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High gain observed in X-ray induced currents in synthetic single crystal diamonds

Lohstroh, A, Sellin, PJ, Boroumand, F and Morse, J (2007) High gain observed in X-ray induced currents in synthetic single crystal diamonds In: 12th Hasselt Diamond Workshop 2007 (SBDD XII), 2007-02-28 - 2007-03-02, Hasselt Univ, Diepenbeek-Hasselt, BELGIUM.

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Abstract

Diamond is considered as tissue equivalent, due to its low atomic number, which makes it a particular attractive material for medical radiation dosimetry applications. X-ray dosimeters made of natural single crystal diamonds are commercially available and routinely used, with typical gain values of about 0.5. The selection of suitable natural diamonds for this purpose is time and cost intensive. We report an X-ray induced current study in synthetic single crystal diamonds. Similar to natural diamond dosimeters, the devices had to be pre-irradiated before use to achieve a reproducible performance. We compare two chemical vapour deposited (CVD) samples grown by Element Six Ltd (UK). D1 was a high purity sample contacted in a sandwich structure with an asymmetric contact pair. Sample D2 was cut vertically and contained some nitrogen rich layers. It was contacted with two Ohmic contacts, which partly covered the high temperature/high pressure substrate material. Particle spectroscopy suggests better charge transport in D1 compared to D2, most likely caused by the lower purity. In contrast to this, large gain values up to 6 x 104 and a sensitivity of similar to 30 mC/Gy were measured at field strengths of 2 kV/cm in D2, and only 7 mu C/Gy in D1, despite their comparable volumes. We deduce that the gain observed in these devices is affected by the electrical properties of the metal-diamond contacts. The response time of the high gain device was in the order of minutes, which is longer than expected by a purely photoconductive process. Long persistent currents have been reported before in diamond under UV irradiation and modifications of gain and response time by surface treatment of UV detectors are known in the literature, highlighting the influence of the surface and contact interface on the device operation. Our results indicate that synthetic single crystal diamond provides a promising material for high sensitivity tissue-equivalent X-ray dosimeters. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Item Type: Conference or Workshop Item (Conference Paper)
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
AuthorsEmailORCID
Lohstroh, AUNSPECIFIEDUNSPECIFIED
Sellin, PJUNSPECIFIEDUNSPECIFIED
Boroumand, FUNSPECIFIEDUNSPECIFIED
Morse, JUNSPECIFIEDUNSPECIFIED
Date : September 2007
Identification Number : 10.1002/pssa.200776332
Contributors :
ContributionNameEmailORCID
PublisherWILEY-V C H VERLAG GMBH, UNSPECIFIEDUNSPECIFIED
Uncontrolled Keywords : CVD DIAMOND, DOSIMETRY APPLICATIONS, RADIATION DETECTOR, PHOTON, BEAM, SENSITIVITY
Additional Information : This is the peer reviewed version of the following article: Lohstroh, A, Sellin, PJ, Boroumand, F and Morse, J (2007) High gain observed in X-ray induced currents in synthetic single crystal diamonds In: 12th Hasselt Diamond Workshop 2007 (SBDD XII), 2007-02-28 - 2007-03-02, Hasselt Univ, Diepenbeek-Hasselt, BELGIUM, which has been published in final form at http://dx.doi.org/10.1002/pssa.200776332. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
Depositing User : Symplectic Elements
Date Deposited : 09 Dec 2015 14:52
Last Modified : 09 Dec 2015 14:52
URI: http://epubs.surrey.ac.uk/id/eprint/7674

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