Importance of CVD-process parameters for the synthesis of novel Al/Al2O3 and Ga/Ga2O3 composite nanostructures

Abstract

Composite Al/Al2O3 films are deposited by chemical vapor deposition (CVD) of the precursor [H2Al(OtBu)]2. Deposition parameters like precursor flow, substrate temperature and deposition time are varied to obtain different layers. They are systematically characterised to investigate their crystallinity (XRD), composition (EDX), structure and morphology (SEM and TEM). Either ball-like core shell structures of aluminium and alumina or with raising temperature (510°C to 600°C) nanowires of aluminium embedded in Al2O3 are produced. Interesting parallelism between the crystalline structure and morphology is drawn to confirm the role of aluminium in the one dimensional growth. No catalysis is needed to produce the different morphologies, as the growth mechanism proceeds in a self catalytic way. Preliminary investigations on layers grown with similar conditions are carried out with the homologue precursor [H2Ga(OtBu)]2. SEM and EDX analysis evidenced high diversity of the layers obtained. Gallium nanodroplets, 1D and 3D nanostructures with varying amount of gallium, Ga2O3 and carbon are synthesised. Particularly, the substrate nature played an important role in this case.