Radiation Sensor

 There is a critical need for advancement of sensor technologies for more rapid and accurate detection of nuclear radiation.  The improved detection technologies have to be robust, versatile, reliable and easily deployable in different domestic geographical areas to counter the threat of nuclear attack posed by terrorists. 

 A range of compound semiconductor materials such as cadmium zinc telluride (CZT), cadmium telluride, gallium arsenide, indium phosphide, mercuric iodide and thallium bromide are available as radiation detector.

 The principal advantage of compound semiconductors is their ability to operate at room temperature without any bulky cryostats, and therefore can be incorporated in portable devices. CZT is considered as a predominant material for detection of low to medium energy gamma radiation and hard X-rays. The main advantages of CZT over other materials are its high spectral resolution (typically about 3% FWHM at 662 keV) and spatial resolution which enable identification of radiation source and location.

 Large volume single-crystals of CdZnTe and AlSb produced by high temperature liquid metallurgy route inherently introduces a large density of defects (such as impurities, dislocations, vacancies) which adversely affect the charge collection efficiency. In addition, the manufacturing process is tedious, expensive and requires ultra high purity starting materials.

 EMD Technologies, LLC synthesizes 1-D (one-dimensional) nanowire arrays of compound semiconductors (CdZnTe and AlSb), which have superior electronic properties, for radiation detection applications. 1-D nanowire arrays of CdZnTe and AlSb are synthesized by the pulsed-potential electrodeposition method using low temperature non-aqueous electrolytes in a controlled atmosphere. 

 The nanowire arrays are integrated into a sensor device that can detect radiation with high spatial and spectral resolution. The expected advantages of the new nanowires based nuclear detectors are low bias voltage (in the order of 2 V), low power requirement, high spatial and spectral resolution.

 Further, the compound semiconductor nanowires arrays can be used in other applications such as medical imaging, avalanche type detectors, IR detectors etc.