Research On The Structural And Optoelectric Properties Of ZnO Thin Films Prepared By Wet Chemical Method

Oxide semiconductor thin films have been widely used in the fields of flat panel displays,solar cells,light-emitting diodes and flexible optoelectronic devices because of their excellent optical transparency and electrical conductivity,and have become one of the hot spots in the field of thin film research.As a new generation of wide-bandgap semiconductor materials,ZnO has been favored by researchers in recent years.ZnO is a semiconductor with hexagonal wurtzite structure.A large number of studies have shown that the photoelectric properties of ZnO thin films can be effectively controlled by doping.In this paper,Fe element and Hf element are selected as the doping source of ZnO thin film and the influence of the doping element on the structural and photoelectric properties of ZnO thin film is explored in depth:1)Zn_1-xFe_xO(x=0,1,2,3%)films were successfully prepared on glass substrates by sol-gel spin coating method.The samples were characterized by different analytical methods.Fe atoms are doped into the ZnO lattice,ZnO still maintains a hexagonal wurtzite structure,and Fe ions coexist in two forms of Fe²⁺and Fe³⁺.At low concentration doping(1%),the content of Fe²⁺is higher,and as the doping concentration increases,Fe ions mainly exist in the form of Fe³⁺.The average value of the transmittance is found to be more than 75%in all samples,Fe dopant have negligible effect on the transmission of ZnO films.Fe doping introduces some impurity levels,which has a great influence on the band structure,especially for valence band,and hence affect the type of transition.1%Fe-doped ZnO thin film exhibited a better photodegradation efficiency compared to other samples.2)ZnO nanorods grown on the Fe-doped ZnO seed layers with doping content from0%?3%were synthesized by a hydrothermal method.Compared with the photocatalytic properties of the Zn_1-xFe_xO film,the photocatalytic properties of ZnO nanorods grown on Zn_1-xFe_xO films have been significantly improved.The photocatalytic effect of 1%Fe-doped samples is the best and it is further proved by electrochemical impedance spectroscopy that it has lower resistance and faster interface charge transfer.The scavengers experiment suggested that;plays an important role in the photocatalytic degradation process.Compared with Fe³⁺,the content of Fe²⁺plays a major role in the photocatalytic effect.With the increase of doping concentration,the content of Fe³⁺increases and Fe³⁺will serve as the recombination center of electron-hole pairs,resulting in a decrease in photocatalytic degradation efficiency.3)Transparent and conducting Zn_1-xHf_xO thin films on flexible polyimide(PI)substrates were successfully synthesized by the sol-gel spin coating procedure.All the films retained a hexagonal wurtzite structure of ZnO and showed preferential c-axis orientation after air andvacuum annealing.The minimum resistivity was obtained in the vacuum annealed film with 3%Hf doping concentration.The carrier concentration increased,while Hall mobility decreased with increasing Hf concentration.For x=0-3%,grain boundary scattering was the major factor of mobility;while for x=5-7%,besides the grain boundary scattering,ionized impurity and natural scattering make main contribution to the variation of the mobility.