Effect of Boron Incorporation on the Structure and Electrical Properties of Diamond-Like Carbon Films Deposited by Femtosecond and Nanosecond Pulsed Laser Ablation
Résumé
The influence of the incorporation of boron in Diamond-Like Carbon (DLC) films on the microstructure of the coatings has been investigated. The a-C:B films have been deposited at room temperature in high vacuum conditions, by ablating graphite targets either with a femtosecond pulsed laser (800 nm, 150 fs, fs-DLC), or with a nanosecond pulsed laser (248 nm, 20 ns, ns-DLC). Doping with boron within the range 2-8 % has been performed by ablating alternatively graphite and boron targets. The film structure and composition have been highlighted by coupling Atomic Force Microscopy, Scanning Electron Microscopy, Electron Energy Loss Spectroscopy and High Resolution Transmission Electron Microscopy. Using the B K-edge, EELS characterization reveals the boron effect on the carbon bonding. Moreover, the plasmon energy reveals a tendency of graphitization associated to the boron doping. The boron particles synthesized by femtosecond PLD have been characterized by HRTEM and reveals that the particles are amorphous or crystallized. The nanostructure of the boron doped ns-DLC and the boron doped fs-DLC are thus compared. In particular, the incorporation of boron in the DLC matrix is highlighted, depending on the laser used for deposition. Electrical measurements will show that some of these films have potentialities to be used in low temperature thermometry (77-300 K range), considering their conductivity and temperature coefficient of resistance (TCR).