Nanoscale Mapping of Layer-Dependent Surface Potential and Junction Properties of CVD-Grown MoS₂ Domains

Abstract

In the present study, nanoscale variations in the work function values and the resulting changes in junction properties of chemical vapour deposited two-dimensional (2D) MoS 2 domains has been investigated as a function of number of layers using Kelvin Probe Force Microscopy (KPFM) and Conductive Atomic Force Microscopy(CAFM) techniques. Raman spectroscopy has been employed to obtain the magnitude of difference between E 2g and A 1g peaks which has been used as a signature of the number of layers. Surface potential of MoS 2 monolayer sample exhibits a value of -427 mV (~7.2 mV for bulk) along with a large spread of about 29mV (~3mV for bulk). The present study shows that the optical and electronic properties of MoS 2 1-2 layer samples exhibit a large difference from its bulk counterpart. These characteristic features remain intact even in the presence of adsorbates and defects which result in spread in surface potential values and corresponding changes in junction characteristics. These results are important for the application of Chemical Vapor Deposition (CVD) grown MoS 2 monolayers for semiconductor devices.

Growth of Highly Crystalline and Large Scale Monolayer MoS2 by CVD: The Role of substrate Position

“…The inset line‐profile shows the contact potential difference (CPD) between tip and the sample or the substrate. The CPD for the ML MoS 2 and the substrate was found to be −200 V and −400 V respectively and hence, the work function to be 4.93 eV and 4.73 eV respectively which is in agreement with the reported work function of ML MoS 2 . Our observed value of work function (4.93 eV) suggests the non‐existence of MoO 3 phase in our sample .…”

Electronic band gaps and exciton binding energies in monolayerMoxW1−xS2transition metal dichalc

“…In the expression for the tunneling probability T, we use Φ s = 5.1 eV (work function of monolayer MoS 2 ) [53][54] or 5.8 eV (work function of monolayer WS 2 ) [55], and Φ t = 4.5 eV (work function of tungsten metal tip). We assume that tunneling is dominated by the behavior at the K/K' points the Brillouin zone and consequently use [56].…”

Quantitative probe for in-plane piezoelectric coupling in 2D materials

“…We have observed that the contribution from the local electrostatic component to the lateral deflection is minimal (in the range of 0.05–0.1 pm/V) in the current measurements. The reasons for the minimal contribution are the large lateral spring constant of the AFM tip used (20–25 N/m) and the smaller surface potential difference for MoS 2 (0.1–0.4 V) 35 , 36 . By extracting various contributions from Eqs.…”