Electron Confinement at the Si/MoS₂ Heterosheet Interface

Abstract

lead to a nontrivial electronic coupling at the Si/MoS 2 heterosheet (HS) interface with possible impact on the electronic and optical applications. Indeed, interfacing MoS 2 with conventional semiconductors recently has recently led to the realization of a subthermionic tunnel FET, [ 12 ] and it was proposed as a feasible avenue for an improved photodetection [ 13 ] and enhanced photoresponsive behavior. [ 14 ] In the present work, our aim is to unravel the electronic band line-up at the HS interface between Si and MoS 2 , and to correlate it with the electrical response of the resultant HS-FET after stabilizing the Si NS with an Al 2 O 3 encapsulation layer. To this purpose, in situ angle-resolved photoemission spectroscopy (ARPES) from a synchrotron radiation (SR) source (photon energy h ν = 100 eV) and in situ nonmonochromatic laboratory X-ray photoemission spectroscopy (XPS) from a Mg Kα (photon energy h ν = 1253.6 eV) source were respectively used to inspect the valence band structure at the Si/MoS 2 HS interface and the chemical stability prior to and after encapsulation. In particular, based on highresolution SR-PES, the Si NS is observed to bend the electronic bands of the MoS 2 topmost layers enough to cause an electron accumulation at the Si/MoS 2 HS interface. This feature deeply infl uences the HS-FET response by inducing an effective n -type doping in the topmost MoS 2 region. Structural Details of the Si/MoS 2 Heterosheet InterfaceThe fi rst Brillouin zone of the prepared MoS 2 (0001) surface (see the Experimental Section) is displayed by the low energy electron diffraction (LEED) pattern in Figure 1 a that reproduces a hexagonal reciprocal lattice cell. A similar LEED pattern has been observed in Figure 1 b after Si NS deposition at 200 °C. This fact is consistent with a pseudomorphic growth of an Si monolayer mimicking the MoS 2 surface structure as previously reported. [ 11 ] The growth of the Si NS has been chemically identifi ed by means of in situ XPS monitoring of the Si 2 p core level photoemission line as a function of the take-off angle (TOA), i.e., the angle between the photoelectron beam and the nominal surface plane. The angular dependence of the Si 2 p line is reported in Figure 1

Influence of MoS2‐Silicon Interface States on Spectral Photoresponse Characteristics

“…Particularly, TMDCs layers have been deposited on the Si surface by various approaches to develop heterojunction device for solar cells and photodiode applications . The MoS 2 ‐layered material‐based photoresponsive devices have shown great potential as they show high optical absorption in the visible spectrum, faster photoresponse, and relative ease of fabrication . Thus, the combination of n‐type MoS 2 with p‐type Si is of significant interest to develop a VdW heterojunction device .…”

“…[20][21][22][23] The MoS 2 -layered material-based photoresponsive devices have shown great potential as they show high optical absorption in the visible spectrum, faster photoresponse, and relative ease of fabrication. [20][21][22][23][24] Thus, the combination of n-type MoS 2 with p-type Si is of significant interest to develop a VdW heterojunction device. [25][26][27] Salahuddin et al has reported the fabrication of heterojunction photodetectors with mechanically exfoliated MoS 2 flake on amorphous Si.…”

A Multilayer‐Graphene/Silicon Infrared Schottky Photo‐Diode

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more, as will be discussed in the following, the optical properties of the metallic layer at longer wavelengths strongly attenuates the photo-conversion.

A promising and widely investigated approach seems to be the exploitation of graphene. As recently reported by different groups, [26,27] a narrow band-gap (2D) semiconductor in intimate contact with a bulk silicon can induce a band-gap narrowing in the latter, leading to the shift of the band-edge absorption spectrum toward longer wavelengths. [21][22][23][24][25], as a possible solution to develop photodetectors able to work in the long-wavelength range.

In this paper, an infrared, lateral Schottky photo-diode based on a multilayer-graphene/intrinsic-silicon (MLG/i-Si) heterojunction is presented.

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“…As recently reported by different groups, [26,27] a narrow band-gap (2D) semiconductor in intimate contact with a bulk silicon can induce a band-gap narrowing in the latter, leading to the shift of the band-edge absorption spectrum toward longer wavelengths. The junction shows a strong gain of the responsivity in the long wavelength region as compared to a standard metal/Si junction.…”

Exfoliated Metal Oxide Nanosheets as Effective and Applicable Substrates for Atomically Dispersed Metal Nanoparticles with Tailorable Functionalities

“…As an emerging member of nanostructured materials, the 2D nanosheets of graphene and layered inorganic solids attract intense research interest because of their unique characteristics such as unusually high structural and morphological anisotropy, diverse physicochemical properties, and valuable functionalities. [1][2][3][4][5][6] While the synthesis of many other nanostructured materials heavily relies on crystal growth mechanism, the 2D nanosheet can be synthesized by soft-chemical exfoliation process of the pristine layered material. [6][7][8][9][10][11][12][13] Such an exfoliation process leads to the separation of layered crystal lattice into individual sheets with single domain.…”