Staircase-like transfer characteristics in multilayer MoS2 field-effect transistors

Takuya Ohoka,Ryo Nouchi

doi:10.1088/2632-959x/ab70e6

Abstract

Layered semiconductors, such as MoS2, have attracted interest as channel materials for post-silicon and beyond-CMOS electronics. Much attention has been devoted to the monolayer limit, but the monolayer channel is not necessarily advantageous in terms of the performance of field-effect transistors (FETs). Therefore, it is important to investigate the characteristics of FETs that have multilayer channels. Here, we report the staircase-like transfer characteristics of FETs with exfoliated multilayer MoS2 flakes. Atomic force microscope characterizations reveal that the presence of thinner terraces at the edges of the flakes accompanies the staircase-like characteristics. The anomalous staircase-like characteristics are ascribable to a difference in threshold-voltage shift by charge transfer from surface adsorbates between the channel center and the thinner terrace at the edge. This study reveals the importance of the uniformity of channel thickness.

Highlights

With regard to the continued efforts to realize highperformance electronic devices, miniaturization of field-effect transistors (FETs) incorporated in integrated circuits has been pursued
Layered semiconductors typified by transition metal dichalcogenides (TMDCs), such as MoS2, have attracted interest because ultrathin channels can be obtained by exfoliation of such layered semiconductors [4-9]
We report a two-tiered staircase-like shape in transfer characteristics of FETs based on an exfoliated multilayer MoS2 flake, which is completely different from the commonly observed one-tiered characteristics

Summary

Introduction

With regard to the continued efforts to realize highperformance electronic devices, miniaturization of field-effect transistors (FETs) incorporated in integrated circuits has been pursued. A dependence of FET performance on the number of layers has shown that the monolayer channel is not advantageous in terms of field-effect mobilities [10,11]. The possibility of the weakening of the interaction between electrons and phonons is discussed [11] All of these features indicate that the performance of FETs is higher with multilayered channels. The difference in the threshold voltage, Vth, between the two distinct parts within the flake is ascribable to a difference in Vth shift by charge transfer from surface adsorbates between the two parts. These considerations are further supported by the investigation of the effect of thermal annealing treatment. This study clearly shows the importance of the uniformity in channel thickness

Experimental

Results and discussion

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Conclusions