Growing crystals and studying structure and electronic properties of Cu₂ZnGe(SSe_1-x)₄ compositions

Single crystals of Cu2ZnGeSe4 and Cu2ZnGeS4 solid solutions were developed and successfully obtained using the chemical vapor transfer method, with iodine acting as a transporter. The structure, compositional dependences of lattice parameters, pycnometric and X-ray densities and microhardness were determined. The chemical composition determined by the X-ray microanalysis satisfactorily corresponds to the nominal one with a tolerance of +/- 5 %. The XRD analysis showed that all the obtained compounds and their solid solutions have unit cell described by tetragonal symmetry. The attice parameters were found to be & acy; = 5.342 +/- 0.005 & Aring;, & scy; = 10.51 +/- 0.01 & Aring; for the & Scy;u(2)ZnGeS(4) compound and & acy; = 5.607 +/- 0.005 & Aring;, & scy; = 11.04 +/- 0.01 & Aring; for the Cu2ZnGeSe4, respectively. Structural studies confirmed the validity of the Vegard's law in relation to the obtained samples. The pycnometric densities of similar to 4.28 g/cm(3) for the Cu2ZnGeS4 and similar to 5.46 g/cm(3) for the Cu2ZnGeSe4 were found to be slightly less than their X-ray densities of similar to 4.32 g/cm(3) and similar to 5.52 g/cm(3), respectively. The maximum microhardness of similar to 398 kg/mm(2) for these solid solutions corresponds to x = 0.60. The melt point of the solid solutions increases from similar to 1180 degrees C for the & Scy;u(2)ZnGeSe(4) up to similar to 1400 degrees C for the & Scy;u(2)ZnGeS(4). Based on X-ray fluorescence analysis and DTA data, the phase diagram of the Cu2ZnGeSe4-Cu2ZnGeS4 system was constructed. Analysis of the obtained diagram indicates its first type according to Rozbom's classification.