Growth of cobalt films at room temperature using sequential exposures of cobalt tricarbonyl nitrosyl and low energy electrons

Cobalt thin films were grown at room temperature using sequential exposures of cobalt tricarbonyl nitrosyl (CTN, Co(CO)3NO) and low energy (75–175 eV) electrons. During this cyclic growth process, the CTN molecules were first adsorbed on the substrate. The electrons then induced the desorption of the carbonyl and nitrosyl ligands from the adsorbed CTN. The removal of CO and NO ligands produced new adsorption sites. Subsequent CTN exposures allowed CTN to react with these new adsorption sites on the substrate. In situ ellipsometry was utilized to monitor the film thickness during the electron enhanced growth. Co growth rates as high as 1.3 A/cycle were observed by in situ ellipsometry depending on the reaction conditions. The in situ ellipsometry also observed the CTN adsorption and the removal of the carbonyl and nitrosyl ligands. Quadrupole mass spectrometer measurements confirmed the desorption of CO and NO during electron exposures. X-ray photoelectron spectroscopy (XPS) measured N XPS signals from the Co films deposited using electron exposures at 200 eV. The N/Co XPS signal ratio was consistent with the dissociation of 13% of the nitrosyl ligands on the CTN precursors that lead to Co deposition. In contrast, the negligible C XPS signals from the Co films indicated that the CO ligands were desorbed completely from CTN by the electron exposures at 200 eV. Under identical reaction conditions at lower incident electron currents, the maximum growth rate was obtained at an electron energy of 125 eV. Because the Co growth depends on the electron flux, the Co films were deposited only on the surface area irradiated by the electron beam. The spatial profile of the Co film deposited using long electron exposure times was mapped by ex situ spectroscopic ellipsometry. This spatial profile displayed a pronounced flat top that was consistent with the electron flux desorbing nearly all the CO and NO surface coverage in the central area of the electron beam during each reaction cycle. The spatial profile was used to calculate an electron induced desorption cross section of σ = 2 × 10−17 cm2 at 200 eV. This cross section was in approximate agreement with the cross sections for the electron impact dissociation of CTN in the gas phase.Cobalt thin films were grown at room temperature using sequential exposures of cobalt tricarbonyl nitrosyl (CTN, Co(CO)3NO) and low energy (75–175 eV) electrons. During this cyclic growth process, the CTN molecules were first adsorbed on the substrate. The electrons then induced the desorption of the carbonyl and nitrosyl ligands from the adsorbed CTN. The removal of CO and NO ligands produced new adsorption sites. Subsequent CTN exposures allowed CTN to react with these new adsorption sites on the substrate. In situ ellipsometry was utilized to monitor the film thickness during the electron enhanced growth. Co growth rates as high as 1.3 A/cycle were observed by in situ ellipsometry depending on the reaction conditions. The in situ ellipsometry also observed the CTN adsorption and the removal of the carbonyl and nitrosyl ligands. Quadrupole mass spectrometer measurements confirmed the desorption of CO and NO during electron exposures. X-ray photoelectron spectroscopy (XPS) measured N XPS signals from the...