We present triethylboron (TEB) as a single-source precursor for chemical vapor deposition (CVD) of B x C thin films and study its gas phase chemistry under CVD conditions by quantum chemical calculations.A comprehensive thermochemical catalogue for the species of the gas phase chemistry of TEB is examined and found to be dominated by b-hydride eliminations of C 2 H 4 to yield BH 3 . A complementary bimolecular reaction path based on H 2 assisted C 2 H 6 elimination to BH 3 is also significant at lower temperatures in the presence of hydrogen. Furthermore, we find a temperature window of 600-1000 1Cfor the deposition of X-ray amorphous B x C films with 2.5 r x r 4.5 from TEB. Films grown at temperatures below 600 1C contain high amounts of H, while temperatures above 1000 1C result in C-rich films. The film density and hardness are determined to be in the range of 2.40-2.65 g cm À3 and 29-39 GPa, respectively, within the determined temperature window. † Electronic supplementary information (ESI) available: Tables with more details of the atomic content and measured densities and hardness of the films, and more details of the computations together with Cartesian coordinates of structures. See

Alkylboranes, such as trimethylboron (TMB) and triethylboron (TEB), are promising alternative precursors in lowtemperature chemical vapor deposition (CVD) of boron-containing thin films. In this study, CVD growth of B−C films using TMB and quantum-chemical calculations to elucidate a gas phase chemical mechanism were undertaken. Dense, amorphous, boron-rich (B/C = 1.5−3) films were deposited at 1000 °C in both dihydrogen and argon ambients, while films with crystalline B 4 C and B 25 C inclusions were deposited at 1100 °C in dihydrogen. A script-based automatization scheme was implemented for the quantum-chemical computations to enable time efficient screening of thousands of possible gas phase CVD reactions. The quantum-chemical calculations suggest TMB is mainly decomposed by an unimolecular α-H elimination of methane, which is complemented by dihydrogen-assisted elimination of methane in dihydrogen.

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