Preparation Of Al-Doped ZnO Thin Film By Atomic Layer Deposition

Al doped ZnO（AZO）thin films have wide practical applications in solar cells,organic display,ultraviolet detection due to their excellent optical and electrical properties.Atomic layer deposition（ALD）technology has the advantages of film thickness controllability and low temperature growth process,which can produce thin films with high quality and good coverage property.AZO thin films were prepared by ALD method.The effects of the grow temperature and Al doping content on crystal quality,transmittance and electrical properties of AZO thin films were investigated in detail by means of XRD,SEM,Hall-effect measurement and UV-Vis absorption.The effect of rapid thermal annealing（RTA）treatment on the properties of AZO thin films was discussed.The main work of the thesis is as following.（1）The effect of different deposition temperature on the properties of AZO films was studied.The results show that the deposition temperature plays a key role in the growth orientation of AZO films.When the substrate temperature is 160℃,the AZO films are polycrystalline.When the temperature is between 200℃and 230℃,the AZO films grow along the preferred orientation of（100）.When the substrate temperature is higher than 240℃,the AZO films grow along the preferred orientation of（002）.When the Al-O/Zn-O cycle ratio is1:45,the resistivity of AZO thin films is～2×10^-3Ω·cm,and the FOM value is～1.6×10^-3Ω^-1.The optimun temperature of AZO thin films growth is 220～240℃.（2）The effect of different Al doping concentrations on the properties of AZO thin films was studied.The results show that the electrical properties and crystal structure properties of AZO thin films depend on the doping concentration of Al.The ZnO without doping exhibits（002）preferred orientation,and AZO thin films are（100）prefered with light Al doping.When the Al-O/Zn-O cycle ratio is 1:24 and above,the films grow along the（002）direction.With the increase of Al doping concentration,the conductivity of AZO films increases first and then decreases.AZO-24 thin films have excellent transparent and electrical conductivity,of which the FOM,resistivity,carrier concentration and mobility are 4.6×10^-3Ω^-1,8.33×10^-4Ω·cm,4.32×10²⁰ cm^-3 and 17.36 cm²/Vs,respectively.The average transmittance in the visible light range is～95%.The doping content of Al for AZO-24 is about 2.17 at.%.（3）The effects of annealing temperature and annealing time on the structure and properties of AZO films were investigated by rapid thermal annealing treatment.The results show that the crystal quality of AZO films is enhanced with the increase of annealing temperature or annealing time.When the annealing temperature is between 700℃and 800℃,the PL NBE of AZO films increases,the mobility increases and the conductivity of AZO films decreases slightly.It should be noted that when the annealing temperature is 650℃,and annealing time is in the range of 10～40 s,the conductivity of AZO films may convert from N-type to P-type conduction.The P-type conductivity may be caused by the activation of C or the formation of defects related to C element in the films during the annealing process.