Thickness-Dependent Interfacial Coulomb Scattering in Atomically Thin Field-Effect Transistors

TL;DR

This study investigates how the thickness of atomically thin MoS2 transistors affects carrier mobility, revealing that interfacial Coulomb impurities significantly degrade performance in monolayer devices due to increased scattering.

Contribution

It introduces a generalized Coulomb scattering model considering device-specific conditions, explaining the thickness-dependent mobility degradation in 2D semiconductors.

Findings

Mobility decreases tenfold in monolayer MoS2 transistors.

Interfacial Coulomb impurities dominate scattering in thin channels.

Surface quality critically impacts electrical transport.

Abstract

Two-dimensional semiconductors are structurally ideal channel materials for the ultimate atomic electronics after silicon era. A long-standing puzzle is the low carrier mobility ({\mu}) in them as compared with corresponding bulk structures, which constitutes the main hurdle for realizing high-performance devices. To address this issue, we perform combined experimental and theoretical study on atomically thin MoS2 field effect transistors with varying the number of MoS2 layers (NLs). Experimentally, an intimate relation is observed with a 10-fold degradation in {\mu} for extremely thinned monolayer channels. To accurately describe the carrier scattering process and shed light on the origin of the thinning-induced mobility degradation, a generalized Coulomb scattering model is developed with strictly considering device configurative conditions, i.e., asymmetric dielectric environments and lopsided carrier distribution. We reveal that the carrier scattering from interfacial Coulomb impurities (e.g., chemical residues, gaseous adsorbates and surface dangling bonds) is greatly intensified in extremely thinned channels, resulting from shortened interaction distance between impurities and carriers. Such a pronounced factor may surpass lattice phonons and serve as dominant scatterers. This understanding offers new insight into the thickness induced scattering intensity, highlights the critical role of surface quality in electrical transport and would lead to rational performance improvement strategies for future atomic electronics.