退火温度对锗薄膜光学性能和表面结构的影响

Effect of Annealing Temperature on Optical Properties and Surface Structure of Germanium Thin Films

摘要:

研究了退火温度对电子束蒸发制备的锗薄膜光学性能和表面结构的影响规律。在硅基底上制备了厚度约850 nm的Ge薄膜，分别在350、400、450和500 ℃下进行退火。通过红外光谱仪测试了薄膜的透射率变化，采用光谱反演法得到了薄膜折射率和消光系数的变化规律，使用X射线衍射和原子力显微镜测试了样品的结晶特性和表面形貌。结果表明，与退火前的薄膜各项参数相比，退火后薄膜的透射率升高，而折射率和消光系数下降。当退火温度从350 ℃升高到500 ℃，透射率和折射率均逐渐减小，而消光系数逐渐变大。在400 ℃以上进行退火处理的薄膜出现结晶现象，Ge(111)晶面为择优生长取向。随着退火温度的升高，晶粒尺寸变大，薄膜表面出现颗粒状物质，并且表面粗糙度升高。

Abstract:

The influence of annealing temperature on optical properties and surface structure of Ge films prepared by electron beam evaporation was investigated. Ge films with a thickness of about 850 nm were prepared on silicon substrate and annealed at 350, 400, 450, and 500 °C. The transmittance of the film was measured by infrared spectrometer. The variation of refractive index and extinction coefficient of thin films was obtained by spectral inversion method. The crystal properties and surface morphology of the specimens were analyzed by X-ray diffraction and atomic force microscope. Results show that compared with the properties of films before annealing, the transmittance of films after annealing is increased, while the refractive index and extinction coefficient become decreased. When the annealing temperature increases from 350 °C to 500 °C, the transmittance and refractive index gradually decrease, while the extinction coefficient gradually increases. Crystallization occurs in the films after annealing above 400 °C and the Ge(111) crystal plane is the preferred growth orientation. With increasing the annealing temperature, the grain size becomes larger, the granular particles appear on the film surface, and the surface roughness is increased.