High‐throughput screening of phase‐engineered atomically thin transition‐metal dichalcogenides for van der Waals contacts at the Schottky–Mott limit

Abstract

A main challenge for the development of two‐dimensional devices based on atomically thin transition‐metal dichalcogenides (TMDs) is the realization of metal–semiconductor junctions (MSJs) with low contact resistance and high charge transport capability. However, traditional metal–TMD junctions usually suffer from strong Fermi‐level pinning (FLP) and chemical disorder at the interfaces, resulting in weak device performance and high energy consumption. By means of high‐throughput first‐principles calculations, we report an attractive solution via the formation of van der Waals (vdW) contacts between metallic and semiconducting TMDs. We apply a phase‐engineering strategy to create a monolayer TMD database for achieving a wide range of work functions and band gaps, hence offering a large degree of freedom to construct TMD vdW MSJs with desired contact types. The Schottky barrier heights and contact types of 728 MSJs have been identified and they exhibit weak FLP (−0.62 to −0.90) as compared with the traditional metal–TMD junctions. We find that the interfacial interactions of the MSJs bring a delicate competition between the FLP strength and carrier tunneling efficiency, which can be utilized to screen high‐performance MSJs. Based on a set of screening criteria, four potential TMD vdW MSJs (e.g., NiTe2/ZrSe2, NiTe2/PdSe2, HfTe2/PdTe2, TaSe2/MoTe2) with Ohmic contact, weak FLP, and high carrier tunneling probability have been predicted. This work not only provides a fundamental understanding of contact properties of TMD vdW MSJs but also renders their huge potential for electronics and optoelectronics.

Mechanistic understanding of the interfacial properties of metal–PtSe2 contacts

“…6a, the FLP factors of several 3D and vdW-type metal–semiconductors are listed for comparison. 32 We found that the overall FLP factors decrease with increasing interfacial binding energy, indicating the increasing strength of FLP effect. In addition, the FLP factor of metal–BL PtSe 2 is smaller than that of metal–ML PtSe 2 due to the larger binding energy in metal–BL PtSe 2 , which is consistent with the overall relationship between the FLP factor and the binding energy.…”

“…S3 †). 32,33 We found that the PtSe 2 -dominated bands always across the Fermi level for all the metal-PtSe 2 systems, demonstrating the hybridization of states of interfacial PtSe 2 and metals. In addition, the degree of hybridization is proportionate to the binding strength between metals and PtSe 2 .…”

“…Therefore, the introduction of a buffer layer to metal–semiconductor systems is proved as an effective scheme to suppress the strong FL effect. Besides, other promising schemes such as the introduction of vdW 2D semimetals 32 and the atomic passivation on the metal surface 37 are also considered as effective ways to suppress the strong FL effect, which will be discussed in our future studies.…”

“…As one of important factors that determine the carrier transport efficiency, we now discuss the Schottky barrier at the vertical interface based on the energy difference between the Fermi level of the metal-PtSe 2 contacts and the band edge energies of PtSe 2 in the metal-PtSe 2 contacts. 32 As shown in Fig. 2, by referring to the original band structures of supercell PtSe 2 in contacts (see Fig.…”

A conformal van der Waals graphene coating enabled high-performance piezo-ionic sensor for spatial, gesture, and object recognition

“…Due to the comparable surface energies of graphene nanosheets (35-115 mJ m −2 ) and Naon lms (14.2 mJ m −2 ), the layer-by-layer structure of graphene nanosheets is easily formed. [27][28][29] By repeating the process, graphene nanosheets accumulated onto the Naon surface, and a vdWGR electrode-assisted Naon sensor (vdWGRNS) was obtained. It is worth mentioning that the thickness of the vdWGR coating cannot grow innitely because of the restriction of shear failure.…”