Controllable Synthesis of Wafer‐Scale Graphene Films: Challenges, Status, and Perspectives

Abstract

However, the high cost of SiC wafers brings an insurmountable barrier toward the batch production. Mature transfer techniques are also under development for the application in microelectronics. Additionally, the number of layers seems not well controlled, resulting in an unsatisfied nonuniformity over the entire 2-in. wafer. [35] Raman mapping for the 2D peak indicates the variation of layer thickness and strain (Figure 2b). [35] Upon correcting the peak shift caused by the strain, the map in Figure 2c ultimately shows that the graphene epitaxially grown on SiC is dominantly 1-2 layers. [35] Meanwhile, reduced graphene oxide (rGO) could also fulfill wafer-scale films affording high uniformity. [33,[36][37][38] Recently, Juvaid et al. reported the synthesis rGO films on target substrates by pulsed laser deposition (PLD), as depicted in Figure 2d. [33] A 4-in. wafer can be attained (Figure 2e), which is featured by smooth surface, high transparency, and excellent uniformity (evaluated by Raman spectroscopy in Figure 2f). [33] Despite these advances, the process of chemical oxidation introduces a large number of defects in the crystalline structure of rGO, resulting in marked decline in the electrical and thermal properties. [12] CVD is found to be the most widely used technique in semiconductor industry to synthesize thin films, which, in particular, is able to produce large-area graphene films on metallic or insulating substrates in controllable fashions. [39][40][41][42][43] In a typical CVD process for graphene synthesis, carbon gaseous precursor flows through the hightemperature reaction zone and generates active reaction species for subsequent nucleation and growth of graphene Figure 1. Various types of devices based on wafer-scale graphene films. The central panel: photos of wafer-scale graphene devices.Reproduced with permission. [16] Copyright 2010, Science. Reproduced with permission. [15] Copyright 2020, Springer Nature. Reproduced with permission. [17] Copyright 2019, Wiley-VCH. Reproduced with permission. [18] Copyright 2019, Wiley-VCH. a) Schematic illustration of the transfer process of CVD graphene onto a single CMOS die containing a read-out circuit of the image sensor. Reproduced with permission. [19] Copyright 2017, Springer Nature. b) 3D schematic illustration of a graphene-based waveguide-integrated electro-absorption modulator. Reproduced with permission. [20] Copyright 2011, Springer Nature. c) Schematic of a dual-gate bilayer graphene transistor device. Reproduced with permission. [21] Copyright 2010, American Chemical Society. d) Tilted view scanning electron microscopy image of a graphene receiver integrated circuit, showing the integration architecture of key components including graphene field effect transistor (GFET). Reproduced with permission. [22] Copyright 2014, Springer Nature. e) Schematic of device architectures proposed in resistive random access memory technology based on graphene and related materials. Reproduced with permission. [23] Copyright 2017, Wiley-VCH. f ) Schematic re...

The Rise of Graphene Photonic Crystal Fibers

“…Due to the advantages of low cost, simple preparation process, strong controllability, and mass production, together with the obvious catalytic effect of a metal substrate on graphene growth, the CVD method has become the mainstream method for the preparation of large-area, high-quality graphene on metal substrates and has been developed to a relatively mature stage. [34][35][36][37][38][39][40][41][42][43][44][45][46][47][178][179][180][181][182][183][184][185] However, the CVD growth strategy of Gr-PCFs is challenging due to the lack of a metal catalyst and the difficulty in gas flow control along the long micrometer-sized holes in a silica PCF. The successful growth of Gr-PCFs benefits from extensive experience in the CVD growth of graphene glass/ insulator substrates.…”

Toward Direct Growth of Ultra‐Flat Graphene

“…[1] Synthesis determines the future: realizing macroscopic flatness of graphene has long been a pursuit of chemical vapor deposition (CVD) and multilayer islands in thus-produced film when tracking the research status in this realm. [10] These limitations necessitate the exploration of disruptive synthetic technology toward the realization of directly grown ultra-flat graphene.…”

Direct-Chemical Vapor Deposition-Enabled Graphene for Emerging Energy Storage: Versatility, Essentiality, and Possibility

“…Chemical vapor deposition (CVD) has been deemed as one of the most promising synthetic routes for achieving the controllable and scalable preparation of graphene architectures (i.e., films). − The CVD-derived graphene over metals is typically processed by a cumbersome transfer procedure for envisaging ultimate applications, − which inevitably gives rise to the metal residues and polymeric contamination . To circumvent these hurdles, the direct (i.e., transfer-free) CVD synthesis has emerged as an appealing alternative to grow conformal graphene over arbitrary substrates. − This straightforward strategy readily bypasses the tedious transfer steps, which can also realize morphologic and electronic modulations of graphene to maximize its practicability.…”