1) Researchers developed an ultrasonic atomizer system to deposit graphene oxide thin films on silicon wafers for applications in semiconductor manufacturing.
2) Graphene oxide was spray coated using the ultrasonic atomizer and then thermally reduced to improve its electrical and thermal conductivity.
3) Characterization of the reduced graphene oxide thin films found they have high coverage area above 90% with uniform thickness, low sheet resistance below 3 kΩ/sq, and thermal conductivity over 1000 W/mK making it suitable as a heat spreader material.
Carbon Nanotubes Effect for Polymer Materials on Break Down Voltage IJECEIAES
Epoxy resin composites reinforced to different types of carbon nano-particles have been fabricated. Carbon black (20, 30 and 40 wt. %), graphene (0.5 to 4 wt. %) and carbon nanotubes (CNT) (0.5 to 2 wt. %) were added with different weight percentages to epoxy. The dielectric strength of composites was tested in several conditions such as (dry, wet, low salinity and high salinity). The mechanical characterization showed that the nano-composite Polymer enhanced by using these particles in the tensile strength. Thermal gravimetric analysis shows effect of these nano-particles on the thermal structure of epoxy resin. Scanning Electron Microscopic test is used to characterize the dispersion of carbon nano-particles and to analysis the fractured parts in the nano scale.
Carbon Nanotubes Effect for Polymer Materials on Break Down Voltage IJECEIAES
Epoxy resin composites reinforced to different types of carbon nano-particles have been fabricated. Carbon black (20, 30 and 40 wt. %), graphene (0.5 to 4 wt. %) and carbon nanotubes (CNT) (0.5 to 2 wt. %) were added with different weight percentages to epoxy. The dielectric strength of composites was tested in several conditions such as (dry, wet, low salinity and high salinity). The mechanical characterization showed that the nano-composite Polymer enhanced by using these particles in the tensile strength. Thermal gravimetric analysis shows effect of these nano-particles on the thermal structure of epoxy resin. Scanning Electron Microscopic test is used to characterize the dispersion of carbon nano-particles and to analysis the fractured parts in the nano scale.
Graphene field-effect transistor simulation with TCAD on top-gate dielectric ...TELKOMNIKA JOURNAL
This paper presents the influence of top-gate dielectric material for graphene field-effect transistor (GFET) using TCAD simulation. Apart from silicon-based dielectric that is typically used for top-gate structure, other high-dielectric constant (high-k) dielectric materials namely aluminum oxide and hafnium oxide are also involved in the analysis deliberately to improve the electrical properties of the GFET. The unique GFET current-voltage characteristics against several top-gate dielectric thicknesses are also investigated to guide the wafer fabrication engineers during the process optimization stage. The improvement to critical electrical parameters of GFET in terms of higher saturation drain current and greater on/off current ratio shows that the use of high-k dielectric material with very thin oxide layer is absolutely necessary.
Modeling of Dirac voltage for highly p-doped graphene field-effect transistor...journalBEEI
In this paper, the modeling approach of Dirac voltage extraction of highly p-doped graphene field-effect transistor (GFET) measured at atmospheric pressure is presented. The difference of measurement results between atmospheric and vacuum pressures was analyzed. This work was started with actual wafer-scale fabrication of GFET with the purposes of getting functional device and good contact of metal/graphene interface. The output and transfer characteristic curves were measured accordingly to support on GFET functionality and suitability of presented wafer fabrication flow. The Dirac voltage was derived based on the measured output characteristic curve using ambipolar virtual source model parameter extraction methodology. The circuit-level simulation using frequency doubler circuit shows the importance of accurate Dirac voltage value to the device practicality towards design integration.
The reinforcing effects of graphene oxide (GO) on portland cement paste are investigated. It is dis- covered that the introduction of 0.05% by weight GO sheets into the cement paste can increase the compressive strength and tensile strength Of the cement composite due to the reduction of the pore structure of the cement paste.The overall results indicate that GO reinforcing the engineering properties of portland cement.
Graphene field-effect transistor simulation with TCAD on top-gate dielectric ...TELKOMNIKA JOURNAL
This paper presents the influence of top-gate dielectric material for graphene field-effect transistor (GFET) using TCAD simulation. Apart from silicon-based dielectric that is typically used for top-gate structure, other high-dielectric constant (high-k) dielectric materials namely aluminum oxide and hafnium oxide are also involved in the analysis deliberately to improve the electrical properties of the GFET. The unique GFET current-voltage characteristics against several top-gate dielectric thicknesses are also investigated to guide the wafer fabrication engineers during the process optimization stage. The improvement to critical electrical parameters of GFET in terms of higher saturation drain current and greater on/off current ratio shows that the use of high-k dielectric material with very thin oxide layer is absolutely necessary.
Modeling of Dirac voltage for highly p-doped graphene field-effect transistor...journalBEEI
In this paper, the modeling approach of Dirac voltage extraction of highly p-doped graphene field-effect transistor (GFET) measured at atmospheric pressure is presented. The difference of measurement results between atmospheric and vacuum pressures was analyzed. This work was started with actual wafer-scale fabrication of GFET with the purposes of getting functional device and good contact of metal/graphene interface. The output and transfer characteristic curves were measured accordingly to support on GFET functionality and suitability of presented wafer fabrication flow. The Dirac voltage was derived based on the measured output characteristic curve using ambipolar virtual source model parameter extraction methodology. The circuit-level simulation using frequency doubler circuit shows the importance of accurate Dirac voltage value to the device practicality towards design integration.
The reinforcing effects of graphene oxide (GO) on portland cement paste are investigated. It is dis- covered that the introduction of 0.05% by weight GO sheets into the cement paste can increase the compressive strength and tensile strength Of the cement composite due to the reduction of the pore structure of the cement paste.The overall results indicate that GO reinforcing the engineering properties of portland cement.
This paper explains the fabrication of thin film using modified Physical Vapor Deposition (PVD) Module. Physical Vapor Deposition (PVD) is a variety of vacuum deposition and is a general term used to describe any of a variety of methods to deposit thin films by the condensation of a vaporized form of the material onto various surfaces. The surface morphology of various such as Titanium Dioxide and Aluminum thin film has been studied. The Titanium Dioxide and Aluminum thin film has been fabricated on Silicon (Si) substrate using modified Physical Vapor Deposition (PVD) module system. The process started with the establishment of process flow, process modules, and process parameters. Two modules were developed. The characteristics prior to the thin film fabrication namely surface morphology, metal thickness characterization and V-I characteristic were recorded. The samples were characterized by Optical Microscope, Atomic Force Microscope (AFM),X-ray diffraction (XRD) and I - V characterization. The result and data were analyzed and applied in the fabrication of thin film using various materials. The thin film fabrication process used Titanium Dioxide (TiO2) nanopowder and Aluminum (Al2O3) nanopowder for the coating process. The result for each processes are presented in this paper.
Process flow of spray pyrolysis techniqueIOSR Journals
The chemical spray pyrolysis technique (SPT) has been, throughout last 3 decades, one amongst the most important techniques to deposit a large type of materials in thin film kind. The prime requisite for getting sensible quality thin film is that the optimization of propaedeutic conditions viz. substrate temperature, spray rate, concentration of solution etc. However, in recent years a stress has been given to a range of atomization techniques like supersonic nebulisation, improved spray reaction, corona spray transformation, electricity spray transformation and microchip primarily based spray transformation. This is often the foremost crucial parameter because it permits management over the scale of the droplets and their distribution over the preheated substrates. An intensive review of thin film materials ready throughout the last ten years is given to demonstrate the flexibility of the chemical SPT. the assorted conditions to get thin films of metal compound, metallic mineral oxides, binary, ternary and quaternary chalcogenides and superconducting oxides are given. The consequences of precursor, dopants, substrate temperature, post tempering treatments, answer concentration etc., on the physico-chemical properties of those films are given likewise. It’s discovered that the properties of thin films rely significantly on the propaedeutic conditions. The properties of the thin film will be simply tailored by adjusting or optimizing these conditions that successively are appropriate for a specific application.
Fabrication of microfluidic channels in glass and siliconYichen Sun
Microfluidic channels in glass and silicon chips are fabricated in the cleanroom. Their acoustic focusing properties are then tested and reported in this project report (MEMS 5801).
Dry Sliding Wear Behaviour of Rheocat Al-5.7Si-2Cu-0.3Mg AlloyDr. Manal Abdullatif
In this study, the effect of improved microstructure of Al-5.7Si-2Cu-0.3Mg alloys by using semisolid process on hardness and dry sliding wear behaviour were investigated. The microstructures of conventional cast alloy were totally dendritic, while in rheocasting the dendrit-ic transfer to fine globular microstructures after using cooling slope casting. Tribological tests were carried out by using a pin-on-disc apparatus in dry sliding conditions. Wear tests were at low sliding speed 1ms-1 ,applied load at 50N and three different sliding distance (i.e., 1.8Km, 5.4Km and 9Km) respectively. An optical microscope and a scanning electron microscope were used to examine the micro-structure and to understand the wear mechanism on the worn surface of both samples. The results showed that, the wear resistance of rheocast alloy was improved and higher than that those produce by conventional casting. The volume loss of rheocast alloy show reduc-tion more than 18% at 1.8Km and 10% at 9Km compared to as-cast alloy. Moderate wear regimes were appeared in both alloys, accord-ing to the range of wear rate. The friction coefficient had increased due to increase in the contact point between pin and disc materials. The dominant wear mechanism for conventional and rheocasting alloys was adhesion wear and abrasive wear respectively.
Influence of Thickness on Electrical and Structural Properties of Zinc Oxide ...paperpublications3
Abstract: Zinc Oxide (ZnO) thin films were prepared on corning (7059) glass substrates at a thickness of 75.5 and 130.5nm by RF sputtering technique. The deposition was carried out at room temperature after which the samples were annealed in open air at 1500C. The electrical and structural properties of these films were studied. The electrical properties of the films were monitored by four-point probe method while the structural properties were studied by X-ray diffraction (XRD). It was found that the electrical resistance of the films decreases with increase in the thickness of the films. The XRD analysis of the films showed that the films have a peak located at 〖34.31^0-34.35〗^0with hkl (002). Other parameters calculated include the stress ( ) and the grain size (D).
A micro-electromechanical system (MEMS) gyroscope is commonly used to monitor the angular rate of a moving body due to its benefits. The most promising advantages include its small size, low cost, and a high degree of integration. MEMS gyroscope has different fabrication processes and micromachining techniques. LIGA (Lithography-Galvanoformung-Abformung), bulk micromachining, surface micromachining, Silicon-on-glass (SOG) and Deep Reactive Ion Etching (DRIE) are the known fabrication techniques for MEMS gyroscope. This paper systematically reviewed the fabrication techniques used to fabricate the MEMS gyroscope. The current review paper also focuses on the performance of MEMS gyroscope which included several recent developments. For the conclusion of results, the variable typically used is the rate of turn (°/s) for MEMS angular rate sensors with respect to bandwidth frequency. Finally based on the review some analysis on fabrication technology, key principles, and performance parameters are discussed.
Grinding graphene characteristics after physical processjournal ijrtem
ABSTRACT : Graphene features higher thermal conductivity than copper. However, despite its superior property, the research on its applicable technology was limited since the van der Waals’ forces between graphene. As a solution to such problem, research on making graphene distributed evenly in solvent is being actively conducted via physical and chemical method. Because the chemical method is likely to have harmful effect on the environment, we used the environmental-friendly process that does not consume toxic chemicals, and suitable for application. In this study, ball milling process controllable a range of experiment conditions more easily and conveniently than other physical methods was conducted so as to disperse graphene evenly in solvent and improve the thermal conductivity. Therefore, the effect of milling process was confirmed in TEM image and Raman ratio, and the shearing force makes the edge of graphene piece defective. When graphene is evenly dispersed, the wide specific surface area absorbs a great deal of light, improving absorbance. We confirmed the absorbance of pristine graphene was showed below milling graphene and considerable thermal conductivity increase compared to pristine graphene.
Keywords: Ball milling, Graphene, Nano-fluid, Physical process, Thermal conductivity
Effect of Temperature on Wear Rate of Si-Epoxy- Eglass Polymer composite Mate...IDES Editor
With the increase use of polymer composites in
erosive work environment, it has become extremely important
to investigate their erosion characteristics. The hybrid
composite consisting of a Epoxy resin reinforced with Eglass
fiber and Si particles was developed. The effect of temperature
on wear rate applied to Si – Epoxy – Eglass polymer composite
has been studied. It has been found that the wear rate increases
as the temperature of carrier media (air) is increased.
Temperature of carrier media is one of the significant factor
influencing the erosion wear. The results were compared with
the plain epoxy composite material. Micrographs of eroded
surface are also presented to study the wear rate and Wear
behavior of composite.
A Study of Pulse by Pulse Microscale Patch Transfer Using Picosecond LaserIJERA Editor
The shape restoring capability of Ti/Ni has potential to overcome the shrinkage of polymer in mould cavity, which has potential of solving the demoulding problems and helps dimension accuracy in micro/nano injection molding. However, the deposition of Ti/Ni film precisely and securely on specific location of the micro mould cavity present difficulties with conventional deposition methods. In this paper, the use of photonic impact forward transfer method to deposit Ti/Ni film patches on specific locations of a substrate is demonstrate using a picosecond laser. Pulse by pulse deposition control parameters affecting position accuracy and spot size were studied in this paper. It was found that although laser power, and distance between donor films and the substrate all influence the spot sizes of pulse by pulse deposited patches, adjusting spot size by changing laser power is better than changing distance due to separated particles being found around the deposited film patches. Results of this study proved the feasibility of depositing Ti/Ni film patches on specific location using pico-second laser with high position accuracy. The potential of using photonic impact forward transfer as a complementing method to laser powder 3D printing of difficult to process material to produce better surface quality microproducts such as micro moulds for micro-injection molding is tremendous.
Similar to Ultrasonic atomization of graphene derivatives for heat spreader thin film deposition on silicon substrate (20)
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
Learn about the latest enhancements to out-of-the-box document processing – with little to no training required
Get an exclusive demo of the new family of UiPath LLMs – GenAI models specialized for processing different types of documents and messages
This is a hands-on session specifically designed for automation developers and AI enthusiasts seeking to enhance their knowledge in leveraging the latest intelligent document processing capabilities offered by UiPath.
Speakers:
👨🏫 Andras Palfi, Senior Product Manager, UiPath
👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
UiPath Test Automation using UiPath Test Suite series, part 4DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 4. In this session, we will cover Test Manager overview along with SAP heatmap.
The UiPath Test Manager overview with SAP heatmap webinar offers a concise yet comprehensive exploration of the role of a Test Manager within SAP environments, coupled with the utilization of heatmaps for effective testing strategies.
Participants will gain insights into the responsibilities, challenges, and best practices associated with test management in SAP projects. Additionally, the webinar delves into the significance of heatmaps as a visual aid for identifying testing priorities, areas of risk, and resource allocation within SAP landscapes. Through this session, attendees can expect to enhance their understanding of test management principles while learning practical approaches to optimize testing processes in SAP environments using heatmap visualization techniques
What will you get from this session?
1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
Topics covered:
Execution from the test manager
Orchestrator execution result
Defect reporting
SAP heatmap example with demo
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
Welocme to ViralQR, your best QR code generator.ViralQR
Welcome to ViralQR, your best QR code generator available on the market!
At ViralQR, we design static and dynamic QR codes. Our mission is to make business operations easier and customer engagement more powerful through the use of QR technology. Be it a small-scale business or a huge enterprise, our easy-to-use platform provides multiple choices that can be tailored according to your company's branding and marketing strategies.
Our Vision
We are here to make the process of creating QR codes easy and smooth, thus enhancing customer interaction and making business more fluid. We very strongly believe in the ability of QR codes to change the world for businesses in their interaction with customers and are set on making that technology accessible and usable far and wide.
Our Achievements
Ever since its inception, we have successfully served many clients by offering QR codes in their marketing, service delivery, and collection of feedback across various industries. Our platform has been recognized for its ease of use and amazing features, which helped a business to make QR codes.
Our Services
At ViralQR, here is a comprehensive suite of services that caters to your very needs:
Static QR Codes: Create free static QR codes. These QR codes are able to store significant information such as URLs, vCards, plain text, emails and SMS, Wi-Fi credentials, and Bitcoin addresses.
Dynamic QR codes: These also have all the advanced features but are subscription-based. They can directly link to PDF files, images, micro-landing pages, social accounts, review forms, business pages, and applications. In addition, they can be branded with CTAs, frames, patterns, colors, and logos to enhance your branding.
Pricing and Packages
Additionally, there is a 14-day free offer to ViralQR, which is an exceptional opportunity for new users to take a feel of this platform. One can easily subscribe from there and experience the full dynamic of using QR codes. The subscription plans are not only meant for business; they are priced very flexibly so that literally every business could afford to benefit from our service.
Why choose us?
ViralQR will provide services for marketing, advertising, catering, retail, and the like. The QR codes can be posted on fliers, packaging, merchandise, and banners, as well as to substitute for cash and cards in a restaurant or coffee shop. With QR codes integrated into your business, improve customer engagement and streamline operations.
Comprehensive Analytics
Subscribers of ViralQR receive detailed analytics and tracking tools in light of having a view of the core values of QR code performance. Our analytics dashboard shows aggregate views and unique views, as well as detailed information about each impression, including time, device, browser, and estimated location by city and country.
So, thank you for choosing ViralQR; we have an offer of nothing but the best in terms of QR code services to meet business diversity!
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.
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
PHP Frameworks: I want to break free (IPC Berlin 2024)Ralf Eggert
In this presentation, we examine the challenges and limitations of relying too heavily on PHP frameworks in web development. We discuss the history of PHP and its frameworks to understand how this dependence has evolved. The focus will be on providing concrete tips and strategies to reduce reliance on these frameworks, based on real-world examples and practical considerations. The goal is to equip developers with the skills and knowledge to create more flexible and future-proof web applications. We'll explore the importance of maintaining autonomy in a rapidly changing tech landscape and how to make informed decisions in PHP development.
This talk is aimed at encouraging a more independent approach to using PHP frameworks, moving towards a more flexible and future-proof approach to PHP development.
SAP Sapphire 2024 - ASUG301 building better apps with SAP Fiori.pdfPeter Spielvogel
Building better applications for business users with SAP Fiori.
• What is SAP Fiori and why it matters to you
• How a better user experience drives measurable business benefits
• How to get started with SAP Fiori today
• How SAP Fiori elements accelerates application development
• How SAP Build Code includes SAP Fiori tools and other generative artificial intelligence capabilities
• How SAP Fiori paves the way for using AI in SAP apps
2. 764 M.R.M. Hussin et al./ Materials Today: Proceedings 7 (2019) 763–769
deposition. The most commonly used deposition technique for high-quality graphene film is through gas phase
Chemical Vapour Deposition (CVD). However, CVD is an expensive process that requires a special substrate for
synthesis with subsequent transferal to another material for practical applications. Another method is liquid phase
approaches which are significantly cheaper than CVD but the final material typically contains defects and impurities.
Spray coating process is one of the liquid phase deposition techniques, which is very attractive for nanomaterials
deposition since it has various advantageous including cost-effective, high-throughput, and industrial scalable
process. This technique also offers a relatively good control of film uniformity and morphology, suitable for large-
area deposition, and flexibility in process parameters adjustment for different types of solvent.
Ultrasonic spray coating process is more advantageous as compared to air pressurized spray coating technique,
especially for applications, which involve expensive materials that require accurate and uniform deposition of
suspensions on substrates. Ultrasonic atomization is a technique to produce micro size of droplets during spray
coating process through vibrational energy of ultrasonic nozzle. In this paper, we will discuss about the development
of ultrasonic atomizer system and process development of thin film graphene derivatives deposition on silicon wafer.
We have also studied the heat transfer characteristic of graphene derivatives deposited on silicon to understand its
thermal effect behavior. As graphene material has remarkable properties with extremely high thermal conductivity, it
has a great potential to be used as a heat spreader material in electronic applications [6-8].
2. Ultrasonic Atomizer System
Ultrasonic atomizer system was developed to improve the process of depositing nanomaterials on silicon wafer
for seamless integration with semiconductor processes. Ultrasonic atomization is a proven spray coating technology
for efficient deposition of expensive chemical solutions on substrate. It helps to matched functional and economic
performance, especially for nanomaterials deposition, which requires accurate and uniform deposition on substrates.
Fig. 1. shows the image of MIMOS Ultrasonic Atomizer System (Mi-Atomizer) that was developed for research and
development in ultrasonic atomization process of nanomaterials. The atomizer system has built-in automatic control
system with graphical user interface (GUI) for users to optimize their process recipes. The main parts of the system
are ultrasonic nozzles, syringe pump, spray chamber and heater plate. The system enables optimization of process
recipes for layer-by-layer deposition to get high uniformity thin film with large percentage of coverage areas.
Ultrasonic nozzle with power rating between 0.5W to 2W and fixed frequency at 120kHz was used in this study
to produce median droplet size about 13um. When the graphene derivatives solution film is placed on a smooth
surface of nozzle outlet (as shown in Fig. 1.) that is set into vibrating motion such that the direction of vibration is
perpendicular to the surface, the solution absorbs some of the vibrational energy, which is transformed into standing
waves. The amplitude of the capillary waves increase when the underlying vibration increased in amplitude. Tiny
drops of solution are ejected from the tops of degenerating waves once the critical amplitude is reached. In
comparison to air pressurized spray techniques, ultrasonic atomization can provide a large reduction in material
usage because they form droplets through low ultrasonic vibration; thereby, imparting lower kinetic energy to the
droplet. The liquid can be dispensed to the spray nozzle by either gravity or a small low pressure metering pump
[9,10].
Fig. 1. (a) Mi-Atomizer system for nanomaterials deposition on silicon wafer and (b) the illustration of ultrasonic atomization process
3. M.R.M. Hussin et al./ Materials Today: Proceedings 7 (2019) 763–769 765
3. Experimental procedure
Test samples were prepared by depositing 3000A of silicon dioxide (SiO2) film onto 8” bare silicon wafer
through Plasma Enhanced Chemical Vapor Deposition (PECVD) process. Deposition of graphene oxide (GO) was
then performed through ultrasonic atomization process in a chamber under control environment. The film thickness
was controlled with the amount of spray volume and the flow rate. This is to prepare the test samples for thin film
heat spreader on silicon wafer. The samples were then annealed under high temperature (>700℃) for thermal
reduction of GO. Sheet resistance of the film were measured using four-point probes system. Atomic Force
Microscopy (AFM) measurements were performed to characterize the film thickness and surface roughness for
correlation study with spray parameters. Field Emission Scanning Electron Microscopy (FESEM) images were
captured from samples to study the percentage of coverage areas by using a scientific image analysis software
(Image J). The chemical and structural parameters of the thin film was analyzed by Raman spectroscopy and X-ray
Photoelectron Spectroscopy (XPS) studies. The transparency of the film was also studied by using UV-Vis
Spectroscopy measurement. Heat transfer characteristics of the thin film was analyzed by using IR thermal imaging
system.
3.1. Test samples and GO solution preparation
There are several sample types were prepared for this study to cater for different analysis requirement. Test
samples for thickness measurement, percentage of coverage areas, sheet resistance measurement, material analysis,
and heat transfer characterization were prepared on 8” silicon wafer. The test sample for UV-Vis measurement on
the other hand are prepared on glass substrate. In this study, GO was used as the coating material. One of the
advantages of GO is its easy dispersability in water and other organic solvents, as well as in different matrixes. This
is due to the presence of the oxygen functionality groups [11]. A modified Hummers’ method was used to prepare
the GO. The GO was dispersed in ethanol (EMSURE® ACS,ISO,Reag. Ph Eur) with concentration of 1mg/ml.
3.2. Ultrasonic Spray coating of GO on Silicon and Glass Substrate
The ultrasonic spray coating of GO were performed using Mi-Atomizer system. Prior to spray coating process,
GO solution was sonicated in ultrasonic bath for 30 to 60 minutes at frequency of 37 kHz. The sonicated solution
was then being filled in the system’s syringe pump and about 10 ml of the solution was needed in order to fill up the
solution line up to the ultrasonic nozzle tip. The solution’s flow rate was setup up to 1 ml/min with nozzle height
(distance from wafer stage) up to 60 mm and hot plate temperature up to 70 °C. Ultrasonic generator power was set
at 1.6 W. The test wafer was then placed onto wafer stage (heater plate), and the spraying process was activated by
choosing the desired recipe. The thickness of GO film deposited was controlled by the number of spray’s passes
onto the wafer.
3.3. Thermal Reduction of Graphene Oxide
GO is known as an electrical insulator with low thermal conductivity, due to the disruption of its sp2
bonding
networks. A reduction of the graphene oxide has to be done in order to recover the honeycomb hexagonal lattice and
the electrical conductivity. The reduction of graphene oxide was thermally done in a high temperature vacuum
chamber. At temperature of 700°C, the reduction process took about 30 minutes while at 1000°C the process time
can be shorten to 10 minutes.
4. 766 M.R.M. Hussin et al./ Materials Today: Proceedings 7 (2019) 763–769
4. Results and Discussions
4.1. Process and Material Characterizations
The sheet resistance (Rs) measurement for reduced GO (rGO) films was carried out using Jandel RM3-AR four-
point probes system. The sheet resistance for different spray passes (representing different thickness) and the
temperature of reduction process were measured and presented in table 1. It was observed that the thicker the film
the lower the sheet resistance value recorded. It was also noticed that GO reduction process at 1000°C produces
significantly lower sheet resistance value than the reduction process at 700°C. To study the uniformity of thin film
coated on silicon wafer, sheet resistance measurement was measured at multiple locations (49 points) on the wafer.
Table 2 showed the average values of sheet resistance for rGO films on different wafers and its percentage of non-
uniformity, which shows the process stability. In summary, the percentage of non-uniformity (%NU) for the rGO
film within wafer is ~18% and between wafers is ~13%.
Table 1. Sheet Resistance of rGO for different thickness
Spray (pass) Reduction
T=700C ; 2hr
Reduction
T=1000C ; 10 min
6X ~ 40 – 50 kΩ/sq ~ 2.6-2.9 kΩ/sq
12X ~ 9.5 – 11 kΩ/sq ~ 1.04 - 1.44 kΩ/sq
18X ~ 6.5 – 8 kΩ/sq ~ 620 - 907.9 Ω/sq
24X ~ 5 – 5.5 kΩ/sq ~ 489-518 Ω/sq
30X ~ 3.5 – 4 kΩ/sq ~ 359 - 397 Ω/sq
Table 2. Sheet Resistance of rGO for different wafers
Wafer # Rs (Ω/sq) %NU
1 2971.61 14.08
2 2875.98 16.83
3 2776.32 21.2
4 2703.96 21.55
5 2204.21 20.69
6 2508.99 16.87
7 2037.69 15.46
8 2358.64 20.49
AVG 2554.68 18.4
%NU between wafers: 13.06%
The thickness of a single droplet of GO solution sprayed on SiO2/Si substrate was measured using Atomic Force
Microscope (AFM) system as shown in Fig. 2 below. This shows that a single droplet of sprayed GO solution can
have a thickness of ~9.43nm. Thickness measurement was performed on several samples with different spray
passes. In average the thickness for single spray pass, double spray pass, and triple spray pass are 11nm, 22nm and
33nm respectively.
5. M.R.M. Hussin et al./ Materials Today: Proceedings 7 (2019) 763–769 767
Fig. 2. 2D and 3D AFM images for a single GO droplet on SiO2/Si substrate
The percentage of coverage areas was investigated using FESEM system. A good spray coverage area was
achieved by applying optimum recipe parameters for the spray process, which includes solution’s flow rate, nozzle
height, N2 pressure, and spray passes. The visual observation of FESEM images are shown in Fig. 3. It was observed
that for single, double and triple passes of spray, the percentage coverage areas increased significantly from around
82.86% to 96.23%. Raman Spectroscopy, a tool using light scattering technique in identifying and qualifying any
given material was used to characterize the GO and rGO samples. The Raman spectrum was obtained by
illuminating the samples with a laser beam of 473 nm (blue laser). For GO and rGO the Raman spectrum can be
referred to Fig. 4. For GO, the Raman shift of D, G and 2D peak occurs at 1359 cm-1
, 1606 cm-1
, and 2701cm-1
respectively. A significant D shift peak for GO may relates to the nature of GO flakes themselves, which constitute
of large edge areas, and ripples. For rGO, the D, G, and 2D peak observed at 1365 cm-1
, 1593 cm-1
, and 2698 cm-1
respectively. The rGO’s ID/IG=0.841 is lower compared to GO’s ID/IG=0.958, which indicate that the recovery of sp2
carbon happened during the reduction process using high temperature.
The Carbon to Oxygen atomic ratio (C/O) of GO and rGO was obtained from the X-ray Photoelectron
Spectrometry (XPS) analysis. In Fig. 5, four components that correspond to carbon atoms in different functional
groups are the non-oxygenated ring C (~284.8 eV), the C in C–O bonds (~ 286 eV), the carbonyl C (~287 eV), and
the carboxylate carbon (O–C = O, ~ 289 eV). The C1s XPS spectrum of GO in Fig. 5(a) shows a considerable
degree of oxidation while the XPS spectrum of rGO in Fig. 5(b) displays similar oxygen functional groups but with
lower peak intensities than that of GO. It is observed that the content of oxygen (O) atoms of rGO is significantly
lower than that of GO which indicates the successful reduction process of GO.
Fig. 3. FESEM images of sprayed GO with (a) 1 pass = 82.86%, (b) 2 passes = 94.72%, and (c) 3 passes = 96.23% coverage area.
(a) (b)
Fig. 4. Raman spectra of (a) GO and (b) rGO
6. 768 M.R.M. Hussin et al./ Materials Today: Proceedings 7 (2019) 763–769
(a) (b)
Fig. 5. The C1s XPS spectra of (a) GO and (b) rGO
GO was sprayed onto glass substrate and the transmittance data was obtained using the UV-Vis system. The UV-
Visible spectrum of the GO and rGO is depicted in Fig. 6. The spectrum is a plot of Percent Transmittance (%T) as a
function of Wavelength (λ). It was observed that rGO has lower percent transmittance compared to GO. It was also
observed that the thicker and denser the film (GO or rGO) the lower the percent transmittance.
Fig. 6. UV-Visible spectrum plot of %Transmittance vs Wavelength.
4.2. Heat Transfer Characteristic
Thermal conductivity describes the transport of energy in the form of heat through a body of mass as the result of
a temperature gradient. Heat conduction in solid materials usually takes place through acoustic phonons and by
electrons. In carbon based materials i.e. Graphene, GO, rGO, the heat conduction is dominated by phonons. As
reported in the literature, graphene and rGO have high thermal conductivity of >3000 W/mK and >1000 W/mK
respectively [2, 8]. Therefore, these materials are suitable to be used as a heat spreader in semiconductor devices. It
can helps to cool down the devices by reducing the localized self-heating effect. Heat produced by the
semiconductor devices can be removed and effectively transferred to the surrounding air as quickly as possible. In
this study, it is found that the functionalized rGO thin film deposited on silicon substrate showed good heat transfer
characteristic. The test results are shown in Fig. 7, where comparison has been made between samples coated with
rGO thin film heat spreader and without heat spreader. Sample with rGO thin film heat spreader showed uniform
temperature across the whole sample when heated at the center. The test system used for this study consist of a
micro-heater plate, a programmable switching D.C. power supply (RS Pro IPS 603), and FLIR IR thermal imaging
system (ETS320).
7. M.R.M. Hussin et al./ Materials Today: Proceedings 7 (2019) 763–769 769
(a) (b)
Fig. 7. Thermal images of test samples (a) with functionalized rGO heat spreader, (b) without heat spreader.
5. Conclusions
The advantages of using Ultrasonic Atomizer System for graphene derivatives deposition are high transfer
efficiency which reduces materials usage, non-clogging, and highly uniform distribution of droplet sizes to help
reduce coating imperfections. Ultrasonic atomization of graphene oxide on 8” silicon wafer showed more than 95%
coverage area with less than 20% non-uniformity with average thickness of about 22 nm. Reduced Graphene Oxide
is also suitable for heat spreader application.
Acknowledgements
The authors acknowledge funding from Government of Malaysia under 11MP (MOSTI) program and thanks to
Multimedia University (MMU), Universiti Perguruan Sultan Idris (UPSI), Universiti Malaysia Perlis (UniMAP),
Universiti Putra Malaysia (UPM) and NSW Automation Sdn. Bhd. for supporting this research.
References
[1] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva, A. A. Firsov, Science 306 (2004) 666–
669.
[2] A. A. Balandin, S. Ghosh, W. Bao, I. Calizo, D. Teweldebrhan, F. Miao, C. N. Lau, Nano Lett. (2008) 8 (3) 902-907.
[3] A. K. Geim, Science 324 (2009) 1530-1534.
[4] A. S. Mayorov, R. V. Gorbachev, S. V. Morozov, L. Britnell, R. Jalil, L. A. Ponomarenko, P. Blake, K. S. Novoselov, K. Watanabe, T.
Taniguchi, A. K. Geim, Nano Lett. (2011) 11 (6) 2396–2399.
[5] R. R. Nair, H. A. Wu1, P. N. Jayaram, I. V. Grigorieva, A. K. Geim, Science 335 (2012) 442-444.
[6] G. Fugallo, A. Cepellotti, L. Paulatto, M. Lazzeri, N. Marzari, F. Mauri, Nano Lett. (2014) 14 (11) 6109–6114.
[7] N.S. Khairir, M.R.M. Hussin, M.I. Khairir, A.S.M.M. Uz-Zaman, W.F.H. Abdullah, M.H. Mamat, A.S. Zoolfakar, Surfaces and Interfaces
000 (2016) 1-8.
[8] N. J. Song, C. M. Chen, C. Lu, Z. Liu, Q. Q. Kong, R. Caib, J. Mater. Chem. A, 2014, 2, 16563.
[9] L. B. M. Lopez, M. Miettinen, J. Riikonen, T. Torvela, C. Pfuller, V. P. Lehto, A. Lahde, J. Jokiniemi, Aerosol Science and Technology
(2015), 49:1, 45-56.
[10] V. N. Khmelev, A. V. Shalunov, M. V. Khmelev, A. V. Shalunova, D. V. Genne, Ultrasonic Atomizers of Nanomaterials, XII International
Conference and Seminar EDM’2011, Section VIII, June 30 - July 4, ERLAGOL (2011).
[11] M. S. Eluyemi, M. A. Eleruja, A. V. Adedeji, B. Olofinjana1, O. Fasakin, O. O. Akinwunmi, O. O. Ilori, A. T. Famojuro, S. A. Ayinde1, E.
O. B. Ajayi, Graphene (2016) 5, 143-154.