Structural, electrical and mechanical properties of BCx films prepared by pulsed laser deposition from mixed and dual boron-diamond/graphite targets

摘要

Relatively low and high deposition rates of BCx films were realized by pulsed laser ablation of mixed B-diamond and dual B-graphite targets, respectively. Deposition was performed at 500 degrees C and the rate of film deposition was determined with respect to the number of atomic monolayers (obviously less or more than one monolayer) grown for one laser pulse. In the case of BCx films formation with a low deposition rate, doping with B facilitated the growth of the nanocomposite structure, which possessed an increased fraction of sp(3) bonds, a very low electrical resistance, and an improved mechanical performance. The change of the sheet resistance of these films as the temperature was reduced from 300 to 65 K had a metallic character. For about 95-nm-thick films with bulk compositions of BC1.7 and BC0.6, the resistivity at room temperature were approximately equal to 1.5 m Omega.cm, and the lowest resistivity of 0.23 m Omega.cm was detected for B-enriched film at 85 K. With an increase in the B atom concentration in such films, the charge carrier (holes) concentration decreased, and their mobility increased from 180 to 10,500 cm(2).V-1.s(-1) due to samples cooling. The application of a higher deposition rate from the dual B-graphite target activated surface migration of condensed atoms, which caused the development of granular morphology, the B segregation and the reduction of the sp(3) bond fraction. The hardness and electrical conductivity of such films were obviously inferior to those of the films obtained by PLD with a low deposition rate.