Fast and sensitive suspended YBaCuO microbolometers using silicon separated by implanted oxygen substrates

Abstract

A process to fabricate epitaxial YBaCuO suspended microbolometers using silicon separated by implanted oxygen (SIMOX) substrates is reported. Unlike the other micromachining techniques, no process step is needed after film deposition and the YBaCuO air-bridge retains excellent superconducting qualities. The support membrane is constituted of a 80-nm-thick CeO2/YSZ buffer layer on a 150-nm-thick silicon layer. The critical temperature Tc(R=0) is 88 K and the transition width is 2.5 K. Current-voltage characteristics directly measured on a 10-μm-wide, 100-μm-long suspended bridge show a critical current density of 7.5×105 A/cm2 at 80 K. The thermal conductance G of this bridge is 2×10−5 W/K. An optical noise equivalent power (NEP) of 6.1×10−12 W/Hz at 1 kHz is deduced from optical sensitivity and noise measurements. The time constant is 6 μs, which is the lowest value reported on such suspended structures. Comparison with a similar suspended bridge fabricated without a silicon layer shows that the sensitivity–bandwidth product of the SIMOX bridge is improved by one order of magnitude, thus demonstrating the feasibility of sensitive and fast YBaCuO bolometers.