Electron-phonon relaxation time in ultrathin tungsten silicon film
Using amplitude-modulated absorption of sub-THz radiation (AMAR) method, we studied electron-phonon relaxation in thin
disordered films of tungsten silicide. We found a response time τR ~ 800 ps at critical temperature Tc = 3.4 K, which scales as
T –3 in the temperature range from 1.8 to 3.4 K. We discuss mechanisms, which can result in a strong phonon bottle-neck
effect in a few nanometers thick film and yield a substantial difference between the measured time, characterizing response at
modulation frequency, and the inelastic electron-phonon relaxation time τe–ph. We estimate the electron-phonon relaxation
time to be in the range τe–ph ~ 100-200 ps at 3.4 K.