Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
Nanoscale. 2019 Nov 21;11(45):21775-21781. doi: 10.1039/c9nr05660b.
Tailoring the electronic anisotropy of two-dimensional (2D) semiconductors with strain-engineering is critical in nanoelectronics. Recently, 2D tellurene has been predicted theoretically and fabricated experimentally. It has potential applications in nanoelectronics, in particular, β-phase tellurene (β-Te) shows a desirable direct band gap (1.47 eV), high carrier mobility (2.58 × 103 cm2 V-1 s-1) and high stability under ambient conditions. In this work, we demonstrated, with first-principles density functional theory calculations, that the highly anisotropic electron mobility and electrical conductance of β-Te can be controlled by strain-engineering. The direction of electrical conductance of β-Te can be changed from the armchair to the zigzag direction at the strain between -1% and 0%. Meanwhile, we found that the bandgap of β-Te under strain experiences an indirect-direct transition with a conduction band minimum (CBM) shift from the X to Γ point. The significant dispersion of the bottom of the conduction bands along the Γ-Y direction switches to the X-Γ direction under uniaxial or biaxial strain which makes the rotation of the effective masses tensor. The qualitative rotation of the spatial anisotropic electron effective masses tensor by 90° also rotates the direction of the electrical conduction as the carrier mobility is inversely dependent on the effective masses. On the another hand, we also found that the deformation potential constant also plays an important role in the rotation of electrical conductance anisotropy. While anisotropic conductance of hole is impregnable under strain. In order to verify that β-Te can sustain large strain, we studied its stability and mechanical properties and found that β-Te shows superior mechanical flexibility with a small Young's modulus (27.46 GPa (armchair)-61.99 GPa (zigzag)) and large anisotropic strain-stress (12.89 N m-1 at the strain of 38% along armchair direction and 25.72 N m-1 at the strain of 26% along zigzag direction). The high anisotropic carrier mobility and superior mechanical flexibility of β-Te make it a promising candidate for flexible nanoelectronics.
通过应变工程来调整二维（2D）半导体的电子各向异性在纳米电子学中至关重要。最近，二维碲烯已在理论上被预测，并在实验中被制造出来。它在纳米电子学中有潜在的应用，特别是β相碲烯（β-Te）具有理想的直接带隙（1.47 eV）、高载流子迁移率（2.58×103 cm2 V-1 s-1）和在环境条件下的高稳定性。在这项工作中，我们通过第一性原理密度泛函理论计算表明，应变工程可以控制β-Te 的高各向异性电子迁移率和电导率。β-Te 的电导方向可以在-1%到 0%的应变范围内从扶手椅方向变为锯齿形方向。同时，我们发现，应变下的β-Te 带隙经历了从间接到直接的转变，导带底（CBM）从 X 点移到Γ点。沿Γ-Y 方向的底部导带的显著色散在单轴或双轴应变下切换到 X-Γ 方向，这使得有效质量张量发生旋转。有效质量张量的空间各向异性电子的旋转90°也会旋转电导率的方向，因为载流子迁移率与有效质量成反比。另一方面，我们还发现，形变势常数在电导率各向异性的旋转中也起着重要作用。而在应变下，空穴的各向异性电导是不可渗透的。为了验证β-Te 可以承受大应变，我们研究了它的稳定性和机械性能，发现β-Te 具有优异的机械灵活性，杨氏模量较小（扶手椅方向为 27.46 GPa（扶手椅）-61.99 GPa（锯齿形）），各向异性应变-应力较大（沿扶手椅方向应变 38%时为 12.89 N m-1，沿锯齿形方向应变 26%时为 25.72 N m-1）。β-Te 的高各向异性载流子迁移率和优异的机械灵活性使其成为柔性纳米电子学的有前途的候选材料。
