Research Projects

Novel Photonic Materials Based on Charge – Ordered Manganese Oxides
Current demands in the areas of computing and communication require increasing speed of computation and information transfer. One solution is to replace "slow" electronic devices with "fast" photonic ones. This requires the development of optical analogues of electronic integrated circuits capable of routing, controlling and processing optical signals. One of the promising approaches is based on photonic band-gap materials, which allow control of dispersion and propagation of light. The necessary condition for the photonic band gap to appear is high (more than 2 to 1) refractive index contrast within the photonic crystal. Creation of a photonic band-gap material is a very difficult technological task.
Mixed valence manganese oxides exhibit unique photosensitivity properties, such as permanent photo-induced reflectivity changes due to local photoinduced insulator to metal transition. Unique and novel feature of this experimental program is based on the extreme sensitivity of the manganite materials to external fields, such as magnetic field, temperature, external illumination, etc. In order to create photonic structures, 500-1000 nm thin films of Bi1-xCaxMnO3 are needed. These thin films are grown in Material Research Lab at Towson University using a Pulsed Laser Deposition (PLD) system.

Nanometer scale Hall effect magnetic field detectors for biotechnology

The ability to fabricate devices on the nanometer scale opens new possibilities for cutting edge research in chemistry, biology, and medicine. Nanotechnology could offer a means to manipulate and test small biological objects such as DNA in an efficient and inexpensive way. To detect or manipulate such biological objects magnetic fields can be used because of their biocompatibility. Locally strong magnetic fields do not harm biological material, and the converse statement is also important: the electrolytic environment of most biological agents neither screens, nor alters magnetic fields. To use magnetic field for the detection and manipulation of biomolecules, biomolecules should be attached to magnetic particles. These particles can then be used to tag, or trace, biological functions and interactions in a non-perturbing way. However, this field of research has been lacking sensitive and effective magnetic field sensors. A successful device must be fabricated on a nanometer size scale, and must be sensitive to local magnetic fields that have field gradients characterized by nanometer lengths. These sensors can be used for the study of nanometer scale magnetic particles, and related biophysics and chemical applications. As a first step to achieving this goal, Hall effect field detectors with lateral dimensions of 1mm and smaller have been fabricated in collaboration with the Naval Research Laboratory, Washington DC. A transport measurement experimental set-up in the Condensed Matter Laboratory allows students to study these unique devises. The fabricated nanometer-scale devices are characterized by measurements of the van der Pauw resistance, the Hall coefficient and current-voltage characteristics.