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Formation of secondary electron cascades in single-crystalline plasma-deposited diamond upon exposure to femtosecond x-ray pulses
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
Element Six Ltd, Ascot SL5 8BP, Berks, England.
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2008 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, no 6, 064909Article in journal (Refereed) Published
Abstract [en]

Secondary electron cascades were measured in high purity single-crystalline chemical vapor deposition (CVD) diamond, following exposure to ultrashort hard x-ray pulses (140 fs full width at half maximum, 8.9 keV energy) from the Sub-Picosecond Pulse Source at the Stanford Linear Accelerator Center. We report measurements of the pair creation energy and of drift mobility of carriers in two CVD diamond crystals. This was done for the first time using femtosecond x-ray excitation. Values for the average pair creation energy were found to be 12.17 +/- 0.57 and 11.81 +/- 0.59 eV for the two crystals, respectively. These values are in good agreement with recent theoretical predictions. The average drift mobility of carriers, obtained by the best fit to device simulations, was mu(h)= 2750 cm(2)/V s for holes and was mu(e)= 2760 cm(2) / V s for electrons. These mobility values represent lower bounds for charge mobilities due to possible polarization of the samples. The results demonstrate outstanding electric properties and the enormous potential of diamond in ultrafast x-ray detectors.

Place, publisher, year, edition, pages
2008. Vol. 103, no 6, 064909
National Category
Physical Sciences Engineering and Technology
URN: urn:nbn:se:uu:diva-110448DOI: 10.1063/1.2890158ISI: 000254536900143OAI: oai:DiVA.org:uu-110448DiVA: diva2:277182
Available from: 2009-11-16 Created: 2009-11-16 Last updated: 2016-10-26Bibliographically approved
In thesis
1. Charge Transport in Single-crystalline CVD Diamond
Open this publication in new window or tab >>Charge Transport in Single-crystalline CVD Diamond
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Diamond is a semiconductor with many superior material properties such as high breakdown field, high saturation velocity, high carrier mobilities and the highest thermal conductivity of all materials. These extreme properties, as compared to other (wide bandgap) semiconductors, make it desirable to develop single-crystalline epitaxial diamond films for electronic device and detector applications. Future diamond devices, such as power diodes, photoconductive switches and high-frequency field effect transistors, could in principle deliver outstanding performance due to diamond's excellent intrinsic properties. However, such electronic applications put severe demands on the crystalline quality of the material.

Many fundamental electronic properties of diamond are still poorly understood, which severely holds back diamond-based electronic device and detector development. This problem is largely due to incomplete knowledge of the defects in the material and due to a lack of understanding of how these defects influence transport properties.

Since diamond lacks a shallow dopant that is fully thermally activated at room temperature, the conventional silicon semiconductor technology cannot be transferred to diamond devices; instead, new concepts have to be developed. Some of the more promising device concepts contain thin delta-doped layers with a very high dopant concentration, which are fully activated in conjunction with undoped (intrinsic) layers where charges are transported. Thus, it is crucial to better understand transport in high-quality undoped layers with high carrier mobilities.

The focus of this doctoral thesis is therefore the study of charge transport and related electronic properties of single-crystalline plasma-deposited (SC-CVD) diamond samples, in order to improve knowledge on charge creation and transport mechanisms. Fundamental characteristics such as drift mobilities, compensation ratios and average pair-creation energy were measured. Comparing them with theoretical predictions from simulations allows for verification of these models and improvement of the diamond deposition process.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 87 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 746
CVD diamond, wide-bandgap semiconductor, single-crystalline diamond, carrier transport, time-of-flight, drift velocity, mobility, compensation, pair-creation, electronic devices, diamond detector, diamond diode
urn:nbn:se:uu:diva-122794 (URN)978-91-554-7815-5 (ISBN)
Public defence
2010-06-04, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Available from: 2010-05-12 Created: 2010-04-20 Last updated: 2010-05-18Bibliographically approved

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