First-Principles Study on Layered C₂N–Metal Interfaces

Abstract

Using first-principles calculations, we perform a comprehensive study of representative metal (Al, Sc, Pd, Ag, Pt, and Au) contacts with monolayer (ML) and bilayer (BL) CN, which is a low-cost and easily synthesized two-dimensional metal-free semiconductor. Through analyzing the geometries, electronic structures, and Fermi level pinning effects of CN-metal interfaces, we find metals Al and Sc top contact with ML CN are Ohmic, which can be ascribed to the strong interactions and large orbital overlaps. Besides, owing to weak van der Waals interactions at interfaces and low work functions of metallic materials, Ohmic contacts can also be realized in ML/BL CN-Ag and BL CN-Sc systems. Furthermore, it was also predicted that CN-Sc and CN-Ag systems still maintain Ohmic features along the edge contacts. Given the lower resistance of the Ag electrode, the CN-Ag electrode should be a more attractive electrode in practical applications. These predictions not only provide insights into the fundamental properties of the layered CN-metal interfaces but also pave way to design high-performance devices using low-cost layered CN.

Tunable ohmic van der Waals-type contacts in monolayer C3N field-effect transistors

“…66 Previous studies have proven that the GGA-PBE calculation based on single-electron approximation works very well in FET simulation to evaluate the SBH at the interfaces because the doped carriers strongly hinder the electron–electron interaction between the channel region and the electrode region. 37,40,42,67–69 For example, the bandgap of the degenerately doped ML MoSe 2 was calculated as 1.52 eV based on the DFT-PBE method, 70 which is in agreement with the values obtained (1.59 eV) from high-level GW calculation 71 and angle-resolved photoemission spectroscopy (1.58 eV). 72…”

“…34,47,67,75 Compared with the other C-based 2D semiconductor ML C 2 N, ML C 2 N–Pd interface forms medium binding with E b of 0.14 eV and d z of 2.55 Å, and the ML C 2 N–Al and Sc interfaces form strong binding with E b of 0.22 eV and 0.78 eV, and d z of 1.80 Å and 1.71 Å, respectively. This indicates that ML C 2 N forms stronger interactions with metals than ML C 3 N. 40…”

“…15,[34][35][36][37][38] Generally, bulk metals are used as electrodes in 2D semiconductor FETs, and the Fermi level pinning (FLP) effect can be observed in these devices as they suffer from strong interface interactions between bulk metals with dangling bonds and 2D semiconductors. [39][40][41][42] Hence, changing the work function of the metal hinders the tailoring of the Schottky barrier height (SBH). In general, the Schottky barrier is tuned freely to suppress FLP using several methods, such as buffer layer insertion, 17,[28][29][30] metal surface passivation with external atoms, 43 and using transferred metal lms.…”

Tuning the electronic, optical and structural properties of GaS/C2N van der Waals heterostructure for photovoltaic application: first-principle calculations

“…The carbon nitride (C 2 N) material, which contains pore and nitrogen atoms, has been successfully synthesised with a bottom-up wet-chemical reaction method [20] with a bandgap energy of ~ 1.96 eV [28][29][30]. Theoretical reports predict that the band edge positions and the bandgap of C 2 N sheet can be tuned by changing their layer number, external electric field and stacking order with promising high-performance photovoltaic properties [31].…”

Pervasive Ohmic Contacts in Bilayer Bi2O2Se–Metal Interfaces

“…In recent years, many research studies have proved that two-dimensional (2D) semiconducting materials can effectively suppress the short-channel effects in field-effect transistors (FETs) owing to atomically thin uniform thickness and dangling-bond-free lateral pristine surfaces. − Thus, 2D semiconducting materials are regarded as very promising candidate channel materials for using them in the next decade electronic and optoelectronic devices. ,,,,− In a practical FET with a 2D semiconductor as the channel material, however, the semiconductor–metal contact is commonly required for the carrier injection due to the absence of an effective substitutional doping scheme for 2D materials. ,,,− A Schottky barrier (SB) usually emerging at the interface of the semiconductor–metal can remarkably lower the carrier injection efficiency and significantly deteriorate the FET performance. ,,, Therefore, to enhance the device performance, it is essential to effectively decrease the contact resistance or seek the Ohmic contact at the semiconductor–metal interfaces for the upcoming 2D FETs. − ,− …”