Shrunk lattice structure and interdiffusion characteristics of 5 nm thick Al(2)O(3) ultrathin films sputtered on...

We report that a 5 nm thick Al(2)O(3) film grown on Si(100) directly by sputtering exhibits strong (110) texture, accompanied by a shrunk lattice structure (Δd/d∼-2.36%). The disordered nature of the film was confirmed by cross-sectional high-resolution transmission electron microscopy, implying the loosened microstructure responsible for enhanced interdiffusion. The oxygen-deficient Al(2+δ)O(3-δ)(δ>0) interdiffusion region with complex interfacial chemical valences was formed between the Al(2)O(3) film and Si substrate, reducing the insulator properties. Using depth profiling in situ x-ray photoemission spectroscopy, we quantitatively reveal the non-stoichiometry deviation of the Al/O ratio at the interdiffusion region. A nominal thickness of 5 nm is required to obtain an actual barrier thickness of approximately 1 nm.