Bulletin Spring‧Summer 1994

Dr. Wong operating the 4-circle X-ray diffraction equipment in the Physics Department Dr. H. K. Wong obtained his B.Sc.andM.Phil. from The Chinese University of Hong Kong, and earned his Ph.D. in physics from Northwestern University in 1985. He worked as a research scientist at IBM San Jose Research Lahoratories for oneyear, and then joined the Physics Department of this university. His research interest is in novel thin film materials. Dr. Wong is concurrently Radiation Protection Officer of the University. The second method is similar, but instead of a laser pulse, it uses argon ions to bombard the target and knock out the atoms. This is known as sputtering. To reduce defects in thin film samples, the substrate material must be carefully selecte d so that the structure of its crystal lattice matches that of the material being deposited. By selecting th e substrate, one can tailor the crystal orientation o f the thin film; this is particularly important as the properties o f ceramic thin films are highly directional. The structure of the thin films at the atomic level is then determined by X-ray diffraction experiments. Dr. Wong and his students built the X-ray facilities in-house, at a fraction of the cost for a factory-made instrument. Materials and Applications The research team has by now studied a number of ceramic thin films. The ceramic Pb(Zr,Ti)O3 is a ferroelectric, and has been deposited on magnesium oxide and spinel crystals. The material YBa2Cu3O7-x is a h i gh temperature superconductor, and has been deposited on sapphire and strontium titanate crystals. These thin f i lm samples can be further processed to make devices. Nonvolatile random access memory ( RAM) for computers can be made from Pb(Zr,Ti)O3 thin films. Superconductors can b e used to make superconducting quantum interference devices ( SQU I DS ), wh i ch are i nc r ed i b ly sensitive instruments for detecting magnetic fields, even brain waves. The same preparation techniques can be applied to many ceramics whic h have other novel properties, and which are object s of study by Dr. Wong and his team. Research Projects 13