Sandeep Chandril - Academia.edu (original) (raw)
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Papers by Sandeep Chandril
Academia letters, Aug 17, 2021
APS, Mar 1, 2010
ABSTRACT One major challenge in the stoichiometric growth of complex oxides, such as YMnO3, is th... more ABSTRACT One major challenge in the stoichiometric growth of complex oxides, such as YMnO3, is the control of the relative compositions of the constituent materials. Desirable properties of oxide materials, such as ferroelectricity, are highly dependent upon material stoichiometry, making stoichiometry control an important issue. While RHEED (Reflection High Energy Electron Diffraction) analysis is typically used as a qualitative tool, RHEED generated x-rays can be used to give quantitative compositional information. The relative compositions of Y and Mn in MBE grown YMnO3 samples were studied using the grazing exit x-rays generated by RHEED electrons. Comparing the results with RBS characterization suggested that the technique has the potential for real-time compositional analysis.
Bulletin of the American Physical Society, Mar 13, 2008
Journal of Applied Physics, Jun 1, 2011
A major challenge in the stoichiometric growth of complex oxide compounds is the control of the r... more A major challenge in the stoichiometric growth of complex oxide compounds is the control of the relative compositions of the constituent materials. A potential avenue for compositional analysis during growth is the use of x-ray fluorescence generated during reflection high energy electron diffraction measurements. Using this technique, relative compositions of Y and Mn in molecular beam epitaxy grown YMnO3 samples were studied. Comparing the results with Rutherford back scattering spectroscopy suggests that the technique has the potential for real-time analysis of elemental fluxes and stoichiometry control during sample growth.
In the present work large area 156.75 mm by 156.75 mm crystalline silicon passivated emitter and ... more In the present work large area 156.75 mm by 156.75 mm crystalline silicon passivated emitter and rear contact (PERC) solar cells are examined at the cell level and at the module level as well. 21% efficient mono crystalline PERC cells are cross sectioned and observed under microscope for local back surface field (LBSF) formation and laser contact opened regions. Quantum efficiency testing was done to see the photo current generated for different wavelengths. Finally the moduling of 72 cells were done and the IV measurements of PERC module before sun soaking and after sun soaking was done to see the effect of light induced degradation (LID) in PERC modules.
Journal of Applied Physics, Jul 15, 2009
Physica status solidi, Jan 23, 2008
Determining fundamental properties of InN is beset with difficulties. Since a conducting surface ... more Determining fundamental properties of InN is beset with difficulties. Since a conducting surface accumulation layer creates difficulties when assessing the impact of dopants, variable magnetic field Hall effect measurements were performed to separate various conducting layers. In addition to verifying p‐type doping with Mg, variable magnetic field Hall effect was used to show that growth of InN on YSZ will greatly reduce the background n‐type concentration for thinner layers, (with n ∼ 2×1017 cm−3, the lowest achieved on half micron thick material), making microns‐thick growth less important than the typical method of growth on sapphire with GaN buffer layers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bulletin of the American Physical Society, Mar 16, 2009
Applied Physics Letters, 2008
Growth of YMnO3 on GaN (0001) using molecular beam epitaxy at temperatures greater than 850°C res... more Growth of YMnO3 on GaN (0001) using molecular beam epitaxy at temperatures greater than 850°C resulted in the spontaneous formation of crystalline prisms, ranging from 20to60nm in height and 50to500nm in lateral size, surrounded by a 6nm thick continuous YMnO3 film. The local dielectric properties were measured using scanning surface probe microscopy. The prisms were ferroelectric at room temperature and their ferroelectric properties were enhanced for taller prisms. This is consistent with these structures being less constrained than the continuous layer, which is clamped by the surrounding unpolarized film.
Journal of Electronic Materials, Jun 1, 2006
Applied Physics Letters, Oct 30, 2006
Journal of Crystal Growth, Jun 1, 2007
IEEE Journal of Photovoltaics, Jul 1, 2020
Light trapping and current losses are critical factors for the performance of a solar cell. The a... more Light trapping and current losses are critical factors for the performance of a solar cell. The analysis of the light trapping is generally carried out by the optical path length and back reflectance estimations using the inverse internal quantum efficiency (IQE) approach or the simulation methods. Simulation tools, such as PC1D or wafer ray tracers, provide an improved estimation as compared with the inverse IQE method but are time-consuming. Another approach for light trapping based on the statistical ray optics has been reported in earlier literature, providing a practical limit against the 4n2 limit. This approach has been studied and compared with the well-studied inverse IQE approach. It is further modified for application to the widely available silicon solar cell structures. Also, the current loss analysis has been carried out using the proposed method that separates the optical losses from the electrical losses in the long-wavelength range without the use of simulation. Further, the accuracy of back reflectance values determined using analytical methods, including the inverse IQE method, is examined using PC1D simulations and the current loss analysis.
Bulletin of the American Physical Society, Mar 10, 2008
International Journal of Renewable Energy Research, 2013
The effect of process parameters such as saw damage removal, gas dilution and silane depletion ar... more The effect of process parameters such as saw damage removal, gas dilution and silane depletion are studied to maximize the efficiency of silicon a-Si/c-Si heterojuction solar cells. Furthermore, the effect of chemical treatment and annealing are also studied to understand their effect on performance of silicon heterojunction solar cells. A smooth and defect free junction is required to exploit the heterojunction properties of the junction and produce high open circuit voltage. Hence a smooth c-Si surface and the incorporation and migration of hydrogen in the amorphous silicon layers, especially the intrinsic amorphous layer, are very important. The process parameters affecting these properties have been studied and direct relation between the process parameters and the cell performance has been found.
ABSTRACT One major challenge in the stoichiometric growth of complex oxides, such as YMnO3, is th... more ABSTRACT One major challenge in the stoichiometric growth of complex oxides, such as YMnO3, is the control of the relative compositions of the constituent materials. Desirable properties of oxide materials, such as ferroelectricity, are highly dependent upon material stoichiometry, making stoichiometry control an important issue. While RHEED (Reflection High Energy Electron Diffraction) analysis is typically used as a qualitative tool, RHEED generated x-rays can be used to give quantitative compositional information. The relative compositions of Y and Mn in MBE grown YMnO3 samples were studied using the grazing exit x-rays generated by RHEED electrons. Comparing the results with RBS characterization suggested that the technique has the potential for real-time compositional analysis.
ABSTRACT RHEED-total reflection x-ray spectroscopy (-TRAXS) is an in-situ chemical and structural... more ABSTRACT RHEED-total reflection x-ray spectroscopy (-TRAXS) is an in-situ chemical and structural characterization technique which is highly surface sensitive. This consists of a grazing-angle electron beam from which characteristic x-rays from the sample are measured also at grazing angles. We have demonstrated that monolayer sensitivity in Y and Mn films on GaN can be achieved. We have also developed a theoretical model for the angular dependence of the x-ray Kalpha peaks for the thin films, based on Parratt's formalism for x-ray reflectivity and the electron trajectory simulation software CASINO, to correct for grazing angle electron beam as a source for x-rays. As the angular dependence is highly dependent upon the film thickness and the smoothness of the film, it can be used to determine the deposition rate of individual elements as well as the interface chemical roughness
Academia letters, Aug 17, 2021
APS, Mar 1, 2010
ABSTRACT One major challenge in the stoichiometric growth of complex oxides, such as YMnO3, is th... more ABSTRACT One major challenge in the stoichiometric growth of complex oxides, such as YMnO3, is the control of the relative compositions of the constituent materials. Desirable properties of oxide materials, such as ferroelectricity, are highly dependent upon material stoichiometry, making stoichiometry control an important issue. While RHEED (Reflection High Energy Electron Diffraction) analysis is typically used as a qualitative tool, RHEED generated x-rays can be used to give quantitative compositional information. The relative compositions of Y and Mn in MBE grown YMnO3 samples were studied using the grazing exit x-rays generated by RHEED electrons. Comparing the results with RBS characterization suggested that the technique has the potential for real-time compositional analysis.
Bulletin of the American Physical Society, Mar 13, 2008
Journal of Applied Physics, Jun 1, 2011
A major challenge in the stoichiometric growth of complex oxide compounds is the control of the r... more A major challenge in the stoichiometric growth of complex oxide compounds is the control of the relative compositions of the constituent materials. A potential avenue for compositional analysis during growth is the use of x-ray fluorescence generated during reflection high energy electron diffraction measurements. Using this technique, relative compositions of Y and Mn in molecular beam epitaxy grown YMnO3 samples were studied. Comparing the results with Rutherford back scattering spectroscopy suggests that the technique has the potential for real-time analysis of elemental fluxes and stoichiometry control during sample growth.
In the present work large area 156.75 mm by 156.75 mm crystalline silicon passivated emitter and ... more In the present work large area 156.75 mm by 156.75 mm crystalline silicon passivated emitter and rear contact (PERC) solar cells are examined at the cell level and at the module level as well. 21% efficient mono crystalline PERC cells are cross sectioned and observed under microscope for local back surface field (LBSF) formation and laser contact opened regions. Quantum efficiency testing was done to see the photo current generated for different wavelengths. Finally the moduling of 72 cells were done and the IV measurements of PERC module before sun soaking and after sun soaking was done to see the effect of light induced degradation (LID) in PERC modules.
Journal of Applied Physics, Jul 15, 2009
Physica status solidi, Jan 23, 2008
Determining fundamental properties of InN is beset with difficulties. Since a conducting surface ... more Determining fundamental properties of InN is beset with difficulties. Since a conducting surface accumulation layer creates difficulties when assessing the impact of dopants, variable magnetic field Hall effect measurements were performed to separate various conducting layers. In addition to verifying p‐type doping with Mg, variable magnetic field Hall effect was used to show that growth of InN on YSZ will greatly reduce the background n‐type concentration for thinner layers, (with n ∼ 2×1017 cm−3, the lowest achieved on half micron thick material), making microns‐thick growth less important than the typical method of growth on sapphire with GaN buffer layers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bulletin of the American Physical Society, Mar 16, 2009
Applied Physics Letters, 2008
Growth of YMnO3 on GaN (0001) using molecular beam epitaxy at temperatures greater than 850°C res... more Growth of YMnO3 on GaN (0001) using molecular beam epitaxy at temperatures greater than 850°C resulted in the spontaneous formation of crystalline prisms, ranging from 20to60nm in height and 50to500nm in lateral size, surrounded by a 6nm thick continuous YMnO3 film. The local dielectric properties were measured using scanning surface probe microscopy. The prisms were ferroelectric at room temperature and their ferroelectric properties were enhanced for taller prisms. This is consistent with these structures being less constrained than the continuous layer, which is clamped by the surrounding unpolarized film.
Journal of Electronic Materials, Jun 1, 2006
Applied Physics Letters, Oct 30, 2006
Journal of Crystal Growth, Jun 1, 2007
IEEE Journal of Photovoltaics, Jul 1, 2020
Light trapping and current losses are critical factors for the performance of a solar cell. The a... more Light trapping and current losses are critical factors for the performance of a solar cell. The analysis of the light trapping is generally carried out by the optical path length and back reflectance estimations using the inverse internal quantum efficiency (IQE) approach or the simulation methods. Simulation tools, such as PC1D or wafer ray tracers, provide an improved estimation as compared with the inverse IQE method but are time-consuming. Another approach for light trapping based on the statistical ray optics has been reported in earlier literature, providing a practical limit against the 4n2 limit. This approach has been studied and compared with the well-studied inverse IQE approach. It is further modified for application to the widely available silicon solar cell structures. Also, the current loss analysis has been carried out using the proposed method that separates the optical losses from the electrical losses in the long-wavelength range without the use of simulation. Further, the accuracy of back reflectance values determined using analytical methods, including the inverse IQE method, is examined using PC1D simulations and the current loss analysis.
Bulletin of the American Physical Society, Mar 10, 2008
International Journal of Renewable Energy Research, 2013
The effect of process parameters such as saw damage removal, gas dilution and silane depletion ar... more The effect of process parameters such as saw damage removal, gas dilution and silane depletion are studied to maximize the efficiency of silicon a-Si/c-Si heterojuction solar cells. Furthermore, the effect of chemical treatment and annealing are also studied to understand their effect on performance of silicon heterojunction solar cells. A smooth and defect free junction is required to exploit the heterojunction properties of the junction and produce high open circuit voltage. Hence a smooth c-Si surface and the incorporation and migration of hydrogen in the amorphous silicon layers, especially the intrinsic amorphous layer, are very important. The process parameters affecting these properties have been studied and direct relation between the process parameters and the cell performance has been found.
ABSTRACT One major challenge in the stoichiometric growth of complex oxides, such as YMnO3, is th... more ABSTRACT One major challenge in the stoichiometric growth of complex oxides, such as YMnO3, is the control of the relative compositions of the constituent materials. Desirable properties of oxide materials, such as ferroelectricity, are highly dependent upon material stoichiometry, making stoichiometry control an important issue. While RHEED (Reflection High Energy Electron Diffraction) analysis is typically used as a qualitative tool, RHEED generated x-rays can be used to give quantitative compositional information. The relative compositions of Y and Mn in MBE grown YMnO3 samples were studied using the grazing exit x-rays generated by RHEED electrons. Comparing the results with RBS characterization suggested that the technique has the potential for real-time compositional analysis.
ABSTRACT RHEED-total reflection x-ray spectroscopy (-TRAXS) is an in-situ chemical and structural... more ABSTRACT RHEED-total reflection x-ray spectroscopy (-TRAXS) is an in-situ chemical and structural characterization technique which is highly surface sensitive. This consists of a grazing-angle electron beam from which characteristic x-rays from the sample are measured also at grazing angles. We have demonstrated that monolayer sensitivity in Y and Mn films on GaN can be achieved. We have also developed a theoretical model for the angular dependence of the x-ray Kalpha peaks for the thin films, based on Parratt's formalism for x-ray reflectivity and the electron trajectory simulation software CASINO, to correct for grazing angle electron beam as a source for x-rays. As the angular dependence is highly dependent upon the film thickness and the smoothness of the film, it can be used to determine the deposition rate of individual elements as well as the interface chemical roughness