Study on the effect of streak defects on properties of CVD ZnS

Chemical vapor deposition of ZnS(CVD ZnS) inevitably suffers from-streaking defects after hot isostatic pressing(HIPping) and annealing treatment. The effect of streak defects on the optical and thermodynamic properties of the materials was investigated by XRD, transmittance analysis and thermodynamic property tests. The results show that the streak defects are caused by the metal catalyst introduced in HIPping, and annealing treatments can aggravate the streak defects and make them difficult to eliminate. The presence of hexagonal phase structure (100) in streak defects disrupts the optical homogeneity of the crystal and causes scattering of the incident light beam. In the long infrared band, the region with streak defects has 0.05%–0.6% lower transmittance than the normal region; in the mid-infrared band, the region with streak defects has 0.1%–1.1% lower transmittance than the normal region; in the visible band, the region with streak defects has about 1.2% lower transmittance than the normal region. Most of the streak defects exist on the surface of the material, resulting in non-uniform grain size, which will affect the grain uniformity, and then affect the mechanical properties of the material. The thermal expansion coefficient of the streak-defective layer is significantly different from the normal region with values of 6.61/10 −6 °C −1 -6.83/10 −6 °C −1 , which is strongly related to the hexagonal phase structure (100) and grain size. Streak defects can be eliminated by removing the streak layer. • Streaking defects are caused by the introduction of metal catalysts during HIPping treatment. • Streak defects have a non-uniform grain size distribution and contain more hexagonal phase structure (100). • Streak defects can destroy the optical uniformity of the crystal and cause scattering of the incident beam.