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Optical Properties of DLC-coated ZnS Substrates in the Mid-infrared Region

중적외선 영역의 DLC 코팅된 ZnS 기판의 광학 특성

  • Kwon, Tae-Hyeong (Electronic Material & Center, Korea Institute of Ceramic Engineering & Technology) ;
  • Yeo, Seo-Yeong (Electronic Material & Center, Korea Institute of Ceramic Engineering & Technology) ;
  • Kim, Chang-Il (Electronic Material & Center, Korea Institute of Ceramic Engineering & Technology) ;
  • Nahm, Sahn (Department of Materials Science and Engineering, Korea University) ;
  • Kwon, Min-Chul (UNIVAC LTD.) ;
  • Chu, Byoung-Uck (AVAS Co.) ;
  • Paik, Jong-Hoo (Electronic Material & Center, Korea Institute of Ceramic Engineering & Technology)
  • Received : 2019.02.08
  • Accepted : 2019.03.22
  • Published : 2019.03.31

Abstract

ZnS substrates with excellent transmittance in the mid-infrared region ($3-5{\mu}m$) were prepared using hot pressing instead of conventional chemical vapor deposition (CVD). Diamond-like carbon(DLC) was coated on either one or both sides of the ZnS substrates to improve their mechanical properties and transmittance. More specifically DLC was coated using CVD with an Ar and $C_2H_2$ mixed gas, and Ge was used as the bonding layer. During CVD, the bias voltage was fixed to 500 V and analyzed by Fourier transform infrared spectroscopy (FT-IR), nanoindenter, scanning electron microscope and energy dispersive spectrometry. Results of hardness analysis using the nanoindenter, showed that DLC coating increased from 5.9 to 17.7 GPa after deposition. The FT-IR spectroscopy results showed that, in the mid-infrared region ($3-5{\mu}m$), the average transmittance of the samples with DLC coating on one and both sides increased by approximately 6% and approximately 11.2% respectively. In conclusion, the DLC coating improved the durability and transmittance of the ZnS substrates.

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Fig. 1. Schematic diagram of the experimental process.

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Fig. 2. SEM images of the DLC coated ZnS substrate suface; (a) 420 nm, (b) 540 nm, (c) 650 nm, (d) 720 nm, (e) 850 nm of thickness (× 30k).

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Fig. 3. SEM images of the DLC coated ZnS substrate fracture; (a) 420 nm, (b) 540 nm, (c) 650 nm, (d) 720 nm, (e) 850 nm of thickness (× 30k).

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Fig. 4. EDS images of the DLC coated ZnS substrate fracture.

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Fig. 5. Nanoindenter load-displacement curves for uncoated ZnS substrate, single side DLC coated.

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Fig. 6. Infrared transmittance of single side DLC coated ZnS substrate various thickness.

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Fig. 7. Infrared transmittance of both sides DLC coated ZnS substrate various thickness.

Table 1. Transmittance of single side DLC coated ZnS substrate by thickness

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Table 2. Transmittance of both sides DLC coated ZnS substrate by thickness

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Acknowledgement

Grant : 스마트기기용 중적외선영역의 보급형 고분산성 TeO2계 광학 유리 및 저분산성 소결형 ZnS 광학 소재 개발

Supported by : 한국산업기술평가관리원

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