Study On Preparation And Megto-thermoelectric Properties Of Zno Thin Films

Zinc oxide is one of the important II-VI group semiconductor material with directband gap（3.37ev），owing to so many advantages such as rich in resources，non-toxicity,easy to realize doping. Because of its super conductivity and wonderful transmittance,ZnO based films have been widely used in the field of luminescent devices, transparentelectrodes and soller cells, etc. Recently, ZnO based thermoelectric oxides havereceived increasing attention for realiazing its good electrical properties, preferabletemperature stability and antioxygenation，so it is necessary to carry out systematicalresearch on ZnO based films to establish its utilization in thermoelectric system.In this paper, ZnO:Ga(GZO) and ZnO:Al(AZO) thin films were deposited on theglass substrates with the method of RF magnetron sputtering and detected by XRD,SEM, XPS, AFM and Hall.etc. We gave a systemic research on surface morphology,electrical and magneto-thermoelectric properties of different Ga doping content(1、3、5、7at.%) of ZnO:Ga thin films (GZO1, GZO2, GZO3, GZO4) and various deposition time(0.5,1.0,1.5,2.0h) of ZnO:Al thin films with the same doping amount(3at.%)(AZO1,AZO2, AZO3, AZO4). Furthermore, the electrical and magneto-thermoelectricproperties of ZnO: Ga and ZnO: Al thin films with same doping content were comparedand investigated. The primary consequences acquired are as follows:①All of the ZnO: Ga and ZnO: Al films were polycrystalline hexagonal wurtzitestructure with a preferred (002) orientation. Zn, Ga, Al exsit in the valence state of Zn2+,Ga3+, Al3+and no other valence was found.②A small amount of Ga doping could improve the GZO thin films structure andcrystal quality to some extent, whereas excessive Ga doping will lead to the decrease ofgrain size. The electrical properties of GZO are improved with the increaseing Gadopingcontent the electrical properties, then become destroyed when the Ga dopingcontent reaches to5at.%which may be attributed to the generated non-conductive oxidegallium.③Both the GZO and AZO thin films with the negative Seebeck coefficientsdisplay obvious thermoelectric effect and n-type conductive behavior. As Ga dopingcontent increases, the absolute values of Seebeck coefficients (|S|) and the power factorof GZO thin films decrease and the GZO film with the1at.%Ga content obtain theoptimal value of5.34×10-4Wm-1k-2. The AZO films are with higher|S|values which decrease with the increasing sputtering time.④Under the condition of applied magnetic field, the|S|value of GZO thin filmsdecrease after the first increase with the increasing magnetic field intensity, theinfluence of magnetic field on the GZO films with various Ga doping content isdiscrepant. The|S|values of AZO films with different sputtering time decrease with theincreasing magnetic field intensity and the AZO film with the sputtering time of0.5hwas greatly affected by the magnetic field.⑤In the existence of magnetic field, the tendency of the|S|values of AZO andGZO thin film prepared on same conditions varying with magnetic field are different.The|S|value of AZO film decreases with the increasing magnetic field intensity,whereas the|S|value of GZO film increases, which is due to that the effect of magneticfield on potential barrier height and the effective amount of electrons are dominant inthe AZO and GZO films respectively.