Schottky Barrier Diodes Based on Freestanding Polycrystalline Diamond Membranes

Polycrystalline diamond (PCD) thin films have been widely used as a coating material to enhance surface properties or protect against wear and tear. However, their implementation as an electronic material has been hindered by inconsistent semiconducting properties arising from their polycrystalline nature and associated processing challenges. In this study, the first demonstration of vertical Schottky barrier diodes fabricated using freestanding PCD membranes (PCDm) is presented, which addresses these limitations by enabling dual-side access to the PCDm. The Schottky contact is formed on the high-quality growth surface with larger grains and high sp³ carbon content, while the ohmic contact is placed on the smoother, sp²-rich bottom side. This configuration enables distinct contact optimization on each surface, eliminating the trade-offs encountered in conventional planar devices based on thin-film PCD. The devices exhibit an excellent rectifying behavior with an on/off ratio of ≈10³ and a breakdown field of 0.25 MV cm⁻¹—among the highest reported for PCD-based Schottky barrier diodes. The result paves the way for the development of high-performance electronic devices based on freestanding and transferable PCDm, positioning it as a cost-effective and scalable wide-bandgap semiconductor for next-generation electronics.