Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2019
Thesis Language: Turkish
Student: Baktiyar Soltabayev
Supervisor: SELİM ACAR
Open Archive Collection: AVESIS Open Access Collection
Abstract:Detecting low concentrations of NO gas is challenging, especially when these minute concentrations could elevate asthma and combustion in the open air. For these two important reasons, gas sensors have been developed in this thesis that can detect low NO gas concentrations. Metal oxide semiconductor structures were synthesized and characterized in two different series as gas sensors. In order to investigate the effect of doping metal and its ratio on gas sensing properties and to optimize, ZnO structures doped with nickel (Zn1-xNixO) and indium (Zn1-xInxO) at different concentrations were grown with Successive Ionic Layer Adsorption and Reaction (SILAR) method. The grown sensors were annealed in a nitrogen gas atmosphere at 300 °C temperature. Structural and morphological properties of the produced thin films were examined by X-ray Diffraction (XRD), Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), Optical Absorption. X-ray films are said to be made of polycrystalline amorphous structure, while the sensors produced show a change in indium and nickel concentration. Depending on the SEM image, it was observed that the morphological properties of the producing sensors changed. AFM images showed that surface roughness (RMS) of the sensors decreased with the addition of indium doping content. Looking at the optical absorption measurements, it was observed to fall in the band gap ranges due to the effect of the doping element. Also, the impedance properties of samples were investigated at the temperature of 27-250 °C in 201,5 MHz frequency range. The gas detection measurements were made at different temperature range to determine the working temperature of the produced gas sensor. In order to determine the operating temperature of the sensors, the gas detection measurements were made in the temperature range of 27-140 ˚C for Zn1-xNixO structures and in the temperature range of 27-187 °C for Zn1-xInxO structures. The optimum working temperature of Zn1-xNixO and Zn1-xInxZnO samples were determined as 85 °C and 167 °C, respectively. The gas sensing measurements were taken at optimal operating temperatures at different gas concentrations for both sensors. It was observed that the sensors produced were receptive to 20 and 100 ppb NO gas concentration. In this thesis, gas sensors detecting low levels of NO gas concentrations used in diagnosing asthma were developed.