Applicability of moissanite, a monocrystalline form of silicon carbide, to retrospective and forensic dosimetry

Although many electronic devices today are based on pure silicon substrates, a number of other substrates are used in various applications. The aim of this study was to characterize the dose response properties of monocrystalline silicon carbide (SiC) manufactured by Cree Inc. Thanks to its physical and electronic properties, SiC has been found to be widely useful as a substrate and wide-bandgap semiconductor in high-frequency, high-power, and high-temperature electronic devices, as well as in short wavelength, radiation resistant opto-electronic devices. Broadband thermoluminescence (TL) emission of gem-quality SiC ("moissanite") shows that the material is sufficiently sensitive to permit the detection of a similar to 0.7 Gy beta dose, with dose response linearity of the 120 and 270 degrees C TL peaks over more than 3 orders of magnitude. The 120 degrees C peak, which shifts from similar to 110 degrees C at very low doses to similar to 160 degrees C following a 10(3) times dose increase, shows second order kinetics. In addition, pre-dosing of the 230 degrees C peak is seen as it becomes readily apparent only after irradiation followed by annealing. TL detection through the BG39 filter masks high-temperature peaks at low doses due to the strong thermal background for T > 350 degrees C, but a 370 degrees C peak does become discernible at high doses. TL glow curves in the UV and violet regions are distinctly different from those detected in the wide visible region, indicating a complex emission spectrum. Luminescence detected in both the violet and near-UV regions during optical stimulation with blue and infrared photons confirms that the material is suitable as an optically stimulated luminescence (OSL) dosimeter. Isothermal decay studies of the OSL and TL signals attest to its long-term thermal stability, an essential criterion for usefulness in retrospective dosimetry and forensically significant scenarios, such as the need to prove a suspected exposure to radiation. Based on the foregoing results, it is recommended that moissanite be added to the list of materials potentially useful in the retrospective dosimetry of the general population. In order to optimize our understanding of how various substrates of electronic devices might also be used for this purpose, further dosimetric studies are recommended for this as well as other forms of crystalline SiC. (c) 2006 Elsevier Ltd. All rights reserved.