Showing papers by "David P. Norton published in 2012"

Plasmon-exciton hybridization in ZnO quantum-well Al nanodisc heterostructures.

Abstract: We demonstrate the formation of a hybridized plasmon-exciton state exhibiting strong exciton-plasmon coupling in ZnO/Zn(0.85)Mg(0.15)O single quantum wells capped with arrays of Al nanodiscs. Tuning the quantum-well width and the diameter and pitch of the Al nanodisc arrays facilitates a transition from the weak-coupling regime into the strong coupling regime. Finite-difference time-domain simulations substantiate the localization of the plasmonic quadrupole moment within the ZnO quantum-well layer, resulting in a hybridized plasmonexciton state demonstrating a Rabi splitting of roughly 15 meV in heterostructures that exhibit a prominent plasmon quadrupole mode. The significant tunability offered by quantum-well heterostructures like those discussed here provides a flexible system for controlling exciton plasmon coupling in a device-compatible thin-film architecture.

Magnetic and magnetotransport properties of Ba2FeMoO6 pulsed laser deposited thin films

Abstract: Phase pure Ba2FeMoO6 thin films were grown by pulsed laser deposition at substrate temperatures ranging from 600 to 900 °C, and the structural, magnetic, and magnetotransport properties were investigated. The grain size, the conductivity, the saturation magnetization, and the coercive field all increase with increasing growth temperature, while the Curie temperature remains relatively constant. All samples showed negative magnetoresistance which is consistent with the half metallic property of double perovskites. Interestingly, the samples grown on the higher temperature substrates showed a small low-field positive magnetoresistance which is not understood. We also have observed an anomalous Hall effect, due to spin-polarized itinerant electrons, in which the saturation field of the hole-like anomalous portion decreases with increasing temperature and at higher temperatures manifests a negative slope (ordinary Hall effect) indicative of negative charge carriers.

The effects of ZnO buffer layers on the properties of phosphorus doped ZnO thin films grown on sapphire by pulsed laser deposition

Abstract: The properties of phosphorus doped ZnO thin films grown on sapphire by pulsed laser deposition were examined, specifically focusing on the effects of undoped ZnO buffer layers. In particular, buffer layers were grown under different conditions; the transport properties of as-deposited and rapid thermal annealed ZnO : P films were then examined. As-deposited films showed n-type conductivity. After rapid thermal annealing, the film on buffer layer grown at a low temperature showed the conversion of carrier type to p-type for specific growth conditions while the films deposited on buffer layer grown at a high temperature remained n-type regardless of growth condition. The films deposited on buffer layer grown at a low temperature showed higher resistivity and more significant change of the transport properties upon rapid thermal annealing. These results suggest that more dopants are incorporated in films with higher defect density. This is consistent with high resolution x-ray diffraction results for phosphorus doped ZnO films on different buffer layers. In addition, the microstructure of phosphorus doped ZnO films is substantially affected by the buffer layer.