Monolayer MoS2 field effect transistor with low Schottky barrier height with ferromagnetic metal contacts

Abstract

Two-dimensional MoS2 has emerged as promising material for nanoelectronics and spintronics due to its exotic properties. However, high contact resistance at metal semiconductor MoS2 interface still remains an open issue. Here, we report electronic properties of field effect transistor devices using monolayer MoS2 channels and permalloy (Py) as ferromagnetic (FM) metal contacts. Monolayer MoS2 channels were directly grown on SiO2/Si substrate via chemical vapor deposition technique. The increase in current with back gate voltage (Vg) shows the tunability of FET characteristics. The Schottky barrier height (SBH) estimated for Py/MoS2 contacts is found to be +28.8 meV (at Vg = 0V), which is the smallest value reported so-far for any direct metal (magnetic or non-magnetic)/monolayer MoS2 contact. With the application of positive gate voltage, SBH shows a reduction, which reveals ohmic behavior of Py/MoS2 contacts. Low SBH with controlled ohmic nature of FM contacts is a primary requirement for MoS2 based spintronics and therefore using directly grown MoS2 channels in the present study can pave a path towards high performance devices for large scale applications.

Edge-Contact MoS2 Transistors Fabricated Using Thermal Scanning Probe Lithography

“…To determine the effect of temperature in the electrical response of the devices, additional I ds ( V ds ) and I ds ( V gs ) measurements were carried out with temperatures starting from 80 K until room temperature (see Supporting Information, section S6). For low temperatures, the response is less linear and I ds is slightly lower, in accordance with previous studies. , The variation in the electrical performance is more noticeable for devices where the performance is lower, which we attribute to a worse contact between the 2DM and the metallic electrode. This set of measurements was also used to obtain the SBH in the thermionic regime, leading to values of 68 and 87 meV for the edge- and top-contact FL devices, respectively (see Figure ).…”

“…For low temperatures, the response is less linear and I ds is slightly lower, in accordance with previous studies. 13,38 The variation in the electrical performance is more noticeable for devices where the performance is lower, which we attribute to a worse contact between the 2DM and the metallic electrode. This set of measurements was also used to obtain the SBH in the thermionic regime, leading to values of 68 and 87 meV for the edge-and top-contact FL devices, respectively (see Figure 5).…”

Accurate Extraction of Schottky Barrier Height and Universality of Fermi Level De‐Pinning of van der Waals Contacts

“…The back-gated FET (Figure 1a) is a popular structure for the extraction of SBH (φ B 0 ) in layered semiconductors. [18,19,26,27,[29][30][31][32][33][34][35][36][37] The effective barrier height (φ B ) is computed at different values of gate voltage (V g ) using Arrhenius equation. From the φ B versus V g plot, the knee-point is identified as the flat-band condition where the transport mechanism switches from purely thermionic to tunneling or thermally assisted tunneling process and thus corresponds to the SBH of that interface.…”

Field-effect at electrical contacts to two-dimensional materials

“…If the current saturation was caused by the switching of the Schottky barrier [19], the current saturation should happen when the inner/outer electrode is used as the drain/source respectively, which is contrary to the above observations. The mere Schottky barrier (without considering field-effect) dominated I-V curves should present increased differential conductance at large VDS, due to the lowered Schottky barrier height and enhanced field/thermal-field emission with increased VDS [38][39][40], as shown in Fig. S3(a) in the ESM.…”