Electrical transport and morphological study of PLD-grown nanostructured amorphous carbon thin films

摘要

Nanostructured carbon thin films have been activey investigated recently for their electroresistance (ER) properties. Furthermore, carbon films with nonlinear current-voltage (I-V) characteristics have potential application in field-emission devices. This has motivated us to study the effect of various growth parameters on the physical and morphological properties of carbon films grown by pulsed laser deposition (PLD). Carbon films have been deposited using a graphite target at different partial pressures of argon. The morphology of film surfaces deposited at various growth conditions was monitored using an atomic force microscope (AFM). AFM studies showed nanostructured grain growth with average grain size of about 80-90 nm. As the deposition time was decreased down to 1 min, the grain size was also found to decrease correspondingly. From Raman spectroscopic measurements an increase in the I (D)/I (G) ratio and a decrease in FWHM (G) clearly revealed the promotion of sp~2 hybridization as the substrate temperature increased. All the films show semiconducting behaviour with the dominant conduction process being the three-dimensional (3D) variable range hopping (VRH) mechanism. Nonlinear I-V curves were obtained for carbon films deposited on p-type Si indicating diode-like behaviour. The most significant result of this study was the observation of a large electroresistance value.