NSLS-II Seminar

"Fully Epitaxial Oxides on Silicon (001)"

Presented by James Reiner, Yale University

Thursday, October 25, 2007, 12:00 pm — NSLS-II Seminar Room, Bldg. 817

Crystalline oxides exhibit a range of interesting and useful phenomena, including magnetism, ferroelectricity, superconductivity, and colossal magnetoresistance. In the last decade, it has become possible to integrate these materials onto a silicon platform in a fully epitaxial structure. This development brings the promise of integrating the rich functionality present in crystalline oxides with the advanced capabilities of modern silicon device technology. To date, the most successful fully epitaxial oxide-silicon (001) heterostructures have been achieved through a single deposition recipe which involves manipulating temperature and oxygen pressure on a layer by layer basis during the deposition of alkaline earth metal. Of these epitaxial oxides, SrTiO3 has received the most experimental and theoretical attention.

We have grown 5 unit cell thick epitaxial SrTiO3 films directly on silicon (001) wafers and measured anomalous x-ray scattering in order to determine the atomic structure of the films. In particular, we examine the possibility of strain-induced ferroelectric polarization by measuring the relative displacements of planes of atoms from the ideal perovskite structure. We have also deposited epitaxial LaAlO3 on silicon by using a 2 unit cell SrTiO3 buffer layer. In situ reflection high energy electron diffraction, x-ray diffraction, and transmission electron microscopy indicate a highly crystalline, epitaxial structure with no SiO2 at the oxide-silicon interface. Metal-oxide-semiconductor capacitors have been fabricated and measured (I-V and C-V characteristics). Inelastic electron tunneling spectroscopy carried out on the LaAlO3 structures indicates a low trap density and the absence of SiO2 at the interface.

Finally, recent work on sub-monolayer strontium deposition on the silicon surface suggests the conventional picture of this structure, upon which the entire crystalline oxides on silicon framework is built, is only a low-temperature pha

Hosted by: John Hill

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