Growth of Chromium Carbide in a Hot Wall DLICVD Reactor

Abstract

Chromium carbide coatings were grown at 748 K in a hot wall CVD reactor fed by sublimation of bis(benzene)chromium, BBC (MOCVD) and by direct liquid injection using a BBC/toluene solution (DLICVD). The two types of coatings exhibit an amorphous structure and the same C content (22 at.%). DLICVD permits delivering higher mass flow rate of precursors and consequently the growth rate is 3 times higher and the thickness uniformity is better than using MOCVD. Chromium metal deposition has also been investigated by DLICVD in this hot wall reactor using BBC/toluene/additive as precursor. The purpose of the additive is to block carbide formation. Two additives have been studied: (i) hexachlorobenzene (C6Cl6) and (ii) thiophenol (C6H5SH). The ratio additive/BBC required for Cr metal deposition is a few percent. In this process, C6Cl6 is not decomposed and only traces of Cl (0.4 at.%) are found in the coatings. For a ratio C6Cl6/BBC > 27% the growth of any coating is blocked. The gas phase containing C6H5SH is more reactive since the onset of deposition occurs approximately 50 K before the temperature of the chlorinated compound. Furthermore, a sulfur contamination of 3 at.% has been analyzed in the coatings revealing a partial decomposition of the additive. The results are detailed and discussed in relation with previous works.

Evidence for a Cr metastable phase as a tracer in DLI-MOCVD chromium hard coatings usable in high temperature environment

“…Many CVD reactor configurations and sizes, as well as deposition conditions have been previously tested to deposit metallic Cr [14,[17][18][19][20][21][22][23][24]. These studies on MOCVD and DLI-MOCVD processes are summarized in Table 2.…”

“…This is the stable body-centered cubic structure of the metal (space group Im-3m). This common phase was obtained by adding a chlorinated [14,17,22,24] or a sulfur-containing [21,24] inhibitor to the bis(arene)chromium precursor. The present work complements these previous studies and is distinguished on several points: (i) the DLI-MOCVD process was used, (ii) with BEBC and C 6 H 5 SH in a unique solution containing both the precursor and the inhibitor, (iii) H 2 was not added in the reactive gas phase, (iv) a larger CVD reactor was used, and (v) operating temperatures were lower than 723 K, as specified in Table 2.…”

“…An even more surprising challenge was to find that when the emerging technology of direct liquid injection (DLI) is implemented for supplying a cold-wall reactor operating under atmospheric pressure with high vapor flow rates, the carbon incorporation inhibitors were still effective while large amounts of hydrocarbon solvent were injected with the precursor [22][23][24]. Indeed DLI-MOCVD is an alternative process where the precursor is diluted or dissolved in a liquid organic solvent.…”

“…An appropriate choice of precursor provides high yields [15]. Thus, DLI-MOCVD process for Cr deposition has been successful using C 6 Cl 6 [22][23][24] and C 6 H 5 SH [24] as inhibitors and bis(arene)chromium as metal source.…”

SiC coatings grown by liquid injection chemical vapor deposition using single source metal-organic precursors

“…Such processes are mainly used in microelectronics to deposit functional oxide thin films [15]. The growth of monolithic [16] and multilayer nanostructured chromium carbide and nitride coatings [17] was also reported by DLICVD. Regarding SiC coatings, a solution of hexamethyldisiloxane ((CH 3 ) 3 SiOSi(CH 3 ) 3 ) in ethanol was injected by a DLI system in a plasma-assisted CVD reactor for the growth of SiC and SiN x O y C z coatings, at 1023 K, using thermal Ar/H 2 and Ar/H 2 /N 2 plasma, respectively [18].…”