Low temperature electron-phonon interaction in disordered metal thin films and applications to fast, sensitive sub-millimeter photon sources and detectors

The electron-phonon interaction in metals becomes very weak at very low temperatures (sub-Kelvin temperatures). It is very challenging to measure such weak interaction with traditional techniques. In this thesis work, we develop a new dynamic microwave noise thermometry technique for the study of low temperature electron-phonon interaction in disordered metal thin films. The high sensitivity and fast time response of the technique allow us to study the electron-phonon interaction in nanoscale disordered metal thin films. Both long diffusive metal wires and short wires in SNS structures are observed. We measure the electron-phonon heat conductance G e-ph in steady states, and the electron-phonon time tau e-ph and electronic heat capacity Ce from the electron thermal dynamic in the time domain. The results of the three quantities are consistent within themselves for each device, and can be explained qualitatively by the theory (Sergeev & Mitin 2000). However, the measured values for Ge-ph and Ce are 10-50 times larger than the expected values.; We also develop a new on-chip calibration scheme for ultra-sensitive submillimeter detectors, with phonon-cooled hot electron sources. The sources are essentially metal thin films, whose hot electron induced Johnson noise is equivalent to one-dimensional blackbody radiation. The weak electron-phonon interaction in the film makes the source very accurate and fast at low temperatures for low photon power generation.