PNNL

Abstract

We have measured the band offsets and materials properties of epitaxial SrTiO3/Si(001) heterojunctions for both n- and p-substrates, with and without an interfacial SiO2 layer. The through-air transfer from the growth chamber to the photoemission system results in significant surface hydroxylation and roughening, although the SrTiO3-Si interface is undisturbed. Surface hydroxylation notwithstanding, the structural quality of 20A thick epitaxial SrTiO3 on Si(001) is comparable to that of bulk SrTiO2(001). We find valence and conduction band offsets of ~2.1eV and ~0.0 eV, respectively, independent of doping type and the presence of SiO2. These results are consistent with theoretical band offset predictions based on the electron affinity rule, modified by the presence of an interface dipole. While measured leakage currents through SrTiO3/SiO2/Si(001) heterostructures are significantly reduced relative to control SiO2/Si(001) specimens, the band offset measurements suggest that the related leakage current is not from an additional conduction band barrier.