In situ Raman monitoring of ultrathin Ge films

We report the in situ interference enhanced Raman spectroscopy of ultrathin crystalline Ge films grown at 300 °C. The Raman spectra of the films show a peak at ∼290 cm−1 attributed to the confined optical phonon and a broadband on the low-frequency side at ∼254 cm−1 for 5 and 10 Å thick films. The latter is attributed to disordered surface with large number of dangling bonds. For thicker films, the low-frequency mode appears at 270 cm−1 assigned to surface optical phonons.