Improving Contacts and Electrical Performances of Nanofilms of MoS₂ Transistors through Ultrastrong vdW Integration with Dirac Semimetal PtTe₂

Abstract

Semiconductor−metal contacts as one major challenge have severely hindered the further progress of two-dimensional (2D) electronics.Here, we present a simple and effective strategy to improve the contacts and electrical performances by fabricating van der Waals (vdW) heterostructures with 2D semiconductor MoS 2 and type-II Dirac semimetal PtTe 2 . The semiconductor MoS 2 and Dirac semimetal PtTe 2 nanoflakes are synthesized through CVD routes separately, followed by systematic material characterizations to confirm their structures. Furthermore, we constructed MoS 2 / PtTe 2 vdW heterostructures via a transfer technology with as-grown MoS 2 and PtTe 2 nanoflakes. The field-effect transistor based on MoS 2 /PtTe 2 heterostructures shows ohmic contact and improved electrical performances, such as two-terminal carrier mobility (∼38.2 cm 2 •V −1 •s −1 ) and ON/OFF ratio (∼10 4 ). We ascribe the improvement of contact and electrical performances to the utilization of ultrahigh-conductive layered PtTe 2 as an interlayer. The theoretical calculations demonstrate that the vdW contact can eliminate the Fermi level pinning effect; meanwhile, the ultrastrong covalent-like interlayer coupling guarantees the high-efficiency carrier injection across PtTe 2 and MoS 2 . The concept that synergizes 2D semiconductors as the channel and Dirac semimetal PtTe 2 as an interlayer will offer a promising approach toward the design of high-performance 2D electronics.

Toward Nanoscale Organic Tunnel Field-Effect Transistors with Small Subthreshold Swing and High On-State Current: A Computational Design Based on Two-Dimensional Covalent-Organic Frameworks

“…The I on is still comparable to that of other TFETs even when the bias is reduced to be as small as 10 –3 V. We note that most inorganic TFETs operate under bias in the range of 0.5–1 V. − While various strategies were proposed to lift the I on in TFETs, , the I on under lower bias is even orders of magnitude smaller than that under the normal bias (0.5–1 V). , As such, our results strongly suggest that the double-layer OTFET designed here is very promising for the LP application. Moreover, it is also instructive to compare our results with other novel heterojunction devices. ,− For instance, the SS of heterojunction FETs, such as those based on IGZO (indium–gallium–zinc oxide) and kagome lattice Si, is usually above 70 mV/dec, which is much higher than that of the double-layer OTFET in this work. It demonstrates that the low-SS characteristic of TFET is retained in the proposed OTFET because of the highly conductive 2D COFs employed in the devices.…”

van der Waals Contact for Two-Dimensional Transition Metal Dichalcogenides

“…The most straightforward integration method to form a m-TMD/TMD vdW contact is the transfer of m-TMD thin flakes onto the target TMD. This strategy has been extensively employed, resulting in the selection of various m-TMD categories, including degenerately doped TMDs, − distorted structure (T′) TMDs, − and intrinsic m-TMDs, − as vdW contacts to TMDs.…”

“…Furthermore, as an important member of the 2D material library, the variety of intrinsic m-TMDs provides potential options as vdW electrodes for various TMDs. − To date, several m-TMDs, such as NbS 2 , , NbSe 2 , VS 2 , VTe 2 , TaS 2 , PtSe 2, , PtTe 2 , NiTe 2 , CoS 2 , and ZrTe 2 , have been used as electrodes to achieve high-performance transistors. For example, a WSe 2 transistor with NbSe 2 contacts exhibited linear output characteristics even at 77 K, as well as MIT behavior and phonon-limited mobility, indicating the near electrical transparency of the WSe 2 contacts (Figure k–n).…”

Investigation on Contact Properties of 2D van der Waals Semimetallic 1T-TiS2/MoS2 Heterojunctions

“…2 For example, several studies have reported the successful formation of ohmic contacts by using vdW and semimetallic TMDCs. 29,30 Notably, most of these approaches are based on transfer-based methods or on the susceptibility of semimetals when exposed to ambient and harsh conditions. 24 These aspects may not be compatible with currently used semiconductor industrial-scale processes.…”

“…Owing to the low density of states near the charge neutrality level, the semimetals could minimize the generation of MIGS, ultimately achieving low SBH and realizing ohmic contact behavior. ,, Consequently, the vdW and semimetallic contacts can be powerful tools for realizing an atomically clean and electronically sharp metal–TMDC interface with minimized gap states and tunable barrier heights . For example, several studies have reported the successful formation of ohmic contacts by using vdW and semimetallic TMDCs. , Notably, most of these approaches are based on transfer-based methods or on the susceptibility of semimetals when exposed to ambient and harsh conditions . These aspects may not be compatible with currently used semiconductor industrial-scale processes.…”