Properties revealed of amorphous carbon thin films prepared by electron-gun evaporation

Massive variations in electrical conductivity observed for amorphous carbon thin films

A great deal of work has been done into understanding the physical properties of amorphous carbon (a-C). These studies have found the relative ratio of different carbon phases strongly determines the physical properties of the material.

In this work, published in AZojomo*, by B. Rebollo-Plata, R. Lozada-Morales, R. Palomino-Merino, J. A. Dávila-PintLe, O. Portillo-Moreno, O. Zelaya-Angel and S. Jiménez-Sandoval from Benemérita Universidad Autónoma de Puebla, a-C thin films grown by electron-gun evaporation (EGE) are studied. There is a limited number of works using the EGE technique to grow a-C films, and with growing interest in carbon based nanotechnology, the researchers believe it is important to widen the knowledge in this direction.

The main experimental parameter varied during growth was the source-substrate distance (SSD), and important changes in the physical properties: vibrational modes, dark conductivity and majority carrier concentration, are studied.

The research revealed that as SSD was altered, along with changes to the make up of the carbon films, there was a dramatic alteration to the electrical conductivity of the samples. The electrical conductivity of the a-C:N sample grown with a SSD of 15.5 cm, was about three orders of magnitude higher than the rest of the samples. However, for films grown with a SSD of 23.5cm the conductivity decreased by nearly seven orders of magnitude.