Jiping Cheng & Ruyan Guo, Pennsylvania State University, DMR-0505946

1. Microwave Growth and Characterization of Zinc Oxide Single Crystal Microtubes for Optoelectronic Applications Jiping Cheng & Ruyan Guo, Pennsylvania State University, DMR-0505946 A novel microwave growth technique is developed for fabrication of high quality and high purity ZnO single crystal microtubes. The microwave grown ZnO microtubes are colorless, fully transparent, and of near-perfect crystallinity with unique crystalline structure. The wall thicknesses of the ZnO microtubes are typically between 0.5 and 1 mm, with various cross-sectional dimensions ranging from 100 to 250 mm and different lengths up to 5 mm. The ZnO single crystal microtubes exhibit some excellent optoelectronic and dielectric properties such as strong near band-edge emission at room temperature, high ultraviolet (UV) photoresponse, strong electric field emission, and extremely high piezoelectric coefficient, promising potential applications in civil and military areas. Microwave grown ZnO microtube The growth technique developed in this research features self-encapsulated and contamination-free growing of ZnO single crystal microtubes. (a) (b) The ZnO microtubes exhibit desired ultraviolet photoresponse characteristics. (a) The ZnO microtubes have their maximum UV photoresponse in wavelengths ranging from 300 to 350 nm, with a cut-off wavelength at 370 nm. (b) The evolution of the photocurrent of the ZnO microtubes upon 365 nm UV illumination revealed reversible switching characteristics and up to five orders of magnitude increase in the photocurrent as the UV light was turned on.

2. Education and Outreach Jiping Cheng & Ruyan Guo, Pennsylvania State University, DMR-0505946 • EE422 Optical Engineering Lab (taught by Dr. Guo). A hands-on interferometric measurement set up has been added to the official course offering in an advanced optical engineering lab for the undergraduate students of Department of Electrical Engineering. • PIs and the students supported by this grant are active participants of the Annual Penn State University Materials Day. More than 200 people from industries and research institutes attended the Materials Day held in Penn Stater Conference Center Hotel, April 10-11, 2007. Two posters were presented to public at this event. • PIs and the students supported by this grant are active participants of the Open House event hosted by Center for Optical Technologies, Commonwealth of Pennsylvania, at Lehigh University. Two posters were presented this past year at the event which showcased our research activity and capability to more than 100 visitors (Pennsylvania industries and high school students). • PIs and the students supported by this grant continue to host undergraduate students participating in NSF REU program by mentoring their research and hosting lab tours for EEREU group (Dr. Ruyan Guo serves as PI in EEREU program).