Research On Gas Sensitive Properties Of ZnO Semiconductor Materials

As a common low-cost metal oxide semiconductor,ZnO is widely used as a gas sensor material due to its excellent physical and chemical properties.In this paper,hexagonal prism-shaped and nano-particle ZnO crystals were synthesized,and gas-sensitivity characteristics research and First-Principles calculations were carried out.By adjusting the material crystal plane,morphology,doping and light field intervention,the optical and electrical properties of gas molecules before and after adsorption are studied,and strategies to improve the selectivity and sensitivity of ZnO materials are proposed.It provides a theoretical basis for guiding the controllable design of the gas sensor.The main tasks are as follows:First,the hexagonal prism-shaped ZnO was synthesized by hydrothermal method and the surface was chemically etched.The gas-sensing properties of ZnO before and after etching were studied.The first-principles calculation results show that the selectivity of the different crystal faces of the hexagonal ZnO to different components of the air determines its photocurrent response,which is consistent with the experimental results.The adsorption characteristics before etching are mainly the chemical adsorption of oxygen molecules on the(002)plane of the hexagonal prism and the chemical adsorption of water molecules on the(200)plane.After etching,a new(110)crystal plane appears on the(002)plane.Protrusions,protruding crystal faces are dominated by chemical adsorption of water molecules.Second,ZnO nanoparticles with uniform morphology and size were prepared by chemical precipitation method,and surface Co2+ doped on them,and the gas-sensing properties of ZnO before and after doping were studied.The First-Principles calculation results show that the surface doping has a significant impact on the photoelectric performance,and the test results of the photocurrent spectrum and the AC impedance spectrum are consistent.The adsorption characteristics of the(200)crystal plane before doping are mainly the chemical adsorption of oxygen molecules,and the chemical adsorption of water molecules on the(110)crystal plane after doping.Third,use the above two materials as gas-sensitive materials to detect ethanol gas.The results showed that the morphology and specific surface area of the hexagonal prism-shaped ZnO changed after etching,the(002)surface decreased,the number of adsorbed oxygen molecules decreased,and the responsivity decreased;the ZnO nanoparticles before and after Co2+doping were performed in an O2 atmosphere.After UV lamp irradiation treatment,it is found that the ZnO nanoparticles irradiated by the UV lamp have higher responsivity,and the change of the responsivity of Co2+doped ZnO is not obvious.The First-Principles calculation results show that ultraviolet light can promote the chemical bonding of oxygen and ZnO crystal planes,and the bonding of the crystal planes and oxygen is restricted after Co2+ doping,which affects its electrical properties.This provides a new idea for improving the gas sensitivity of materials.