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Congratulations to Sha Xue for defending her Doctoral Dissertation titled "Design, Fabrication and Evaluation of 2D and 3D Structure 4H-SiC Alpha-voltaic Battery"

Abstract of Dissertation:

Long-lived power sources are needed for remote and extreme environment applications, which traditional chemical batteries may be infeasible or prematurely fail. An alpha-voltaic battery converts the decaying energy of an alpha source directly to electrical power could be applied to mini-medical pacemakers, maintenance-free-sensors, wireless sensors, and space missions that need stable, reliable, long term operating power supplies.

The major roadblock that hinders the development of alpha-voltaic is the low conversion efficiency and the radiation damage incurred to the host material. The highest reported efficiency is less than 3.6 % for alpha-voltaic. In this work, theoretical analysis was conducted to understand the current generating mechanism of an alpha-voltaic battery. Results of the theoretical analysis of the alpha-voltaic battery indicated that the maximum efficiency for a planar structure 4H-SiC Schottky barrier diode-based alpha-voltaic using an 4 ┬ÁCi 241Am alpha source is only 2.96 %, and 6.77 % for a planar structure 4H-SiC p-n diode-based alpha-voltaic. Three power conversion efficiency (PCE) enhancing methods were proposed and verified experimentally. The three methods included: 1) add a thin layer material as the energy degrader to increase the stopping power of the alpha particles in the conversion volume; 2) add a scintillator in between the source and the semiconductor transducer to collect the radioluminescence induced photons which could contribute to the output power, and 3) using a micro-trenched structure energy converter that forms a larger depletion volume compared with the planar structure energy transducer to collect the electron-hole pairs more effectively. Experimental tests showed that the output power had increased two folds by adding a scintillator, and the deposited energy in the semiconductor device has increased when the energy degrader is used. The 3D micro trenched SiC Schottky diode alpha-voltaic using 241Am source were successfully fabricated for the first time to the best of our knowledge, and their electrical performance was compared with the planar structure 2D 4H-SiC Schottky diodes. The 3D micro-trenched structure SiC Schottky diode-based alpha-voltaic showed a maximum threefold power increase compared to the 2D devices. This work provides some insights of developing an alpha-voltaic with higher efficiency, and more efforts are required to fabricate an alpha-voltaic with long lifetime and high power conversion efficiency.