title: The impact of thickness and thermal annealing on refractive index for aluminum oxide thin films deposited by atomic layer deposition.
abstract: The aluminum oxide (Al2O3) thin films with various thicknesses under 50 nm were deposited by atomic layer deposition (ALD) on silicon substrate. The surface topography investigated by atomic force microscopy (AFM) revealed that the samples were smooth and crack-free. The ellipsometric spectra of Al2O3 thin films were measured and analyzed before and after annealing in nitrogen condition in the wavelength range from 250 to 1,000 nm, respectively. The refractive index of Al2O3 thin films was described by Cauchy model and the ellipsometric spectra data were fitted to a five-medium model consisting of Si substrate/SiO2 layer/Al2O3 layer/surface roughness/air ambient structure. It is found that the refractive index of Al2O3 thin films decrease with increasing film thickness and the changing trend revised after annealing. The phenomenon is believed to arise from the mechanical stress in ALD-Al2O3 thin films. A thickness transition is also found by transmission electron microscopy (TEM) and SE after 900°C annealing.
authors: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Department of Optical Science and Engineering, Laboratory of Micro and Nano Photonic Structures, Ministry of Education, Fudan University, Shanghai, 200433 China.
authors: Zi-Yi
authors: ZY
authors: Wang
authors: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Department of Optical Science and Engineering, Laboratory of Micro and Nano Photonic Structures, Ministry of Education, Fudan University, Shanghai, 200433 China.
authors: Rong-Jun
authors: RJ
authors: Zhang
authors: State Key Laboratory of ASIC & System, Fudan University, Shanghai, 200433 China.
authors: Hong-Liang
authors: HL
authors: Lu
authors: National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083 China.
authors: Xin
authors: X
authors: Chen
authors: National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083 China.
authors: Yan
authors: Y
authors: Sun
authors: National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083 China.
authors: Yun
authors: Y
authors: Zhang
authors: Key Laboratory of Infrared Image Materials and Devices, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, 200083 China.
authors: Yan-Feng
authors: YF
authors: Wei
authors: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Department of Optical Science and Engineering, Laboratory of Micro and Nano Photonic Structures, Ministry of Education, Fudan University, Shanghai, 200433 China.
authors: Ji-Ping
authors: JP
authors: Xu
authors: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Department of Optical Science and Engineering, Laboratory of Micro and Nano Photonic Structures, Ministry of Education, Fudan University, Shanghai, 200433 China.
authors: Song-You
authors: SY
authors: Wang
authors: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Department of Optical Science and Engineering, Laboratory of Micro and Nano Photonic Structures, Ministry of Education, Fudan University, Shanghai, 200433 China.
authors: Yu-Xiang
authors: YX
authors: Zheng
authors: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing, Department of Optical Science and Engineering, Laboratory of Micro and Nano Photonic Structures, Ministry of Education, Fudan University, Shanghai, 200433 China.
authors: Liang-Yao
authors: LY
authors: Chen
keywords: ALD; Al2O3 thin film; Optical properties; Spectroscopic ellipsometry