Germanium Thin Film Growth and Annealing

The Ge precursors were deposited on SiO₂ glass substrates using the Knudsen cell of a molecular beam deposition system (base pressure: 5 × 10⁻⁷ Pa). The deposition rate was 1.0 nm/min where the sample substrate was not heated. The deposition time was 100 min. The Ge source, manufactured by Furuuchi Chemical Corporation, had a purity of 99.999%. The substrate temperature during the deposition, T_d, ranged from 50 to 200 °C. We note that T_d spontaneously rises from room temperature to 50 °C without heating the substrate because of the heat propagation from the Knudsen cell. The samples were then loaded into a conventional tube furnace in a N₂ atmosphere and annealed at 375 °C for 140 h, 400 °C for 40 h, and 450 °C for 5 h to induce SPC.