Effect of Buffer Termination on Intermixing and Conductivity in LaTiO$_3$/SrTiO$_3$ Heterostructures Integrated on Si(100).

The control of chemical exchange across heterointerfaces formed between ultra-thin functional transition-metal oxide layers provides an effective route to manipulate the electronic properties of these systems. We show that cationic exchange across the interface between the Mott insulator, LaTiO$_3$(LTO) grown epitaxially on SrTiO$_3$(STO)-buffered Silicon by molecular beam epitaxy depends strongly on the surface termination of the strained STO buffer. Using a combination of temperature-dependent transport and synchrotron X-ray crystal truncation rods and reciprocal space mapping, an enhanced conductivity in STO/LTO/SrO- terminated STO buffers compared to heterostructures with TiO$_2$-terminated STO buffers is correlated with La/Sr exchange and the formation of metallic La$_{1-x}$Sr$_x$TiO$_3$. La/Sr exchange effectively reduces the strain energy of the system due to the large lattice mismatch between the nominal oxide layers and the Si substrate.