Peculiarities of linear thermal expansion of CuInS2 single crystal

Full text : I-III-VI2 chalcopyrire semiconductors have made rapid progress in recent years. In addition chalcopyrite semiconductors show unique thermal properties. Usually, liner thermal expansion in semiconductors increases with increasing temperature. However, liner thermal expansion of most chalcopyrite semiconductors decreases at low temperature. For example, AgGaSe2 shows decreasing the liner thermal expansion below 100 K1, 2). It is well known that high-quality single crystals of the I-III-VI2 compounds are difficult to grow because most of the compounds grow through a peritectic reaction or a solid state transition during the cooling process. CuInS2 single crystal can be grown by traveling heater method (THM), which is one of the solution growth techniques. Advantages of the THM growth are following that growth temperature is low compared with that of the other melt growth and larger crystals can be grown compared with a conventional solution growth. In a previous study, CuGaS2, CuGaSe2, CuGaTe2, CuInSe2 ternary compounds have been obtained by the THM technique. In this work, it is investigated a liner thermal expansion of single crystal CuInS2 by using X-ray diffraction. Measurement temperature was changed from 10 K to 300 K. From results of XRD measurement, it is calculated lattice constants of a and c axes and the liner thermal expansion. As a result, lattice constants of a axis increase with increasing temperature, that of c axis decreases with increasing temperature. The liner thermal expansion decreases for T < 150 K. It is shown experimentally anomalous behavior of CuInS2 single crystal at low temperature