纳米尺度砷化硼的超大拉伸弹性

Significant tensile elasticity of nanoscale boron arsenide

砷化硼(BAs)是一种具有超高热导率的半导体,未来集成到功能器件会不可避免地承受外部应力,因此对BAs弹性和强度的研究非常紧迫.在这项工作中,我们从BAs单晶中制备了长度为1–3μm,宽度为100–300 nm的BAs纳米桥,并沿着[100],[101]和[111]取向进行了原位单轴拉伸试验.试验结果表明,BAs单晶纳米桥的拉伸弹性具有明显的取向依赖性,其中[100]取向纳米桥的拉伸应变高达9%,相应拉伸强度高达34.8 GPa.另外,我们从理论上探讨了拉伸应变对BAs电子结构和热输运的影响.结果表明,随着应变的增加,BAs的带隙会减小,晶格热导率显著降低.其中,若沿[111]方向发生12%的拉伸应变,BAs将由间接带隙转变为直接带隙半导体;而在相同应变量下,沿[100]方向的拉伸应变对BAs热导率的影响要显著低于[101]和[111]方向.这些发现为BAs的能带调控和热管理提供了重要的启示,如在实际器件中可通过“应变工程”实现BAs电和热的调控.

Different from the commonly accepted criteria,cubic boron arsenide(BAs)with the zincblende structure was theoretically predicted to have a remarkable lattice thermal conductivity(κ)of 1260–2240 W m^(−1)K^(−1)[1,2],which was verified later experimentally with a value of 1000–1300 W m^(−1)K^(−1)at room temperature[3–5].Note that,unlike traditional high-thermalconductivity materials that typically are either insulator or conductor(e.g.,diamond,boron nitride,and copper),BAs is a semiconductor with a band gap of ca.2.0 eV[6–9]and surprisingly exhibits simultaneously high electron and hole mobility(1600 cm^(2)V^(−1)s^(−1)for electron-hole pairs)at room temperature[10,11].Such excellent thermal and electrical properties are highly desired for improving the thermal management and extending the roadmap of electronics,making BAs appealing as a next-generation semiconductor.However,characterization of the fundamental properties and identification of effective methods to tune the properties remain inadequate for this promising material,due to limited access to high-quality BAs single crystals only available very recently.