Presented in this paper is an online mass spectrometry study of the gas phase during the CVD of nickel films from nickelocene under various conditions. The results are illustrated by means of calibrated molar ratios of C5H8/C5H10 and CH4/(C5H8+C5H10). These ratios describe the relative advancement of two types of reactions leading to deposition of pure nickel, and to the incorporation of carbon in the films. Their evolution with deposition time, temperature, pressure, hydrogen flow rate, and nickelocene molar fraction in the input gas is investigated and compared with equilibrium calculations performed under similar conditions. The information obtained is combined with previously reported results on the morphology and growth rate,[1] the composition (especially the carbon content) of the deposits,[2] the adsorption mode, and the decomposition of nickelocene and of the cyclopentadienyl derivatives. It is proposed that, for low surface coverage by nickelocene molecules, a Langmuir–Hinshelwood mechanism prevails for the deposition, following which nickelocene competes with H2 for the occupation of most of the adsorption sites. For high surface coverage, reaction between neighboring nickelocene molecules also occurs, and this reaction is responsible for the incorporation of carbon in the deposits.
Carbon-rich vanadium carbonitride films have been grown by MOCVD at low temperature using the tetrakis(diethylamid0) vanadium complex V( NEt,), as a single-source precursor. The main volatile byproducts formed during its thermal decomposition were identified by NMR and on-line mass spectrometric analyses. Under the growth conditions, an equimolecular ratio of HNEt, and EtN=CHMe was found in addition to CH,CN and C2H4. From these results, an elimination mechanism of the NEt, ligands is proposed. It accounts for their high lability and therefore the low nitrogen content of the films. The possible origin of the incorporation of the metalloid elements is also discussed.
The OMCVD method has been used to deposit highly pure metal particles on porous divided substrates in order to prepare metal supported catalysts. A fluidized bed reactor has been especially designed and the requirements of CVD and fluidization have been taken into account to select convenient experimental conditions. Three organometallic compounds of rhodium have been selected and their thermal decomposition under He and Hem2 mixtures studied by infrared spectroscopy and on-line mass spectromehy analyses. The deposition are carried out at a total pressure of 100 Torr and substrate temperatures as low as 100 ' C. The solid deposits have been characterized by XPS, the size and dispersion of the particules have been determined by chemisorption methods or measured by TEM. These catalysts can be used without further treatment and their performances have been compared to those of conventionally prepared ones.
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