Integration of functional oxides on silicon for novel devices

The epitaxial growth of metal oxides on silicon opens the possibility of incorporating unique electronic properties with silicon-device technology. Heteroepitaxy of SrTiO₃ (STO) on Si (001) has motivated intense researches over past several years, initially for the purpose of replacing SiO₂ dielectric in the CMOS technology. Although STO turns out eventually not to be suitable for the high k application due to its nearly zero band offset with respect to silicon, the study of STO/Si (001) system remains a highlight considering its potential application as a template to integrate functional oxides with perovskite structure on silicon. Crystalline perovskites form a class of materials which covers a wide range of electrical properties such as superconductivity, ferroelectricity, ferromagnetism. Diverse devices (RF filters, electro-optic coupler, etc.) have been developed based on perovskite films grown on STO substrates. STO buffered Si templates would advantageously replace STO substrates, offering an industry compatible integration solution for functional oxides. We have already successfully in situ grown SrTiO₃ crystalline film on Si(001) by MBE epitaxy without any post-deposition annealing leading to a higher film structure quality with a sharp interface between the SrTiO₃ film and the silicon substrate. On this STO/Si template, ferromagnetic and ferroelectric perovskite films were then successfully deposited.