Sulfide and Oxide Heterostructures For the SrTiO3 Thin Film Growth on Si and Their Structural and Interfacial Stabilities

Epitaxial SrTiO3 (STO) thin films with high electrical properties were grown on Si using ZnS single- and SrS/MnS hetero-buffer layers. STO films on both ZnS-buffered and SrS/MnS-buffered Si showed two growth orientations, (100) and (110). The temperature dependence of the growth orientation for STO films was different for the ZnS single-buffer layer in comparison with the SrS/MnS heterobuffer layers. (100) growth of STO films on SrS/MnS-buffered Si became dominant at high temperatures about 700 ?C, while (100) growth of STO films on ZnS-buffered Si became dominant at a relatively low growth temperature of 550 ?C. STO(100) films on ZnS-buffered and SrS/MnS-buffered Si showed lattice and domain matches for epitaxial relationships with [001]ZnS?[011]STO and SrS[001]?[011]STO, respectively via 45? in-plane rotation of STO films relative to both ZnS and SrS layers. The ZnS buffer layer contained many stacking faults because of the mismatch between ZnS and Si, however, those defects were terminated at the ZnS/STO interface. In contrast, the MnS buffer was very stable against stacking defect formation. Transmission electron microscopy measurements revealed the presence of a disordered region at the ZnS/Si and MnS/Si interfaces. Auger electron spectroscopy and transmission electron microscopy results showed that a good MnS/Si interface at the initial growth stage degraded to a SiS2-x-rich phase during MnS deposition and again into a SiO2-x-rich phase during STO deposition at the high growth temperature of 700 ?C. It was also observed that STO on SrS/MnS-buffered Si showed a markedly high dielectric constant compared with that of STO on ZnS-buffered Si.