Electronic properties of polymorphic two-dimensional layered chromium disulphide

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) Cr-based materials are promising for spintronics.
• Theoretical studies suggest 2D chromium disulfide (CrS2) possesses unique magnetic and electronic properties.
• Experimental synthesis and characterization of 2D CrS2, especially monolayer, remain limited.

Purpose of the Study:

• To report the first synthesis of 2D layered CrS2 flakes down to the monolayer using chemical vapor deposition (CVD).
• To investigate the phase structures and electronic properties of synthesized monolayer CrS2.
• To explore the potential applications of 2D CrS2 in nanoelectronics, valleytronics, and spintronics.

Main Methods:

• Chemical vapor deposition (CVD) for synthesizing 2D CrS2 flakes.
• Experimental characterization of phase structures and electronic properties.
• Density Functional Theory (DFT) calculations (PBE and DFT+U) and molecular dynamics simulations for theoretical analysis.

Main Results:

• Successful synthesis of 2D layered CrS2 flakes, including monolayer, via CVD.
• Observation of coexisting 2H, 1T, and 1T' phases in monolayer CrS2, with 1T' phase formation from 1T via metal atom dimerization.
• Theoretical prediction of 2H-CrS2 as a direct bandgap semiconductor (0.95 eV), and 1T/1T'-CrS2 as metallic/semi-metallic, with distinct magnetic properties for different phases and spin configurations.

Conclusions:

• The synthesis of multifunctional 2D CrS2 opens new avenues for advanced electronic and spintronic applications.
• The coexistence of multiple phases (2H, 1T, 1T') in monolayer CrS2, termed '1T and 1T' puddling phenomenon', offers tunable electronic and magnetic properties.
• CrS2-based field-effect transistors demonstrate p-type behavior, highlighting their potential in device fabrication.