Back biasing technique in preventing clogging of pores on the porous silicon templates for the deposition of zinc oxide
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The main objective of this thesis is to study the thin layer that seemed to have been formed during the electrochemical etching process and devise a method to remove this layer and subsequently deposit Zinc Oxide using Vapor Condensation method. The first step of the process involves cleaning the substrates in isopropanol, methanol and deionized water. The pores are then formed using Electrochemical etching of silicon. The electrolyte containing a mixture of hydrofluoric acid (HF) and ethanol in 1:3 ratios is used in this process. The electrolyte concentration and the etching time are kept constant in this process.In order to reduce a layer that is blocking the nanowire growth in the pores, the polarities of the constant current source used in this process are switched and the process is carried out for different time periods. This is called "Back Biasing". The growth was carried out using Vapor Condensation method with source material as Zinc powder (99.99%) and the target material as the Porous silicon templates under constant flow of argon gas. All the resultant samples were then characterized using FESEM (Field Emission Scanning Electron Microscopy) to study the morphology, X ray Diffraction to confirm the presence of ZnO and UV-Vis Spectroscopy for the optical properties.