Sunil C. Vattappalam

Appraisal on Textured Grain Growth and Photoconductivity of ZnO Thin Film SILAR

ZnO thin films were prepared by successive ionic layer adsorption reaction (SILAR) method. The textured grain growth along c-axis in pure ZnO thin films and doped with Sn was studied. The structural analysis of the thin films was done by X-ray diffraction and surface morphology by scanning electron microscopy. Textured grain growth of the samples was measured by comparing the peak intensities. Textured grain growth and photo current in ZnO thin films were found to be enhanced by doping with Sn. ZnO thin film having good crystallinity with preferential (002) orientation is a semiconductor with photonic properties of potential benefit to biophotonics. From energy dispersive X-ray analysis, it is inferred that oxygen vacancy creation is responsible for the enhanced textured grain growth in ZnO thin films.

Effect of electron irradiation on gas sensing properties of Al-Zno

Abstract Al–ZnO thin films are prepared by Silar method and are annealed at 450°C for 1 h. A selected number of samples are irradiated by high-energy electron beam and all are characterized by XRD, SEM and energy-dispersive X-ray spectroscopy. Both irradiated and non-irradiated samples are then placed independently inside a gas chamber kept at rotary vacuum. The gas chamber is maintained at a pressure of 0.20 mb and at a temperature of 350°C. Ethanol vapour is admitted in a controlled manner into the chamber and the resistance of the film is measured continuously before, during and after the admittance of the ethanol vapour. The experiment is repeated for different dosages of irradiation and different doping concentrations of Al and the resistance of the film getting reduced fast and considerably at the admittance of ethanol has been observed. The response and recovery time of the irradiated samples is compared with that of non-irradiated samples of the same doping concentration. It has been noted that both irradiated and non-irradiated samples show a response time of 1 s and recovery time of the irradiated samples is shorter than that of non-irradiated samples.

Cd Doped ZnO Thin Films By Silar For Gas Sensing Applications.

Cd-ZnO thin films are prepared by Silar and are characterized by XRD, SEM and EDX. The samples are then placed inside a gas chamber kept at rotary vacuum and at pressure and temperature of 0.20 mb and 350 0 C. Ethanol vapour is admitted in a controlled manner into the chamber. Resistance of the film is measured continuously before, during and after the admittance of Ethanol vapour. The experiment is repeated for different doping concentrations of Cd. And it has been observed that the resistance of the film reduces fast and considerably at the admittance of Ethanol. The response time was found to be one second and it has been noted that recovery time of the films varies with doping concentrations.

Oriented grain growth in ZnO thin films by Iodine doping

ZnO thin films were prepared by Successive Ionic Layer Adsorption Reaction (SILAR) method. Oriented grain growth in Iodine doped ZnO thin films were studied. The oriented grain growth in samples was studied by comparing the peak intensities from X-ray diffraction data and surface morphology by scanning electron microscopy. It is found that oriented grain growth significantly enhanced by Iodine doping. When the oriented grain growth increases, crystallinity of the thin film improves, resistance and band gap decrease. ZnO thin films having good crystallinity with preferential (002) orientation is a prerequisite for the fabrication of devices like UV diode lasers, acoustic- optic devices etc. A possible mechanism for the oriented grain growth is also investigated. It is inferred that creation of point defects is responsible for the enhanced oriented grain growth in ZnO thin films when doped with iodine.

Studies on effect of oxygen flow rate in textured grain growth of ZnO thin films

ZnO thin films were deposited on glass substrate by Successive Ionic Layer Adsorption Reaction (SILAR) method. Effect of oxygen flow rate in textured grain growth, resistance and band gap of the thin films have been done. Textured grain growth of the samples were measured by comparing the peak intensities from XRD. Textured grain growth was found to be maximum when the oxygen flow rate is 2.5 litre/minute. It is found that as the oxygen flow rate increases above this limit, textured grain growth decreases and resistance the samples increases. The optical band gap of ZnO film was found to be increased with the increase of oxygen flow rate.

Band gap and conductivity variations of ZnO nano structured thin films annealed under Vacuum

Zinc Oxide thin films were prepared by Successive Ionic layer adsorption and reaction technique(SILAR). The samples were annealed under vacuum and conductivity of the samples were taken at different temperatures. UV Spectrograph of the samples were taken and the band gap of each sample was found from the data. All the results were compared with that of the sample annealed under air. It was observed that the band gap decreases and concequently conductivity of the samples increases when the samples are annealed under vacuum.

Band gap and conductivity variations of ZnO thin films by doping with Aluminium

Zinc Oxide thin films were prepared by Successive Ionic layer adsorption and reaction technique(SILAR). Aluminium was doped for different doping concentrations from 3 at.% to 12 at.% in steps of 3 at.%. Conductivity of the samples were taken at different temperatures. UV Spectrograph of the samples were taken and the band gap of each sample was found from the data. It was observed that as the doping concentration of Aluminium increases, the band gap of the samples decreases and concequently conductivity of the samples increases.