RESEARCH INTERESTS

1. Nanometer Scaled Porous Alumina Template

Ordered nanometer scaled materials, such as porous alumina, have attracted much attention recently due to the utilization as templates for synthesizing nanostructures (1 nm = 1 billionth of a meter). These materials have huge potential for applications such as optoelectronic sensors, and single electron devices. We are using an electrochemical method in the laboratory to fabricate such nanotemplates. The above images, acquired using the scanning electron microscope (SEM) in the Keck Microanalysis laboratory, show that the diameter of each pore is about 80 nm, and the distance between two adjacent pores is about 100 nm. Different materials are being inserted into these pores, such as ZnO and ZnS, to study the quantum size effect.

2. Dilute Magnetic Semiconductors

Magnetic semiconductors are materials that exhibit both ferromagnetism and semiconductor properties. Recently, nanometer scaled ZnO has received considerable interest because of its wide band-gap and therefore possible applications in optoelectronics. If diluted with magnetic impurities, it could also provide a new type of control of conduction of electrons, i.e., spins, which hopefully can be manipulated for different devices. To that end, dilute magnetic semiconductors have recently become a major focus of magnetic semiconductor research. Using an electrochemical method, we are making Co-doped ZnO samples in the laboratory and characterizing them using facilities in the Keck lab, such as X-ray diffraction, scanning electron miroscope (SEM) and energy dispersive X-ray spectroscopy (EDX).

3. Some Recent Publications

  • Influence of Mg-doping on the optical properties of ZnO thin films prepared via electrochemical deposition
    Hongtao Shi, Cristhyan F. Alfaro, Kalie R. Barrera, Timothy L. Hessong, and Stephanie R. Halbert
    Phys. Status Solidi A, 210, 1163 (2013)
  • Interface biquadratic coupling and magnon scattering in exchange-biased ferromagnetic thin films grown on epitaxial FeF2
    David Lederman, Prasanta Dutta1, Mohindar S. Seehra, and Hongtao Shi
    J. Phys.: Condens. Matter, 24, 186001 (2012)
  • Mg-induced enhancement of ZnO optical properties via electrochemical processing
    Hongtao Shi, Kalie R. Barrera, Timothy L. Hessong, and Cristhyan F. Alfaro
    Materials Research Society (MRS) Proceedings, 1449, mrss 12-1449-bb03 07 doi:10.1557/opl.2012.958 (2012)