X-ray powder diffraction studies of ordered vacancy compounds CuIn3Te5 and CuGa3Te5, prepared by the vertical Bridgman–Stockbarger technique, show that these materials exhibit a tetragonal chalcopyrite-related structure. The unit cell parameters a and c are, respectively, 6.1639(3) and 12.346(2) Å for CuIn3Te5, and 5.9321(8) and 11.825(4) Å for CuGa3Te5. From electrical resistivity characterization as a function of temperature a shallow acceptor level, with an activation energy lower than 30 meV, is found in both these compounds. Their direct energy gaps at room temperature are 1.013 and 1.092 eV for CuIn3Te5 and CuGa3Te5, respectively.
X-ray powder diffraction measurements and differential thermal analysis (DTA) were made on polycrystalline samples of the Cu 2 Cd 1−z Mn z GeSe 4 and Cu 2 Cd 1−z Fe z GeSe 4 alloy systems. The diffraction patterns were used to show the equilibrium conditions and to derive lattice parameter values. The effect of the annealing temperature and cooling rate to room temperature are discussed. For the Cu 2 Cd 1−z Fe z GeSe 4 system, only two single solid phase fields, the tetragonal stannite ␣ and the wurtz-stannite ␦ structures were found to occur in the diagram. For the Cu 2 Cd 1−z Mn z GeSe 4 system, in addition to the tetragonal stannite ␣ and the wurtz-stannite ␦ phases, MnSe was found to exist in the diagram. The DTA experiments showed that the cooling curves for both systems exhibited effects of undercooling.
A new method to grow single crystals with stoichiometry close to 1:1:2 of CuInTe 2 , an important member of the Cu-III-VI 2 family of semiconductors is described. This consists of tellurization in the liquid phase of stoichiometric Cu and In and later solidification under directional freezing. It is found from energy dispersive spectroscopy that the ingots obtained with the evaporation temperature (T t ) of Te at 590 and 635°C were very close to the ideal stoichiometry 1:1:2. Samples of all ingots obtained with T t between 530 and 690°C, as studied by xray and differential thermal analysis, were of single phase having chalcopyrite structure and p-type conductivity. Optical and electrical characterization of different ingots were made. The acceptor ionization energy E A and the density of states effective mass m p * of the holes are estimated from the temperature dependence of the hole concentration p in samples of different ingots. m p * = (0.78 ± 0.02) m e agrees quite well with the reported value. From a combined analysis of the variation of E A with p 1/3 and the knowledge of molecularity and valence stoichiometry of each sample, it is established that the shallow acceptor level observed in different samples with E A (0) − 30 meV is due to V In .
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