| 1. |
- Kaushik, Priya Darshni, et al.
(författare)
-
Modifications in structural, optical and electrical properties of epitaxial graphene on SiC due to 100 MeV silver ion irradiation
- 2018
-
Ingår i: Materials Science in Semiconductor Processing. - : Pergamon Press. - 1369-8001 .- 1873-4081. ; 74, s. 122-128
-
Tidskriftsartikel (refereegranskat)abstract
- Epitaxial graphene (EG) on silicon carbide (SiC) is a combination of two robust materials that are excellent candidates for post silicon electronics. In this work, we systematically investigate structural changes in SiC substrate as well as graphene on SiC and explore the potential for controlled applications due to 100 MeV silver swift heavy ion (SHI) irradiation. Raman spectroscopy showed fluence dependent decrease in intensity of first and second order modes of SiC, along with decrease in Relative Raman Intensity upon ion irradiation. Similarly, Fourier-transform infrared (FTIR) showed fluence dependent decrease in Si-C bond intensity with presence of C = O, Si-O-Si, Si-Si and C-H bond showing introduction of vacancy, substitutional and sp(3) defects in both graphene and SiC. C1s spectra in XPS shows decrease in C = C graphitic peak and increase in interfacial layer following ion irradiation. Reduction in monolayer coverage of graphene after ion irradiation was observed by Scanning electron microscopy (SEM). Further, UV-Visible spectroscopy showed increase in absorbance of EG on SiC at increasing fluence. I-V characterization showed fluence dependent increase in resistance from 62.9 O in pristine sample to 480.1 Omega in sample irradiated at 6.6 x 10(12) ions/cm(2) fluence. The current study demonstrates how SHI irradiation can be used to tailor optoelectronic applicability of EG on SiC.
|
|
| 2. |
- Kaushik, Priya Darshni, et al.
(författare)
-
Structural and Optical Modification in 4H-SiC Following 30 keV Silver ion irradiation
- 2018
-
Ingår i: INTERNATIONAL CONFERENCE ON INVENTIVE RESEARCH IN MATERIAL SCIENCE AND TECHNOLOGY (ICIRMCT 2018). - : AMER INST PHYSICS. - 9780735416710
-
Konferensbidrag (refereegranskat)abstract
- The market of high power, high frequency and high temperature based electronic devices is captured by SiC due to its superior properties like high thermal conductivity and high sublimation temperature and also due to the limitation of silicon based electronics in this area. There is a need to investigate effect of ion irradiation on SiC due to its application in outer space as outer space is surrounded both by low and high energy ion irradiations. In this work, effect of low energy ion irradiation on structural and optical property of 4H-SiC is investigated. ATR-FTIR is used to study structural modification and UV-Visible spectroscopy is used to study optical modifications in 4H-SiC following 30 keV Ag ion irradiation. FTIR showed decrease in bond density of SiC along the ion path (track) due to the creation of point defects. UV-Visible absorption spectra showed decrease in optical band gap from 3.26 eV to 2.9 eV. The study showed degradation of SiC crystallity and change in optical band gap following low energy ion irradiation and should be addressed while fabricationg devices based on SiC for outer space application. Additionally, this study provides a platform for introducing structural and optical modification in 4H-SiC using ion beam technology in a controlled manner.
|
|
| 3. |
- Kaushik, Priya Darshni, et al.
(författare)
-
Structural Modifications in Epitaxial Graphene on SiC Following 10 keV Nitrogen Ion Implantation
- 2020
-
Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 10:11
-
Tidskriftsartikel (refereegranskat)abstract
- Modification of epitaxial graphene on silicon carbide (EG/SiC) was explored by ion implantation using 10 keV nitrogen ions. Fragments of monolayer graphene along with nanostructures were observed following nitrogen ion implantation. At the initial fluence, sp(3) defects appeared in EG; higher fluences resulted in vacancy defects as well as in an increased defect density. The increased fluence created a decrease in the intensity of the prominent peak of SiC as well as of the overall relative Raman intensity. The X-ray photoelectron spectroscopy (XPS) showed a reduction of the peak intensity of graphitic carbon and silicon carbide as a result of ion implantation. The dopant concentration and level of defects could be controlled both in EG and SiC by the fluence. This provided an opportunity to explore EG/SiC as a platform using ion implantation to control defects, and to be applied for fabricating sensitive sensors and nanoelectronics devices with high performance.
|
|
| 4. |
- Kaushik, Priya Darshni, et al.
(författare)
-
Surface functionalization of epitaxial graphene on SiC by ion irradiation for gas sensing application
- 2017
-
Ingår i: Applied Surface Science. - : ELSEVIER SCIENCE BV. - 0169-4332 .- 1873-5584. ; 403, s. 707-716
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, surface functionalization of epitaxial graphene grown on silicon carbide was performed by ion irradiation to investigate their gas sensing capabilities. Swift heavy ion irradiation using 100 MeV silver ions at four varying fluences was implemented on epitaxial graphene to investigate morphological and structural changes and their effects on the gas sensing capabilities of graphene. Sensing devices are expected as one of the first electronic applications using graphene and most of them use functionalized surfaces to tailor a certain function. In our case, we have studied irradiation as a tool to achieve functionalization. Morphological and structural changes on epitaxial graphene layers were investigated by atomic force microscopy, Raman spectroscopy, Raman mapping and reflectance mapping. The surface morphology of irradiated graphene layers showed graphene folding, hillocks, and formation of wrinkles at highest fluence (2 x 10(13) ions/cm(2)). Raman spectra analysis shows that the graphene defect density is increased with increasing fluence, while Raman mapping and reflectance mapping show that there is also a reduction of monolayer graphene coverage. The samples were investigated for ammonia and nitrogen dioxide gas sensing applications. Sensors fabricated on pristine and irradiated samples showed highest gas sensing response at an optimal fluence. Our work provides new pathways for introducing defects in controlled manner in epitaxial graphene, which can be used not only for gas sensing application but also for other applications, such as electrochemical, biosensing, magnetosensing and spintronic applications. (C) 2017 Elsevier B.V. All rights reserved.
|
|
| 5. |
- Kaushik, Priya Darshni, et al.
(författare)
-
Surface functionalization of epitaxial graphene using ion implantation for sensing and optical applications
- 2020
-
Ingår i: Carbon. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0008-6223 .- 1873-3891. ; 157, s. 169-184
-
Tidskriftsartikel (refereegranskat)abstract
- Surface functionalization has been shown to allow tailoring of graphene lattice thus making it suitable for different applications like sensing, supercapacitance devices, drug delivery system and memory devices. In this work, surface functionalization of epitaxial graphene on SiC (EG/SiC) was done by ion beam technology (30 keV Ag- ions at fluences ranging from 5 x 10(12) ions/cm(2) to 5 x 10(14) ions/cm(2)), which is one of the most precise techniques for introducing modifications in materials. Atomic force microscopy showed presence of nanostructures in ion implanted samples and Photoluminescence and X-ray photoelectron spectroscopy revealed that these are probably silicon oxy carbide. High-resolution transmission electron microscopy (HRTEM) showed decoupling of buffer layer from SiC substrate at many places in ion implanted samples. Further, HRTEM and Raman spectroscopy showed amorphization of both graphene and SiC at highest fluence. Fluence dependent increase in absorbance and resistance was observed. Gas sensors fabricated on pristine and ion implanted samples were able to respond to low concentration (50 ppb) of NO2 and NH3 gases. Detecting NH3 gas at low concentration further provides a simple platform for fabricating highly sensitive urea biosensor. We observed response inversion with increasing fluence along with presence of an optimal fluence, which maximized gas sensitivity of EG/SiC. (C) 2019 Elsevier Ltd. All rights reserved.
|
|
| 6. |
- Kazemi, Amin, et al.
(författare)
-
The effect of Cl- and N-doped MoS2 and WS2 coated on epitaxial graphene in gas-sensing applications
- 2021
-
Ingår i: SURFACES AND INTERFACES. - : ELSEVIER. - 2468-0230. ; 25
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, epitaxial graphene (EG) was grown on a 6H-SiC (0001) substrate via the thermal decomposition of SiC. Undoped and Cl- or N-doped molybdenum disulfide (MoS2) and tungsten disulfide (WS2) ultrathin films were spin-coated on the graphene surface. The scanning electron microscopy (SEM) images and topological atomic force microscopy (AFM) analysis showed good distribution of thin MoS2 and WS2 flakes on the EG surface. The X-ray photoelectron spectroscopy (XPS) confirmed the presence of Mo-related peaks of 3d(5/2) and 3d(3/2) at similar to 232.2 eV and 235.1 eV, respectively. It also represented peaks of W 4f(7/2) and 5p(5/2) at around 36.1 eV and 37.9 eV, respectively. Moreover, XPS results showed peaks at around 167.4 eV and 168.4 eV corresponding to S 2p for MoS2 and WS2, respectively. The XPS results also confirmed the presence of dopant elements in MoS2 and WS2 flakes. We fabricated sensors using undoped and chlorine- or nitrogen-doped MoS2 and WS2 ultrathin films for gas-sensing applications. These sensors were surveyed for ammonia (NH3) and nitrogen dioxide (NO2) gas sensing. As in NO2, both undoped sensors react with a decrease in relative sensor responses to NH3, hence showing n-type behavior. Doping MoS2 and WS2 with chlorine led to a higher response vis-a-vis the nitrogendoped sensors. The absolute relative response of Cl-doped WS2 and MoS2 was about 3.5 and 1.8 times more than that of their undoped counterparts toward NH3. A change of direction with a slightly smaller response (approximately x 0.8), however, could also be observed in the doping of MoS2 and WS2 with nitrogen. When exposed to NO2, the Cl-doped WS2 sensor response was 1.2 more than the N-doped one, while for MoS2 these values changed in the range of 1.2 - 1.6 for different flows of gas.
|
|
