Monolayer hexagonal boron nitride can serve in optoelectronics or as a dielectric in graphene and other two-dimensional (2D) electronics due to its ultra-wide band gap. As there is no center of symmetry, monolayer hexagonal boron nitride (h-BN) also shows piezoelectricity. However, these applications require h-BN to sustain large uniform elastic deformation, which has yet to be demonstrated. Here, we report, by tensile testing, that a large elastic strain up to 6.2% is achieved for defect-scarce polycrystalline h-BN monolayers, with corresponding 2D Young’s modulus ∼200 N/m, close to the ideal value measured by atomic force microscopy (AFM). Furthermore, samples containing voids of ∼100 nm can be strained up to 5.8%. Atomistic and continuum simulations show that compared to the imperfections introduced during sample preparation, the elastic limit of h-BN is virtually immune to naturally occurring atomistic defects and is gradually lowered by submicrometer voids. The mechanical robustness of h-BN monolayers, along with the large uniform elasticity, is encouraging for strain engineering and piezoelectronics applications.

单层六方氮化硼由于其超宽带隙，可以用于光电或石墨烯和其他二维（2D）电子中的电介质。由于没有对称中心，因此单层六方氮化硼（h-BN）也显示出压电性。但是，这些应用要求h-BN维持较大的均匀弹性变形，这尚待证明。在这里，我们通过拉伸测试报告，对于缺陷少的多晶h-BN单层，其弹性应变高达6.2％，对应的2D杨氏模量约为200 N / m，接近于通过原子力测得的理想值显微镜（AFM）。此外，包含约100 nm空隙的样品可以拉大至5.8％。原子模拟和连续模拟显示，与样品制备过程中引入的缺陷相比，h-BN的弹性极限实际上不受自然发生的原子缺陷的影响，并因亚微米空隙而逐渐降低。h-BN单层的机械坚固性以及较大的均匀弹性，对于应变工程和压电应用而言是令人鼓舞的。