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Single crystals of intrinsic ZnSe were grown by the seeded physical vapor transport method and the diffusion doping was utilized to incorporate Cr in these crystals. The radiative recombinations in these samples with Cr concentration in the range 1.0–10.2×1019 cm−3 were studied by the steady state photoluminescence technique. It was found that the Cr deep centers inhibit the band-to-band emission in Cr-doped ZnSe. Except in undoped single crystals, no emission corresponding to the band-to-band transition was observed from any of the doped samples. Instead, the higher wavelength emissions associated with Cr deep levels were obtained. This capture of photoexcited carriers by deep centers was verified using different excitation wavelengths. The role of chromium impurities in nonradiative recombination processes was also evidenced from the sharp decreases in the deep level emission intensity with increasing Cr concentration.

Micro-Raman spectroscopy and x-ray diffraction measurements have been used to identify the presence of hexagonal diamond polytypes in chemical vapor deposited diamond films. The presence of additional reflections, in addition to the normal cubic diamond reflections in the diffraction spectra and bands at 1306 and 1193 cm−1 in the Raman spectra, are attributed to the presence of diamond 6H polytype. The presence of the 1324 cm−1 band in addition to the main diamond peak in the expanded spectra is attributed to regions with hexagonal symmetry, thus supporting the presence of hexagonal diamond polytypes. The compressive strain in diamond layers on the Si substrate is believed to create regions of hexagonal symmetry and vice versa.