Thermal Strain of In films deposited onto Si and GaAs Substrates

研究了在300k和77k温度下沉积在Si和GaAs衬底上的in薄膜的热应变，然后冷却到低至20k。利用x射线衍射技术测量了in、Si和GaAs的热膨胀差异引起的in中的应变。此外，20k时的应变大小与使用双轴应变模型的热膨胀系数差计算的应变值接近。对于In薄膜，在计算中考虑了热膨胀系数和杨氏模量的晶体各向异性。在10^<-7> ~ ^<-6>真空蒸发条件下，In薄膜表面形貌由岛状变为连续状。在真空室中对铟进行预蒸发，得到连续膜。因此，膜形态的变化似乎是由真空室中的氧气浓度引起的。In薄膜的厚度为100 ~ 140 nm。由于In薄膜的热膨胀系数大于Si和GaAs衬底的热膨胀系数，当温度降至室温至20k时，在薄膜的垂直方向上产生压应变。测量和计算的应变值对晶体取向有很强的依赖性。（001）取向晶粒获得了-1.0%的大菌株，（111）、（001）和（313）取向晶粒获得了-0.6%的小菌株。实测应变值与计算应变值对晶粒取向的依赖性较好。虽然随着薄膜厚度的减小和薄膜的连续性，测量应变值有所增加，但测量应变值仅达到计算期望应变值的-70%。这意味着薄膜由于塑性变形而发生松弛。

An investigation has been carried out of the thermal strain in In films deposited onto Si and GaAs substrates at 300k and 77k and then cooled down to temperatures as low as 20k. The strain in the In caused by differences in thermal expansion of In, and Si and GaAs was measured using X-ray diffraction techniques. Also the magnitude of the strain at 20k was found to approximate the strain value calculated from the difference in the thermal expansion coefficients using the biaxial strain model. For the In films, the crystallographic anisotropy both of the thermal expansion coefficient and Young's modulus was considered in calculations. The surface morphologies of In films evaporated in a vacuum of 10^<-7>-^<-6>were changed from island to continuous structures. The continuous films were obtained after that pre-evaporation of In was carried out in a vacuum chamber. Therefore, the change of film morphologies appeared to be caused by the oxygen concentration in the vacuum chamber. The thicknesses if In films were 100 to 140 nm. Since the thermal expansion coefficient of In film was greater than that of Si and GaAs substrates, compressive strain in the vertical direction of film was occurred according as the temperature was down room temperature to 20k. The measured and calculated strain values have a strong dependence on the crystal orientations. A large strain of -1.0%was obtained for (001) oriented grain and small strains of -0.6%were (111), (001) and (313) oriented grains. The dependence on the grain orientation of measured strain values was well agree with calculated strain values. Although the measured strain value were increased as the thickness of films decreased and films were more continuous, the measured strain values merely reached to -70%of the strain values expected by calculation. This mean that the film occurred the relaxation by plastic deformations.