Abstract
The electronic properties of single-layer make it an ideal two-dimensional (2D) material for application in electronic devices. Experiments show that can undergo structural phase transitions. Applications of single-layer will require firm laboratory control over the phase formation. Here we compare the stability and electronic structure of the three experimentally observed single-layer phases, , and , and an in-plane metal/semiconductor heterostructure. We reveal by density-functional theory calculations that charge doping can induce the phase transition of single-layer from the to the structure. Further, the structure undergoes a second phase transition due to the occurrence of a charge-density wave (CDW). By comparing the energies of several possible resulting CDW structures, we find that the orthorhombic structure is the most stable one, consistent with experimental observations and previous theoretical studies. We show that the underlying CDW transition mechanism is not due to Fermi surface nesting, but nonetheless, can be controlled by charge doping. In addition, the stability landscape is highly sensitive to charge doping, which can be used as a practical phase selector. We also provide a prescription for obtaining the structure via growth or deposition of on a Hf substrate, which transfers electrons uniformly and with minimal structural distortion. Finally, we show that lateral heterostructures formed by the and structures exhibit a low interfacial energy of 0.17 eV/Å, a small Schottky barrier of 0.3 eV for holes, and a large barrier of 1.6 eV for electrons.
1 More- Received 3 April 2017
- Revised 8 August 2017
DOI:https://doi.org/10.1103/PhysRevB.96.165305
©2017 American Physical Society