1) The document describes using Kelvin probe force microscopy combined with localized photoexcitation to diagnose the performance of individual subcells in a multi-junction solar cell.
2) Experiments were able to selectively excite different subcells by focusing laser light onto specific semiconductor layers. This allowed measuring the surface photovoltage response of each subcell.
3) Measurements showed dips and peaks in the photovoltage profiles that matched simulations and could be used to identify the weakest performing subcell, which ultimately limits the efficiency of the entire multi-junction solar cell.
Printed UWB Circular and Modified Circular Disc Monopole AntennasIDES Editor
In this paper, we have investigated printed
monopole antennas, which is basically printed microstrip
antenna with etched ground plane for UWB applications. In
particular, we have simulated two types of UWB printed
monopole antennas: circular and modified circular disk
monopole antennas. Simple rectangular microstrip lines are
used for feeding the printed monopole antennas. This UWB
monopole antenna designed works well for the whole UWB
frequency band 3.1-10.6GHz from the IE3D simulation
results.
NS2 installation guideline for the student to install the software . It use for student to install and download the software. The software is about the experimental of communication technology.
Circular antenna array has gained immense
popularity in the field of communications nowadays. It has
proved to be a better alternative over other types of antenna
array configuration due to its all-azimuth scan capability,
and a beam pattern which can be kept invariant. This paper is
basically concerned with the thinning of a large multiple
concentric circular ring arrays of uniformly excited isotropic
antennas based on Improved Particle Swarm Optimization
(IPSO) method. In this paper a 9 ringed Concentric Circular
Antenna Array (CCAA) with central element feeding is
considered. The computational results show that the number
of antenna array elements can be brought down from 279 to
147 with simultaneous reduction in Side Lobe Level of about
20 dB with a fixed half power beamwidth.
Mushroom-Like EBG to Improve Patch Antenna Performance for C-Band Satellite A...IJECEIAES
In order to suppress the surface waves excitation that are caused by thick substrate in a patch antenna, a mushroom-like EBG (Electromagnetic Band Gap) structure is used. Such structures enhance its characteristics of gain, directivity, bandwidth and efficiency. Firstly, we determined frequency band gap characteristics of mushroom like EBG unit cell value by using CST software with 3mm (0.06λ ) for covering 6 GHz. The periodic arrangement of such mushroom-like EBG structures was not limited by any interconnecting microstrip lines. Four columns of EBGs shifted inwards to antenna edges by 0.3mm (0.06λ o ) or a gap of its design around the patch from the left and right sides. Different configurations were also examined in order to get the better improvement in antenna performance. The final design of this mushroom-like shifted periodic structure shows an effective increase in the directivity by 77%, gain by 108%, bandwidth by 29% and the efficiency by 20% for the antenna. This structure has diversified application possibility for wireless and satellite communications. o
Printed UWB Circular and Modified Circular Disc Monopole AntennasIDES Editor
In this paper, we have investigated printed
monopole antennas, which is basically printed microstrip
antenna with etched ground plane for UWB applications. In
particular, we have simulated two types of UWB printed
monopole antennas: circular and modified circular disk
monopole antennas. Simple rectangular microstrip lines are
used for feeding the printed monopole antennas. This UWB
monopole antenna designed works well for the whole UWB
frequency band 3.1-10.6GHz from the IE3D simulation
results.
NS2 installation guideline for the student to install the software . It use for student to install and download the software. The software is about the experimental of communication technology.
Circular antenna array has gained immense
popularity in the field of communications nowadays. It has
proved to be a better alternative over other types of antenna
array configuration due to its all-azimuth scan capability,
and a beam pattern which can be kept invariant. This paper is
basically concerned with the thinning of a large multiple
concentric circular ring arrays of uniformly excited isotropic
antennas based on Improved Particle Swarm Optimization
(IPSO) method. In this paper a 9 ringed Concentric Circular
Antenna Array (CCAA) with central element feeding is
considered. The computational results show that the number
of antenna array elements can be brought down from 279 to
147 with simultaneous reduction in Side Lobe Level of about
20 dB with a fixed half power beamwidth.
Mushroom-Like EBG to Improve Patch Antenna Performance for C-Band Satellite A...IJECEIAES
In order to suppress the surface waves excitation that are caused by thick substrate in a patch antenna, a mushroom-like EBG (Electromagnetic Band Gap) structure is used. Such structures enhance its characteristics of gain, directivity, bandwidth and efficiency. Firstly, we determined frequency band gap characteristics of mushroom like EBG unit cell value by using CST software with 3mm (0.06λ ) for covering 6 GHz. The periodic arrangement of such mushroom-like EBG structures was not limited by any interconnecting microstrip lines. Four columns of EBGs shifted inwards to antenna edges by 0.3mm (0.06λ o ) or a gap of its design around the patch from the left and right sides. Different configurations were also examined in order to get the better improvement in antenna performance. The final design of this mushroom-like shifted periodic structure shows an effective increase in the directivity by 77%, gain by 108%, bandwidth by 29% and the efficiency by 20% for the antenna. This structure has diversified application possibility for wireless and satellite communications. o
Application of Bio-Inspired Optimization Technique for Finding the Optimal se...IDES Editor
In this paper the maximum sidelobe level (SLL) reductions
of three-ring concentric circular antenna arrays
(CCAA) without and with central element feeding are examined
using two different classes of evolutionary optimization
techniques to finally determine the global optimal three-ring
CCAA design. Apart from physical construction of a CCAA,
one may broadly classify its design into two major categories:
uniformly excited arrays and non-uniformly excited arrays.
The present paper assumes non-uniform excitations and uniform
spacing of excitation elements in each three-ring CCAA
design and a design goal of maximizing SLL reduction associated
with optimal beam patterns and beam widths. The design
problem is modeled as an optimization problem for each CCAA
design. Binary coded Genetic Algorithm (BGA) and Bacteria
Foraging Optimization (BFO) are used to determine an optimum
set of normalized excitation weights for CCAA elements,
which, when incorporated, results in a radiation pattern with
optimal (maximum) SLL reduction. Among the various CCAA
designs the three-ring CCAA containing (N1=4, N2=6, N3=8)
elements along with central element feeding proves to be global
optimal design. BFO yields global minimum SLL (-34.18
dB) and global minimum BWFN (81.50) for the optimal design.
Performance of Groundplane Shaping in Four-Element Dualband MIMO AntennaTELKOMNIKA JOURNAL
This work presents performance of groundplane shaping and its effect in four element dualband
multiple input multiple output (MIMO) antenna. This proposed four element dualband MIMO antenna
consists of four bowtie dipole antenna which operates at 1800 MHz (low frequency) and 2300 MHz (high
frequency). This proposed four element dualband MIMO antenna occupies a 270 x 210 x 100 mm3 of FR
4 substrate. We use four types of groundplane pattern i.e. full groundplane, cornered spatial groundplane,
crossed middle groundplane, and spiral groundplane. These various grounplane patterns influence the
performance of main parameters of dualband MIMO antenna. Cornered spatial groundplane pattern yields
a largest bandwidth (VSWR ≤ 2) 282 MHz or 15.24% of center frequency at low frequency. Full
groundplane pattern creates 135.2 MHz at high frequency. In addition, cornered spatial groundplane
pattern also generates a lowest VSWR that is valued 1.21 at both low frequency and high frequency. The
S parameters, basically both cornered spatial and full groundplane pattern produce a better return loss
than two others. All four groundplane patterns deliver equally a mutual coupling parameter.The last, this
proposed four element dualband MIMO with various groundplane patterns gives a good farfield properties
i.e. gain, radiation pattern, H-E field.
Circular Patch Antenna Performance using EBG StructureIDES Editor
Electromagnetic Band-Gap (EBG) structures are a
popular and efficient technique for microwave applications.
EBG may be combined with microstrip antenna to increase
the diversity gain, the radiation efficiency and/or to suppress
surface waves, to reduce the side lobes of the radiation pattern
and to increase the bandwidth. In this paper, two different
structures will be presented and discussed, which involve: (1)
EBG structure fed by circular patch antenna, and (2) circular
patch antenna surrounded by one row of EBG structure. The
influence of the EBG structure on the radiation patterns is
investigated. The effect of the surface waves is also considered.
Finally, the reduction of the side lobes of the radiation pattern
to increase the bandwidth is presented.
Variable radiation pattern from co axial probe fed rectangular patch antenna ...eSAT Journals
Abstract The idea of obtaining variable radiation patterns from the same antenna is important aspect in achieving the adaptive antenna systems. In the EM signal processing the change of radiation signifies the information to be transmitted, its rate of transmission, the geographical changes and direction to transmit etc. i.e. each time when the requirement arises to change the radiation pattern it has to be done to satisfy the conditions. Electronically steerable antennas were used where the antenna radiation will be altered by varying the feed and similar case is applied for shaped patterns from array antenna where the feed to be given will be calculated and given accordingly. In the present concept the metamaterials are used to obtain different radiation patterns occurred at different operating frequencies using the same antenna without changing the antenna physically are varying its feed. Key Words: Inductance, capacitance, operating frequency, variable radiation, enhancement, radiation cancellation.
Compact Vertical Patch Antenna for Dual-Band WLAN OperationSaou-Wen Su
A new compact patch antenna, which is arranged perpendicular to a circular ground plane, for WLAN operation is presented. The antenna consists mainly of one driven patch and one shorted parasitic patch, which both wind along two concentric circles. A constructed prototype covering the 2.4 and 5 GHz WLAN bands is demonstrated. Good broadside radiation characteristics are obtained across the operating bands. Details of the proposed patch antenna and experimental results are presented and discussed.
Novel High-Gain Narrowband Waveguide-Fed Filtenna using Genetic Algorithm Yayah Zakaria
Filtenna is an antenna with filtering feature. There are many ways to design a filtenna. In this paper, a high-gain narrowband waveguide-fed aperture filtenna has been proposed and designed. A patterned plane, which is designed using genetic algorithm has been used at the open end of the waveguide fed, mounted on a conducting ground plane. To design the patterned pattern, magnetic field integral equation of the structure has been derived, so it has been solved using method of moments. The proposed filtenna has been simulated with HFSS that confirms the results obtained by method of moments. Finally, an unprinted dielectric as a superstrate has been used to enhance the gain of the filtenna. The filtenna bandwidth is 1.76% (160 MHz) which has the gain of 15.91 dB at the central frequency
of 9.45 GHz.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Application of Bio-Inspired Optimization Technique for Finding the Optimal se...IDES Editor
In this paper the maximum sidelobe level (SLL) reductions
of three-ring concentric circular antenna arrays
(CCAA) without and with central element feeding are examined
using two different classes of evolutionary optimization
techniques to finally determine the global optimal three-ring
CCAA design. Apart from physical construction of a CCAA,
one may broadly classify its design into two major categories:
uniformly excited arrays and non-uniformly excited arrays.
The present paper assumes non-uniform excitations and uniform
spacing of excitation elements in each three-ring CCAA
design and a design goal of maximizing SLL reduction associated
with optimal beam patterns and beam widths. The design
problem is modeled as an optimization problem for each CCAA
design. Binary coded Genetic Algorithm (BGA) and Bacteria
Foraging Optimization (BFO) are used to determine an optimum
set of normalized excitation weights for CCAA elements,
which, when incorporated, results in a radiation pattern with
optimal (maximum) SLL reduction. Among the various CCAA
designs the three-ring CCAA containing (N1=4, N2=6, N3=8)
elements along with central element feeding proves to be global
optimal design. BFO yields global minimum SLL (-34.18
dB) and global minimum BWFN (81.50) for the optimal design.
Performance of Groundplane Shaping in Four-Element Dualband MIMO AntennaTELKOMNIKA JOURNAL
This work presents performance of groundplane shaping and its effect in four element dualband
multiple input multiple output (MIMO) antenna. This proposed four element dualband MIMO antenna
consists of four bowtie dipole antenna which operates at 1800 MHz (low frequency) and 2300 MHz (high
frequency). This proposed four element dualband MIMO antenna occupies a 270 x 210 x 100 mm3 of FR
4 substrate. We use four types of groundplane pattern i.e. full groundplane, cornered spatial groundplane,
crossed middle groundplane, and spiral groundplane. These various grounplane patterns influence the
performance of main parameters of dualband MIMO antenna. Cornered spatial groundplane pattern yields
a largest bandwidth (VSWR ≤ 2) 282 MHz or 15.24% of center frequency at low frequency. Full
groundplane pattern creates 135.2 MHz at high frequency. In addition, cornered spatial groundplane
pattern also generates a lowest VSWR that is valued 1.21 at both low frequency and high frequency. The
S parameters, basically both cornered spatial and full groundplane pattern produce a better return loss
than two others. All four groundplane patterns deliver equally a mutual coupling parameter.The last, this
proposed four element dualband MIMO with various groundplane patterns gives a good farfield properties
i.e. gain, radiation pattern, H-E field.
Circular Patch Antenna Performance using EBG StructureIDES Editor
Electromagnetic Band-Gap (EBG) structures are a
popular and efficient technique for microwave applications.
EBG may be combined with microstrip antenna to increase
the diversity gain, the radiation efficiency and/or to suppress
surface waves, to reduce the side lobes of the radiation pattern
and to increase the bandwidth. In this paper, two different
structures will be presented and discussed, which involve: (1)
EBG structure fed by circular patch antenna, and (2) circular
patch antenna surrounded by one row of EBG structure. The
influence of the EBG structure on the radiation patterns is
investigated. The effect of the surface waves is also considered.
Finally, the reduction of the side lobes of the radiation pattern
to increase the bandwidth is presented.
Variable radiation pattern from co axial probe fed rectangular patch antenna ...eSAT Journals
Abstract The idea of obtaining variable radiation patterns from the same antenna is important aspect in achieving the adaptive antenna systems. In the EM signal processing the change of radiation signifies the information to be transmitted, its rate of transmission, the geographical changes and direction to transmit etc. i.e. each time when the requirement arises to change the radiation pattern it has to be done to satisfy the conditions. Electronically steerable antennas were used where the antenna radiation will be altered by varying the feed and similar case is applied for shaped patterns from array antenna where the feed to be given will be calculated and given accordingly. In the present concept the metamaterials are used to obtain different radiation patterns occurred at different operating frequencies using the same antenna without changing the antenna physically are varying its feed. Key Words: Inductance, capacitance, operating frequency, variable radiation, enhancement, radiation cancellation.
Compact Vertical Patch Antenna for Dual-Band WLAN OperationSaou-Wen Su
A new compact patch antenna, which is arranged perpendicular to a circular ground plane, for WLAN operation is presented. The antenna consists mainly of one driven patch and one shorted parasitic patch, which both wind along two concentric circles. A constructed prototype covering the 2.4 and 5 GHz WLAN bands is demonstrated. Good broadside radiation characteristics are obtained across the operating bands. Details of the proposed patch antenna and experimental results are presented and discussed.
Novel High-Gain Narrowband Waveguide-Fed Filtenna using Genetic Algorithm Yayah Zakaria
Filtenna is an antenna with filtering feature. There are many ways to design a filtenna. In this paper, a high-gain narrowband waveguide-fed aperture filtenna has been proposed and designed. A patterned plane, which is designed using genetic algorithm has been used at the open end of the waveguide fed, mounted on a conducting ground plane. To design the patterned pattern, magnetic field integral equation of the structure has been derived, so it has been solved using method of moments. The proposed filtenna has been simulated with HFSS that confirms the results obtained by method of moments. Finally, an unprinted dielectric as a superstrate has been used to enhance the gain of the filtenna. The filtenna bandwidth is 1.76% (160 MHz) which has the gain of 15.91 dB at the central frequency
of 9.45 GHz.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Global Cool is an innovative green lifestyle charity the creates innovative campaigns around home energy use, public transport, flight-free holidays and recycling.This document outlines the impact of our campaigns to combat climate change.
Med denne Powerpoint prøver jeg at beskrive, hvad Netværksskolen går ud på. Kort fortalt er Netværksskolen en skolevision, som tager udgangspunkt i de sociologiske og teknologiske grundvilkår i netværkssamfundet. Dowlnload præsentationen og se den på skærmen.
Se mere på www.facebook.com/netvaerksskolen
- David Garde Tschertok, pædagogisk uddannelseschef - Microsoft
3 d single gaas co axial nanowire solar cell for nanopillar-array photovoltai...ijcsa
Nanopillar array photovoltaics give unique advantages over today’s planar thin films in the areas of
optical properties and carrier collection, arising from their 3D geometry. The choice of the material
system, however, is essential in order to gain the advantage of the large surface/interface area associated
with nanopillars. Therefore, a well known Si and GaAs material are used in the design and studied in this
nanowire application. This work calculates and analyses the performance of the coaxial GaAs nanowire
and compared with that of Si nanowire using a semi-classical method. The current-voltage characteristics
are investigated for both under dark and AM1.5G illumination. It is found that GaAs nanowire gives almost
double efficiency with its counterpart Si nanowire. Their TCAD simulations can be validated reasonably
with that of published experimental result.
Simulation of AlGaN/Si and InN/Si ELECTRIC –DEVICESijrap
In this work, efficient solar-blind metal-semiconductor photodetectors grown on Si (111) by
molecular beam epitaxy are reported. Growth details are described,the comparison enters the
properties electric of InN/Si and AlGaN/Si photodectors with 0.2 μm of AlGaN and InN layers.
Modeling and simulation were performed by using ATLAS-TCAD simulator. Energy band
diagram, doping profile, conduction current density,I-V caracteristic , internal potential and
electric field were performed.
Simulation of AlGaN/Si and InN/Si ELECTRIC –DEVICESijrap
In this work, efficient solar-blind metal-semiconductor photodetectors grown on Si (111) by
molecular beam epitaxy are reported. Growth details are described,the comparison enters the
properties electric of InN/Si and AlGaN/Si photodectors with 0.2 µm of AlGaN and InN layers.
Modeling and simulation were performed by using ATLAS-TCAD simulator. Energy band
diagram, doping profile, conduction current density,I-V caracteristic , internal potential and
electric field were performed
Simulation Of Algan/Si And Inn/Si Electric - Devicesijrap
In this work, efficient solar-blind metal-semiconductor photodetectors grown on Si (111) by
molecular beam epitaxy are reported. Growth details are described,the comparison enters the
properties electric of InN/Si and AlGaN/Si photodectors with 0.2 µm of AlGaN and InN layers.
Modeling and simulation were performed by using ATLAS-TCAD simulator. Energy band
diagram, doping profile, conduction current density,I-V caracteristic , internal potential and
electric field were performed.
International Refereed Journal of Engineering and Science (IRJES)irjes
The core of the vision IRJES is to disseminate new knowledge and technology for the benefit of all, ranging from academic research and professional communities to industry professionals in a range of topics in computer science and engineering. It also provides a place for high-caliber researchers, practitioners and PhD students to present ongoing research and development in these areas.
Extended electrical tuning of quantum cascade lasers with digitalSepehrAzureSky
In this report, the sampled grating distributed feedback laser architecture is modified with digital
concatenated gratings to partially compensate for the wavelength dependence of optical gain in a
standard high efficiency quantum cascade laser core. This allows equalization of laser threshold
over a wide wavelength range and demonstration of wide electrical tuning. With only two
control currents, a full tuning range of 500 nm (236 cm1
) has been demonstrated. Emission is
single mode, with a side mode suppression of >20 dB. V C 2013 AIP Publishing LLC.
[http://dx.doi.org/10.1063/1.4841635]
In this work, the performances of a solar cell based on InGaN were simulated under the illumination conditions of one sun by employing SILVACO software.
GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
Kubernetes & AI - Beauty and the Beast !?! @KCD Istanbul 2024Tobias Schneck
As AI technology is pushing into IT I was wondering myself, as an “infrastructure container kubernetes guy”, how get this fancy AI technology get managed from an infrastructure operational view? Is it possible to apply our lovely cloud native principals as well? What benefit’s both technologies could bring to each other?
Let me take this questions and provide you a short journey through existing deployment models and use cases for AI software. On practical examples, we discuss what cloud/on-premise strategy we may need for applying it to our own infrastructure to get it to work from an enterprise perspective. I want to give an overview about infrastructure requirements and technologies, what could be beneficial or limiting your AI use cases in an enterprise environment. An interactive Demo will give you some insides, what approaches I got already working for real.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
91mobiles recently conducted a Smart TV Buyer Insights Survey in which we asked over 3,000 respondents about the TV they own, aspects they look at on a new TV, and their TV buying preferences.
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
All of this illustrated with link prediction over knowledge graphs, but the argument is general.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
Keynote at DIGIT West Expo, Glasgow on 29 May 2024.
Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
The key trends across hardware, cloud and open-source; exploring how these areas are likely to mature and develop over the short and long-term, and then considering how organisations can position themselves to adapt and thrive.
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
Accelerate your Kubernetes clusters with Varnish Caching
Solar Cell AFM optics
1. NTEGRA Spectra: Solar Cell Diagnostics
Solar Cell Diagnostics by Combination of
Kelvin Force Microscopy with Local Photoexitation
A. V. Ankudinov,
Ioffe Physical-Technical Institute of the Russian Academy of Science
National Research University of Information Technologies, Mechanics and Optics
INTRODUCTION
The Sun is an abundant, easily accessible power
source that is currently underutilized, will possibly Ga0.99In0.01As-n
+
500 nm
become the no-alternative choice for electrical power Al0.51In0.49P-n 30 nm
of humankind [1]. It is believed that the most Ga0.51In0.49P-n 50 nm
3
Ga0.51In0.49P-p 680 nm
promising way to convert solar power is by the
Al0.25Ga0.25In0.5P-p 50 nm
photoelectric method used in solar cells (SCs) [2]. The Al0.4Ga0.6As-p++ 15 nm
energy program of the European Union envisions that GaAs-n++ 15 nm
no less than 3 % of electric power will be provided Al0.51In0.49P-n 30 nm
Ga0.51In0.49P-n 100 nm
from solar installations by 2020 [3]. In the United
Ga0.99In0.01As-n 100 nm
States, the Solar America Initiative program 2
Ga0.99In0.01As-p ~ 2500 nm
anticipates that the volume of the "photovoltaic" Ga0.51In0.49P-p 100 nm
market will already be $5-10 billion by 2015, with an Al0.25Ga0.25In0.5P-p 30 nm
increase to $20-30 billion by 2030 [4]. Interestingly, the Al0.4Ga0.6As-p++ 30 nm
++
GaAs-n 30 nm
factor hindering more intense development of the SC Al0.53In0.47P-n 50 nm
market is the high cost per Megawatt of produced Ga0.99In0.01As-n 1000 nm
electricity, rather than the energy conversion Ga0.53In0.47P-n 100 nm
efficiency of SCs. Ge-substrate (n doped) ~ 300 nm
1
Ge-substrate (p doped)
FORMULATION OF THE PROBLEM
Fig.1.
At present, the highest efficiencies, some exceeding Schematic of an MJ SC with three subcells.
40%, are exhibited by multijunction (MJ) SCs based on Designations: various tints of pink, p-type layers
semiconductor nanoheterostructures [5]. MJ SCs of the heterostructure; light blue tints, n-type layers;
and yellow, highly conducting layers of tunnel diodes
consist of several subcells with p-n junctions and and contact layers. The digits show the p-n junctions
barrier layers of various semiconductor materials. in the subcells based on (1) Ge, (2) GaAs, and (3) GaInP2.
These subcells are arranged in order of decreasing
energy bandgaps from the photosensitive surface to efficiencies. It is, however, important to note that the
the substrate, being linked by oppositely connected most inefficient subcell determines the overall
tunnel diodes. efficiency of an MJ SC. Diagnostics of the constituent
Each subcell converts into electricity the energy of layers of such a composite device is commonly made
the short-wavelength part of the incident spectrum using indirect, integral measurement techniques and
and transmits its long-wavelength part to the next mathematical simulation (see, e. g., [6]). Information
subcell. Thus, the energy of the whole solar spectrum obtained this way is not always unambiguous because
is segmented and collected, resulting in high it requires the solution of multivariate inverse
www.ntmdt.com
http://www.ntmdt.com/device/ntegra-spectra
2. NTEGRA Spectra: Solar Cell Diagnostics
a) b)
Ge GaAs GaInP2 100x
high NA
objective
Electrical AFM probe
1 2 3
Multi-junction solar cell
c) d)
cantilever cantilever
Fig. 2.
(a) Schematic of layers in an MJ SC with the same color designations as those in Fig. 1. The three p-n junctions are shown by arrows.
(b) Schematic of experiment. Optical micrographs of the edge of the cleaved surface of a SC during a KPFM experiment
under focused photoexcitation of (c) the p-n junction in Ge with a blue laser (473 nm) and (d) p-n junction in GaAs with a red laser
(785 nm). Latin numerals designate: (I) Ge substrate, (II) III-V layers (GaAs and GaInP ), (III) free space,and (IV) KPFMcantilever.
The optical microscope is focused on the Ge substrate in Fig. 2c,and on the III-V layers in Fig. 2d.
problems. An unambiguous determination of the position of a laser excitation source. According to
weakest segment will likely require separate the schematic of the layers in Fig. 1, the distance
monitoring of the operation of all the constituent between the p-n junctions of neighboring subcells
subcells. (From the standpoint of circuitry, it is based on GaAs and GaInP2 is shorter than a
necessary to find the least efficient element in a set of micrometer. The monitoring of the response,
series-connected photodiodes). surface potential variation, of a separate subcell
was enabled by focusing the excitation laser into a
EXPERIMENTAL RESULTS AND DISCUSSION submicrometer spot. An objective with a numerical
Below is considered an example of how the NTEGRA
aperture of 0.7 and resolving power of 400 nm,
Spectra «AFM – confocal – Raman – fluorescence»
was used in the confocal laser microscope
Probe NanoLaboratory (PNL) is used to study MJ SCs
integrated in the NTEGRA Spectra PNL. An AFM
based on a GaInP2/GaAs/Ge heterostructure with three
cantilever is positioned below the objective
p-n junctions. The total number of layers exceeds 20,
allowing simultaneous optical excitation and AFM
and individual layers less than 20 nm thick (see Fig. 1).
measurements (Fig. 2b). Importantly, the
The method of Kelvin probe force microscopy
instrument allows both independent and
(KPFM) was used to measure the surface potential
synchronized scanning of laser spot (using piezo-
profile variations of a cross-section-cleaved SC in
driven mirror) and the sample (using a sample
relation to the intensity, wavelength, and beam
piezo-scanner). Figures 2c and 2d show optical
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3. NTEGRA Spectra: Solar Cell Diagnostics
micrographs of cleaved surfaces of an MJ SC during an (a)
experiment. Near the edge of cleaved surfaces, spots
of light from blue and red lasers focused on the p-n
junctions can be seen in the subcells of Ge and GaAs,
respectively.
A topographic image and a map of the contact
potential difference signal in the region in which the
main MJ SC layers are located is shown in Fig. 3. The
left half of the topographic image in Fig. 3a shows a
(b)
sharp change in the surface topology. In this region,
the smooth relief of the Ge substrate (situated on the
left) abruptly changes to the striated topology of the
III-V layers. The significant difference between the
topographies of Ge and III-V layers is also seen in the
optical micrographs in Figs. 2b and 2c. Crystals of III--V
materials are easily cleaved to form perfectly planar
and atomically smooth surface, but only along {110} (c)
basal planes. This intrinsic property is, for example,
used in the fabrication of mirrors for injection lasers
based on III-V compounds [7]. Crystals of Ge (and also
Si) preferentially cleave along different crystal planes. 1 2 3
The Ge substrate is two orders of magnitude thicker
Fig. 3. KPFM study of the cleaved surface of an MJ SC in
than all the other layers in the MJ SC, and therefore,
the dark. During measurements both contacts to the MJ SC
cleavage propagation directions are predominantly were grounded. (a) Topographic image of the cleaved surface
based on the substrate. The cleaved Ge surface is profile, measured in semi-contact mode (the color-scale
contrast spans the height variations of 0.85 µm).
significantly non-coincident with the basal plane of III-
(b) Map of the CPD signal measured in the second pass
V layers. It is this lack of coincidence that leads to the in the absence of an external photoexcitation (the color-scale
formation of the strongly visible stepped topography contrast spans the CPD variations of 1.05 V).
(c) Smoothed equilibrium profile of the built-in potential
on the cleaved surface of III-V layers.
(from model). Schematic of the layers: arrows with digits
The map of the contact potential difference (CPD) in show the p-n junction positions in the subcells (see also color
Fig. 3b shows features in good agreement with the designations in Fig. 1). Measurement parameters: AFM
laser with a wavelength of 650 nm used in the system
expected built-in potential differences in the bulk
for cantilever deflection detection, noncontact VIT_P probe,
heterostructure under full darkness conditions. The resonance at 257 kHz, surface potential signal was measured
model profile of the built-in potential is shown in Fig. at 100 nm lift height and Uac=2 V.
3c above the schematic of layers of the
heterostructure. The small potential drops across thin Fig. 3b. The light band region corresponds to well-
tunnel-transparent layers are disregarded and the doped transition layers between Ge and the GaAs
simulation describes a smoothed variation of the subcell. These discrepancies occur because the surface
potential. The CPD map, however, shows that near the potential of the semiconductor structure differs from
p-n junction on the surface of the GaAs subcell, there the potential in the bulk by the amount of near-
is only a subsequent decrease in the CPD signal surface band bending, which is not known for an
instead of the expected peak (see Fig. 3c). The arbitrarily cleaved sample. The best agreement
variation of the built-in potential, see Fig. 3c marker 1, between the results of simulation and the
is not observed the light band region in the image in experimental data can be achieved by studying
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4. NTEGRA Spectra: Solar Cell Diagnostics
distributions of the external voltage applied to the laser wavelength, and NA = 0.7 is the numerical
contacts of the structure [8,9] and surface aperture of the objective. The surface photovoltage
photovoltage (SPV) distributions [10]. Below, the profile was determined by the difference of CPD
second case is analyzed in more detail. values measured under photoexcitation and in the
When the semiconductor surface is exposed to light dark. The simulation process, as described in the
with a photon energy exceeding the energy bandgap preceding paragraph, was performed with the
of the material, the separation of photocarriers by the following conditions; the contacts to the MJ SC are
near-surface field results in minority carriers emerging shorted,the photovoltage appearing in the bulk of a
at the surface, which makes the band bending smaller p-n junction exposed to light is distributed among the
[11]. This mechanism is operative for semiconductors barriers of two nonilluminated p-n junctions. For
with surfaces depleted of majority carriers, in which simplicity, the capacitances of these two junctions are
the surface photovoltage has the opposite sign to that considered to be equivalent. The light from the blue
of majority carriers. In a complex structure, laser is absorbed by all layers in the MJ SC and light
photocarriers can be separated not only in the near- from the red laser is not absorbed by the wide-
surface field, but also in the bulk due to the field of bandgap GaInP2 layers. The photoexcitation intensity
built-in barriers. For example, it is possible to predict gradually decreases away from the focusing region.
changes in the surface potential upon illumination of In the experimental photovoltage profiles, the
a single p-n junction. Because of the photocarrier arrows show a dip in Fig. 4b and a peak in Fig. 4c. The
separation in the near-surface field, the p side is simulation also predicts these specific features. The
charged negatively, and the n side positively. By mechanism of their appearance is discussed in more
contrast, the separation of photocarriers in bulk detail below. The GaAs subcell is insulated from the
material from the field of the p-n junction charges the contacts to the MJ SC by the potential barriers at the
p side positively, and the n side negatively. If, for p-n junctions of the neighboring subcells. If it is
example, the number of photocarriers separated in exposed to blue light, separation of photocarriers in
the field of the p-n junction exceed those separated in the field of the p-n junction results in electrons
the near-surface field, then the surface photovoltage ejected into the n layers of this subcell. For this reason,
will decrease, passing from the p side to the n side. If a negative potential appears in the bulk of these n
the contacts to the p and n sides are shorted, then the layers and in the p layers of the GaInP2 subcell.
contribution from the bulk separation is eliminated, Because of the photocarrier separation in the near-
and the surface photovoltage will increase upon such surface field, the surface of the p layers is also
a transition. Qualitatively, the photovoltage profile can negatively charged relative to the bulk. The joint effect
be simulated in the same way in more complex of both processes forms a deep dip in the surface
compound structures, such as MJ SCs. photovoltage profile when it passes across the p layers
Figure 4 shows two sets of simulated and measured of the GaInP2 subcell, as seen in Fig. 4b. If blue light is
photovoltage profiles from a cleaved surface in replaced with red light, no photocarriers are
alternate photoexcitation of p-n junctions in three generated in the wide-bandgap GaInP2 layers. As a
subcells of MJ SCs. The first set, Figs. 4a-4c, was result, the dip should be less pronounced, which is
obtained with blue laser excitation (wavelength indeed observed in Fig. 4e. When the GaInP2 subcell is
l = 473 nm), and the second, Figs. 4d-4f, with red laser exposed to blue light, a positive potential appears in
excitation ( l = 785 nm). The photoexcitation densities the bulk of its p layers and is transferred to the n layers
were approximately the same in both cases, of the GaAs subcell. The photoeffect at the surface of
2-3 mW/µm2. The focal spot diameter D was calculated the n layers is also positive, and a peak corresponding
using the Rayleigh criterion D = 1.22 l/NA, where l is to these layers appears in the photovoltage profile
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5. NTEGRA Spectra: Solar Cell Diagnostics
1 2 3 1 2 3
Fig. 4. Comparison of experimental and simulated data. (a-c) Photoexcitation with laser light (l = 473 nm) focused
on the p-n junctions in (a) Ge, (b) GaAs, and (c) GaInP2. (d-f) Photoexcitation with laser light (l = 785 nm) focused
on the p-n junctions in (d) Ge, (e) GaAs, and (f) GaInP2. Designations: SPV, experimental surface photovoltage profile.
A simulated profile is also given above each plot. Below, under all the plots are shown schematics of layers in MJ SCs
(with the same color designations as those in Figs. 1-3).omparison of the experimental and simulated data.
(a-c) Photoexcitation with laser light (l = 473 nm) focused.
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6. NTEGRA Spectra: Solar Cell Diagnostics
(Fig. 4c). These considerations are helpful in the ACNOWLEDGMENTS
qualitative explanation of the shape of all of the The author is grateful to his colleagues at the Ioffe
profile curves Institute: V. M. Lantratov for the MJ SC samples he
provided, A. S. Gudovskikh for assistance in simulating
CONCLUSIONS the built-in potential profile in a sample, and
The study of a solar cell with three subcells based on M. S. Dunaevskiy for helpful remarks on presentation of
Ge, GaAs, and GaInP2 in a NTEGRA Spectra PNL the results. Many thanks for skillful measurements to
demonstrated that operation of each subcell could be Artem Shelaev and Pavel Dorozhkin from NT-MDT.
separately monitored. The experimental surface-
photovoltage profiles obtained are in good References:
agreement with results of the qualitative simulation. [1] Zh. I. Alferov, V. M. Andreev and V. D. Rumyantsev. Solar
photovoltaics: Trends and prospects. Semiconductors, 38(8), pp. 899-
The agreement between the simulation results and
908 (2004)
experimental data also indicates that there are no [2] S. M. Sze. Kwo K. Ng. Physics of semiconductor devices. Chapter 13.
parasitic barriers in the multijunction solar cell under Photodetectors and Solar Cells. Third eition. Wiley, N.Y. (2007).
study for the chosen photoexcitation densities. [3] http://www.eupvplatform.org/publications/strategic-research-
agenda-implementation-plan.html#c2643
It should be noted that the NTEGRA Spectra PNL,
[4] http://www.eere.energy.gov/solar/solar_america
integrating AFM with confocal optical spectroscopy [5] Karam N. H., Sherif R. A. and King R. R. //Springer Ser. In Opt. Sci.
techniques, offers a substantially broader set of 2007 Vol.130 .P.199–219.
capabilities for solar cell diagnostics than that [6] S. A. Mintairov, V. M. Andreev, V. M. Emelyanov, N. A. Kalyuzhnyy and
N. K. Timoshina, M. Z. Shwarz, V. M. Lantratov. Study of minority carrier
considered in the present communication. The
diffusion lengths in photoactive layers of multijunction solar cells.
NTEGRA Spectra PNL provides the following Semiconductors 44(8), pp. 1084-1089 (2010).
measurement techniques with submicrometer and [7] C. Casey, Jr. and M. B. Panish, Heterostructure Lasers, Academic
nanometer spatial resolution: surface topography; Press, 1978.
[8] S. B. Kuntze, D. Ban, E. H. Sargent, St. J. Dixon-Warren, J. K. Whiteand,
local conductivity; variations of potentials and
K. Hinzer. Electrical Scanning Probe Microscopy: Investigating the Inner
charges, built-in or induced by external bias or Workings of Electronic and Optoelectronic Devices. Critical Reviews in
photoexcitation; evaluation of compositional Solid State and Materials Sciences, 30, 71–124, 2005.
homogeneity and material defects; spatial and [9] A. V. Ankudinov, V. P. Evtikhiev, E. Yu. Kotelnikov, A. N. Titkov and
R. Laiho. Voltage distributions and nonoptical catastrophic mirror
spectral variations of transmittance, reflectance, and
degradation in high power InGaAs/AlGaAs/GaAs lasers studied by
other optical properties; localization of nonradiative Kelvin probe force microscopy. J. Appl. Phys. 93, 432-438 (2003).
recombination regions; monitoring of p-n junction [10] D. K. Schroder. Surface voltage and surface photovoltage: history,
positions; monitoring of heterointerface transitions; theory and applications. Meas. Sci. Technol. 12, R16–R31 (2001).
[11] L. Kronik, Y. Shapira. Surface photovoltage phenomena: theory,
and mapping of mechanical stresses. All of these
experiment, and applications. Surface Science Reports 37, 1-206 (1999).
measurement scan be used to optimize the solar cell
technology. For example, the internal design of solar
cells can be optimized via correlation of regions
having the maximum photovoltaic conversion
efficiency with data on variation of the chemical
composition, layer thickness, profile, defects, optical
parameters, etc.
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7. NTEGRA Spectra: Solar Cell Diagnostics
AFM - Raman - SNOM - TERS
NTEGRA Spectra
Interdisciplinary Research at the Nanometer Scale
100x
high NA
objective
100x
high NA
objective
Atomic Force Microscopy (>30 modes)
Confocal Raman / fluorescence microscopy
Wide-field microscopy
Scanning near-field optical microscopy (SNOM)
Tip Enhanced Raman Scattering (TERS) and other
tip-assisted optical techniques (s-SNOM, TERM etc.)
Controlled Environment
Temperature – Humidity – Gases – Liquid – Electrochemical – Magnetic Field
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