溶胶-凝胶法制备ZnO纳米薄膜的工艺和应用

ZnO是一种重要的功能材料和新型的Ⅱ-Ⅵ族宽禁带半导体材料.采用溶胶-凝胶(Sol-gel)工艺在Si(100)、Si(111)和c面蓝宝石衬底上成功制备出高质量的ZnO纳米薄膜,并用XRD、SEM、AFM等方法研究了薄膜的特性.首次以制备的ZnO纳米薄膜为缓冲层,在n型Si(100)衬底上采用低压化学气相沉积(LPCVD)工艺外延生长了SiC薄膜,得到了低载流子浓度、高电子迁移率和高空穴迁移率的两种SiC薄膜样品,分析了该薄膜的性能.

Preparation of Nano-scale ZnO Thin Films by Sol-gel Process and Its Application

Zinc oxide is an important functional and navel material of Ⅱ-Ⅵ wide bandgap semiconductor.ZnO thin films has a direct bandgap of 3.37 eV with exciton binding energy of 60 meV,and is being considered as a new kind of rapidly developing photoelectric material follows after ZnSe,GaN based materials,and showing enormous developing prospect for applications in the field of LEDs,LDs,and UV detectors.Various growth techniques of ZnO thin films have been extensively studied,including,magnetron sputtering,PLD,MOCVD,MBE,spray pyrolysis,and sol-gel methods,etc.The sol-gel process is regarded as a powerful and cost-effective technique for fabricating nano-materials,and has been successful used for preparation of various kinds of oxide films,such as PT,PZT,PLT,PLZT,SrTiO₃,and ZnO films,etc.However,there are few papers on ZnO nanofilms prepared by sol-gel process and served as the buffer layer for SiC thin film grown on Si substrate by LP CVD.The research results on those issues will be introduced.ZnO nanofilms with highly c-axis orientation were prepared by sol-gel process using zinc acetate(Zn(CH₃COO)₂·2H₂O)as starting material.A colorless transparent,homogeneous,stable and undoped ZnO sols with a concentration of 0.2～0.5 mol/L were obtained and served as the coating solutions.Si(100),Si(111)and c-plane sapphire were used as substrate.The wet films were spin-coated on substrate at a speed of 3000 r/min for about 40 seconds,and pre-heated at 150℃ for 30 minutes after each coating,and post-heated in air at different temperature from 500～900℃ for an hour.The prepared ZnO nanofilms are colorless,transparent,homogeneous and crack-free,mirror-like films.The microstructures and the surface morphology of ZnO nanofilms are investigated by XRD,AFM,SEM,Hall analyzer,and ellipsometer etc.The grain size,roughness,refractive index and thickness of ZnO nanofilms were measured.The results showed that the orientation of ZnO nanofilm samples are highly caxis oriented,and it was a surprised that the ZnO(002)diffraction peak of the sample prepared on Si(100)substrate and post-heated at 600℃ is evidently shift from the normal position 2θ=34.42°to the lower angle direction at 2θ=32.90°,the shift value is-1.52°,and the strength of this peak is the strongest,and also in the left side of this peak,i.e.2θ=32.64°,there is an unknown diffraction peak.This can be attributed to the microstructure changes occurred in ZnO nanofilm samples.The strength of ZnO(002)diffraction peak is decreased with increasing post-heated temperature from 600℃ to 900℃.The surface morphology of ZnO nanofilm samples post-heated at different temperature is quite difference,some are similar to the quantum dots,and others are quite flat.Two kinds of SiC thin films had been grown on n-type Si(100)substrate using undoped ZnO nanofilm as buffer layer by low pressure chemical vapor deposition.The structure and electrical properties of SiC/ZnO/Si(100)samples had been measured and analyzed.