SnxPy Monolayers: a New Type of Two-Dimensional Materials with High Stability, Carrier Mobility, and Magnetic Properties

Growth, Raman Scattering Investigation and Photodetector Properties of 2D SnP

As an important metal phosphides material, 2D tin phosphides (SnP_x 0 <  x ≤ 3) have been theoretically predicted to have intriguing physicochemical properties and potential applications in electronics, optoelectronics, and energy fields. However, the synthesis of high-quality 2D SnP single crystal has not been reported due to the lack of efficiency and reliable growth method. Here, a facile atmospheric pressure chemical vapor deposition (APCVD) method is developed to realize the growth of high-quality 2D SnP nanosheets, by employing tin (Sn) foil as both liquid metal substrates and reaction precursor. Temperature-dependent and angle-resolved polarization Raman spectra observed Raman peaks located at 142.6, 303.3, and 444.2 cm^-1 are concluded to belong to A_1g mode, which are consistent with the theoretical calculation results. Moreover, the field-effect transistor (FET) devices based on SnP nanosheets show a typical n-type characteristic with an on/off ratio of 10³ at 200 K. SnP nanosheets also demonstrate excellent photoresponse performance under the illumination of 473, 532, and 639 nm lasers, which can be tuned by V_gs , V_ds , and light power density. It is believed that these findings can provide the first-hand experimental information for the future study of 2D SnP nanosheets.

Structural, Electronic, and Optical Properties of Hexagonal XC6 (X=N, P, As, and Sb) Monolayers

Based on first-principles calculations, a novel family of two-dimensional (2D) IV-V compounds, XC₆ (X=N, P, As and Sb), is proposed. These compounds exhibit excellent stability, as determined from the cohesive energies, phonon dispersion analysis, ab initio molecular dynamics (AIMD) simulations, and mechanical properties. In this type of structure, the carbon atom is sp² hybridized, whereas the X (N, P, As and Sb) atom is nonplanar sp³ hybridized with one 2p_z orbital filled with lone pair electrons. NC₆ , PC₆ , AsC₆ and SbC₆ monolayers are intrinsic indirect semiconductors with wide bandgaps of 2.02, 2.36, 2.77, and 2.85 eV (based on HSE06 calculations), respectively. After applying mechanical strain, PC₆ , AsC₆ and SbC₆ monolayers can be transformed from indirect to direct semiconductors. The appropriate bandgaps and well-located band edge positions make XC₆ monolayers potential materials for photocatalytic water splitting. XC₆ family members also have high absorption coefficients (∼10⁵  cm^-1 ) in the ultraviolet region and higher electron mobilities (∼10³  cm²  V^-1  s^-1 ) than many known 2D semiconductors.