Evaluation of tetra-alkylchromium precursors for organometallic chemical vapor deposition II: Unusual low temperature chromium carbide deposition from Cr[C(CH3)3]4

The tetra-tert-butylchromium compound Cr[C(CH3)3]4 was found to be appropriately volatile and sufficiently thermally stable to be used as a chromium source in organometallic chemical vapor deposition. Thin films of chromium carbide were deposited using this precursor in the exceptionally low temperature range 100-150 °C. The films were X-ray amorphous and the atomic ratio of carbon to chromium was in the range 1.2-1.4, even using hydrogen as carrier gas. Without stringent precautions the films may be partially oxidized owing to the reactivity of this precursor towards traces of oxygen and moisture. Chemical bonding analysis using X-ray photoelectron spectroscopy data revealed carbon incorporation both in carbidic form and free carbon form (about 50%). The ?-elimination mechanism probably initiates the decomposition but carbon incorporation may be due to side heterogeneous reactions involving carrier gas molecules because the carbon contamination of films grown under dynamic vacuum was very low.