Comparative study of chemically synthesized and exfoliated multilayer MoS2 field-effect transistors

Abstract

We report the realization of field-effect transistors (FETs) made with chemically synthesized multilayer 2D crystal semiconductor MoS 2 . Electrical properties such as the FET mobility, subthreshold swing, on/off ratio, and contact resistance of chemically synthesized (s-) MoS 2 are indistinguishable from that of mechanically exfoliated (x-) MoS 2 , however flat-band voltages are different, possibly due to polar chemical residues originating in the transfer process.Electron diffraction studies and Raman spectroscopy show the structural similarity of s-MoS 2 to x-MoS 2 . This initial report on the behavior and properties of s-MoS 2 illustrates the feasibility of electronic devices using synthetic layered 2D crystal semiconductors.

Bulk transport and contact limitation of MoS2 multilayer flake transistors untangled via temperature-dependent transport measurements

“…More importantly, we show that such flakes can be operated at drain‐source voltages ( V DS ) as high as 20 V and can support currents as large as 38 μA/μm – with a sizable I ON / I OFF ratio of 10 5 for the best sample. This current density is in line with recent reports on multilayer flakes, while highly integrated MoS 2 devices were reported to reach about 300 μA/μm . We attribute the normally on state of the FETs, the small I ON / I OFF ratio in some of our devices compared to other multilayer studies as well as the non‐saturating output curves to a substantial doping of the bulk of the MoS 2 flake.…”

“…From the slope of the output curve at 300 K in Fig. , which is almost the same up to 2V V DS for high gate biases, we can estimate a maximum contact resistance of R C = 495 ± 156 kΩ · μm (average over all samples at room temperature at V GS = 80 V and low V DS ), which is higher but comparable to previous results on multilayer flakes at the order of 1–80 kΩ μm . An explanation for this difference is, first, that we did not anneal our samples in formation gas prior to the measurements and second, that we used a thicker dielectric which is expected to exhibit poorer capacitive coupling to the semiconductor.…”

High-voltage field effect transistors with wide-bandgap β-Ga2O3 nanomembranes

“…A low contact resistance can thus boost the current drive significantly [5]. The subthreshold swing (SS) of the device shown in FETs with an identical process flow [23], but is much higher than that of conventional Si and III-V FETs of ~0.1 Ωmm [24]. The contact resistance can be further lowered by using low work function metals and by increasing the electron density by local ion-implantation doping under the contacts.…”

Fabrication of blue luminescent MoS 2 quantum dots by wet grinding assisted co-solvent sonication

“…The main issue with MoS 2 is, its exfoliation, MoS 2 is exfoliated from bulk layer to few or monolayer by various mechanical and chemical methods involving ultra-sonication [12][13][14], mechanical cleavage [11,[15][16][17], Li-intercalation [18,19], Sodium naphthalenide [20]. The mono or few-layer exfoliated MoS 2 has intriguing applications such as super capacitor [21], electro catalyst for hydrogen evolution reaction (HER) [22,23], sensor [24], field effect transistor [25,26], and solar cells [27,28].…”