Growth of Fractal Crystalline C Films on Hexagonal Boron Nitride With Efficient Charge Transport Property.

The growth of organic semiconductor films with long-range ordered structures on device substrates is crucial for transistor performance and functionality. Wide-bandgap 2D materials, characterized by their atomic-level cleanness and inert surface properties, are considered ideal for growing high-quality organic films. However, there is still a lack of sufficient understanding regarding the growth behavior of organic molecules on 2D materials. Herein, a systematic study is presented on the crystal growth process of fullerene (C) films from the nanoscale to the microscale and obtained its fractal growth mode and large-sized C layered crystalline thin films on mechanically exfoliated hexagonal boron nitride (h-BN) crystals. The balanced intermolecular interaction and molecule-substrate interaction, in conjunction with the high step edge barrier, are the primary factors contributing to the fractal but island growth of C films are revealed. Furthermore, based on these large-sized and highly crystalline polycrystalline thin films, high-electron-mobility phototransistors are fabricated and the resulting devices present high photoresponse performance with rapid photo-switching characteristics. This research offers a thorough investigation into the growth of highly crystalline organic thin films and advances our understanding of their optoelectronic properties.