The Investigation of Piezoresistive, Optical and Electrical Properties of Diamond Like Carbon Films Synthesized by Ion Beam Deposition and PECVD

Abstract

In the present research ion energy effects on piezoresistive properties of hydrogenated diamond like carbon (DLC) films
deposited by hydrocarbon ion beam deposition and radio frequency plasma enhanced chemical vapor deposition
(PECVD) were studied. Comparative analysis of the influence of silicon oxide and silicon doping on gauge factor of
DLC films was performed. Only weak dependence of piezoresistive properties of the DLC films deposited from
acetylene gas by ion beam deposition using closed drift ion source on ion energy was observed and that was explained as
a result of the competing effects of ion energy and ion/neutral ratio during the diamond like carbon film deposition
process. In the case of PECVD deposited DLC films the dependence of gauge factor on substrate bias was observed.
Doping by silicon and silicon oxide resulted in decrease of the DLC film gauge factor. Possible relations between the
gauge factor of DLC films and their optical parameters such as optical bandgap, Urbach energy and B parameter were
studied as well. It was found, that the gauge factor increases with the increased separation between valence and
conduction π band in DLC films and/or decrease size of sp2 cluster as well as with the decrease of the topological
disorder (range in which vary size of sp2 clusters) and/or density of sp2 states and ammount of sp2 bonded carbon phase.
Resistivity of the investigated DLC films deposited by both methods decreased with the increase of the ion energy and
no correlation between the piezoresistive properties of DLC films and their resistance was found. The observed behavior
was explained by dependence of resistivity on hydrogen ammount in DLC films.