 37 (2019) 030908;
DOI:10.1116/1.5093620
Normalized saturation profile ( coverage)
* Enables extraction of lumped sticking
coefficient, but:
* Effect of e.g. temperature on GPC lost
pillarhall.com
35
37. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Conclusion
1. Surface coverage(s) in ALD
central for describing surface
chemistry. Many definitions
may cause confusion
2. “Cartoon” / “ball” models help
to see the big picture
3. TMA-water ALD process needs
better understanding of surface
chemistry
37
38. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Thank you! Discussion?
• Thanks to Dr. Fatemeh Hashemi for organizing the workshop &
Prof. Ruud van Ommen for inviting me to visit TU Delft
”All men by nature desire to know”
Tuomo Suntola Aristotle
#SuntolaQuote
38
2018
Millennium
Technology Prize
39. Puurunen, ALD fundamentals workshop, Delft 3.7.2019
Additional materials
Web of Knowledge
Puurunen RL citation analysis
with papers indicated
39
2005 Puurunen review
2013 update+crystallinity
2019 conformality review
2003 Cartoon model
40. Puurunen, ALD fundamentals workshop, Delft 3.7.2019 Web of Knowledge, 30.6.2019
Web of Knowledge citation analysis, 30.6.2019, for author: Puurunen RL
2003 Cartoon
model of ALD
GPC
Island growth model
40
2005 Puurunen
review (APR)
2013 update +
crystallinity
(APR)
2019
conformality
review (APR)
New!
Appl. Phys. Rev. :
https://doi.org/10.1063/1.50
60967
41. Puurunen, ALD fundamentals workshop, Delft 3.7.2019 Web of Knowledge, 30.6.2019
Island growth model: cases
Cartoon model GPC: cases
Cartoon model GPC: case
41
42. Puurunen, ALD fundamentals workshop, Delft 3.7.2019 Web of Knowledge, 30.6.2019
Cartoon model GPC: case
Surface chemistry case
TMA on alumina
TMA on silica
“non-growth ligand exchange”
42
43. Puurunen, ALD fundamentals workshop, Delft 3.7.2019 Web of Knowledge, 30.6.2019
Random deposition model
43
44. Puurunen, ALD fundamentals workshop, Delft 3.7.2019 44
• Puurunen @rlpuu, 2017:
“Haukka's ending slide: great
#ALDep cartoon from years
ago. But who is the original
artist? Can Twitter find out?
#ALDALE2017
#RealTimeChem”
• Twitter found out!
By: Nick Kim,
http://www.lab-initio.com
ALD cartoons!
& The power of Twitter!