Single-crystal two-dimensional material epitaxy on tailored non-single-crystal substrates

Abstract

The use of single-crystal substrates as templates for the epitaxial growth of single-crystal overlayers has been a primary principle of materials epitaxy for more than 70 years. Here we report our finding that, though counterintuitive, single-crystal 2D materials can be epitaxially grown on twinned crystals. By establishing a geometric principle to describe 2D materials alignment on high-index surfaces, we show that 2D material islands grown on the two sides of a twin boundary can be well aligned. To validate this prediction, wafer-scale Cu foils with abundant twin boundaries were synthesized, and on the surfaces of these polycrystalline Cu foils, we have successfully grown wafer-scale single-crystal graphene and hexagonal boron nitride films. In addition, to greatly increasing the availability of large area high-quality 2D single crystals, our discovery also extends the fundamental understanding of materials epitaxy.

Graphene Growth across the Twin Boundaries of Copper Substrate

“…Recently, we demonstrated the epitaxy of single‐crystal graphene on tailored twinned copper, and a majority of twinned Cu (56.7% of all twinned Cu surfaces) were found to be the ideal substrates for the growth of aligned graphene islands on both sides of the twin boundaries. [ 8 ] By subjecting raw Cu foils to deformation and annealing treatments, a variety of twin structures were obtained and wafer‐scale single‐crystal graphene was grown on them, which provides a unique approach for growing single‐crystal graphene on the non‐single‐crystal substrate. However, the interplay of graphene with different copper substrates as it grows across twin boundaries is unclear.…”

Wafer‐Scale Single Crystal Hexagonal Boron Nitride Layers Grown by Submicron‐Spacing Vapor Deposition

“…However, the limited lateral size and uncontrollable thickness of exfoliated h-BN flakes have seriously hindered practical device applications. Currently, 2D few-layer h-BN has been synthesized by various methods, [11][12][13][14][15][16][17][18][19][20][21] among them chemical vapor deposition (CVD) has been proven to be an efficient and successful method for growing large-area 2D h-BN layers on catalyzing metal or alloy substrates. [17][18][19][20][21] Nevertheless, a complicated and tedious wet transfer process from metal substrates to dielectric substrates is usually required for most of the device applications of h-BN.…”

“…Currently, 2D few-layer h-BN has been synthesized by various methods, [11][12][13][14][15][16][17][18][19][20][21] among them chemical vapor deposition (CVD) has been proven to be an efficient and successful method for growing large-area 2D h-BN layers on catalyzing metal or alloy substrates. [17][18][19][20][21] Nevertheless, a complicated and tedious wet transfer process from metal substrates to dielectric substrates is usually required for most of the device applications of h-BN. The contamination and mechanical damage caused by the transfer process inevitably degrade the quality of h-BN layers and thus the performance of corresponding devices, limiting its widespread applications.…”

Lateral Homoepitaxy Growth of Organic Single-Crystal Arrays for Large-Scale and High-Performance Organic Field-Effect Transistors

“…Meanwhile, the single-crystal device shows a small SS of 0.84 V dec −1 , a near-zero V th of 0.07 V, and a very small hysteresis (Figure S15), manifesting the low trap density within the lateral homoepitaxial C 8 −BTBT single crystals. According to this result, we can estimate the maximum density of bulk traps (D bulk max ) within the C 8 −BTBT SCAs: i k j j j j j y { z z z z z D C q q k T SS ln (10) 1…”

“…Epitaxythe procedure of crystal growth occurring on top of a lattice-matched substrateis an advanced and prevalent method to produce high-quality single-crystalline semiconducting thin films with structural perfection and high purity. − The significant progress in modern electronics in the last few decades has been closely linked with the development of various epitaxial techniques, such as molecular beam epitaxy, − chemical/physical vapor deposition, − liquid-phase epitaxy − and so on. Analogous to inorganic electronics, the development of high-performance organic electronic devices strongly relies on the production of high-quality organic semiconducting single crystals (OSSCs), which has motivated considerable efforts in exploring organic single-crystal growth techniques. − Nevertheless, owing to the large lattice mismatch between organic materials and inorganic monocrystalline substrates and the absence of large-sized organic single crystals as epitaxial substrates, traditional epitaxial growth methods are hardly applicable to organic semiconductor materials.…”