Study On The Controlled Preparation Of Semiconductor Oxide Defects And Its Chemical Sensing Properties

Wide-gap oxide semiconductors,as a sustainable functional material,have been widely studied and applied in recent years.The introduction of appropriate dopants into materials could cause structural defects or carrier concentration changes in the material,so that the material has special physical and chemical properties.Currently,the application of semiconductor oxides has involved the fields of photocatalysis,optoelectronic materials,and sensitive materials.However,there is still room for improvement regarding crystal defect formation methods and processes.The mechanism of related defect formation still needs to be further studied.Based on the above problems,zinc oxide and tin dioxide are used as the research objects of this article.The controllable formation of material defects is achieved through a certain process method.The synthesized materials were tested by a series of characterizations of Raman spectroscopy,X-ray photoelectron spectroscopy,fluorescence spectroscopy.The influence of defects on the material structure is analyzed.When the material is used as a humidity sensor,the application performance has been tested,and the mechanism process of defect formation is discussed emphatically.The main research results are as following:1.The tetragonal rutile tin dioxide doped with antimony oxide was successfully synthesized by hydrothermal method.The analysis results show that the average crystallite size of tin dioxide decreases from 29.59 nm to 20.53nm with the increase of the doping proportion of antimony oxide.The morphology of tin dioxide samples before and after doping showed a spherical structure.With the increase of the doping ratio,the optical band gap value of the tin dioxide samples increased from 3.6 e V to 3.86 e V and then decreased to3.47 e V,showing a trend of first increasing and then decreasing.During the doping process,oxygen vacancy defects and Sb _Sn substitutional defects were formed,which changed the electronic effect of tin element to increase the binding energy and increased the oxygen vacancy concentration.Compared with pure tin dioxide samples,the humidity sensitivity test data shows that tin dioxide materials with a doping ratio of 1%have the best sensitivity and linearity at a working frequency of 100 Hz.2.The reducing agent sodium borohydride is used to tune the defect structure of Zn O.The characterization results show that the prepared samples are zinc oxide with hexagonal wurtzite structure.The morphology of the samples changed significantly before and after the sodium borohydride solution treatment.A large number of oxygen vacancies were formed in the samples treated with sodium borohydride solution,which caused the optical band gap value to decrease from 3.28 e V to 3.07 e V.The analysis of Raman spectroscopy and X-ray photoelectron spectroscopy also proved once again that the concentration of oxygen vacancies in the processed sample material has increased significantly.The humidity sensitivity test data shows that the zinc oxide material treated with 0.5 mol/L sodium borohydride solution has better impedance response and linearity.This is attributed to the high surface roughness and a large number of oxygen vacancy defects in the treated zinc oxide material,which provides more active sites for the attachment of water molecules.3.Using glucose as a carbon source,zinc oxide materials doped with different carbon contents were successfully synthesized.The results show that the synthesized samples are all zinc oxide with hexagonal wurtzite structure.The crystallite size increases with the increase of carbon doping.Through the field emission scanning electron microscope,the morphology of the zinc oxide sample was observed.The size of the samples are about 400-500 nm,and the doped samples have the phenomenon of carbon microsphere adhesion.In addition,with the increase of carbon doping,the optical band gap value of the sample decreased from 3.16 e V to 2.79 e V,showing a decreasing trend.The results of Raman spectroscopy show that the increase of carbon doping would cause the crystal quality of the sample to decrease and the oxygen vacancy concentration to decrease.Photoluminescence spectroscopy found that all zinc oxide samples had oxygen vacancy defects and deep-level double ionized oxygen vacancies.The carbon-doped samples showed an increasing in the proportion of interstitial zinc（Zn_i）defects and a decreasing in the O_Znconcentration of substitutional defects.