English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

ELECTRICAL AND OPTICAL PROPERTIES OF ZINC OXIDE FOR SCINTILLATOR APPLICATIONS Xiaocheng Yang Zinc oxide (ZnO) is a wide-band-gap semiconductor suitable for many optical and optoelectronic applications. Among these is to use single crystal, powder, or ceramic forms of ZnO as a fast UV scintillator. In this work, the electrical and optical properties of ZnO were studied using photoluminescence, X-ray-induced luminescence, optical absorption, and Hall Effect techniques. This study included single crystal ZnO and ZnO:Ga samples grown from high-pressure-melt (HPM), seeded chemical-vapor-transport (SCVT), and hydrothermal (HYD) techniques; powder samples synthesized using both solution and solid-state processes, and purchased from different commercial sources; and ceramic samples prepared by hot-uniaxial-pressing and spark-plasma-sintering methods. Temperature-dependent PL and Hall measurements were combined to establish the luminescence origins in the n-type ZnO and ZnO:Ga single crystals. Based on a PL line-shape analysis, including band-gap renormalization, the direct (e,h) transition is the main luminescent channel in highly n-type ZnO:Ga, while FX and FX-LO recombinations are responsible for the UV PL from as-grown ZnO. An intrinsic mobility limit for n-type ZnO was established by including three major phononscattering mechanisms. Analysis of Hall data from single-crystal samples including both neutraland ionized-impurity scatterings provided donor and acceptor concentrations and energy levels. High n-type single-crystal ZnO samples prepared either by Ga doping and codoping, or by after-growth treatments, were also studied. Absorption and reflectance data were used to obtain free carrier concentrations from the Ga-doped and co-doped crystals, and it was found that several samples with n ~ high-10 to low-10 cm had optimum UV luminescence. Anneal treatments in reducing atmospheres increased free carrier concentrations in HPM and HYD samples, but an induced absorption band due to oxygen vacancies limited the UV emission from these samples. PL and X-ray-induced luminescence studies on powder ZnO:Ga samples demonstrated that high Ga-doping levels and H-anneal treatments can improve UV emission, while impurities such as Cu and Li enhance the lower energy visible emissions and affect the UV output. For ceramic forms of ZnO, reduction of scattering losses remains as the main challenge for improved scintillation. ACKNOWLEDGMENTS I really couldn’t find a right word to express my gratitude to Dr. Nancy Giles, my advisor. I would like to thank her for her support and guidance for my study and research here at her lab, but what I appreciate more is her exemplary dedication to research and teaching. Working with Dr. Giles, I learned not only that I can do research, but I can enjoy it, not only how to focus on the present project, but how to see the whole forest. Each time we talked about science, I benefited from her insightful and inspiring discussions. At times that I experienced personal frustrations, she always encouraged me to chin up again. Thanks are also due to Dr. Larry Halliburton, for his help and encouragement on my study, and for his willingness to share his knowledge as well as his optimism and wisdom. I’d like to thank my committee members Dr. Wathiq Abdul-Razzaq, Dr. Feruz Ganikhanov, and Dr. Charter Stinespring for sacrificing their priceless time to serve in my committee. I would also like to acknowledge the support of Dr. John Neal at ORNL for his support, and thank our colleagues at ORNL and UC-Davis: Dr. Lynn Boatner, Dr. Zuhair Munir, Dr. David DeVito, Dr. Mei Hong, Beth Armstrong, Joanne Ramey, Banu Kesanli, and Jane Howe, for allowing me to be a member of a strong and fruitful team. I appreciate the help and friendship I received from Shan Yang, Dr. Lihua Bai, Dr. Ming Luo, Dr. Chunchuan Xu, Dr. Yongquan Jiang, and Dr. Sean Evans. Last but not least, I’d like to thank my wife Daisy for her support and understanding over these years, thank my son for his cheers, and thank my mother and my siblings for their encouragement from the other side of the globe.

Electrical and optical properties of zinc oxide for scintillator applications