Frédéric Schuster

Characterization of chromium nitride and carbonitride coatings deposited at low temperature by organometallic chemical vapour deposition

Abstract Chromium nitride and carbonitride hard coatings were deposited by organometallic chemical vapour deposition in the temperature range 350–550 °C. Bis(benzene) chromium and NH 3 or N 2 H 4 were used as chromium and nitrogen vapour sources respectively. The chemical and structural characterization of these coatings is presented. Amorphous films were obtained below 450 °C. Above this temperature, a different phase, namely Cr 7 C 3 , Cr 2 (N,C) or CrN could be prepared depending on the gas phase composition. Electron probe microanalysis and X-ray photoelectron spectroscopy gave evidence for a slight contamination of the films with free carbon. The experimental results are in good agreement with a thermodynamic calculation which has been fruitful in giving information about the feasibility of growing chromium nitride phases under these chemical vapour deposition conditions. The microhardness of the coating in each case was comparable with that of similar material deposited by other techniques.

INFLUENCE OF ORGANOCHROMIUM PRECURSOR CHEMISTRY ON THE MICROSTRUCTURE OF MOCVD CHROMIUM CARBIDE COATINGS

Abstract Chromium carbide coatings were prepared in the same hot-wall low-pressure chemical vapour deposition reactor using Cr(CO)6, Cr(C6H6)2, Cr(C6H5C3H7)2 and Cr(C5H5)2, chosen as representative organochromium precursors. The structural characterization of the films is described and the ability of the organochromium compounds to deposit a particular phase is discussed. A cubic CrC1−x phase is obtained using the carbonyl derivative, and the main component of the coatings prepared with bis(arene) chromium is the Cr7C3 phase. Free carbon contamination of the films is found regardless of the precursor.

Assessment of tetra-alkylchromium compounds for low temperature organo-metallic chemical vapour deposition of Cr-based coatings

Abstract Chromium carbide films have been deposited by organo-metallic chemical vapour deposition using the tetra-alkylchromium compounds Cr[C(CH3)3]4 and Cr[CH2C(CH3)3]4 under reduced pressure in the temperature ranges 100–150 °C and 250–350 °C respectively. The blocking of β-decomposition mechanisms increases the thermal stability of the second precursor, and subsequently increases the deposition temperature range and palliates the reagent depletion in the gas phase. Both the higher thermodynamic stability of Cr[CH2Si(CH3)3]4 and the lower kinetic lability of the ligand CH2SiMe3 result in a significantly higher temperature range of deposition (450–515 °C). However, the decomposition of this third precursor is not as clean as expected, even under hydrogen atmosphere, since Si and C are incorporated in the films leading to an original amorphous material containing a mixture of metallic and covalent bonds. Comparison of the results from the different precursors leads to the hypothesis that a cyclometallation mechanism could be a dominant initial step for the removal of CH2C(CH3)3 and CH2Si(CH3)3 ligands.