Mansi Sharma; Deepika Chaudhary; S. Sudhakar; Preetam Singh; K. M. K. Srivatsa; Sushil Kumar
Abstract
The structural transition in accordance to nano sized grain distribution within the amorphous silicon matrix has been described on the basis of spectroscopic analysis as a result of variable input power applied during growth via plasma enhanced chemical vapor deposition (PECVD) process. For this, characterization ...
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The structural transition in accordance to nano sized grain distribution within the amorphous silicon matrix has been described on the basis of spectroscopic analysis as a result of variable input power applied during growth via plasma enhanced chemical vapor deposition (PECVD) process. For this, characterization techniques like micro-ellipsometer, Raman, Field emission Scanning electron microscope (FESEM), and Fourier transform infrared spectroscopy (FTIR) have been effectively utilized to identify transitions in these films particularly in terms of crystallite size (within 1-4 nm) and optical constants. These results indicate that at and above 30 W applied power the separation of two zones takes place as ultranano to nano, leading to the formation of denser matrix having uniformly distributed nano-crystallites. Moreover, these results indicate the presence of unrevealed fine crystallites (ultranano-crystalline phase) as a dominating part of grain boundaries, which may be as ultranano-crystallite phase. The blending of fine nano-crystallites within the amorphous phase might be the possible reason for the formation of nano-crystallites from ultranano-crystallites.
Deepak Chhikara; K. M. K. Srivatsa; M. Senthil Kumar; Preetam Singh; Sourav Das; O. S. Panwar
Abstract
Vertically well aligned and highly dense ZnO nanowires (NWs) have been grown on biaxially textured Ni substrates by a simple thermal evaporation technique over a large area without using any catalyst. The grown ZnO NWs have crystallized in wurtzite hexagonal structure and have grown along [0001] direction. ...
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Vertically well aligned and highly dense ZnO nanowires (NWs) have been grown on biaxially textured Ni substrates by a simple thermal evaporation technique over a large area without using any catalyst. The grown ZnO NWs have crystallized in wurtzite hexagonal structure and have grown along [0001] direction. It is also observed that the degree of vertical alignment of NWs increases with increasing growth temperature. An intense photoluminescence peak at 383 nm with a negligible deep band emission revealed the good crystalline quality of ZnO NWs. Field emission properties of the grown NWs have been examined and a field enhancement factor of 1573 has been obtained, indicating the suitability of grown nanowires for field emission applications.
K.M.K. Srivatsa; Preetam Singh; Sourav Das
Abstract
Considerable attention has been gained on the deposition of CeO2 thin films with (200) single orientation as hetero-epitaxial buffer layer on (200) oriented biaxially textured flexible Ni substrates, in the fabrication of superconductor and semiconducting epitaxial thin films for device applications. ...
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Considerable attention has been gained on the deposition of CeO2 thin films with (200) single orientation as hetero-epitaxial buffer layer on (200) oriented biaxially textured flexible Ni substrates, in the fabrication of superconductor and semiconducting epitaxial thin films for device applications. In this work we have deposited (200) oriented CeO2 thin films on biaxially textured Ni-W substrate in a single-step process by RF magnetron sputtering, using CeO2 target. X-ray diffraction analysis shows that for the CeO2 thin film deposited at RF sputtering power below 200 W and for the substrate temperature of 700 o C, the film assumes single (200) orientation. For the substrate temperature below 700 o C and RF sputtering powers above 200 W the film shows polycrystalline nature with (111) and (200) orientations. The Raman spectrum of single oriented (200) CeO2 thin film shows only one sharp peak at about 464 cm -1 corresponds to the presence of F2g mode of CeO2. The ellipsometry studies reveal the value refractive index and optical band gap of single oriented film as 2.52 and 3.41 eV, respectively.
Preetam Singh; K. M. K. Srivatsa;Sourav Das
Abstract
Single oriented nanocrystalline CeO2 thin films have been deposited over Si (100) substrate by RF magnetron sputtering in the temperature range 600-700 o C, using CeO2 target. X-ray diffraction pattern for the as deposited CeO2 film at 700 o C shows the dominant (111) orientation with corresponding FWHM ...
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Single oriented nanocrystalline CeO2 thin films have been deposited over Si (100) substrate by RF magnetron sputtering in the temperature range 600-700 o C, using CeO2 target. X-ray diffraction pattern for the as deposited CeO2 film at 700 o C shows the dominant (111) orientation with corresponding FWHM value of 0.378 o and the crystallite size 21.50 nm. The refractive index and the optical band gap both were found to increase from 2.35 to 2.66 and 3.25 to 3.43 eV, respectively with increasing substrate temperature. Atomic force microscopy results reveal highly smooth surface of the deposited films with surface roughness below 1.15 nm for the entire range of deposition temperatures. Further, the contact angle measurements on the as deposited CeO2 films showed variation from 122.36 to 81.67 o with respect to the substrate temperature, transforming the wetting property from hydrophobic to hydrophilic in nature. These results indicate the possibility of producing CeO2 films with varying properties for various device applications simply by controlling the substrate temperature.
Preetam Singh; K. M. K. Srivatsa; Sourav Das
Abstract
Polycrystalline Si (Poly-Si) film with highly crystalline nature, and having most of the grains in the range of 50-100 µm has been grown over biaxially textured Ni-W substrate by Hot-wire chemical vapor deposition technique, using a single buffer layer of CeO2 thin film. This result has been achieved ...
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Polycrystalline Si (Poly-Si) film with highly crystalline nature, and having most of the grains in the range of 50-100 µm has been grown over biaxially textured Ni-W substrate by Hot-wire chemical vapor deposition technique, using a single buffer layer of CeO2 thin film. This result has been achieved for the SiH4 source gas diluted to 95% with added H2 gas, and for the substrate temperature of 840±10oC and a deposition pressure of 40 mTorr. XRD analysis shows that the Poly-Si films have grown with (111) and (200) orientations. Raman studies reveal that a crystalline volume fraction of 95.3% has been achieved. The imaginary part of pseudo dielectric function, <ε2>, as extracted from ellipsometric data, shows two prominent shoulders at energy positions 3.4 eV and 4.2 eV corresponding to the optical absorption of crystalline Si, indicating a high crystallinity of the Poly-Si film. SEM micrograph shows that the grown Poly-Si film is following the morphology and grain size as that of biaxially textured Ni-W substrate. SIMS analysis of the total multilayer structure shows a formation of very sharp interfaces, with no diffusion between Si and Ni, indicating that a single buffer layer of CeO2 is sufficient to avoid the formation of nickel silicide while growing Si over Ni substrate. Thus, these results are very encouraging for the fabrication of Poly-Si film based solar cells with increased efficiency by minimizing the undesired recombination of charge carriers at grain boundaries.
