Work in Prof. Altman’s group is primarily focused on surfaces and interfaces of transition metal oxides.  The motivation for the work is both fundamental and applied.  On the fundamental side, we are interested in how metal cations interact in complex oxides to create catalysts that are more active and selective than any of the component binary oxides.  This research involves advanced epitaxial growth techniques to create test structures where the environment around the transition metal cation is both well defined and controllable, adsorption and reaction studies, and atomic-resolution scanning probe microscopy to characterize the structure of the active sites.  Another project is focused on the surfaces and interfaces of ferroelectric materials.  A ferroelectric is a material that develops a macroscopic switchable electric field in a manner analogous to a ferromagnetic material.  The ferroelectric field is a result of a non centro-symmetric crystal structure that creates a dipole moment; thus the atomic arrangement at the surface depends on the poling direction.  We have shown that this leads to polarization- dependent adsorption energies of polar molecules such as acetic acid.  We are now working on investigating exploiting this phenomenon to create surfaces with switchable reactivity and chemical sensors.  With the Center for Research on Interface Structure and Phenomena, we are working on understanding how crystalline oxides can be grown epitaxially on semiconductor surfaces without oxidizing the semiconductor.  Applications include new gate dielectrics for the field effect transistors in computer chips and new functionality integrated with existing microelectronics technology, such as the ferroelectric chemical sensor described above.  In Prof. Altman’s group we are using scanning tunneling microscopy to get an atomic scale picture of how the oxide grows which will be used to help understand how new types of oxides can be deposited onto semiconductors, such as superconductors, ferroelectrics, and ferromagnets.  Finally, with Prof. Schwarz of the Mechanical Engineering Department, we are developing new atomic force microscopy techniques that will enable atomic-scale mapping of the chemical functionality and reactivity of surfaces.  This work involves unique low temperature non-contact atomic force microscopy equipment at Yale and development of methods to stably sensitive tips to specific chemical properties.