The subject of epitaxial nucleation and growth has been of great interest in recent years. Unique structural phases, unstable in the corresponding bulk materials, can be stabilized in thin films by epitaxy onto a suitable substrate. These structural phases, combined with the loss of the third dimension (and its associated bonds and symmetry) result in the possibility of unique chemical and magnetic properties.
We have begun the study of the nucleation and growth of heteroepitaxial alloy metal on metal thin films. These studies will contribute to the knowledge and understanding of alloy formation in thin films, the structure of bimetallic alloys for catalytic applications, and the structure of magnetic thin films on non-magnetic single crystal substrates. The detailed knowledge of the structure of these films will contribute greatly to the understanding of their physical, chemical, and magnetic properties.
The alloy system of FexNi1-x on Cu(111) is important to the understanding of the giant magnetoresistive (GMR) effect which is used in thin film disk heads today. We use low energy electron microscopy (LEEM) and scanning tunneling microscopy (STM) to measure structural properties of the films. Magnetic spectroscopy and microscopy studies have recently been performed at the Advanced Light Source (ALS), a 3rd generation synchrotron light source, at Lawrence Berkeley National Laboratory. Magnetic spectroscopy by X-ray Magnetic Linear Dichroism (XMLD) has been performed on the Spin Spectrometer at Beamline 7.0 in collaboration with Dr. James Tobin's group at Lawrence Livermore National Laboratory. Magnetic microscopy/spectroscopy using a new photoelectron emission microscopy (PEEM) instrument studies on these alloy films were were performed in collaboraiton with Dr. Andreas Scholl at Lawrence Berkeley National Laboratory. We will also perform magnetic characterization with surface magneto-optic Kerr effect (SMOKE) in our own laboratory.
PEEM Imaging of FexNi1-x on Cu(111)
XMLD Measurements on FexNi1-x on Cu(111)
Another recent study, performed in collaboration with Dr. Robert Hwang's group at Sandia National Laboratories, has used STM to examine the role of stress in thin film alloy formation of Co and Ag on Ru(0001). The interplay between alloying and dislocation formation was studied as a function of the proportion of Ag in the overlayer. Close agreement with theoretical predictions was found.
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© Shirley Chiang - 2001.