CVD-Grown Diamond Extreme-UV Detectors Show Promise

Extreme-ultraviolet detectors fabricated from single-crystal diamond films grown by chemical vapor deposition (CVD) avoid the performance problems encountered in previous devices, report scientists at Università di Roma "Tor Vergata" and the Associazione Euratom-ENEA sulla Fusione, both in Rome. The results suggest that such detectors may find application in astrophysics and nuclear fusion research.

In the work, they grew 150-µm-thick films of single-crystal diamond on a low-cost commercial diamond substrate in a modified microwave plasma chemical vapor deposition reactor. They fabricated interdigitated aluminum contacts on the film using a photolithographic process and evaluated the response of the completed device at wavelengths between 20 and 2400 nm, generated using DC gas discharge sources and an optical parametric oscillator tunable laser.

The detector displayed a UV-to-visible rejection ratio of approximately six orders of magnitude, with a signal drop of four orders of magnitude at 225 nm. Helium emission lines at 25.6, 30.4 and 58.4 nm were clearly evident, despite an output photocurrent in the picoampere range. The measured intrinsic response time in the extreme-UV was 0.2 s, limited by the time constant of the electrometer preamplifier employed in the experiments.