Amorphous Diamond Films Deposited by Pulsed-Laser Ablation: the Optimum Carbon-Ion Kinetic Energy and Effects of Laser Wavelength

Abstract

A systematic study has been made of changes in the bonding and optical properties of hydrogen-free tetrahedral amorphous carbon (ta-C) films, as a function of the kinetic energy of the incident carbon ions measured under film-deposition conditions. Ion probe measurements of the carbon ion kinetic energies produced by ArF and KrF laser ablation of graphite are compared under identical beam-focusing conditions. Much higher C+ kinetic energies are produced by ArF-laser ablation than by KrF for any given fluence and spot size. Electron energy loss spectroscopy and scanning ellipsometry measurements of the sp3 bonding fraction, plasmon energy, and optical properties reveal a well-defined optimum kinetic energy of 90 eV to deposit ta-C films having the largest sp3 fraction and the widest optical (Tauc) energy gap (equivalent to minimum near-gap optical absorption). Tapping-mode atomic force microscope measurements show that films deposited at near-optimum kinetic energy are extremely smooth, with rms roughness of only ~ 1 Å over distances of several hundred nm, and are relatively free of particulates.

Preparation of carbon nanoparticles by plasma-assisted pulsed laser deposition method—size and binding energy dependence on ambient gas pressure and plasma condition

“…In this figure, any differences between the ratios for both ambiences are hardly seen. In order to understand the dependence of the sp 3 /sp 2 carbon ratio on pAr, we will introduce the 8 following surface chemistry model [18][19][20][21] and related data on kinetic energy εC+ of Cn + and Cn (n = 1-3) reported so far [9][10][11][12]22].…”

Les dépôts en couches minces par ablation laser en régime d'impulsions ultra-courtes : état de l'art et perspectives

“…Bien que des recherches exploratoires aient ete menees tres recemment, par ablation laser reactive, sur la croissance de films de nitrures [18,20] et d'oxydes [21,22], l'essentiel du travail a porte sur le carbone amorphe, type DLC (Diamond-Like-Carbon), dont il est interessant d'analyser plus en details les resultats. Le tableau II presente une comparaison de quelques proprietes caracteristiques de films DLC, prepares dans les deux regimes d'ablation : nanoseconde [23] et femtoseconde [15]. Le pourcentage de liaisons sp 3 dans la couche de carbone, et sa largeur de bande interdite (EG), atteignent une valeur maximale en regime nanoseconde, pour des energies cinetiques (Ec) des ions carbone dans le plasma de 1'ordre de 90 eV.…”

Field Emission from Carbon Films Deposited by Controlled-Low-Energy Beams and CVD Sources

“…The two PLA systems and the procedures used in this work have been described elsewhere [26][27][28]. Briefly, films were deposited in vacuum chambers evacuated by turbomolecular pumps to a base pressure of 3 x 10-8 Torr.…”

“…An important simplification in this work was that,,.because the short-wavelength ArF laser was used, the ablated flux consisted primarily of monatomic ionized and neutral carbon species [29,30]. Consequently, an ion probe could be used to measure the travel time of @e ablated ions and, knowing their mass, to infer their mean kinetic energy [26][27][28]. The time corresponding to the arrival of the ion current peak ("icp") was used ' to calculate a velocity and corresponding kinetic energy, KEiC~, for the ions arriving at the position of the substrate [27].…”

“…The time corresponding to the arrival of the ion current peak ("icp") was used ' to calculate a velocity and corresponding kinetic energy, KEiC~, for the ions arriving at the position of the substrate [27]. This information was used to make the first systematic studies of changes in the bonding, optical properties, and surface morphology of pulsed-laser deposited a-D films as a fiction of the KEiC~of the incident species [26][27][28].…”