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Charge transport through localized states in sputtered amorphous silicon suboxides

Published online by Cambridge University Press:  21 March 2011

J.J. van Hapert
Affiliation:
Debye institute, Utrecht University, P.O.Box 80.000, 3508 TA Utrecht, The, Netherlands
N. Tomozeiu
Affiliation:
Debye institute, Utrecht University, P.O.Box 80.000, 3508 TA Utrecht, The, Netherlands
E.E. van Faassen
Affiliation:
Debye institute, Utrecht University, P.O.Box 80.000, 3508 TA Utrecht, The, Netherlands
A.M. Vredenberg
Affiliation:
Debye institute, Utrecht University, P.O.Box 80.000, 3508 TA Utrecht, The, Netherlands
F.H.P.M. Habraken
Affiliation:
Debye institute, Utrecht University, P.O.Box 80.000, 3508 TA Utrecht, The, Netherlands
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Abstract

Using an RF magnetron sputtering technique, thin layers (∼500 nm) of amorphous silicon suboxides (a-SiOx) were deposited, with oxygen/silicon ratios x ranging from 0 to 1.8. These layers contain a large density (1020−1021 cm−3) of, mostly silicon dangling bond, defect states. The level of conduction decreases several orders of magnitude with increasing x. The temperature dependence of the DC conductivity showed that the variable range hopping conduction mechanism is dominant for all x, over the temperature range 30- 330 K. In this mechanism the extent of localization and density of states around the Fermi level determine the conductance. We conclude that the decrease in conductance with increasing oxygen content must, for a large part, be due to a variation in the localization, since Electron Spin Resonance (ESR) measurements showed no decrease in defect density with increasing x. We performed DC conduction measurements at both low and high electric field strengths, showing phenomena, which are consistently desribed within the variable range hopping (VRH) model. These measurements allow the extraction of quantitative information, concerning both the localization and the density of the states involved in the hopping process.

Type
Research Article
Copyright
Copyright © Materials Research Society 2001

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References

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