PROCEEDINGS ARTICLE | September 28, 2011
Proc. SPIE. 8142, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XIII
KEYWORDS: Gold, Polishing, Sensors, Etching, Electrodes, Crystals, Chlorine, Thallium, Bromine, Surface finishing
TlBr is a material of interest for use in room temperature gamma ray detector applications due to is wide bandgap 2.7 eV
and high average atomic number (Tl 81, Br 35). Researchers have achieved energy resolutions of 1.3 % at 662 keV,
demonstrating the potential of this material system. However, these detectors are known to polarize using conventional
configurations, limiting their use. Continued improvement of room temperature, high-resolution gamma ray detectors
based on TlBr requires further understanding of the degradation mechanisms. While high quality material is a critical
starting point for excellent detector performance, we show that the room temperature stability of planar TlBr gamma
spectrometers can be significantly enhanced by treatment with both hydrofluoric and hydrochloric acid. By
incorporating F or Cl into the surface of TlBr, current instabilities are eliminated and the longer term current of the
detectors remains unchanged. 241Am spectra are also shown to be more stable for extended periods; detectors have been
held at 2000 V/cm for 52 days with less than 10% degradation in peak centroid position. In addition, evidence for the
long term degradation mechanism being related to the contact metal is presented.
