纳米尺度HfO_2薄膜不同厚度对光学性质的影响

Optical Properties Research of Nanoscale HfO_2 Thin Films with Different Thicknesses

Hf O_2薄膜厚度达到纳米级别时,其光学性质会发生变化。光谱椭偏仪能够同时得到纳米尺度薄膜的厚度和光学常数,但是由于测量参数的关联性,光学常数的结果不准确可靠。本文采用溯源至SI单位的掠入射X射线反射技术对纳米尺度Hf O_2薄膜厚度进行准确测量,再以该量值为准确薄膜厚度参考值。利用光谱椭偏仪测量Hf O_2膜厚和光学常数时,参考膜厚量值,从而得到对应相关膜厚的薄膜准确光学参数。研究了以Al2O_3作为薄膜缓冲层的名义值厚度分别为2,5,10 nm的超薄Hf O_2薄膜厚度对光学性质的影响。实验结果表明,随着Hf O_2薄膜厚度的增加,折射率也逐渐增大,在激光波长632.8 nm下其折射率分别为1.901,2.042,2.121,并且接近于体材料,而消光系数始终为0,表明纳米尺度Hf O_2薄膜在较宽的光谱范围内具有较好的增透作用,对光没有吸收。

When the thickness of HfO 2 film reaches nanometer level,its optical properties will change.The spectral ellipsometer can obtain the thickness and optical constant of the film at the same time.However,due to the relevance of the measurement parameters,the results of optical constants are not accurate and reliable.In this paper,the thickness of HfO 2 film is accurately measured by the grazing incidence X-ray reflex technique which can be traced to SI units.Then,the thickness of the HfO 2 film and the optical constant were measured by the spectral ellipsometer to obtain the accurate optical parameters of the film corresponding to the thickness of the film.The influence of the thickness of ultra-thin HfO 2 films with the nominal thickness of 2,5,10 nm on the optical properties was studied,using Al 2O 3 as the film buffer layer.The experimental results show that the refractive index increases with the increase of HfO 2 film thickness,but the refractive index is 1.901,2.042,2.121 at the laser wavelength,and is close to the bulk material,but the extinction coefficient is always zero.It is shown that the nanoscale HfO 2 thin films have a good effect on the broad spectrum and it does not absorb light.