This document discusses a new method for fabricating graphene electrodes for supercapacitors using inkjet printing and thermal reduction of graphene oxide. Graphene oxide dispersed in water was inkjet printed onto titanium foil substrates and then thermally reduced at 200°C in nitrogen gas. The resulting graphene electrodes, called inkjet printed graphene electrodes (IPGEs), showed specific capacitances ranging from 48 to 132 F/g depending on the scan rate, comparable to other graphene electrode fabrication methods. This new process allows for designing interdigitated electrode arrays with high spatial resolution for flexible micro-supercapacitors.
Heterostructures, HBTs and Thyristors : Exploring the "different"Shuvan Prashant
This presentation aims at presenting the concepts of heterostructures : a structure resulting from semiconductors of different band gaps are used to form junctions. These junctions could have interesting effects due the potentials formed by the bands at the interfaces.
Heterostructures, HBTs and Thyristors : Exploring the "different"Shuvan Prashant
This presentation aims at presenting the concepts of heterostructures : a structure resulting from semiconductors of different band gaps are used to form junctions. These junctions could have interesting effects due the potentials formed by the bands at the interfaces.
Graphene_complete description_Introduction_history_synthesis_electrical appliactions other other miscellineus applcations,challeneges explained with full of animated diagrams.
If you need in PPT file with full of beautiful animations and transitions for FREE, then just email me on this adress:
kashifwattu798@gmail.com
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Perovskite Solar Cells
a short general overview presentation
hadi maghsoudi
device structure
crystal structure
preparation synthesis method
review papers
GRAPHENE WILL BECOME THE GAME CHANGER - it is a thinnest and strongest material ever tested and high efficient capacity to overcome in all fields especially in biomedical and energy storage applications.
PresenWide Bandgap Semiconductor Materials for Improved Performance Microwave...Realsim, Fanavaran Sharif
Wide bandgap semiconductors such as SiC (Silicon Carbide), GaN
(Gallium Nitride) and related heterostructures are characterised by
a much higher breakdown voltage and therefore they may allow fabrication of devices with an order of magnitude improved RF output power compared to traditional solid state devices.
Have an overview of the most conventionally utilized crystal growth techniques: process, diagrams, advantages, and disadvantages. This is the presentation of my "PV cells and materials" course at the MSc Engg. level.
This presentation summarizes history and recent development of perovskite solar cells. If you have any questions or comments, you can reach me at agassifeng@gmail.com
For free download Subscribe to https://www.youtube.com/channel/UCTfiZ8qwZ_8_vTjxeCB037w and Follow https://www.instagram.com/fitrit_2405/ then please contact +91-9045839849 over WhatsApp.
Graphene Presentation
This presentation showcased first part of our work on graphene-based transistors as our final year project at NIT Patna under guidance of Prof.Wasim akram
Graphene_complete description_Introduction_history_synthesis_electrical appliactions other other miscellineus applcations,challeneges explained with full of animated diagrams.
If you need in PPT file with full of beautiful animations and transitions for FREE, then just email me on this adress:
kashifwattu798@gmail.com
ENJOY ...!!!
Perovskite Solar Cells
a short general overview presentation
hadi maghsoudi
device structure
crystal structure
preparation synthesis method
review papers
GRAPHENE WILL BECOME THE GAME CHANGER - it is a thinnest and strongest material ever tested and high efficient capacity to overcome in all fields especially in biomedical and energy storage applications.
PresenWide Bandgap Semiconductor Materials for Improved Performance Microwave...Realsim, Fanavaran Sharif
Wide bandgap semiconductors such as SiC (Silicon Carbide), GaN
(Gallium Nitride) and related heterostructures are characterised by
a much higher breakdown voltage and therefore they may allow fabrication of devices with an order of magnitude improved RF output power compared to traditional solid state devices.
Have an overview of the most conventionally utilized crystal growth techniques: process, diagrams, advantages, and disadvantages. This is the presentation of my "PV cells and materials" course at the MSc Engg. level.
This presentation summarizes history and recent development of perovskite solar cells. If you have any questions or comments, you can reach me at agassifeng@gmail.com
For free download Subscribe to https://www.youtube.com/channel/UCTfiZ8qwZ_8_vTjxeCB037w and Follow https://www.instagram.com/fitrit_2405/ then please contact +91-9045839849 over WhatsApp.
Graphene Presentation
This presentation showcased first part of our work on graphene-based transistors as our final year project at NIT Patna under guidance of Prof.Wasim akram
Performance analysis of high-k materials as stern layer in ion-sensitive fiel...TELKOMNIKA JOURNAL
High-k materials as a STERN Layer for Ion-Sensitive-Field-Effect-Transistor (ISFET) have improved ISFET sensitivity and stability. These materials decrease leakage current and increase capacitance of the ISFET gate toward highest current sensitivity. So far, many high-k materials have been utilized for ISFET, yet they were examined individually, or using numerical solutions rather than using integrated TCAD environment. Exploiting TCAD environment leads to extract ISFET equivalent circuit parameters and performs full analysis for both device and circuit. In this study we introduce a comprehensive investigation of different high-k material, Tio2, Ta2O5, ZrO2, Al2O3, HfO2 and Si3N4 as well as normal silicon dioxide and their effects on ISFET sensitivity and stability. This was implemented by developing commercial Silvaco TCAD rather than expensive real fabrication. The results confirm that employing high-k materials in ISFET outperform normal silicon dioxide in terms of sensitivity and stability. Further analysis revealed that Titanium dioxide showed the highest sensitivity followed by two groups HfO2, Ta2O5 and ZrO2, Al2O3 respectively. Another notable exception of Si3N4 that is less than other materials, but still have higher sensitivity than normal silicon dioxide. We believe that this study opens new directions for further analysis and optimization prior to the real cost-ineffective fabrication.
OFET Preparation by Lithography and Thin Film Depositions ProcessTELKOMNIKA JOURNAL
The length of the channel OFET based thin film is determined during preparation takes place
using the technique of lithography and mask during the metal deposition process. The lithography
technique is the basic process steps in the manufacture of semiconductor devices. Lithography is the
process of moving geometric shapes mask pattern to a thin film of material that is sensitive to light. The
pattern of geometric shapes on a mask has specifications, as follows: long-distance source and drain
channels varied, i.e. 100 μm, the width of the source and drain are made permanent. Bottom contact
OFET structure has been created using a combination of lithography and thin film deposition processes.
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3. Author's personal copy
356 L.T. Le et al. / Electrochemistry Communications 13 (2011) 355–358
inkjet-printed GO samples were reduced in flowing N2 at 200 °C for the GO surface (Fig. 1a). At room temperature, the viscosity and
12 h using a Microtherm MT furnace (The Mellen Company) in a glass surface tension of the GO ink were 1.06 mPa s and 68 mN/m,
tube. The uniformity and surface morphology of the resulting respectively, and were similar to those of de-ionized water
graphene electrodes were characterized by Nikon C-BD115 optical (0.99 mPa s and 72 mN/m). The physical properties of the GO ink
microscopy (Nikon Instrument) and Zeiss Auriga FIB-SEM scanning were outside of the ranges recommended by the manufacturer for
electron microscopy (Carl Zeiss NTS). normal operation of the printer (i.e., 10–12 mPa s and 28–32 mN/m).
IPGEs' electrochemical performance was evaluated with cyclic Nevertheless, as shown in Fig. 1b, we found that manipulating the
voltammetry (CV) and constant current charge/discharge measure- firing voltage of the piezoelectric nozzles as a function of time was
ments made using a VersaStat 3 system (Princeton Applied Research). effective in generating spherical ink droplets at a velocity of ~7.5 m/s.
Two IPGEs printed on Ti substrates were clamped together in a Teflon During the first segment of droplet generation, we rapidly increased
block using a Celgard 3401 membrane (Celgard) as a separator and the voltage to the maximum over 5 μs to force rapid pressure buildup
1M H2SO4 electrolyte in order to make constant current charge/ in the nozzles for droplet ejection. In the second segment, we
discharge measurements as a full, though unpackaged device. Two decreased the voltage at a slower rate of over 28 μs to cutoff droplet
samples were evaluated to confirm the reproducibility of our results. tails and therefore form spherical droplets. This “waveform function”
optimization was performed through real-time observations of
3. Results and discussion droplet generation using a built-in video camera.
After hitting the Ti foil surface, spreading, and solvent evaporation,
The as-received GO ink was observed to be dispersion-stable for each 10 pL droplet produced a disk-shaped GO dot with a diameter
months due to the presence of hydrophilic functional groups [14] on of ~50 μm. For example, the circular GO dot shown in Fig. 1c was
Fig. 1. IPGE ink and morphology: (a) GO dispersed in water at 0.2 wt.% as a stable ink; (b) spherical ink droplets generated by piezoelectric nozzles; (c) SEM image of a circular GO dot
printed on the Ti foil surface after 20 printing passes at a spatial resolution of ~ 50 μm; and (d), (e) and (f) SEM images of IPGE printed on the Ti surface used for electrochemical
evaluation.
4. Author's personal copy
L.T. Le et al. / Electrochemistry Communications 13 (2011) 355–358 357
produced with 20 printing passes at 20 min between passes to: It was interesting to observe the island features of ~ 1–2 mm on the
(1) build GO thickness sufficient for microscopy characterization IPGE surface (i.e., “white” areas in Fig. 1d). SEM characterization
and (2) show that drop-to-drop placement and alignment could be indicated that there were almost no graphene present in the “black”
repeated to increase the GO thickness with a minimum spatial boundaries. The island formation occurred right after inkjet printing
resolution of ~ 50 μm. The droplets were overlapped at a spacing of and was not caused by the reduction step. The island formation was
15 μm between the center locations of two neighboring droplets to also observed to be much less pronounced on more hydrophilic
print a continuous GO thin-film of 1 cm × 1 cm on the Ti surface substrates and appeared to be dependent on the hydrophobicity of the
(Fig. 1d). The printing step was repeated 100 times to deposit initial surface. Within each island, graphene appeared to be densely
sufficient GO for electrochemical measurements. The resistance of the stacked with the appearance of secondary boundaries (i.e., “white”
as-printed GO on Kapton was measured by a voltmeter to be infinite lines in the SEM image of Fig. 1e) that were continuously networked
whereas that of the thermally reduced GO film in N2 at 200 °C (i.e., over an average distance of ~ 20–30 μm. At high magnification
IPGE) was measurable at less than ~ 1 MΩ. Also, the color of the GO (Fig. 1f), the graphene sheets appear to be more wrinkled and
film changed from light brown to black upon thermal reduction. These stacked less uniformly at these boundaries than in the areas within
observations were consistent with the prior finding of Zangmeister the boundaries. This morphological development was observed on
[11] who treated GO at 220 °C in air and confirmed the reduction of other substrate materials.
GO to graphene by Fourier transform infrared spectroscopy and X-ray As shown in Fig. 2a, IPGEs exhibited fairly rectangular CV curves
photoemission spectroscopy. at scan rates in the range of 0.01 to 0.5 V/s which is indicative of
6
(a) 140 (b)
Specific Capacitance (F/g)
4
Current Density (mA/g)
120
2
0 100
-2 0.02 V/s 80
0.05 V/s
0.1 V/s
-4 0.2 V/s
0.5 V/s 60
-6
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0 200 400 600 800 1000 1200 1400
Potential (V) Cycle number
0.6
(c) 140 (d)
Specific Capacitance (F/g)
0.4
120
0.2
100
Potential (V)
0.0
80
-0.2
60
-0.4 40
-0.6 20
-0.8 0
0 200 400 600 800 1000 1200 1400 1600 0.0 0.1 0.2 0.3 0.4 0.5 0.6
Time (s) Scan Rate (V/s)
10
(e)
Specific Power (kW/kg)
1
0.1
0.01
0.1 1 10
Specific Energy (Wh/kg)
Fig. 2. Electrochemical properties of IPGE: (a) cyclic voltammograms measured at different scan rates, (b) specific capacitance retained as a function of CV cycles, (c) constant current
charge/discharge curves, (d) specific capacitance as a function of voltage scan rates and (e) Ragone plot.
5. Author's personal copy
358 L.T. Le et al. / Electrochemistry Communications 13 (2011) 355–358
capacitive behavior. The specific capacitance decreased from 125 to Acknowledgment
121 F/g over 1000 CV cycles at a constant scan rate of 50 mV/s
(Fig. 2b) demonstrating 96.8% capacitance retention. Fig. 2c shows The authors thank the U.S. Army — ARDEC for funding this project
that the charging/discharging curves were fairly linear, again under the contract of W15QKN-05-D-0011.
demonstrating capacitive behavior. Also, at the device level, the
specific capacitance was measured to be 48 to 132 F/g in the scan References
range of 0.5 to 0.01 V/s (Fig. 2d). The energy and power density of
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