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High Temperature Surface Conductivity of Hydrogenated Diamond Films Exposed to Humid Air

100%

Stec K., Szroeder P., Benzhour K.

issue 3

511-514

Surface conductivity of thin diamond films was measured as a function of temperature up to 450°C. Hydrogenated diamond was synthesized by chemical vapor deposition in hydrogen/carbon plasma. Low values of charge carrier activation energy ( ≈ 10 meV) were observed, when hydrogenated diamond films were exposed to the ambient humid air. However, the activation energy increased by two orders of magnitude as film temperature exceeded 300°C. We have attributed this behavior to the desorption of the H_2O adlayer. The jump of the activation energy did not occur, when experiment was performed in vacuum. We have also shown that donor doping leads to the up-shift of the Fermi level much above the acceptor-like band gap levels induced by surface C-H bonds, which cannot be compensated by transfer of electrons from diamond to the double H-H_2O layer.

Luminescence from β-Irradiated Graphene Layers

88%

Chruścińska A., Przegiętka K., Szroeder P., Oczkowski H., Rozpłoch F.

We found that β-irradiated samples of crystallite graphite and multi-walled carbon nanotubes emit light during heating above room temperature. This behaviour is rather surprising for semimetals. Due to the lack of deep enough energy gap, this optical emission cannot be associated with interband transitions, as it is usually assumed in a thermally stimulated luminescence model. We suppose that the reported accumulated luminescence is the result of thermally stimulated relaxation of some kind of defects created in graphene structures by ionising radiation and therefore we offer to name it the relaxoluminescence. We anticipate the relaxoluminescence to be a starting point for developing a new spectroscopic method for nanotechnology. It can also throw a new light on the nature of defects, which are suspected of being responsible for strange magnetic effects in carbon.

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2 Acta Physica Polonica A

1 2010

1 2006

2 Szroeder P.

1 Benzhour K.

1 Chruścińska A.

1 Oczkowski H.

1 Przegiętka K.

1 Rozpłoch F.

1 Stec K.

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High Temperature Surface Conductivity of Hydrogenated Diamond Films Exposed to Humid Air

Luminescence from β-Irradiated Graphene Layers