No, defects are not always bad. Vacancies, antisites, or impurities are in general trapped at the... more No, defects are not always bad. Vacancies, antisites, or impurities are in general trapped at the grain boundaries and contribute to scattering (of charge carriers). In general, grain boundaries reduce the performance (efficiency of the solar cell). However, there are certain materials where the defects enhance performance. CdTe, CuInSe2 (CIS), Cu2ZnSnS4 (CZTS) are a few examples. The present work involves CAFM studies on CZTS films deposited to Si and soda-lime glass substrate to explore the underlying physics behind unique grain boundary physics in CZTS. Discussions are made in the light of the reactions that take place on CZTS surface and corresponding energy band diagrams are drawn
Integration of lead zirconate titanate (PZT) thin film on diamond substrate offers a great deal o... more Integration of lead zirconate titanate (PZT) thin film on diamond substrate offers a great deal of potential for the application of multifunctional devices under extreme conditions. However, fabrication of perovskite PZT thin films on diamond substrate without a buffer layer has not been realized to date. We report for the first time on the successful deposition of PZT thin film directly on a diamond substrate without any buffer layer using the pulsed-laser deposition technique. The perovskite phase was realized only under specific growth conditions. X-ray diffraction and Raman studies confirmed the perovskite phase. The ferroelectric behaviour of the deposited PZT thin film was confirmed using piezo response microscope phase image and ferroelectric hysteresis loop.
Cu2ZnSnS4 and its alloy based thin film solar cells have shown better photovoltaic performance un... more Cu2ZnSnS4 and its alloy based thin film solar cells have shown better photovoltaic performance under Cu-poor and Zn-rich conditions. However, the effect of Cu-stoichiometry on the coexistence of kesterite (KS), stannite and/or partially disordered kesterite (PD-KS) phases and their influence on photovoltaic performance is not clearly understood. Raman studies were carried out on Cu2−xZn1.3SnS4 (x = 0, 0.3, and 0.5) thin films by changing the intensity of the incident laser beam. It was observed that both Cu-stoichiometry and incident laser beam intensity induce a disorder in the system. Disorder induced transformation of KS (I4¯) to PD-KS (I4¯2m) is explained by Raman studies.
Abstract Tribo-layer formation and frictional characteristics of the SiC ball were studied with t... more Abstract Tribo-layer formation and frictional characteristics of the SiC ball were studied with the sliding test against nanocrystalline diamond coating under atmospheric test conditions. Unsteady friction coefficients in the range of 0.04 to 0.1 were observed during the tribo-test. Friction and wear characteristics were found to be influenced by the formation of cohesive tribo-layer (thickness ~ 1.3 μm) in the wear track of nanocrystalline diamond coating. Hardness of the tribo-layer was measured using nanoindentation technique and low hardness of ~ 1.2 GPa was observed. The presence of silicon and oxygen in the tribo-layer was noticed by the energy dispersive spectroscopy mapping and the chemical states of the silicon were analyzed using X-ray photoelectron spectroscopy. Large amount of oxygen content in the tribo-layer indicated tribo-oxidation wear mechanism.
Formation of ordered defect compounds and anomalous grain boundary physics are unique to Cu chalc... more Formation of ordered defect compounds and anomalous grain boundary physics are unique to Cu chalcogenides CuInX 2 (S/Se) and its alloys. X-ray photoelectron spectroscopy (XPS) studies were carried on Cu 2-x Zn 1.3 SnS 4 (x = 0.0, 0.3, 0.5 and 0.7) to determine the position of valence band edge and explore the formation of ordered vacancy compounds along with absorption studies. Conductive atomic force microscopy (C-AFM) studies were carried out Cu 2 ZnSnS 4 (CZTS) film deposited on Si and sodalime glass substrates to understand grain boundary physics.
In this article, we report our recent results on the synthesis of nano-ink and drop-casted films ... more In this article, we report our recent results on the synthesis of nano-ink and drop-casted films of CuInGaS2 (CIGS), which acts as the absorber material for CIGS-based solar cells. The morphological and optical property changes of CIGS films have been compared to those of nano-CuInS2 (CIS) films deposited on glass substrates. It is found that the microstructure and morphology of these films depend strongly on the presence of Ga. High-resolution transmission electron microscopy reveals that CIGS nanoparticles are 4–5 times larger than CIS nanoparticles. The roughness of CIGS films could be reduced on preheating the drop-casted films prior to sulphurisation. The absorption onset for CIGS is lower than that of CIS due to Ga substitution in place of In. Raman spectra showed a noticeable contribution from Cu–Au mode in CIGS films. Larger nanoparticles in CIGS are attributed to faster growth kinetics due to higher Cu:In ratio than in CIS.
No, defects are not always bad. Vacancies, antisites, or impurities are in general trapped at the... more No, defects are not always bad. Vacancies, antisites, or impurities are in general trapped at the grain boundaries and contribute to scattering (of charge carriers). In general, grain boundaries reduce the performance (efficiency of the solar cell). However, there are certain materials where the defects enhance performance. CdTe, CuInSe2 (CIS), Cu2ZnSnS4 (CZTS) are a few examples. The present work involves CAFM studies on CZTS films deposited to Si and soda-lime glass substrate to explore the underlying physics behind unique grain boundary physics in CZTS. Discussions are made in the light of the reactions that take place on CZTS surface and corresponding energy band diagrams are drawn
Integration of lead zirconate titanate (PZT) thin film on diamond substrate offers a great deal o... more Integration of lead zirconate titanate (PZT) thin film on diamond substrate offers a great deal of potential for the application of multifunctional devices under extreme conditions. However, fabrication of perovskite PZT thin films on diamond substrate without a buffer layer has not been realized to date. We report for the first time on the successful deposition of PZT thin film directly on a diamond substrate without any buffer layer using the pulsed-laser deposition technique. The perovskite phase was realized only under specific growth conditions. X-ray diffraction and Raman studies confirmed the perovskite phase. The ferroelectric behaviour of the deposited PZT thin film was confirmed using piezo response microscope phase image and ferroelectric hysteresis loop.
Cu2ZnSnS4 and its alloy based thin film solar cells have shown better photovoltaic performance un... more Cu2ZnSnS4 and its alloy based thin film solar cells have shown better photovoltaic performance under Cu-poor and Zn-rich conditions. However, the effect of Cu-stoichiometry on the coexistence of kesterite (KS), stannite and/or partially disordered kesterite (PD-KS) phases and their influence on photovoltaic performance is not clearly understood. Raman studies were carried out on Cu2−xZn1.3SnS4 (x = 0, 0.3, and 0.5) thin films by changing the intensity of the incident laser beam. It was observed that both Cu-stoichiometry and incident laser beam intensity induce a disorder in the system. Disorder induced transformation of KS (I4¯) to PD-KS (I4¯2m) is explained by Raman studies.
Abstract Tribo-layer formation and frictional characteristics of the SiC ball were studied with t... more Abstract Tribo-layer formation and frictional characteristics of the SiC ball were studied with the sliding test against nanocrystalline diamond coating under atmospheric test conditions. Unsteady friction coefficients in the range of 0.04 to 0.1 were observed during the tribo-test. Friction and wear characteristics were found to be influenced by the formation of cohesive tribo-layer (thickness ~ 1.3 μm) in the wear track of nanocrystalline diamond coating. Hardness of the tribo-layer was measured using nanoindentation technique and low hardness of ~ 1.2 GPa was observed. The presence of silicon and oxygen in the tribo-layer was noticed by the energy dispersive spectroscopy mapping and the chemical states of the silicon were analyzed using X-ray photoelectron spectroscopy. Large amount of oxygen content in the tribo-layer indicated tribo-oxidation wear mechanism.
Formation of ordered defect compounds and anomalous grain boundary physics are unique to Cu chalc... more Formation of ordered defect compounds and anomalous grain boundary physics are unique to Cu chalcogenides CuInX 2 (S/Se) and its alloys. X-ray photoelectron spectroscopy (XPS) studies were carried on Cu 2-x Zn 1.3 SnS 4 (x = 0.0, 0.3, 0.5 and 0.7) to determine the position of valence band edge and explore the formation of ordered vacancy compounds along with absorption studies. Conductive atomic force microscopy (C-AFM) studies were carried out Cu 2 ZnSnS 4 (CZTS) film deposited on Si and sodalime glass substrates to understand grain boundary physics.
In this article, we report our recent results on the synthesis of nano-ink and drop-casted films ... more In this article, we report our recent results on the synthesis of nano-ink and drop-casted films of CuInGaS2 (CIGS), which acts as the absorber material for CIGS-based solar cells. The morphological and optical property changes of CIGS films have been compared to those of nano-CuInS2 (CIS) films deposited on glass substrates. It is found that the microstructure and morphology of these films depend strongly on the presence of Ga. High-resolution transmission electron microscopy reveals that CIGS nanoparticles are 4–5 times larger than CIS nanoparticles. The roughness of CIGS films could be reduced on preheating the drop-casted films prior to sulphurisation. The absorption onset for CIGS is lower than that of CIS due to Ga substitution in place of In. Raman spectra showed a noticeable contribution from Cu–Au mode in CIGS films. Larger nanoparticles in CIGS are attributed to faster growth kinetics due to higher Cu:In ratio than in CIS.
Uploads
Papers by Sunil Kumar Samji