Progress in preparation of 2D atomic crystal materials
Xu Hua, associate professor of Shaanxi Normal University's School of Materials Science and Engineering, has led his team to make major progress in the preparation of 2D atomic crystal materials.
Materials are the core of semiconductor chip. As Silicon chip has been developed to the limits, developing new types of semiconductor materials to replace the traditional silicon-based semiconductors is expected to create the next myth of the semiconductor chip development.
Two-dimensional (2D) atomic crystal is a new type semiconductor material, which has excellent optical and electrical properties. The material can be prepared into smaller size and higher performance electronic components and is expected to be the core materials of the next generation chip.
Disulfide rhenium (ReS2) is one of the very important 2D materials. The low lattice symmetry endows it unique 2D in-plane anisotropy optical and electrical properties, which make it possible for promising application in future electronic devices. However, the variable-valence state Re oxide as precursor to synthesize ReS2 always suffers from low crystal quality, while the high-melting point Re powder (3180 °C) as precursor inevitably brings about low growth efficiency. In addition, the distorted 1T structure and the interlayer decoupling of ReS2 make it prefer to grow into dendritic structure and thick flakes. All these problems pose great challenge to the controllable synthesis of ReS2 materials.
Recently, Xu Hua, associate professor of Shaanxi Normal University's School of Materials Science and Engineering, working with students Cui Fangfang, Li Xiaobo and Wang Cong, has overcome these problems.
Based on the intensive study of the problems and challenges in the preparation of ReS2, Xu's team has developed a eutectic-assisted epitaxial growth method to synthesize ReS2. Benefiting from the lower eutectic temperature of Re-Te binary alloy, they have grown large-area, highly crystalline ReS2 with uniform monolayer thickness on mica substrate. Moreover, their study of temperature dependent growth behavior of ReS2 indicates a specially off-symmetry growth mode of ReS2, which is significant for guiding the growth of the lower lattice symmetry 2D materials.
Angle-resolved polarized Raman spectroscopy and angle-dependent electrical measurements demonstrate superior anisotropic optical and electrical properties of the CVD-grown ReS2. In addition, the ReS2 filed-effect transistor displays n-type conduction with mobility up to 4.1 cm2V−1s−1 measured under ambient condition. This work not only promotes the large-scale application of ReS2 in high performance electronic devices, but also opens up new avenues for the synthesis of the materials where high-melting point precursor is required.
The research was recently published under the title “Tellurium-Assisted Epitaxial Growth of Large-Area, Highly Crystalline ReS2 Atomic Layers on Mica Substrate” in the Advanced Materials (Impact Factor: 17.493) (Advanced Materials, 2016, DOI: 10.1002/adma.201600722).