Some electronic applications of high-temperature superconductors require multilayer structures made from films with a thickness of less than a millionth of a meter (one micron), about 1% of the diameter of a human hair. High-performance electronic devices require high-quality films. Scientists at the CSR have earned a worldwide reputation for depositing excellent films, primarily by laser ablation, in which a pulsed laser beam evaporates a ceramic target of the material and the vapors condense on a heated subtrate.

Laser ablation method for the preparation of ultra-thin films and superlattices, and superconductivity circuits.

To deposit high-quality films, it is necessary to develop an advanced materials capability. For example, one must discover what happens at the interface between two materials. Do atoms diffuse from one material into the next? Does the upper material grow epitaxially -- that is, using the lower material as a template? Can this material grow with different crystal orientations, and if so, how can we control them? These are basic questions in thin film science.

Blue plume from laser evaporation of a superconductor is seen inside a high vacuum chamber.

One focus of research at CSR is deposition of ultra-thin HTS films, only a few unit cells thick, (A "unit cell" consists of the minimum group of atoms capable of showing the entire crystal structure of the compound; a unit cell of yttrium barium copper oxide is 12 Angstroms, about a billionth of a meter, in thickness). CSR researchers have deposited films of yttrium barium copper oxide (YBCO) only 1 or 2 unit cells thick with large current carrying capability, even in strong magnetic fields.

AFM image provided courtesy of Vitaly Talyansky

Achieving smooth defectless surfaces of deposited films is vital for HTS device fabrication. The surface of a 200 nm thick YBCO film depicted in this AFM scan is quite close to the ideal. Spiral growth is evidenced by the unit cell (1.2 nm) thick step formation on the surface.

1. Laser Ablation
2. Thin Film Devices
3. Research Projects
4. Oscillatory Exchange Coupling in All-Compound Superlattices

Center for Superconductivity Research, University of Maryland, College Park, MD 20742-4111
Phone: 301.405.6129 Fax: 301.405.3779
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