Mechanical and electrical properties of borophene and its band structure modulation via strain and electric fields: a first-principles study

The basic electronic and mechanical properties of 2-Pmmn borophene and their strain and electric field-dependence are studied by the first-principles calculations. The Young's moduli are 236 and 89 GPa in the armchair and zigzag directions, respectively, indicating that the borophene has giant mechanical anisotropy. We also find that the borophene presents anisotropic electronic properties. The borophene is electroconductive in armchair direction but has a bandgap in the zigzag direction. To modulate the band structure, we applied strain and electric fields on borophene, and find that, the resistance of borophene decreases with the increase of applied strain, while the applied electric field has almost no effect on its band structure. The enhanced conductivity of borophene upon applied strain is ascribed to the expansion of the buckled structure through the analysis of the charge density of the strained borophene.