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Electronic and electrical contact applications of TiN require a detailed understanding of the surface chemistry behavior in a variety of operating environments. For electromechanical contacts, contact resistance is the figure of merit and is a strong function of the structure and chemistry of the surface region. Thin (on the order of a few monolayers) insulating or semiconducting overlayers on a metallic conductor can raise contact resistance several orders of magnitude. In this study low temperature (22-100 °C) oxidation kinetics of reactively sputtered Ti and TiN, coatings of varying composition exposed at three humidity levels have been examined by x-ray photoelectron spectroscopy (XPS) depth profiling, angle resolved XPS, and contact resistance measurements. Equilibrium overlayer conductivities can be up to nine orders of magnitude greater for TiN 10 than Ti metal.

Articles you may be interested inThe electronic spectrum of the fluoroborane free radical. II. Analysis of laser-induced fluorescence and single vibronic level emission spectraThe electronic spectrum of the fluoroborane free radical. I. Theoretical calculation of the vibronic energy levels of the ground and first excited electronic statesThe laser-induced fluorescence spectrum, Renner-Teller effect, and molecular quantum beats in the à 2 Π i -X̃ 2 Π i transition of the jet-cooled HCCSe free radical Investigation of the pure rotational spectrum of magnesium monobromide by Fourier transform microwave spectroscopyThe à 2 ⌺ ϩ -X 2 ⌸ i transition of jet-cooled silicon methylidyne, SiCH, has been recorded by laser-induced fluorescence in the 850-600 nm region. The radical was produced in an electric discharge using tetramethylsilane as the precursor. Fifteen cold bands of SiCH and 16 bands of SiCD have been assigned vibrationally, giving the upper state frequencies as v 2 Јϭ715/558 cm Ϫ1 and v 3 Јϭ1168/1127 cm Ϫ1 for SiCH/SiCD. Rotational analysis of the 0 0 0 and 3 0 3 bands for each isotopomer has given the following molecular structures: r 0 Љ͑Si-C͒ϭ1.692 52͑8͒, r 0 Љ͑C-H͒ϭ1.0677͑4͒, r 0 Ј͑Si-C͒ϭ1.6118͑1͒, and r 0 Ј͑C-H͒ϭ1.0625͑5͒ Å. The silicon-carbon bond length in the X 2 ⌸ ground state of SiCH ͑electron configuration ... 2 3 ͒ is typical for a SiϭC double bond; in the à 2 ⌺ ϩ excited state (... 1 4 ) it corresponds to a triple bond. This work provides the first experimental measurement of the length of the carbon-silicon triple bond.

The electronic spectrum of germylidene (H2C=Ge), the simplest unsaturated germylene, has been observed for the first time. Jet-cooled H2CGe and D2CGe were produced by an electric discharge through tetramethylgermane diluted in argon at the exit of a supersonic expansion. High-resolution spectra of H2C74Ge and D2C74Ge, obtained from (CH3)474Ge prepared from isotopically enriched 74Ge metal, have been rotationally analyzed to yield the following r0 structures: r0″(CGe)=1.7908(2) Å, r0″(CH)=1.1022(5) Å, θ0″(HCH)=115.05(5)°, r0′(CGe)=1.914(4) Å, r0′(CH)=1.082(9) Å, and θ0′(HCH)=139.3(11)°. The 367–354 nm B̃1B2–X̃ 1A1 band system consists of prominent perpendicular bands involving the CGe stretching (ν3) and CH2 scissors (ν2) vibrations and a weaker series of vibronically induced parallel bands involving the CH2 rocking mode (ν6). Vibronic bands involving Δv=2 changes in ν6(b2) and ν4(b1) have also been assigned. The fluorescence decays of single rotational levels of the 000 band of H2C74Ge exhibit molecular quantum beats for about 70% of the levels surveyed. Density of states arguments reveal that most of the beats originate from interactions with high rovibronic levels of the ground state. In one case, hyperfine splittings in the Fourier transform of the beat pattern indicate an accidental coincidence with an excited triplet state level. The less frequent occurrence of quantum beats in germylidene compared to silylidene, where they are almost universal, can be attributed to the smaller density of ground state levels at the zero-point energy of the S2 state in the former.

The ground state vibrational energy levels of jet-cooled SiCH and SiCD have been studied by a combination of laser-induced fluorescence and wavelength-resolved fluorescence techniques. The radicals were produced by a pulsed electric discharge at the exit of a supersonic expansion using tetramethylsilane or methyltrichlorosilane as the precursor. Emission spectra have been obtained by pumping both perpendicular and parallel (vibronically induced) bands, providing complementary information on the Si–C stretching and Si–C–H bending modes. Ground state energy levels up to 4000 cm−1 have been assigned and fitted using a vibrational Hamiltonian that incorporates Renner–Teller, spin–orbit, vibrational anharmonicity, and Fermi resonance interactions. The validity of the derived parameters has been tested using the isotope relations.