Restricted Channel Migration in 2D Multilayer ReS₂

Abstract

When thickness-dependent carrier mobility is coupled with Thomas−Fermi screening and interlayer resistance effects in two-dimensional (2D) multilayer materials, a conducting channel migrates from the bottom surface to the top surface under electrostatic bias conditions. However, various factors including (i) insufficient carrier density, (ii) atomically thin material thickness, and (iii) numerous oxide traps/defects considerably limit our deep understanding of the carrier transport mechanism in 2D multilayer materials. Herein, we report the restricted conducting channel migration in 2D multilayer ReS 2 after a constant voltage stress of gate dielectrics is applied. At a given gate bias condition, a gradual increase in the drain bias enables a sensitive change in the interlayer resistance of ReS 2 , leading to a modification of the shape of the transconductance curves, and consequently, demonstrates the conducting channel migration along the thickness of ReS 2 before the stress. Meanwhile, this distinct conduction feature disappears after stress, indicating the formation of additional oxide trap sites inside the gate dielectrics that degrade the carrier mobility and eventually restrict the channel migration. Our theoretical and experimental study based on the resistor network model and Thomas−Fermi charge screening theory provides further insights into the origins of channel migration and restriction in 2D multilayer devices.

High Temperature Carrier Scattering Mechanisms in Multilayer ReS2 Field-Effect Transistors

“…A clear linearity regardless of V G is presented in these figures at small V D regimes (< 0.5 V), which indicate negligible Au-ReS 2 Schottky barrier (SB) effects [9,11,13]. However, a non-monotonic behavior gradually appears after V D exceeds 1 V. This distinct behavior has been mainly ascribed to the suppressed R IT and/or enhanced carrier mobility effects on conducting channel migration in the ReS 2 multilayers [10,14]. Moreover, typical n-type behavior is clearly exhibited, in which electron population increases with increasing V G .…”

“…At T = 300 K [Fig. 3(c)], two g m /V D plateaus are evident under relatively small V D regimes (V D < 200 mV), demonstrating the emergence of conducting channel migration from the bottom surface to the top surface, which is triggered by the reduced interlayer resistance via increasing V G [10]. This anomalous carrier transport feature of 2D multilayers can be further supported by the larger amplitude of the 2 nd g m peak compared to that of the 1 st g m peak, which indicates enhanced field-effect mobility 𝜇 FE (= g m ⋅L/(W⋅C OX ⋅V D )) via reduced R IT and/or R CT with increasing V G .…”

“…The fabricated device was thermally annealed for 10 h at 200 ∘ C under a high vacuum of less than 10 −6 Torr. The detailed fabrication method employed in this study is described in the literature [9][10][11]. The optical Raman spectrum of 11 nm-thick ReS 2 was obtained using a laser excitation wavelength (𝜆 EX ) with a laser power (P) of 5 mW.…”

Analyzing Anisotropy in 2D Rhenium Disulfide Using Dichromatic Polarized Reflectance

“…

Among anisotropic 2D materials, rhenium disulfide (ReS 2 ) is unique due to its highly asymmetric structure. [28][29][30][31][32] Its distorted 1T crystal structure has only triclinic symmetry, that is, no symmetry except a center of inversion, [2,28,33,34] and thus is expected to exhibit strongly anisotropic properties. Furthermore, ReS 2 has a number of remarkable features: i) it has a rich Raman spectrum (18 Raman-active modes); ii) relative intensity of its Raman peaks exhibits strong polarization-dependence; iii) it shows much better material stability for most measurements [35] compared with some other anisotropic 2D materials (such as black P, [36,37] WTe 2 , [38] and MoTe 2 [39] ).

…”

Discerning the Vibrational Nature of ReS2 Raman Modes Using Solid-Angle-Resolved Raman Spectroscopy

“…Among anisotropic 2D materials, rhenium disulfide (ReS 2 ), a group VII transition metal dichalcogenide (TMDC), has been attracting increasing research interest for its rich physical properties. − Compared with group VI TMDCs ( e.g. , MoS 2 , MoSe 2 , WS 2 , and WSe 2 ), ReS 2 crystals exhibit reduced crystal symmetry (known as triclinic symmetry) that leads to high in-plane anisotropy.…”