Germanium (Ge) films were deposited on substrates whose temperature was kept at room (Ge-RT) or liquid nitrogen temperature (Ge-LNT) by the cluster-beam evaporation technique. The Raman spectra of both films with a double peak suggest that the crystal structure is not the ordinary diamond but the tetragonal one. The critical temperature for the phase transformation from the tetragonal into the diamond structure is found much higher than that for the Ge nanostructures deposited by the gas-evaporation technique. The Ge-LNT sample exhibits photooxidation and photoluminescence (PL) when it is exposed to the UV light. Their PL and optical absorption characteristics are strongly influenced by a combination of the photo-oxidation and thermal annealing treatments.