Plasma-Enhanced Chemical Vapor Deposition of Two-Dimensional Materials for Applications

Abstract

Conspectus Since the rise of two-dimensional (2D) materials, synthetic methods including mechanical exfoliation, solution synthesis, and chemical vapor deposition (CVD) have been developed. Mechanical exfoliation prepares randomly shaped materials with small size. Solution synthesis introduces impurities that degrade the performances. CVD is the most successful one for low-cost scalable preparation. However, when it comes to practical applications, disadvantages such as high operating temperature (∼1000 °C), probable usage of metal catalysts, contamination, defects, and interstices introduced by postgrowth transfer are not negligible. These are the reasons why plasma-enhanced CVD (PECVD), a method that enables catalyst-free in situ preparation at low temperature, is imperatively desirable. In this Account, we summarize our recent progress on controllable preparation of 2D materials by PECVD and their applications. We found that there was a competition between etching and nucleation and deposition in PECVD, making it highly controllable to obtain desired materials. Under different equilibrium states of the competition, various 2D materials with diverse morphologies and properties were prepared including pristine or nitrogen-doped graphene crystals, graphene quantum dots, graphene nanowalls, hexagonal boron nitride (h-BN), B–C–N ternary materials (BC x N), etc. We also used mild plasma to modify or treat 2D materials (e.g., WSe2) for desired properties. PECVD has advantages such as low temperature, transfer-free process, and industrial compatibility, which enable facile, scalable, and low-cost preparation of 2D materials with clean surfaces and interfaces directly on noncatalytic substrates. These merits significantly benefit the as-prepared materials in the applications. Field-effect transistors with high motilities were directly fabricated on graphene and nitrogen-doped graphene. By use of h-BN as the dielectric interfacial layer, both mobilities and saturated power densities of the devices were improved owing to the clean, closely contacted interface and enhanced interfacial thermal dissipation. High-quality materials and interfaces also enabled promising applications of these materials in photodetectors, pressure sensors, biochemical sensors, electronic skins, Raman enhancement, etc. To demonstrate the commercial applications, several prototypical devices were studied such as distributed pressure sensor arrays, touching module on a robot hand for braille recognition, and smart gloves for recording sign language. Finally, we discuss opportunities and challenges of PECVD as a comprehensive preparation methodology of 2D materials for future applications beyond traditional CVD.

Recent progress of heterostructures based on two dimensional materials and wide bandgap semiconductors

“…The fabrication and reliable integration techniques of 2D/WBS heterostructures are of great importance for further research and device applications. Currently, the methods to realize 2D/WBS heterostructures are divided into three approaches, including exfoliation and transfer, [68,69] direct preparation methods such as Chemical Vapor Deposition (CVD) [70][71][72] and Pulsed Laser Deposition (PLD) [73][74][75] , and the combination methods of physical or chemical approaches with exfoliation and transfer. [76] By optimizing the exfoliation and technologically scalable transfer technology, high-quality 2D heterostructures can be effectively obtained.…”

Plasma modified and tailored defective electrocatalysts for water electrolysis and hydrogen fuel cells

“…54,56,57,76,78,79 Plasma-enhanced chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD) are common methods for nano manufacturing, and compared to conventional thermal deposition, the conditions are milder due to the lower nucleation barrier rendered by the plasma. 82,83 In addition, plasma exfoliation has been used to exfoliate graphene and layered double hydroxides into monolayers with insignificant chemical contamination 84,85 and plasmas can be coupled with magnetic, electric, and ultrasonic fields to produce complex and multiscale structures in materials.…”

Continuous orientated growth of scaled single-crystal 2D monolayer films

“…What is more, there are other advantages for the PECVD method, such as transfer-free and industrial compatibility. 117 Secondly, improving the yield capacity should be deeply considered during industrialization. At present, there are two main methods to produce 2D materials with high throughput named as batch-to-batch (B2B) and roll-to-roll (R2R).…”