Anomalous vibrational properties of cubic boron arsenide

Abstract

BoronbasedIII-Vcompounds withzincblendelatticehavebeen best known for the excellent mechanical and thermalproperties of cubic boron nitride (c-BN). Cubic BN has thehighestsecondtodiamondhardnessandthermalconductivity,highbulkmodulus,alowfrictioncoefficient,andhighmeltingpoint [1]. Recently, BAs, another member of this family,is predicted to have thermal conductivity on par with thatof diamond [2]. This result is somewhat surprising for theseries c-BN, BP, BAs, and BSb, where the most importantproperties needed for an outstanding thermal conductivityvary in a way that BAs is not particularly distinguishable.The authors of Ref. [2] ascribe the diamondlike value ofthermalconductivitytoanadvantageouscombinationoflatticevibrationalpropertiesofBAsasalargefrequencygapbetweenoptical and acoustic modes, close packing (bunching) ofacoustic branches, and weak influence of isotopes on phononscattering. Cubic BAs, however, has been studied very little,andmanyofthecomputationallypredictedpropertiesstillneedto be tested experimentally.In this paper, we present a Raman study of the vibrationalproperties of BAs complemented with density-functionalperturbation theory (DFPT) lattice dynamics simulations. TheRamanspectraofBAspreparedwithnaturalisotopicabundantboron