Search

CVD ZnS was prepared by chemical vapor deposition, and multispectral ZnS was obtained by hot isostatic pressing treatment. XRD, transmittance and bending strength were used to characterize the samples. The effects of CVD ZnS crisp layer on the optical and mechanical properties of materials before and after hot isostatic pressing were studied systematically. It was found that there were relatively few hexagonal phases in the standard ZnS crisp layer, with stress concentration, grain size significantly larger than the normal zone and the bending strength lower than the normal zone 10%. When the wavelength is less than 660 nm, the transmittance of the crisp layer can be higher than that of the normal region. When the wavelength is greater than 660 nm, the transmittance of the crisp layer is lower than that of the normal region, with a difference of 11% at 2 μm. The transmittance of the far-infrared region was basically same. After hot isostatic pressing treatment, the stress concentration in the crisp layer and the hexagonal phase of each layer was eliminated. The grain size tended to be uniform, but the bending strength of the crisp layer was still lower than that of the normal area 4%. The overall transmittance was significantly improved, and the transmittance of the crisp layer was higher than that of the normal area. The difference gradually decreased with the increase in wavelength, and the difference was 3% at 450 nm.

Abnormal large grains influencing highly the optical and electrical properties are commonly observed in the bottom part of CVD-ZnS layers. We have analyzed the films using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and infrared transmittance tests. Compared to normal grains, more homogeneous and simpler structures have been observed in abnormal large grains in CVD-ZnS. In addition to the obvious difference in sizes, the crystalline outline and interior structure of normal and abnormal large grains are found to be markedly different. Distorted structures and stacking faults, such as wurtzite phase and polytypes of ZnS, are not detected in the large grain areas. Preferred orientation of abnormal large grains is found to be sphalerite (1 1 1). These results could be explained as due to the recrystallization mechanism of abnormal large grains. Samples with large grains show lower infrared absorption band (at 6.2 µm wavelength) compared to samples with normal size grains. However, the infrared transmittance is found to be lower for the samples with large grains. Microstructure patterns show the presence of plenty of microdefects in boundaries between large grains, which indicates that the recrystallization in the volume with large grains is not as perfect as the recrystallization in hot isostatic pressure process (HIP).

In this paper, X-ray diffraction, selective area electron diffraction, and transmission electron microscope (TEM) were used to study the twins at different positions and textures in different direction in CVDZnS. It was found that the CVDZnS twin showed streaks under TEM. The narrower the streaks, the higher the content of twins, and the content of twins in CVDZnS normal layer was higher than that in bright layer. There are textures in CVDZnS, and the main texture of P surface (perpendicular to the direction of growth) is different from S surface (parallel to the growth direction of surface). The main texture in P is {010} 〈001〉, and the S is {101} 〈 $$\overline{1} \overline{3}$$ 1〉.

Chemical vapor-deposited zinc selenide samples were subjected to hot isostatic pressing (HIP) conditions in argon. X-ray diffraction, metalloscope, transmission spectra and so on were used to characterize the samples. The effects of HIP temperature (700 °C, 800 °C and 900 °C) and time (10 h, 20 h and 30 h) on the structure, microstructure and optical properties were studied. The results indicated that hot isostatic pressed (HIPed) ZnSe has recrystallized after HIP, the grain size increased significantly with the increase in HIP temperature, and the hot isostatic pressing eliminates the impurities in the material and makes the material evenly distributed. Both the samples HIPed at 900 °C for 10 h and HIPed at 800 °C for 30 h will result in the appearance of large grains; the samples HIPed at 800 °C for 20 h perform the best in transmission at same pressure (80 MPa).