Highly-Crystallized Ge:H Film Growth from GeH 4 Very High Frequency Inductively-Coupled Plasma: Crystalline Nucleation Initiated by Ni Nanodots

We prepared Ni nanodots (Ni-NDs) by exposing ultrathin Ni films to very high frequency inductively-coupled plasma (VHF-ICP) of pure H 2 without any external heating and demonstrated the feasibility of introducing Ni-NDs for subsequent Ge film growth with high crystallinity. A ∼2.0-nm-thick Ni film/quartz was exposed to H 2 plasma generated by inductive coupling with an external single-turn antenna connected to a 60-MHz power generator, and a Ge film was subsequently grown from GeH 4 VHF-ICP. When the Ge film was grown on Ni-NDs from GeH 4 VHF-ICP at 250 °C, the growth of highly crystallized Ge films with crystallinity as high as 95% at a rate as high as ∼15 nm/s, being ∼2 times higher than the rate obtained by VHF-ICP without Ni-NDs, was realized without an amorphous phase near the Ge film/quartz substrate interface. This result is attributed to heat generation due to the efficient recombination of atomic hydrogen on the Ni surface and heat transfer from the NDs to the precursors for the Ge film adsorbed on the Ni-NDs at the initial stage of VHF-ICP from GeH 4 diluted with H 2 to initiate crystalline nucleation and growth.