Fabrication of high-strength unsupported metal membranes

Abstract
Metal membranes ?1 μm thick would be useful as diaphragms for capacitance manometers and acoustic transducers, as x‐ray windows, and as deformable mirrors in optical systems. The high strength‐to‐density to Ti makes that metal particularly suitable for fast‐response deformable membranes. Ti films 1/4–2 μm thick and 2–12 cm in diameter were vacuum‐deposited at 20–100 Å/s from an electron‐beam source at 2×10−7 Torr onto Corning 0317 glass substrates which were held at 500°C by contacting with Ga to a Ti heating block. These substrates are very smooth and match the thermal expansion of Ti to a few percent. Pre‐evaporation of a 300 Å thick CaF2 parting layer allowed membrane removal by water‐assisted peeling. Pressure testing showed membranes to have bulk tensile strength of 4.6–6.2×109 dyn/cm2 (68–92 Kpsi) and to behave elastically. They could be mounted under high tension by heating while clamped to a high thermal expansion coefficient Nylon flange.