Ankur Soam

Charge storage properties of SiNWs grown by hot-wire chemical vapor process technique as electrodes in electrochemical capacitors

Silicon nanowires (SiNWs) synthesized by Hot-Wire Chemical Vapor Process (HWCVP) via vapor-liquid-solid mechanism are explored as electrodes for supercapacitor application. The electrochemical properties of SiNWs in two electrode configuration were evaluated by galvanostatic charge/discharge test and cyclic voltammetry at different scan rates. A specific capacitance of 800 μF/cm2 at 10 mV/sec scan rate is obtained and the capacitive behavior is maintained even at higher scan rates. All electrochemical measurements were carried out in 1M Na2SO4 aqueous electrolyte. Scanning Electron Microscopy was also employed for characterization of SiNWs morphology.

Controlling the Size of Interior Core of Silicon Nanowires

As the physical and electrical properties of silicon nanowires (SiNWs) are determined by their dimension, it is necessary to control their dimension to integrate them in a device. SiNWs were synthesized via Vapor-Liquid-Solid (VLS) mechanism in hot-wire chemical vapor process (HWCVP) technique using silane as a Si source and Sn as a catalyst. Different sizes of nano-template have been made by depositing of different amount of Sn using thermal evaporation method. The size of nano-template is found to be increased with the quantity of Sn. The diameter of resulted SiNWs depends on the size of the nano-template and it increases with the nano-template size. However, the diameter of SiNWs is found to be much larger than the used nano-template which is due to the deposition of silicon film on the sidewalls of the growing SiNWs. It is demonstrated here that the diameter of the interior core of SiNWs can be controlled desirable by adjusting the size of the nano-template.

Synthesis and characterization of lanthanum complex (5-choloro-8-hydroxy quinoline) bis (2-2’bipyridine) lanthanum La(Bpy)2(5-Clq)

Lanthanum complex, (5-choloro 8-hydroxy quinoline) bis (2-2’bipyridine) has been synthesized and characterized by different techniques. Lanthanum complex, La(Bpy)2(5-Clq) was characterized for structural, thermal and photoluminescence analysis. Structural analysis of this material was done by Fourier transformed infrared spectroscopy (FTIR) and mass spectroscopy. Thermal analysis of this material was done by thermal gravimetric analysis (TGA) and material shows the thermal stability up to 400°C. Absorption and emission spectra of the material was measured by UV-visible spectroscopy and photoluminescence spectroscopy. Solution of this material La(Bpy)2(5-Clq) in ethanol showed absorption peak at 332 nm, which may be attributed due to (π − π*) transitions. The photoluminescence spectra of La(Bpy)2(5-Clq) in ethanol solution showed intense peak at 505 nm.

Synthesis and Characterization of SiNW-MnO2 Core-Shell Structure

A simple and low temperature approach has been used for the deposition of manganese oxide (MnO2) film and nanoparticles on silicon nanowires (SiNWs). Firstly, SiNWs were grown using hot wire chemical vapour process (HWCVP) technique via Vapor-Liquid-Solid (VLS) mechanism using Sn as a catalyst and then electrophoretic deposition method (EPD) was used to deposit MnO2 on them. Since SiNWs have good electron transportation and high aspect ratio, the role of SiNWs is thus for improving the electrical conduction and the surface area for MnO2 for its application in a desired form. First the deposition parameters were optimized on a transparent conductive oxide (TCO) coated glass substrate to control the thickness of the MnO2 film and then it was synthesized on SiNWs. The deposition of MnO2 has been confirmed by FEG-SEM and EDX. This structure of MnO2-SiNWs could be useful for various applications.

Isotropic etching of polycrystalline silicon wafer by acidic solution

In photovoltaic technology, texturing of base wafer has great importance since it reduces the reflectance of incident light that leads to improvement in the conversion efficiency. Due to different orientations present in polycrystalline silicon wafer an isotropic etching and the texturing without grain boundary delineation is great challenge. In this study, an attempt has been made to get isotropic etching by acidic solution. The volume ratios of HF/HNO3/ CH3COOH have been chosen in such a way that it fell in lower part of iso-etch curve where the solution is HNO3 rich. The presence of high concentration of HNO3 leads to the rapid oxidation of silicon surface and hence makes the etching rate limited through the diffusion of HF into the SiO2. This study shows the isotropic etching of poly-Si wafer which is confirmed by scanning electron microscopy. Moreover, the reflectance measurements show that the average reflectance reduces from 20.5 to 8.5 % over 350 to 800 nm range.