Exposure Of Cu Research Articles

Temperature and adsorbate dependence of the image-potential states on Cu(100).

We report a systematic study of the dependence of image-potential states on surface temperature and oxygen adsorption on Cu(100) using two-photon photoemission spectroscopy. The binding energy of the n=1 image-potential state is found to be insensitive to temperature, in agreement with inverse-photoemission measurements. In the temperature range 300--963 K, the image-peak amplitude is found to have a weak temperature dependence. The exposure of Cu(100) to oxygen (1.5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}6}$ Torr s) reduces the intensity of the image-potential peak and causes a shift of the position of this peak toward higher kinetic energy by an amount comparable to the change in the work function. A technique is described for eliminating space-charge effects, which can be a problem in pulsed-laser two-photon measurements.

Quartz crystal microbalance applied to studies of atmospheric corrosion of metals

AbstractThe possibility of using the quartz crystal microbalance technique in studies of atmospheric corrosion of metals is demonstrated in experiments involving both laboratory and field exposures. The inherent mass sensitivity of the technique provides the possibility of obtaining in situ information on mass changes during atmospheric corrosion. Laboratory exposures involve studies of kinetics during exposure of Cu or Ni covered quartz crystals to humidified air to which SO2 and/or NO2 or a vapour phase inhibitor have been added. Field exposures involve Ag covered quartz crystals exposed in benign museum storage rooms. With an observed mass resolution better than 10−8 g cm−2, corrosion effects can be observed under present conditions corresponding to less than 1 h laboratory exposure or less than 1 day of field exposure.

Combined SIMS/TPD investigations of UHV-prepared tolyltriazole overlayers on Cu, Ni and Au

The corrosion inhibitor tolyltriazole (TTA) has been investigated by combined secondary ion mass spectrometry (SIMS) and temperature programmed desorption mass spectrometry (TPD). TTA overlayers in the submonolayer to multilayer range are produced by in situ molecular beam exposure of Cu, Ni and Au substrates under UHV conditions. TPD yields information on different binding states and layer thickness. Molecular cluster ions as (2M−2H+Me) −, indicating the formation of TTA molecules in quasipolymeric chains, are emitted from all three substrates. Only for Cu we found a TTA desorption peak at high target temperatures (580 K), correlated to the emission of characteristic secondary ions, mainly (MH) − and (2M−2H+Cu) −. It is obviously the corresponding stable TTA monolayer on Cu that is responsible for the strong corrosion protection effect.

The etching of Cu(100) with Cl2

Modulated beam mass spectrometry has been used to investigate the etch products, surface chemistry and product desorption mechanisms for interaction of Cl2 with Cu(100). The dominant etch product is Cu3Cl3 for T<∼580 °C and CuCl for T>650 °C. Exposure of Cu(100) to Cl2 at temperatures below 150 °C leads to the growth of a copper chloride layer whose thickness increases linearly with time for exposures greater than approximately 1000 langmuirs. The rate of growth of the chloride layer decreases with increasing temperature. Temperature programmed desorption experiments indicate that the chloride desorbs as Cu3Cl3 with zero order kinetics and an activation energy for desorption of about 33 kcal/mol. The zero order desorption kinetics suggest that the quantity of chlorine on the immediate surface remains constant until the chlorine in the bulk is depleted. The activation energy for desorption of 33 kcal/mol is within experimental error equal to the heat of sublimation of Cu3Cl3 from pure copper chloride. This result suggests that etching is simply a ‘‘compound growth’’-evaporation reaction. Ion bombardment is shown to suppress the etch rate which is probably a consequence of ion-induced dissociation of Cu3Cl3 and possibly a decreased concentration of chlorine in the surface region.