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  • Received: Mar. 28, 2020

    Accepted: Jun. 1, 2020

    Posted: Jul. 30, 2020

    Published Online: Aug. 3, 2020

    The Author Email: Hongbo He (hbhe@siom.ac.cn)

    DOI: 10.3788/COL202018.103101

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    Meng Guo, Hongbo He, Kui Yi, Shuying Shao, Guohang Hu, Jianda Shao. Optical characteristics of ultrathin amorphous Ge films[J]. Chinese Optics Letters, 2020, 18(10): 103101

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Chinese Optics Letters, Vol. 18, Issue 10, 103101 (2020)

Optical characteristics of ultrathin amorphous Ge films

Meng Guo1,2,3, Hongbo He1,3,*, Kui Yi1,3, Shuying Shao1,3, Guohang Hu1,3, and Jianda Shao1,3,4

Author Affiliations

  • 1Laboratory of Thin Film Optics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
  • 2Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
  • 3Key Laboratory of Materials for High Power Laser, Chinese Academy of Sciences, Shanghai 201800, China
  • 4Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China

Abstract

Ultrathin Ge films with thickness of about 15 nm at different deposition temperatures were prepared by electron beam evaporation. Spectral measurement results showed that as the deposition temperature increased from 100°C to 300°C, the transmittance of the films in the wavelength range from 350 nm to 2100 nm decreased. After annealing in air at 500°C, the transmittance significantly increased and approached that of uncoated fused quartz. Based on the Tauc plot method and Mott–Davis–Paracrystalline model, the optical band gap of Ge films was calculated and interpreted. The difference in optical band gap reveals that the deposition temperature has an effect on the optical band gap before annealing, while having little effect on the optical band gap after annealing. Furthermore, due to oxidation of Ge films, the optical band gap was significantly increased to ~5.7 eV after annealing.

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