Investigation and Batch Fabrication of G-Band Broad Band and Low Loss Monocrystalline Diamond Window for Vacuum Electron Devices

The batch fabrication of G-band broad band and low loss pill-box window with monocrystalline diamond (MD) is introduced in this letter. Design and thermal simulations demonstrate advantages over sapphire, including the broader frequency band and the greater heat dissipation capacity. Following chemical vapor deposition (CVD) production, the surface roughness and the thickness deviation of the MD sheets are effectively controlled within 0.5nm and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5~\mu $ </tex-math></inline-formula>m by polishing technology, respectively. Tiny ring regions on the sheet are metallized using the Ti-Mo-Ni magnetron sputtering technology, followed by vacuum brazing. Test results for batch fabrication show a 90% yield with a vacuum leak rate of less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${5}\times {10} ^{-{12}}$ </tex-math></inline-formula> Pa<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula>m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>/s and a 10% (20GHz) relative bandwidth with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}_{{21}} -1$ </tex-math></inline-formula>dB and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S}_{{11}} \lt -10$ </tex-math></inline-formula>dB simultaneously. The MD window products indicate significant potential for applications in broad-band and high-power terahertz vacuum electron devices.