Nanostructured interfaces

Nanostructured interfaces are interfaces between two materials (or grains of a material), where the number of atoms at the interface gets close to the order of magnitude of atoms in the bulk. In collaboration with Prof. Duscher’s group at North Carolina State University, we examine the structure and electronic properties at mostly nanostructured interfaces through a combination of theory and experiment.

Example: Atomically Sharp Ge/SiO₂ Interface*

We examine the interfaces between Si and SiO₂ and between Ge and SiO₂ for the first time with atomic-resolution EELS in comparison to theoretical spectra (Fig. 1). Kinetic-Monte Carlo simulations of high-temperature oxidized Ge-implanted Si shows that the repulsive interaction between Ge and O leads to the previously reported “snowplowing” effect, where the oxidation front compacts the Ge into a compact Ge-only layer. At high Ge concentrations, the process leaves some Ge atoms behind in the oxide, similar to snow falling over the upper edge of the snow shovel when it is full. The interface between oxide and Ge is atomically sharp, never observed for the Si/SiO₂ interface. The electronic properties of the sharp interface are superior to those of the graded Si/SiO₂ interface, potentially enabling strongly improved electronic devices.

* S. Lopatin, G. Duscher, T. Liang, and W. Windl (to be published); preliminary results in W. Windl, T. Liang, S. Lopatin, and G. Duscher, Investigation of the Detailed Structure of Atomically Sharp Ge/SiO₂ Interfaces, Proc. of the 2003 International Conference on Simulation of Semiconductor Processes and Devices, September 3-5, 2003, Boston, MA, p. 143. This work has been reported in many newspapers worldwide, for example in Innovations Report.