Thermodynamics of Boron Arsenide Crystal Growth and Characterizations



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Diamond has been known as the best material for conducting heat for decades, but it is scarce, and the synthetic production of diamond is very expensive, slow growth rates, and low quality and has a different thermal expansion rate when it is paired with a semiconductor device. Recently, cubic Boron Arsenide (c-BAs) has represented a new class of high thermal conductivity by both calculations and experimental efforts. Calculation shows the ultrahigh thermal conductivity value of 1400 W m-1 K-1 in BAs at room temperature which is the highest thermal conductivity among semiconductor materials. In this work, BAs single crystal growth with the optimization of chemical vapor transport (CVT) method has been studied and the grown crystals has shown the thermal conductivity value up to 1300 W m-1 K-1. The average lattice constant and density of BAs single crystal was also measured as 4.79 ± 0.01 Å and 5.182 (g cm-3), respectively. Moreover, 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 1200 K and compared with the predicted data. The thermodynamic properties of BAs at 800 K were calculated to be H =-8.6 kJ mol-1, S =81.0 J mol-1 K-1, and G =-73.4 kJ mol-1, and we found that its formation reaction becomes endothermic at 984 K. We also analyzed the experimental findings from growing BAs single crystals (SCs) 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 SCs 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 gaseous species, and their results are compared for possible optimization of the BAs SC growth process by CVT.



Boron Arsenide, BAs, CVT, Thermodynamics, High thermal conductivity, Semiconductors


Portions of this document appear in: Ziyaee, Hamidreza, Geethal Amila Gamage, Haoran Sun, Fei Tian, and Zhifeng Ren. "Thermodynamic calculation and its experimental correlation with the growth process of boron arsenide single crystals." Journal of Applied Physics 126, no. 15 (2019): 155108.