Recent Ph.D. Graduates and Dissertations




Weikai Yin, dissertation title: Hydrogen centers and the conductivity of In2O3 single crystals studied by FTIR spectroscopy, Lehigh University (2015).  The vibration properties and microscopic structures of hydrogen centers responsible for unintentional n-type conductivity of In2O3 have been determined for single crystal specimens by vibrational spectroscopy.

Figen Bekisli, dissertation title: Hydrogen in the semiconducting oxides SnO2 and TiO2 studied by FTIR spectroscopy, Lehigh University (2013).  Hydrogen in TiO2 that is slightly reduced gives rise to a neutral OH center with an extra electron.  Vibrational spectroscopy and theory find that this extra electron becomes trapped at a nearby Ti site and acts as a small polaron rather than as an effective-mass-like free carrier.

Haoxiang Zhang, dissertation title: Light-element impurities in multi-crystalline Si, Lehigh University (2013).  The microscopic structures and electrical properties of defects containing nitrogen and oxygen impurities have been determined for the multi-crystalline Si materials used for the fabrication on solar cells.

Lanlin Wen, dissertation title: Experimental study of the H-N-H centers in dilute III-N-V alloys by low-temperature vibrational spectroscopy and uniaxial-stress methods, Lehigh University (2010).  The introduction of hydrogen into dilute III-N-V alloys produces large shifts in the band gap of the host crystal.  The structure and microscopic properties of the H-N-H complex that is responsible for this novel effect are determined by vibrational spectroscopy in conjunction with applied uniaxial stress.

Chao Peng, dissertation title: Hydrogen in semiconductors studied by vibrational spectroscopy, Lehigh University (2010).  The rate of the ortho-para transition for the interstitial H2 molecule in Si has been investigated at room temperature and at 77K by infrared absorption spectroscopy.

Suppawan Kleekajai, dissertation title: N-H2 complexes in dilute III-N-V semiconductors and hydrogenation methods used to fabricate solar cells (2007).  The vibrational properties of N-H2 complexes in GaAsN:H and GaPN:H that shift the band gaps of these dilute alloys have been compared and contrasted.   

Gang Shi, dissertation title: Physics of H in ZnO and H2 in Si from vibrational spectroscopy, Lehigh University (2006).  Hydrogen defects responsible for the n-type conductivity of ZnO were investigated by vibrational spectroscopy.  The H2 molecule in ZnO was found to be a surprising reservoir for hydrogen in ZnO that can liberate hydrogen shallow donor centers upon annealing.

Additional Ph.D advisees

Fan Jiang (2003), E Chen (2002), Marcie Weinstein (2002), Jing Zhou (2000), Michael Evans (1998), Stephen Uftring (1998), Jie-Fei Zheng (1996), Ying Cheng (1994), Ioly Veloarisoa (1992), David Kozuch (1992)