Research Information System
Thesis Type: Postgraduate
Institution Of The Thesis: Gazi Üniversitesi, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2016
Student: ÖZLEM BARİN
Supervisor: SELİM ACAR
Open Archive Collection: AVESIS Open Access Collection
Abstract:In this study, HfO2 thin films are produced by Atomic Layer Deposition Method (ALD) with 3,3 nm thickness and these samples are annealed at different temperatures. The surface properties of the annealed films are investigated depending on annealing temperature. Morphological and structural investigations are carried out on all samples by Atomic Force Microscopy (AFM) and X-ray diffraction (XRD) method. X-ray diffraction shows that all the films have an amorphous phase. The surface roughness is increased with increasing annealed temperature and surface roughness values are calculated as 0,650 for thin film 500 ° C, at 700 ºC and 800 C annealed thin films, 0,813, 1,082 and 1,978 respectively. These results show the topography and surface morphology are dependent on the annealing temperature which plays a crucial role during the crystalline transformation. The NO2 gas sensing properties of samples are investigated with different temperatures from 30 to 250 C for obtaining temperature with constant 30 ppm. The operating temperature of the samples is determined as 200 °C. To investigate the effect of NO2 sensing properties at 200 C, the response of samples are exposure to different NO2 gas concentrations. The response is 32 % for annealed at 800 °C, whereas it is found 22 % for annealed at 700 °C, 7 % for annealed at 500 °C and 5 % for as grown thin film towards NO2 gas. The gas sensing measurements are carried out under UV light irradiation for reducing the operating temperature. Acceptable responses are obtained at room temperature. Metal oxide gas sensor parameters such as repeatability, response and recovery time, reusable are investigated under UV light irradiation and try to explain these gas sensing parameters. There is no response obtained for 1 ppm depending on temperature, however there is an acceptable response obtained for 1 ppm under UV light irradiation. The response is 7 % for annealed at 800 °C, whereas it is found 3 % for annealed at 700 °C, 4 % for annealed at 500 °C and 1 % for as grown thin film towards 1 ppm NO2 gas.