Tungsten disulfide nanosheet (WS? nanosheet), as a typical transition metal sulfide material, is a semiconductor material with a hexagonal crystal structure (space group P6?/mmc). Each layer is a sandwich structure formed by a W atomic layer sandwiched between two S atomic layers. Research indicates that a single layer of WS? has a direct band gap of about 1.8eV, enabling it to exhibit a quantum efficiency superior to that of indirect-band-gap semiconductors in the optoelectronic device field. The room-temperature carrier mobility of a single-layer WS? nanosheet can reach 100-300cm2/V?s, and the electron concentration is approximately 1×1012cm?2, significantly outperforming traditional silicon-based materials. Notably, the electron mobility of WS? nanosheet shows obvious thickness dependence. For instance, the mobility of a 10-layer structure can drop to below 50cm2/V?s, closely related to the enhancement of interlayer phonon scattering.
The carrier mobility of WS? nanosheet is a key indicator for measuring its electrical properties. At room temperature, the carrier mobility of field-effect transistors (FETs) based on WS? nanosheet can reach 531.41cm2·V?1·s?1, close to the theoretical value. Additionally, WS? nanosheet has a small electron effective mass (0.738m?), facilitating the achievement of higher electron mobility.
The electrical properties of WS? nanosheet are closely associated with its number of layers. As the number of layers decreases, the quantum-confinement effect intensifies, leading to an increase in its band gap and substantial changes in electrical properties. For example, a single-layer tungsten disulfide nanosheet exhibits higher carrier mobility and switching ratio, while a multilayer structure is more suitable for applications demanding higher conductivity.
It is worth noting that WS? nanosheet is widely applied in the energy-storage field due to its excellent electrochemical properties, which can remarkably enhance the energy density of batteries. Moreover, the tungsten disulfide nanosheet also has good cycle stability and rate performance, endowing it with important application potential in high-performance battery-electrode materials.
