Wafer-Scale Growth\nof Ultrauniform 2D PtSe<sub>2</sub> Films with Spatial and Thickness\nControl through Multi-step Metal\nConversion

Metal conversion processes have been instrumental in\nadvancing\nsemiconductor technology by facilitating the growth of thin-film semiconductors,\nincluding metal oxides and sulfides. These processes, widely used\nin the industry, enhance the semiconductor manufacturing efficiency\nand scalability, offering convenience, large-area fabrication suitability,\nand high throughput. Furthermore, their application to emerging two-dimensional\n(2D) semiconductors shows promise in addressing spatial control and\nlayer number control challenges. In this work, we designed a multi-step\nmetal conversion process for 2D materials to synthesize a high-quality\nand ultrauniform film. PtSe<sub>2</sub> is introduced to utilize its\nwide-band-gap tunability, which exhibits both semiconductor and metallic\nproperties. Our multi-step-grown PtSe<sub>2</sub> film shows extremely\nlow roughness (<i>R</i><sub>a</sub> = 0.107 nm) and improved\ninterlayer quality compared to the single-step PtSe<sub>2</sub> film.\nAdditionally, we explored the growth mechanism of the metal conversion\nprocess and how the multi-step method contributes to the thickness\nuniformity of the film. We demonstrated a thin PtSe<sub>2</sub> channel\nfield-effect transistor (FET) array with p-type behavior with a maximum\non/off ratio ∼10<sup>3</sup>. The FET fabricated by the MoS<sub>2</sub> channel with the semimetallic multi-step PtSe<sub>2</sub> electrode shows an enhanced performance in mobility and contact\nresistance compared to the conventional single-step PtSe<sub>2</sub> electrode FET.