Sol - Gel Preparation Of Zno Conductive Film

ZnO film is aⅡ-Ⅵdirect compound semiconductor with wide band gap energy of 3.37eV and a exciton binding energy 60meV at room temperature.ZnO thin film is used widely and effectively in the fields of surface acoustic wave devices,solar cell,gas sensors,varistors and so on because of its excellent piezoelectrical performance.It also has the tremendous potential applications for ultraviolet detectors,LEDs,LDs.Al-doped ZnO(ZAO)thin films are emerging as an alternative potential candidate for ITO(Sn-doped In₂O₃)flims recently not only because of their comparable optical and electrical properties to ITO films,but also because of their higher thermal and chemical stability under the exposure to hydrogen plasma than ITO.P-type doping of ZnO thin films also attract lots of attentions.In this paper,the various growth techniques of ZnO films and the progresses in the internal and overseas researchs of ZnO were reviewed.In this paper,the ZnO thin films were prepared on glass substrate(microscope slides)by Sol-Gel process from ethanol and 2-methoxyethanol solution prepared by zinc acetate as premonitormonoe then olamine as stabilizer and glacial acet homogenous as activator.The transparent and conductive,polycrystalline ZnO thin film was formed finally by dipping coating and spin coating conducted for film-plate on substrate,drying,pre-heat-treatment,anealing.A method using first principles and pseudopotentials based on density functional theory was applied to calculate the geometric structure and the band structure of ZnO doped with Al³⁺,Ag⁺,Li⁺.The calculations were carried out with a powerful package called Material Studio.And 16-atom supercells(2×2×1)were used to perform the total energy calculation.The calculated results show that some complexes of Al_Znbring donor level to the band structure of ZnO and improved the hotoelectric properties.Some complexes of Ag_Zn' and Li_Zn' bring deep acceptor level to the band structure of ZnO and the intrinsic defect of Zn_i^·and Ag_i^·and Li_i^·will equalize the deep acceptor level.These will cause ideal P-type semiconductor difficultly to be prepared.X-ray diffraction(XRD),scanning electron microscope(SEM),Energy dispersive scanning(EDS),four point resistivity test system and ultraviolet-visible spectrum(UVS)were used to characterize the crystallization behavior,orientation and surface morphology of the ZnO thin films.It is revealed that the thin films with strongly preferred orientation of C-axis perpendicular to the substrate surface which surface was homogenous,dense and crackfree was the crystalline phase of hexagonal wurtzite.The thin film was composed of plentiful meshy crystal.The average transmittance of thin film in visible region was above 80%.The optical band gap was widened with the increase of Al/Zn molar ratio.The ZnO:Al films resistivity was found to be 4.88x10^-1～2.24x10^-4Ω·cm.The ZnO:Li thin films had as the same crystalline phase of hexagonal wurtzite and preferred orientation of C-axis as ZnO:Al.The ZnO:Li films resistivity was biger than ZnO:Al which was found to be 90～1.53×10^-1Ω·cm.Prepared technical parameters were optimized by L₉(3⁴)experiment analysis.The optimization parameter that is 15 layers,2%at(Al³⁺),250℃(pre-heating temperature),600℃(annealing temperature)was fished out by large numbers of experiment.The relationship between the ZnO:Al films resistivity and the meshy surface was researched,the result proved that the denser of the meshy surface the better of the ZnO:Al films resistivity.