Wafer-Scale Growth of Ultrauniform 2D PtSe₂ Films with Spatial and Thickness Control through Multi-step Metal Conversion

Metal conversion processes have been instrumental in advancing semiconductor technology by facilitating the growth of thin-film semiconductors, including metal oxides and sulfides. These processes, widely used in the industry, enhance the semiconductor manufacturing efficiency and scalability, offering convenience, large-area fabrication suitability, and high throughput. Furthermore, their application to emerging two-dimensional (2D) semiconductors shows promise in addressing spatial control and layer number control challenges. In this work, we designed a multi-step metal conversion process for 2D materials to synthesize a high-quality and ultrauniform film. PtSe₂ is introduced to utilize its wide-band-gap tunability, which exhibits both semiconductor and metallic properties. Our multi-step-grown PtSe₂ film shows extremely low roughness (R_a = 0.107 nm) and improved interlayer quality compared to the single-step PtSe₂ film. Additionally, we explored the growth mechanism of the metal conversion process and how the multi-step method contributes to the thickness uniformity of the film. We demonstrated a thin PtSe₂ channel field-effect transistor (FET) array with p-type behavior with a maximum on/off ratio ∼10³. The FET fabricated by the MoS₂ channel with the semimetallic multi-step PtSe₂ electrode shows an enhanced performance in mobility and contact resistance compared to the conventional single-step PtSe₂ electrode FET.