Investigating point defects in irradiated boron-doped diamond films by temperature-dependent electrical properties and s
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John Farmer Missouri University Research Reactor, and Department of Physics, University of Missouri–Columbia, Columbia, Missouri 65211
Dario Daghero and Renato Gonnelli Department of Physics, C.so Duca degli Abruzzi 24, Politecnico di Torino, Italy 10129 (Received 14 August 2009; accepted 20 October 2009)
We report temperature-dependent electrical resistivity (or dc conductivity, sdc) down to 4 K for pristine and gamma-irradiated microwave plasma-assisted chemical vapordeposited boron-doped diamond films with [B]/[C]gas = 4000 ppm to gain insights into the nature of conduction mechanism, distribution, and kinetics of point defects generated due to gamma irradiation prompted by the article [Gupta et al., J. Mater. Res. 24, 1498 (2009)]. The pristine samples exhibit typical metallic conduction up to 50 K and with reduction in temperature to 25 K, the sdc decreases monotonically followed by saturation at 4 K, suggesting “disordered” metal or “localized” behavior. For irradiated films, continuous increasing resistivity with decreasing temperature demonstrates semiconducting behavior with thermal activation/hopping conduction phenomena. It is intriguing to propose that irradiation leads to substantial hydrogen redistribution leading to unexpected low-temperature resistivity behavior. Scanning tunneling microscopy/ spectroscopy helped to illustrate local grain and grain boundary effects.
I. INTRODUCTION
Traditional and doped diamond films are used for multiple technological applications such as electrochemical microelectrodes high-temperature, high-power, and high-frequency devices1–3 due to its impressive combination of physical (mechanical, thermal, electrical, electrochemical,4 and biocompatibility) properties. In addition, it is reputed for being radiation hard and thus predestined its usage over the existing semiconductors (Si, GaAs, and AlGaN) and outweighing SiC, widespread in (pulsed) power electronics.5 In view of the harsh and remote environment of space and nuclear fields and related applications such as high-performance UV LED,6 deep UV photodiode (220 nm),7 medical radiotherapy, and novel atomic microbattery, reliability and qualification are the crucial issues that prevent diamond from playing a larger role in radiation-hard electronics. However, due to multifunctionality, diamond is qualified as a 21st Century engineering material.8–10 a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0064
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http://journals.cambridge.org
J. Mater. Res., Vol. 25, No. 3, Mar 2010 Downloaded: 14 Mar 2015
The choice of diamond in “extreme/space environment” stems from the strongest C-C bonding strength, high thermal conductivity to dissipate heat, low Z number and tissue equivalence, wide band gap-suppressing thermal carriers, and defect recombination/generation current. Nevertheless, the development of diamondbased electronic devices is practically limited to single crystal and/or homoepitaxial. The inception of chemical vapor deposition (CVD) technology producing high
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