Surface photoplastic effects in ZnO

ZnO is among a unique and interesting class of materials which exhibit an increase (or decrease) of hardness or flow stress with illumination, referred to as the positive (or negative) photoplastic effect (PPE). Whereas the effect has been observed in the bulk compression testing of several II-VI compounds including ZnO, little has been reported on the near surface material response to illumination. Currently we are using nanoindentation and a "white" light source to study the near surface photoplastic effect in single crystal ZnO. Our studies have indicated that there is a significant increase in hardness within the first 100 nm of the surface when the surface is illuminated. We are currently further exploring this effect and its dependence on crystallographic directions.

Funding provided by:

NSF and OCAST

Relevant publication:

Klopfstein, M.J., Lucca, D.A., Cantwell, G., "Effects of Illumination on the Response of (0001)ZnO to Nanoindentation", physica status solidi (a), 196, (2003) R1-R3.