| Metadata | Details |
|---|
| Publication Date | 2020-09-22 |
| Journal | The Journal of Chemical Physics |
| Authors | Shunda Chen, Virginia L. Johnson, Davide Donadio, Kristie J. Koski, Shunda Chen |
| Institutions | University of California, Davis, George Washington University |
| Citations | 9 |
| Analysis | Full AI Review Included |
This research investigates the structural, vibrational, and electronic properties of Manganese (Mn) intercalated Molybdenum Diselenide (Mn-MoSe2) under high hydrostatic pressure, demonstrating its potential as a tunable Dilute Magnetic Semiconductor (DMS).
- Spintronic Viability: Mn-MoSe2 exhibits significant spin polarization, generating a high concentration of spin-polarized carriers (up to ~2 x 1020 cm-3), making it highly promising for spintronic applications.
- Tunable Properties: The electronic structure and carrier concentration are chemically and thermodynamically tunable via Mn concentration and applied pressure (up to 7 GPa).
- Electronic Structure Modification: Mn intercalation shifts the Fermi level into the conduction band, rendering the system an n-type semiconductor or nearly metallic, while retaining the total magnetic moment corresponding to single Mn atoms.
- Pressure-Induced Bonding: High pressure activates previously Raman-forbidden phonon modes (A2u, E12g) in both pristine and intercalated MoSe2. A new Mn-Se collective vibrational mode (~250 cm-1) appears upon decompression, suggesting the formation of Mn-Se bonds and a localized structural transition (1Tâ phase or interstitial Mn trapping).
- Synthesis Advancement: The combination of intercalation and compression/decompression offers a viable post-growth route to achieve interstitial doping of transition metals, bypassing typical concentration limitations in conventional doping methods.
| Parameter | Value | Unit | Context |
|---|
| Maximum Applied Pressure | 7 | GPa | Hydrostatic conditions achieved using methanol:ethanol fluid in DAC |
| Experimental Mn Concentration | 1-2 | atomic % | Achieved via wet chemical intercalation (Mn0.02MoSe2) |
| Pristine MoSe2 Band Gap (0 GPa, DFT) | 0.8 | eV | Narrows to 0.4 eV at 6.66 GPa |
| Mn0.03MoSe2 Magnetic Moment (0 GPa) | 5.00 | ”B | Overall supercell magnetic moment |
| Maximum Spin-Polarized Carrier Concentration (2H phase) | ~2 x 1020 | cm-3 | Predicted at low Mn concentration (3%) |
| Pristine MoSe2 Bulk Modulus (DFT) | 47.9 | GPa | Isothermal bulk modulus (BT) |
| Mn0.125MoSe2 Bulk Modulus (DFT) | 51.3 | GPa | Intercalation increases material stiffness |
| Experimental In-Plane Lattice Expansion (a) | 1.5 | % | Measured for Mn0.02MoSe2 vs. pristine MoSe2 |
| New Raman Mode Frequency | ~250 | cm-1 | Mn-Se collective mode observed post decompression |
| Ambient Pressure Raman Mode A1g | 240.6(6) | cm-1 | Out-of-plane mode (Pristine MoSe2, Experimental) |
| Ambient Pressure Raman Mode E12g | 286(1) | cm-1 | In-plane mode (Pristine MoSe2, Experimental) |
| Intercalation Temperature | 48 | °C | Decomposition of dimanganese decacarbonyl |
- MoSe2 Preparation: Molybdenum diselenide (MoSe2) single-crystal platelets (1-100 ”m thickness) were deposited onto fused silica substrates.
- Manganese Intercalation (Wet Chemical Route):
- Zero-valent manganese was intercalated post-growth via the decomposition of dimanganese decacarbonyl (C10O10Mn2).
- The process was conducted under an inert atmosphere (N2) in extra-dry acetone at 48 °C for approximately 2.5 hours total.
- High Pressure Generation:
- Pressures up to 7 GPa were generated using an Alamax EasyLab mini-Bragg Diamond Anvil Cell (DAC).
- A 4:1 v/v methanol:ethanol solution was used as the pressure transmitting fluid to maintain hydrostatic conditions. Ruby spheres were used for pressure calibration.
- Vibrational and Structural Characterization:
- Pressure-dependent Raman scattering was performed using a 532 nm laser (<1 mW) and a high-resolution 1800 groove/mm grating.
- Structural confirmation (hexagonal structure, lattice expansion) was achieved using Selected Area Electron Diffraction (SAED) and X-ray Diffraction (XRD). Elemental mapping was done via Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX).
- First-principles Calculations (DFT):
- Electronic structure and magnetic properties were modeled using Density Functional Theory (DFT) within the Local Spin Density Approximation (LSDA) + U method (Ueff = 4 eV for Mo and Mn).
- Phonon frequencies and Raman shifts were calculated using Density-Functional Perturbation Theory (DFPT).
- Carrier concentrations were calculated from DFT spin-polarized Kohn-Sham states using the BoltzTrap software.
| Industry/Sector | Relevance to Mn-MoSe2 Technology |
|---|
| Spintronics | The primary application. The material functions as a Dilute Magnetic Semiconductor (DMS) with a high, controllable concentration of spin-polarized carriers, essential for developing spin-based transistors and memory devices. |
| Advanced 2D Material Synthesis | The demonstrated method (intercalation + compression/decompression) provides a novel, post-growth route for interstitial doping of transition metals into 2D layered materials, overcoming solubility limits of traditional doping. |
| Pressure Sensing/Actuation | The strong correlation between applied pressure and the materialâs electronic structure (band gap narrowing, spin carrier concentration) suggests potential for highly sensitive pressure sensors or electromechanical actuators. |
| Catalysis (Hydrogen Evolution) | Mn doping/intercalation in MoSe2 is known to promote additional active defect sites, enhancing efficiency for hydrogen evolution reactions (HER). |
| Tunable Optoelectronics | The ability to tune the electronic band structure and spin states via pressure and intercalation provides a pathway for developing optoelectronic devices with dynamically adjustable properties. |
View Original Abstract
Intercalation offers a promising way to alter the physical properties of two-dimensional (2D) layered materials. Here, we investigate the electronic and vibrational properties of 2D layered MoSe2 intercalated with atomic manganese at ambient and high pressure up to 7 GPa by Raman scattering and electronic structure calculations. The behavior of optical phonons is studied experimentally with a diamond anvil cell and computationally through density functional theory calculations. Experiment and theory show excellent agreement in optical phonon behavior. The previously Raman inactive A2u mode is activated and enhanced with intercalation and pressure, and a new Raman mode appears upon decompression, indicating a possible onset of a localized structural transition, involving the bonding or trapping of the intercalant in 2D layered materials. Density functional theory calculations reveal a shift of the Fermi level into the conduction band and spin polarization in MnxMoSe2 that increases at low Mn concentrations and low pressure. Our results suggest that intercalation and pressurization of van der Waals materials may allow one to obtain dilute magnetic semiconductors with controllable properties, providing a viable route for the development of new materials for spintronic applications.
- 2010 - First-principles theory of dilute magnetic semiconductors [Crossref]
- 2010 - A ten-year perspective on dilute magnetic semiconductors and oxides [Crossref]
- 2010 - A window on the future of spintronics [Crossref]
- 2014 - Dilute ferromagnetic semiconductors: Physics and spintronic structures [Crossref]
- 2013 - Mn-doped monolayer MoS2: An atomically thin dilute magnetic semiconductor [Crossref]
- 2013 - Long-range ferromagnetic ordering in manganese-doped two-dimensional dichalcogenides [Crossref]
- 2016 - Robust ferromagnetism in Mn-doped MoS2 nanostructures [Crossref]
- 2015 - Manganese doping of monolayer MoS2: The substrate is critical [Crossref]
- 2018 - Tunable magnetic coupling in Mn-doped monolayer MoS2 under lattice strain [Crossref]
- 2017 - Intrinsic ferromagnetism in Mn-Substituted MoS2 nanosheets achieved by supercritical hydrothermal reaction [Crossref]