Mechanical and Electrical Properties of Free-standing Polycrystal Diamond Membranes

In this study, we demonstrate a novel approach for synthesizing free-standing and transferable polycrystalline diamond membranes (PCDm) to overcome these constraints, thus enabling a much wider spectrum of applications. Two types of PCDm cantilevers -Top-Surface-Up (TSU) and Bottom-Surface-Up (BSU) are fabricated, each with two different sets of dimensions: 150 µm (width) × 1200 µm (length) and 300 µm (width) × 2000 µm (length). Their mechanical and electrical properties are systematically investigated. Atomic Force Microscopy (AFM) analysis revealed that TSU-PCDm has a higher elastic modulus than BSU-PCDm, attributed to differences in grain size and defect distribution. Despite these differences, all PCDms in our work exhibit consistently high modulus values with minimal mechanical degradation across various cantilever geometries. Bandgap measurements using X-ray Photoelectron Spectroscopy (XPS) and UV-vis absorption spectroscopy indicated a lower bandgap for TSU-PCDm due to boron incorporation, while BSU-PCDm exhibited a higher bandgap due to increased hydrogen content. Electrical characterization showed that the sheet resistance of TSU-PCDm decreases under strain, whereas BSU-PCDm maintains stable resistance. These findings unveil the material properties of PCDm and their potential usage for myriad diamond-based electronic applications.