Ren, Zhifeng2022-06-29May 20212021-05May 2021Portions of this document appear in: Sun, H.; Chen, K.; Gamage, G. A.; Ziyaee, H.; Wang, F.; Wang, Y.; Hadjiev, V. G.; Tian, F.; Chen, G.; Ren, Z., Boron isotope effect on the thermal conductivity of boron arsenide single crystals. Materials Today Physics 2019, 11 100169.https://hdl.handle.net/10657/10198With the rapid development of modern microelectronic devices, materials with high thermal conductivities are essential for effectively cooling high-power-density electronic and optoelectronic devices due to the smaller dimensions and compacting units. In principle, heat is transferred via conduction, convection and radiation, of which direct conduction is the easiest and most efficient way. Thus, finding suitable materials with ultrahigh isotropic thermal conductivity for heat dissipation in high-power-density electronic devices is imperative. Boron arsenide (BAs) with a zinc blende structure has recently been discovered to exhibit unusual and ultrahigh thermal conductivity of over 2000 W m-1 K-1 at room temperature by first-principles calculations, rendering it a close competitor for the diamond which holds the highest thermal conductivity among bulk materials, providing a new outlook for research on BAs and other high thermal conductivity materials. Technology for BAs crystal growth has been continuously improving, however, the influence of boron isotopes, pure or mixed, on the thermal conductivity in BAs is still not completely clear. Here we report detailed studies on the growth of single crystals of BAs with different isotopic ratios and demonstrate that the thermal conductivity of isotopically pure BAs is at least 10% higher than that of BAs grown from natural boron. We obtained the highest thermal conductivity of 1260 W m-1 K-1 for the 10BAs and 1180 W m-1 K-1 for the 11BAs. Raman spectroscopy characterization shows differences in scattering among various BAs samples and suggests good crystalline quality. The presented results will help to guide further studies on the influence of isotopes on optimizing thermal conductivity of BAs.application/pdfengThe author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. UH Libraries has secured permission to reproduce any and all previously published materials contained in the work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).CVTSemiconductorCrystal growth2022-06-29Thesisborn digital