Topic: Development of Room-Temperature Radiation Detectors for Homeland Security, Medical and Industrial Applications

Speaker: Dr. Stephen Babalola, Center of Irradiation of Materials, AAMU

Date & Time: Tuesday, October 1, 2013, 1:00 PM

Place: Room 140 VMC (Chambers Hall)



Radiation detectors are devices that detect the presence of radioactive materials. Such devices are useful in many applications, including homeland security, medical (x-ray and gamma ray imaging, nuclear medicine), industrial (oil well logging, environmental remediation) and astrophysics including space exploration. The research is focused on developing advanced radiation detector devices that work as spectrometers thereby having the ability to identify radioisotopes from the energies of their photopeaks. These devices are in high demand due to the need for heightened border security to deter illicit trafficking of nuclear materials for nuclear nonproliferation initiatives. Si and Ge detectors are have excellent energy resolutions but due to their small energy bandgap (0.67eV and 1.1eV respectively), require cryogenic cooling, resulting in bulky, usually stationary and expensive devices. There is a need to develop smaller, portable detectors that will operate at ambient temperatures, are rugged and compact for field operations with the potential of being incorporated into existing electronic devices for covert operations. CdZnTe has emerged as the most promising material due to its excellent properties, including wide, tunable band-gap, high mobility-lifetime (μτ) product for electrons, high resistivity and good electron transport properties. CdZnTe is a direct bandgap material that is obtained by alloying CdTe and ZnTe. CdTe has a bandgap energy of 1.5eV, and with the addition of Zn, Zn atoms substitute Cd atoms in the lattice thereby increasing the bandgap energy to ranges of 1.6 – 1.8 eV. Charge transport calculations predict an excellent energy resolution of less than 1% FWHM at 662 KeVgamma for CdZnTe based detectors, but in reality much lower resolutions (6-3% FWHM) are achieved. The deterioration in detector performance is attributed to defects in crystals as well as defects induced through device-fabrication. This research is focused on identifying and characterizing the defects that limit the performance of CdZnTe crystals. Extensive material characterization and defect analyses were performed using IR microscopy, internal electric field imaging (Pockels Electro-Optic Effect), Etch-pit analysis, XDT, AFM, PL, Microscale X-ray response 3-D mapping, These studies resulted in better understanding of the formation of crystal defects such as Te inclusions and precipitates, voids, twin boundaries and grain boundaries. The research has also improved the crystal growth process of the detector materials.


Dr. Babalola is currently a post-doctoral research professor at Alabama A&M University and a guest scientist at Brookhaven National Laboratory. Prior to joining AAMU, Dr. Babalola held appointments as a Researcher and Co-op Engineer at Brookhaven National Laboratory, Long Island, NY., and a Research Associate in the Physics Department at Fisk University. Dr. Babalola received his Ph.D degree in Interdisciplinary Materials Science at Vanderbilt University in 2010. Dr. Babalola is the PI and lead of the DOE-NNSA sponsored Minority Serving Institution Partnership Program consortium of six universities and four national laboratories. Since establishing the consortium in 2012, Dr. Babalola has attracted over $3 Million in funding to support minority STEM research, education and outreach programs. In addition to that, Dr. Babalola has attracted over $800,000 in research funding to AAMU. He has trained and mentored numerous students and has extensive teaching experience and course development. Babalola currently manages the Center of Irradiation of Materials at AAMU, where he supports students and faculty research.

Refreshments will be served at 12:45 PM

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