The physical and chemical properties of wide bandgap semiconductors silicon carbide and diamond make these materials an ideal choice for device fabrication for applications in many different areas, e.g. light emitters, high temperature and high power electronics, high power microwave devices, micro-electromechanical system (MEMS) technology, and substrates. These semiconductors have been recognized for several decades as being suitable for these applications, but until recently the low material quality has not allowed the fabrication of high quality devices. Silicon carbide and diamond based electronics are at different stages of their development. An overview of the status of silicon carbide's and diamond's application for high temperature electronics is presented.

/pdf/silicon-carbide-and-diamond-for-high-temperature-device-4k4olc05az.pdf

Silicon carbide and diamond for high temperature device applications

Diamond radiation detectors

The dose rate dependence and current/voltage characteristics of a PTW Riga diamond detector in the dosimetry of a 6 MV photon beam have been investigated. Diamond detectors are radiosensitive resistors whose conductivity (i) varies almost in proportion to dose rate and (ii) is almost independent of bias voltage for a constant dose rate. At the recommended bias of +100 V, and also at +200 V, the detector is operating with incomplete charge collection due to the electron-hole recombination time being shorter that the maximum time for an electron to be collected by the anode. As dose rate is varied by changing FSD or depth (changing dose per pulse), detector current and dose rate are related by the expression i alpha DDelta where Delta is approximately 0.98. This manifests itself in an overestimate in percentage depth-dose at a depth of 30 cm of approximately 1% when compared to ionization chamber results. A similar sublinearity is seen when pulse repetition frequency is varied, indicating that the dependence is an on average rather than an instantaneous dose rate. The dose rate dependence is attributed to the reduction in recombination time as dose rate increases.

https://iopscience.iop.org/article/10.1088/0031-9155/39/8/003/pdf

Dose rate dependence of a PTW diamond detector in the dosimetry of a 6 MV photon beam

The effect of beam energy, dose rate and temperature on seven commercial diamond electrical conductivity detectors was studied. The diamond dimensions were approximately 1 mm X 1 mm X 3 mm. Clinical photon nd electron beams were used for irradiation. The photon energy response normalised to 60Co was observed to have a maximum of 1.37 +/- 0.06 at 122 keV and the dose rate response was slightly non-linear, in agreement with the theory for insulators. Temperature effects were small and different for each detector. Two of the seven detectors gave repeatable results (+/- 5%) over five years, two others were much less satisfactory and three were rejected after preliminary tests. It is concluded that natural diamond can be used for the manufacture of reliable, small and near soft-tissue-equivalent dosemeters but that until the crystal selection and final product testing have been adequately standardised, the user needs to select the reliable dosemeters from a batch.

http://iopscience.iop.org/article/10.1088/0031-9155/25/3/011/pdf

Evaluation of diamond radiation dosemeters

The suitability of a natural diamond detector with a special contact system for the measurement of relative dose distributions in selected radiotherapy applications was studied. The performance of the diamond detector was analysed by comparison with measurements using an ionization chamber and a silicon diode detector. The good stability, high response and good spatial resolution of the diamond detector were demonstrated by relative measurements in high-energy photon and electron beams and around the 137Cs source of an afterloading device. The application of the diamond detectors for relative as well as absolute dose measurements of beta ray ophthalmic applicators was also highlighted. It is concluded that the diamond with the special contact system is a suitable detector for relative dose measurements in a wide variety of applications, especially when high response and high spatial resolution are required.

http://iopscience.iop.org/article/10.1088/0031-9155/38/1/013/pdf

Application of a natural diamond detector for the measurement of relative dose distributions in radiotherapy.

Some characteristics of diamond detectors have been investigated with a view to finding out the possibilities of their application for X-ray and δ-radiation dosimetry in medical radiology. The results of this investigation are described. The design of a tissue-equivalent diamond dosimeter is shown. It possesses a uniform energy dependence and threshold sensitivity of lμR/s to the dose rate.

Diamond dosimeter for x-ray and δ-radiation

Some characteristics of diamond detectors have been investigated with a view to finding out the possibilities of their application for x-ray and ..gamma..-radiation dosimetry in medical radiology. The results of this investigation are described. The design of a tissue-equivalent diamond dosimeter is shown. It possesses a uniform energy dependence and threshold sensitivity of 1..mu..R/s to the dose rate.

M. L. Meilman

Papers

Diamond dosimeter for x-ray and δ-radiation

Diamond dosimeter for x-ray and. gamma. -radiation