Physical vapor transport and crystal growth of GeSe_xTe_1−x solid solutions

Abstract

Physical vapor transport studies of GeSexTe1–x (x = 0.1, 0.2, 0.3, and 0.4) solid solutions demonstrated, that individual, large single crystals of these materials can be grown in closed ampoules. A compositional analysis of the grown crystals revealed, that the mass transport (crystal growth) process under steady‐state conditions is pseudo‐congruent and controlled by diffusion processes in the source material. From these experiments, the degree of nonstoichiometry (Ge‐vacancy concentrations) of GeSexTe1–x single crystals could be estimated. The effects of the cubic to rhombohedral phase transformation during cooling on the microstructure and morphology of the grown mixed crystals are observed. This work provides the basis for subsequent defect studies and electrical measurements on these crystals.

Chemical Vapour Transport of Bismuth and Antimony Chalcogenides M2Q3 (M = Sb, Bi, Q = Se, Te)

“…The enthalpy of formation results in evaluation of the function of equilibrium constant (14). The entropy is concluded from the gas phase equilibrium (15). The obtained value is well consistent with pertinent standard entropies of similar species: S 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 …”

Electrophysical properties of GeSexTe1−x single crystals grown by physical vapor transport (PVT)

“…All singlc crystals grown by thc PVT method display a n octahedral growth habit and wcll developed (1 11) oriented planes. The details of crystal growth have been described earlier [3]. The composition ot thc bulk single crystals was determined by lattice paramelet measurements based on Dcbye-Scherrer X-ray diffraction tcchniques.…”

“…An incrcase in Se content leads to an increase in the thcrmopower and to a decrease in the elcctrical conductivity and Hall mobility for the GeSe,Te,-, alloyh in the range The growth of large single crystals of GeSe,Te,-, (x = 0.1 -0.4) by PVT [3] provides an opportunity to study thc electrophysical propertics of the single crystals. This work is concerned with an investgation of the composition dependcnces of the lattice parameter, mass density, thermopower, Hall constant, and carricr mobility of GeSe,Te, --y single crystals.…”

Defect Morphology of GeSexTe1−x Single Crystals grown by physical vapor transport

“…The crystal growth experiments were performed in the same ampoule using a growth temperature of 590 "C and temperature differences of 10-15 "C between the source and growth region. Further details of the growth of a single large crystal in an ampoule, of the ampoule pretreatment, and of the temperature profile employed for this purpose have been discussed earlier [3]. After growth, the crystals in the ampoules were either passively cooled to room temperature in the furnace by turning off the power or were quenched in air by removing the growth ampoules from the furnace.…”

“…At higher temperatures, a more progressive increase was observed as a approaches 90" of the cubic phase. The influence of the Se content on the mass transport properties of these solid solutions has been observed during the growth of mixed crystals of these materials by physical vapor transport [3]. An investigation of the electronic properties and valence band structure of GeSe,Te,, single crystals [4] shows an increase in the valence band splitting and a decrease of the carrier density with increasing Se content of the mixed crystals.…”