The future of information technology requires low-power, high-performance transistors, the future semiconductor technology roadmap depicts the future of the transistor channel length of less than 10 nanometers.In recent years, one of the research hot spots two-dimensional (2D) atomic crystal materials compared with traditional semiconductor materials, Has the advantages of small scattering, high mobility, easy preparation of stacked heterostructures and easy regulation of electrical properties, and has become one of excellent candidate materials for making future transistors In the two-dimensional atomic crystal materials that have been discovered, The single-layer materials of group IV elements such as graphene, silsesquioxane, germylene, and tin diene have high carrier mobility, but their band gap is zero or approaches zero, limiting their use in field effect transistors Application prospects in other electronic devices.
In contrast, layered materials composed of Group V elements in the periodic table, such as black phosphorus, have a large band gap and high carrier mobility, etc. However, black phosphorus is unstable under atmospheric conditions , The applicability of the device made from it has been limited.A recent study by monolayer antimonene, a group V antimony element, has led to the theoretical prediction that the bandgap of stibine varies with layer thickness , Especially for monolayers of antimony, theoretically predicted to have a bandgap of 2.28 eV. Meanwhile, antimony has a higher charge carrier mobility than graphene.Based on these characteristics, antimony is widely used in related electronic devices and There are potential applications in the field of optoelectronic devices.Therefore, how to obtain the growth of this material, especially the high-quality monolayer antimony, has attracted much attention.
Chinese Academy of Sciences, Chinese Academy of Sciences Institute of Physics / Beijing Condensed Matter Physics National Research Center researcher led by Gao Hongjun research team, for many years committed to the preparation of new two-dimensional crystal materials, physical properties and application of basic research has made a series of research achievements.Recently, The group of PhD students Wu Xu, Shao Yan and researcher Wang Ye-liang, etc., prepared a single layer of stirene, and its structure and properties were studied in the photoelectron spectroscopy, the research team and Beijing Synchrotron Radiation Center, Wang Jiou cooperation; in theoretical calculations, they associate with the Institute of Physics and other disciplines such as Sun Jiatao; the use of two telluride palladium (PdTe2) single crystal substrate by the physical researcher Shi Youguo provided.
In the design of the specific experimental scheme, researchers consider that the surface of the layered transition metal disulfide family (TMD) PdTe2 is chemically stable with a hexagonal symmetry, lattice period (4.10 Å) and antimony single crystal The periodicity (4.12 Å) lattice matching in the layer is only 2.3% more than the theoretically predicted monolayer antimony (period 4.01 Å). Therefore, they chose PdTe2 as the substrate and utilized molecular beam epitaxy Method to obtain high-quality monolayer antimony.The fine atomic arrangement structure of monolayer antimony was studied by means of low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) Can clearly distinguish the antimony atoms formed a hexagonal honeycomb structure, is stirene; LEED experiments show that they have obtained a large area, high-quality antimony single crystal (Figure 1). Combined with X-ray photoelectron spectroscopy experiments and electronic bureau The theoretical calculation results of the domain function reveal that the local electronic states between the monolayer antimony and the substrate are very few with only weak van der Waals interactions (Figure 2 and Figure 3). Further STM and XPS experimental observations show that ( Figure 4), a single layer of antimony Ethylene in the air with high chemical stability, exposure to air is not oxidized, this feature is further important antimony metal for practical applications.
The work provides a method for preparing high-quality monolayer antimony, and also provides a new idea for preparing a two-dimensional material heterostructure with an atomically flat interface by directly using a TMD material as a substrate for epitaxial growth of a monolayer Two-dimensional atomic crystal materials provide a valuable reference for the study of two-dimensional material heterojunction devices.At the same time, stirene as a new type of two-dimensional atomic crystal materials graphene-like structure, expanding non-carbon-based two-dimensional honeycomb crystals Materials research field, and it has wide band gap, high mobility characteristics, stable in the atmosphere, the future of electronic devices has potential applications.
Relevant results have been published in Advanced Materials, which won the support of NSFC, MOST and CAS.
(A), a wide range of STM images and LEED diffraction spots (b), atomic resolution STM (c) and the corresponding lateral cross-section of the diagram (e, f), and atomic structure top and side views (d).
Figure 2. The atomic structure model (a, d), the corresponding STM simulation image (b), the experimental image (c), the top view and the echelon image (e, f) of the electronic local function of Pd on the surface of PdTe2.
XPS measurements (a, b) of Pd and Te elements before and after the monolayer of antimony was grown on the surface of the PdTe 2 substrate. XPS measurements of Sb element in the monolayer antimony (c) showed that the substrate and the monolayer antimony There is almost no charge transfer between.
Figure 4. Chemical stability of monolayers of antimony enamel The combined experiments of STM (a, b, c) and XPS (d) show that monolayers of antimony do not change after exposure to air and exhibit excellent chemical stability.
