Nitu Badera

INVESTIGATION OF Fe-DOPED AND -UNDOPED NiO NANOCRYSTALLINE FILMS

The NiO and Fe-doped NiO thin films have been prepared by using spray pyrolysis technique. The effects of change in the volumetric concentration and substrate temperature on the film characteristics have been investigated. With the increase in volumetric concentration, the grain size and the roughness of the film increase; while the number of voids has been reduced. In case of NiO thin films the activation energy was found to increase from 0.33 eV to 0.40 eV with the increase in the film thickness. The analysis of the data suggests that the density of states at the Fermi level increase with the thickness of the film. In Fe-doped NiO film the density of states was found to increase with the increase in the substrate temperature. The optical measurements show that the maximum transmittance (≈77.13%) occurs for the film corresponding to the lowest volumetric concentration. On increasing the substrate temperature the transmittance also increases, thus displaying the decrease in the film thickness.

Flow rate effect on surface morphology of Cu doped CdS thin film by spray pyrolysis technique

Cadmium sulfide (CdS) is a potential material whose functional properties can be tuned by introducing nano-structuring. Here we report the results of flow rate variation in spray technique where in Cu (1%) doped thin film was prepared with varying flow rate of deposited precursor solution. CdS thin film sets in many nano features like grains, nano-rods etc. XRD and AFM techniques are used for the analysis of film morphology. There is a systematic change is morphology which can be explained in the light of models pertaining to the Ostwald ripening.

Temperature Dependent Photosensitivity of Cu Doped CdS Thin Film

Structural, morphological, electrical and photoconductive properties of Cu doped CdS thin film are reported here. All the films are formed in hexagonal structure with polycrystalline nature. Cu alters the rods of pure CdS into small grains. Activation energy rises with Cu incorporation in CdS film. Temperature dependent photosensitivity and photocurrent on pure and Cu doped CdS thin are investigated. Cu doped films show quick photo‐response characteristic. Photosensitivity rises at lower temperature in Cu doped films.

Slow Positron Studies of Defects in Si-Doped GaAs

The mechanism of slow positron annihilation in Si-doped GaAs has been discussed in terms of the diffusion trapping model (DTM). The trapping of positrons has been considered in SiAs acceptors i.e. shallow defects and in VGa-SiGa vacancy complexes. The model has been used to obtain the Doppler broadening line shape parameter (S-parameter) and average positron lifetime in Si-doped GaAs, for a temperature range 20K to 290K and for different doping concentrations. Observations are made regarding the effect of doping on the nature and concentration of point defects. The change in point defect concentration due to Si- doping has been found to be proportional to the doping concentration. The effect of detrapping from the shallow defects has been found to be important at higher temperatures.