Future information technology requires low-power, high-performance transistors, and the future semiconductor transistor roadmap described by the International Semiconductor Technology Roadmap is less than 10 nanometers in length. One of the research hotspots in recent years is that two-dimensional (2D) atomic crystal materials have the characteristics of small scattering, high mobility, easy fabrication of laminated heterostructures, and easy control of electrical properties, making it a transistor of the future. One of the best candidates. In the discovered two-dimensional atomic crystal material, single-layer materials composed of Group IV elements in the periodic table (for example, graphene, silylene, decene, and tinene, etc.) have high carrier mobility, but due to Band gap is zero or close to zero, limiting their application prospects in electronic devices such as field effect transistors. In contrast, a layered material composed of a group V element in the periodic table, such as black phosphorus, has a large bandgap and a high carrier mobility. However, black phosphorus is unstable under atmospheric conditions and the applicability of devices made from it is limited. Recently, the monolayer of terpenoids (antimonene) made up of Group V elements has attracted great interest from researchers. It has been predicted that the band gap of terpene changes with the change of the layer thickness, especially for monolayer terpenes, the theory predicts that the band gap is 2.28 eV. At the same time, terpenes have higher carrier mobility than graphene. Based on these characteristics, terpenes have potential application prospects in the fields of related electronic devices and optoelectronic devices. Therefore, how to obtain such materials, especially high-quality monolayer terpene growth, has attracted attention. The research team led by Academician of Chinese Academy of Sciences, Institute of Physics, Chinese Academy of Sciences / Researcher of National Center for Condensed Matter Physics, Gao Hongji, has devoted many years to research on the preparation, properties, and applications of new two-dimensional crystal materials, and has obtained a series of research results. Recently, the research team of doctoral students Wu Xu, Shao Yan and researcher Wang Yeliang, etc., prepared a monolayer of terpene, and its structure and characteristics were studied. In the area of ​​photoelectron spectroscopy, the research team cooperated with Wang Jiaou, an associate researcher at the Beijing Synchrotron Radiation Center; and in terms of theoretical calculations, they collaborated with Sun Jiatao, an associate researcher at the Institute of Physics, and used the PdTe2 single crystal liner. The bottom is provided by Shi Youguo, a researcher at the Institute of Physics. In the specific experimental design process, the researchers took into account the layered transition metal disulphide compound (abbreviated to TMD) PdTe2 surface chemical stability, and has six-sided symmetry, lattice period (4.10 Å) and single crystal The lattice period (4.12 Å) within the layer is lattice-matched, and the lattice mismatch of the monolayer terpene (period 4.01 Å) predicted by the theory is only 2.3%. Therefore, they used PdTe2 as a substrate and used molecular beam epitaxy to obtain a high-quality monolayer of terpene. The low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) techniques were used to study the fine atomic structure of the monolayers of terpenes grown. From the STM plot, it was possible to clearly identify the He atoms in the Hexagonal honeycomb. The structure is terpene; LEED experiments show that they obtained large-area, high-quality terpene monocrystals (Figure 1). Combining X-ray photoelectron spectroscopy experiments and electronic localization function calculation results, it is revealed that there are few local electronic states between monolayer terpenes and the substrate, and only weak van der Waals interactions (Fig. 2, Fig. 3). Further STM and XPS experimental observations have shown (Fig. 4) that monolayers of terpene have high chemical stability in air and are not oxidized after exposure to air. This characteristic is crucial for the further application of limonene to practical applications. This work provides a method for preparing a high-quality monolayer of terpene, and also provides a new idea for preparing a two-dimensional material heterostructure with an atomically flat interface, that is, using TMD material directly as a substrate to epitaxially grow a single layer. Two-dimensional atomic crystal materials provide a valuable reference for the study of two-dimensional material heterojunction devices. At the same time, terpene as a novel two-dimensional atomic crystal material with graphene-like structure expands the research field of non-carbon-based two-dimensional honeycomb crystal materials, and it has the characteristics of wide band gap and high mobility and is stable in the atmosphere. There are potential applications for future electronic devices. The related results were published on Advanced Materials. The study was supported by the National Natural Science Foundation of China, the Ministry of Science and Technology, and the Chinese Academy of Sciences. Figure 1. Epitaxially grown monolayers of terpene. PdTe2 surface growth monolayer terpene schematic diagram (a), wide-range STM image and LEED diffraction spot (b), atomic resolution STM diagram (c) and corresponding lateral section (e, f), and atomic structure top view Side view (d). Figure 2. Atomic structure model of a monolayer of terpene on the PdTe2 surface (a, d), corresponding STM simulated image (b), experimental image (c), top view of the electronic local function and section (e, f). Figure 3. XPS measurements of Pd and Te elements before and after growth of a monolayer of terpene on a PdTe2 substrate surface (a,b), XPS measurements of Sb elements in a monolayer of terpene (c), indicating substrate and monolayer of terpene There is almost no charge transfer between. Figure 4. Monolayer terpene chemical stability test. The combined experiments of STM (a,b,c) and XPS (d) showed that the monolayer of terpene did not change after exposure to air and showed excellent chemical stability.
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Progress in research on two-dimensional atom crystalline terpenes at the Institute of Physics