Isotope-selective chemical vapor deposition via vibrational activation

A narrow bandwidth infrared (IR) laser selectively excites and activates one isotopic variant of a gas phase precursor to permit isotope-selective chemical vapor deposition. We show that selective vibrational excitation of the (CH4)-C-12 or (CH4)-C-13 isotopologue of methane controls the carbon isotope ratio of adsorbates deposited on a Ni substrate and permits significant isotope enrichment in a single reaction step. A model of the process based on known reaction probabilities and process variables predicts the enrichment we observe. While our current laser system permits a 9-fold enhancement of C-12 or C-13 deposition, optimization of deposition and detection strategies and use of a more powerful, commercially available laser source suggest isotope enrichment factors of 100-fold or more are readily attainable. Other gas-surface reactions activated by vibrational energy may also be candidates for this approach to isotope-selective deposition.