The effect of X-ray irradiation on formation and decay of the incommensurate phase in TlInS sub(2) crystals

The influence of the X-ray irradiation on the crystal structure of TlInS sub(2) C and 2C polytypes were studied by single-crystal X-ray diffraction method. The scanning of the reciprocal space in the planes (0kl)*, (h0l)*, (hhl)* were carried out for initial and irradiated samples (absorbed doses are 0.9 and 2.9kGy) in the temperature range 180-300K. It was found that after irradiation, the incommensurate phase satellites q(- delta , 0, +0.25) and q(+ delta , 0, -0.25) ( delta =0.04) were observed even at room temperature in the C-TlInS sub(2) samples. Their intensities vary in direct proportion to the dose and significantly differ from each other. The 10h annealing at 430K completely destroyed these incommensurate structures. The temperature dependences of the incommensurate and commensurate phases volume fractions were obtained for unirradiated, irradiated, and annealed C-TlInS sub(2) samples. The modulation satellites of the incommensurate and commensurate phases were not observed in the temperature range of 180-300K in the irradiated as well as unirradiated samples of the 2C-polytype TlInS sub(2). The role of defect density waves in the formation of the modulated structures in the irradiated TlInS sub(2) crystals is discussed.