凯发

In this presentation, I will show our recent progress on the chemical vapor deposition (CVD) growth of graphene and other two-dimensional (2D) materials. For the CVD growth of graphene, we have developed an ambient-pressure CVD process to grow millimeter-size single-crystal graphene on Pt [1], observed the edge-dependent growth behavior of graphene [2], and found an efficient way to heal the defects in graphene [2,3]. Importantly, we have proposed a nondestructive electrochemical bubbling transfer method [1], and realized the continuous production of large-area graphene transparent conductive films (TCFs) by integrating the bubbling method with the scalable roll-to-roll process. With these graphene TCFs as electrodes, we have fabricated 7 inch flexible touch panels and 4 inch flexible OLEDs.

For the CVD growth of other layered 2D materials, we have developed an ambient-pressure CVD process with Au foils as substrate to realize the self-limited catalytic surface growth of uniform monolayer WS2 single crystals of millimeter size and large-area films [4]. The weak interaction between the WS2 and Au enables the intact transfer of the monolayers to arbitrary substrates using the electrochemical bubbling method without sacrificing Au. The WS2 shows high crystal quality and optical and electrical properties comparable or superior to mechanically exfoliated samples. We also demonstrated the roll-to-roll/bubbling production of large-area flexible films of uniform monolayer, double-layer WS2 and WS2/graphene heterostructures, and batch fabrication of large-area flexible monolayer WS2 film transistor arrays.

Beside layered 2D materials, we have also realized the CVD growth of large-size high-quality non-layered ultrathin 2D transition metal carbides (TMC) crystals, such as Mo2C, WC, and TaC, by using Cu/transition metal foils bilayer as substrate [5]. For instance, the 2D α-Mo2C crystals obtained are a few nanometers thick, over 100 m in lateral size, and very stable under ambient conditions. They show 2D characteristics of superconducting transitions that are consistent with Berezinskii–Kosterlitz-Thouless behavior and show strong anisotropy with magnetic field orientation, and strong dependence of superconductivity on thickness of the crystals. These ultrathin TMC crystals further expand the large family of 2D materials.