Enhanced charge separation at 2D MoS2/ZnS heterojunction: KPFM based study of interface photovoltage

Abstract

Two dimensional (2D) MoS2/ZnS heterojunctions with MoS2 thickness varying from monolayer to bulk have been prepared by sulfurization of a controlled thickness of Mo deposited on the ZnS thin films. Kelvin probe force microscopy measurements on MoS2/ZnS junction having varying thicknesses of MoS2 layers are carried out in the surface and junction modes, under white light exposure. Differences in the surface potential values of the surface and junction modes represent interface photovoltages at heterojunctions. Enhanced interface photovoltage is observed in junctions having the mono and few layer MoS2 in comparison to bulk MoS2 layer. This suggests the active participation of 2D MoS2 layer in photon absorption and charge separation processes taking place close to the junction. The present study is an effort towards the integration of 2D layered materials with 3D semiconductors, which may be advantageous for the development of 2D material based optoelectronic devices.

Large‐Area, Flexible Broadband Photodetector Based on ZnS–MoS2 Hybrid on Paper Substrate

“…The electron affinity reported for ZnS and few‐layer MoS 2 are 3.9 and 4.0 eV, respectively. At the ZnS and MoS 2 interface, the flow of electrons from ZnS to MoS 2 results in the alignment of Fermi levels thereby reaching the equilibrium condition . Under UV light illumination, photogeneration of electron–hole pairs occurs in ZnS microspheres when the energy of the illumination is greater than or equal to the bandgap energy of ZnS.…”

“…Coupling the tunable layer dependent behavior of MoS 2 with above‐mentioned properties makes it suitable for a wide range of optoelectronic applications, especially photodetectors. Moreover, combining MoS 2 with other semiconductors results in the efficient charge separation, high electron transfer rate, and increases the solar light absorption …”

“…Since wurtzite ZnS is also a sulfur‐based compound and has lattice parameters close to that of hexagonal MoS 2 , there exists a synergistic effect that facilitates the growth of ZnS–MoS 2 hybrids. ZnS–MoS 2 hybrids have been prepared using various methods such as sulfurization of Mo on RF magnetron sputtered ZnS thin film, surfactant assisted exfoliation for MoS 2 followed by hydrothermal and using MoS 2 with metal–organic framework Zeolitic imidazolate framework‐8 (ZIF‐8) . Among the various methods available, hydrothermal synthesis is the most versatile method as it provides the ability to synthesize hybrid nanostructures at low cost with distinct morphologies and high phase purity …”

Interface Characterization and Control of 2D Materials and Heterostructures

“…A type‐II band alignment is deduced and schematically shown at the bottom of Figure e. Further applications of KPFM include extracting band offsets in MoS 2 heterostructures with different layer numbers, mapping surface potential differences in MoS 2 /ZnS and MoS 2 /WSe 2 lateral heterostructures, and examining the electrical properties of MoS 2 GBs . Although EFM and KPFM have shown high sensitivity to electrostatic interactions, even higher charge resolution down to the single electron limit has been realized using scanning single‐electron transistor microscopy .…”

Hybrid van der Waals SnO/MoS2 Heterojunctions for Thermal and Optical Sensing Applications

“…So far, hybrid vdWHs including the following combination of materials have been demonstrated: p‐organic/n‐2D, p‐2D/n‐oxide, and p‐oxide/n‐2D . These vdWHs have been used as p–n junctions, Schottky junctions, memristors, and photovoltaic devices . Apart from the excellent performance exhibited by the vdWHs, unfortunately, most devices are made using difficult processes with low yield, which are difficult to scale.…”