skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Pure spin current injection of single-layer monochalcogenides
Abstract We compute the spectrum of pure spin current injection in ferroelectric single-layer SnS, SnSe, GeS, and GeSe. The formalism takes into account the coherent spin dynamics of optically excited conduction states split in energy by spin–orbit coupling. The velocity of the electron’s spins is calculated as a function of incoming photon energy and angle of linearly polarized light within a full electronic band structure scheme using density functional theory. We find peak speeds of 520, 360, 270 and 370 Km s−1for SnS, SnSe, GeS and GeSe, respectively which are an order of magnitude larger than those found in bulk semiconductors, e.g., GaAs and CdSe. Interestingly, the spin velocity is almost independent of the direction of polarization of light in a range of photon energies. Our results demonstrate that single-layer SnS, SnSe, GeS and GeSe are candidates to produce on demand spin-current in spintronics applications.  more » « less
Award ID(s):
2015639
PAR ID:
10478442
Author(s) / Creator(s):
; ; ;
Editor(s):
Cao, Yi; Wu, Judy
Publisher / Repository:
IOP
Date Published:
Journal Name:
Materials Research Express
Volume:
10
Issue:
3
ISSN:
2053-1591
Page Range / eLocation ID:
035003
Subject(s) / Keyword(s):
Spin current, DFT
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; (, Small)
    Abstract Performance of the group IV monochalcogenide GeSe in solar cells, electronic, and optoelectronic devices is expected to improve when high‐quality single crystalline material is used rather than polycrystalline films. Crystalline flakes represent an attractive alternative to bulk single crystals as their synthesis may be developed to be scalable, faster, and with higher overall yield. However, large – and especially large and thin – single crystal flakes are notoriously hard to synthesize. Here it is demonstrated that vapor‐liquid‐solid growth combined with direct lateral vapor‐solid incorporation produces high‐quality single crystalline GeSe ribbons with tens of micrometers size and controllable thickness. Electron microscopy shows that the ribbons exhibit perfect equilibrium (AB) van der Waals stacking order without extended defects across the entire thickness, in contrast to the conventional case of substrate‐supported flakes where material is added via layer‐by‐layer nucleation and growth on the basal plane. Electrical measurements show anisotropic transport and a high Hall mobility of 85 cm2 V−1 s−1, on par with the best single crystals to date. Growth from mixed GeSe and SnSe vapors, finally, yields ribbons with unchanged structure and composition but with jagged edges, promising for applications that rely on ample chemically active edge sites, such as catalysis or photocatalysis. 
    more » « less
  2. ; ; ; ; (, 2D Materials)
    Abstract Germanium sulfide (GeS) is a 2D semiconductor with potential for high-speed optoelectronics and photovoltaics due to its near-infrared band gap and high mobility of optically excited charge carriers. Here, we use time-resolved THz spectroscopy to investigate the differences in ultrafast carrier dynamics in GeS following near-band gap photoexcitation (1.55 eV), which penetrates deep into the multilayer GeS, and excitation with above-band gap photon energy (3.1 eV), which is absorbed within a sub-20 nm surface layer. We find that the photoexcited carriers in the bulk have significantly longer lifetimes and higher mobility, as they are less impacted by trap states that affect carrier behavior in the surface layer. These insights are important for designing GeS-based photodetectors, solar energy conversion devices, and sensors that leverage the sensitivity of surface-layer photoexcited carriers to trap states. 
    more » « less
  3. ; ; ; ; ; ; ; ; (, Proc. SPIE 12683, Terahertz Emitters, Receivers, and Applications XIV, 126830B (4 October 2023))
    Razeghi, Manijeh; Jarrahi, Mona (Ed.)
    GeS and GeSe are 2D semiconductors with band gaps in the near infrared and predicted high carrier mobility. We find that excitation with 800 nm pulses results in long-lived free photocarriers, persisting for hundreds of picoseconds, in GeS and GeSe noribbons. We also demonstrate that zerovalent Cu intercalation is an effective tool for tuning the photoconductive response. Intercalation of ~ 3 atomic % of zerovalent Cu reduces the carrier lifetime in GeSe and GeS. In GeS, it also shortens the photoconductivity rise and improves carrier mobility. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; (, Small)
    Abstract Tin monochalcogenides SnS and SnSe, belonging to a family of Van der Waals crystals isoelectronic to black phosphorus, are known as environmentally friendly materials promising for thermoelectric conversion applications. However, they exhibit other desired functionalities, such as intrinsic linear dichroism of the optical and electronic properties originating from strongly anisotropic orthorhombic crystal structures. This property makes them perfect candidates for polarization‐sensitive photodetectors working in near‐infrared spectral range. A comprehensive study of the SnS and SnSe crystals is presented, performed by means of optical spectroscopy and photoemission spectroscopy, supported by ab initio calculations. The studies reveal the high sensitivity of the optical response of both materials to the incident light polarization, which is interpreted in terms of the electronic band dispersion and orbital composition of the electronic bands, dictating the selection rules. From the photoemission investigation the ionization potential, electron affinity and work function are determined, which are parameters crucial for the design of devices based on semiconductor heterostructures. 
    more » « less
  5. ; ; ; ; ; ; ; (, Advanced Optical Materials)
    Abstract Group IV‐VI van der Waals crystals (MX, where M = Ge, Sn, and X = S, Se) are receiving increasing attention as semiconducting thermoelectric materials with nontoxic, earth‐abundant composition. Among them, SnSe is considered the most promising as it exhibits a remarkably high thermoelectric figure of merit (ZT), initially attributed to its low lattice thermal conductivity. However, it has been shown that the electronic band structure plays an equally important role in thermoelectric performance. A certain band shape, described as a “pudding mold” and characteristic for all MXs, has been predicted to significantly improveZTby combining good electrical conductivity with high Seebeck coefficient. This subtle feature is explored experimentally for GeS, SnS, and SnSe by means of angle‐resolved photoemission spectroscopy. The technique also allows for the determination of the effective mass and Fermi level position of as‐grown undoped crystals. The findings are supported by ab initio calculations of the electronic band structure. The results greatly contribute to the general understanding of the valence band dispersion of MXs and reinforce their potential as high‐performance thermoelectric materials, additionally giving prospects for designing systems consisting of van der Waals heterostructures. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email