Conductive Atomic Force Microscopy of Semiconducting Transition Metal Dichalcogenides and Heterostructures.

Filippo Giannazzo,Fabrizio Roccaforte,Giuseppe Greco,Emanuela Schilirò

doi:10.3390/nano10040803

Filippo Giannazzo, Fabrizio Roccaforte + Show 2 more

Open Access

https://doi.org/10.3390/nano10040803

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Journal: Nanomaterials	Publication Date: Apr 22, 2020
Citations: 36	License type: CC BY 4.0

Affiliation: Institute for Microelectronics and Microsystems

Abstract

Semiconducting transition metal dichalcogenides (TMDs) are promising materials for future electronic and optoelectronic applications. However, their electronic properties are strongly affected by peculiar nanoscale defects/inhomogeneities (point or complex defects, thickness fluctuations, grain boundaries, etc.), which are intrinsic of these materials or introduced during device fabrication processes. This paper reviews recent applications of conductive atomic force microscopy (C-AFM) to the investigation of nanoscale transport properties in TMDs, discussing the implications of the local phenomena in the overall behavior of TMD-based devices. Nanoscale resolution current spectroscopy and mapping by C-AFM provided information on the Schottky barrier uniformity and shed light on the mechanisms responsible for the Fermi level pinning commonly observed at metal/TMD interfaces. Methods for nanoscale tailoring of the Schottky barrier in MoS2 for the realization of ambipolar transistors are also illustrated. Experiments on local conductivity mapping in monolayer MoS2 grown by chemical vapor deposition (CVD) on SiO2 substrates are discussed, providing a direct evidence of the resistance associated to the grain boundaries (GBs) between MoS2 domains. Finally, C-AFM provided an insight into the current transport phenomena in TMD-based heterostructures, including lateral heterojunctions observed within MoxW1–xSe2 alloys, and vertical heterostructures made by van der Waals stacking of different TMDs (e.g., MoS2/WSe2) or by CVD growth of TMDs on bulk semiconductors.

Highlights

In the last years, transition metal dichalcogenides (TMDs) have attracted an increasing scientific interest because of their unique and tunable electronic structure, holding great promise for generation applications in electronics and optoelectronics [1,2]
SSeecctitoionn 2 iinnccluluddeessrerceecnetnsttusdtuiedsieosf tohfe cthuerrecnutrirnejnetctionnjecmtieocnhamniescmhsanatistmhesmaettathl/Te MmDestajul/nTcMtioDnss. juNnacntioosncsa.lNe arensooslcuatlieonrecsoulruretinotnscpuercrternotscsoppecytraonsdcompyapapndinmg abpypCin-Ag bFyMCp-AroFvMidepdroivnifdoerdmiantfioornmoantiothne on the Schottky barrier height (SBH) uniformity and shed light on the mechanisms responsible for the Fermi level pinning commonly observed at the metal/TMDs interface
The electronic transport properties of semiconducting TMD layers are strongly dependent on point and extended defects present in their crystalline structure

Summary

Introduction

Transition metal dichalcogenides (TMDs) have attracted an increasing scientific interest because of their unique and tunable electronic structure, holding great promise for generation applications in electronics and optoelectronics [1,2]. JuNnacntioosncsa.lNe arensooslcuatlieonrecsoulruretinotnscpuercrternotscsoppecytraonsdcompyapapndinmg abpypCin-Ag bFyMCp-AroFvMidepdroivnifdoerdmiantfioornmoantiothne on the Schottky barrier height (SBH) uniformity and shed light on the mechanisms responsible for the Fermi level pinning commonly observed at the metal/TMDs interface The application of this approach to nanoscale mapping of the SBH distribution in MoS2 thin films subjected to oxygen plasma prefunctionalization is illustrated, and the practical implications of these results in the realization of ambipolar MoS2 transistors are demonstrated. Schottky barrier height (SBH) uniformity and shed light on the mechanisms responsible for the Fermi level pinning commonly observed at the metal/TMDs interface Recent studies of the Fermi level pinning in TMDs using C-AFM are discussed

C-AFM Investigations of Fermi Level Pinning in TMDs

Nanoscale Mapping of MoS2 Schottky Barrier Tuned by Oxygen Plasma Treatments

Local Resistance Mapping at Grain Boundaries in CVD Grown MoS2

Findings

Conclusions and Perspectives