Thermodynamic calculation and its experimental correlation with the growth process of boron arsenide single crystals

Abstract

The reported high thermal conductivity of boron arsenide (BAs) has prompted scientists to characterize the various properties of this material. Thermodynamic data for the enthalpy (H), entropy (S), and Gibbs free energy (G) of BAs were previously predicted from theory. Here, its thermodynamic properties were determined from experimental measurements of its heat capacity (CP) over the temperature range of 298 to 1150 K and compared with the predicted data. The thermodynamic properties of BAs at 800 K were calculated to be H=−8.6kJmol−1, S=81.0Jmol−1K−1, and G=−73.4kJmol−1, and we found that its formation reaction becomes endothermic at 984 K. We also analyzed the experimental findings from growing a BAs single crystal (SC) by the chemical vapor transport (CVT) method. Thermodynamic concepts were applied to show that iodine is the most suitable transport agent among the halogens for obtaining BAs SC by CVT. Additionally, three different combinations of precursors were employed during BAs SC growth by CVT. The three approaches are described in terms of differences in partial pressure of a gaseous species, and their results are compared for possible optimization of the BAs SC growth process by CVT.