AVS 49th International Symposium
    Thin Films Friday Sessions
       Session TF-FrM

Paper TF-FrM6
Surface Chemistry of TaCl@sub 5@ on Polycrystalline Ta and Cu

Friday, November 8, 2002, 10:00 am, Room C-101

Session: Fundamentals of Thin Flm Growth
Presenter: A.M. Lemonds, The University of Texas at Austin
Authors: A.M. Lemonds, The University of Texas at Austin
J.M. White, The University of Texas at Austin
J.G. Ekerdt, The University of Texas at Austin
Correspondent: Click to Email
The surface chemistry of TaCl@sub 5@ on polycrystalline Ta and Cu was studied by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) following adsorption at 130 K. XPS determined that no surface reactions occurred during adsorption at 130 K on Ta, and binding energy shifts in the Ta 4f and Cl 2p XP spectra suggested interactions between TaCl@sub 5@ molecules in contact with the Ta substrate. TPD analysis from 130 to 900 K showed the desorption of two molecular states between 200 and 300 K from Ta, and the higher temperature state is more structurally ordered than the low temperature state. Chemical reaction between the TaCl@sub 5@ interfacial layer and O absorbed in the Ta lattice was observed for the 250 K annealing of multilayers adsorbed at 130 K. Surface coverages estimated by XPS were less than coverages estimated by TPD for adsorption on Ta, and the discrepancy is explained by the forward scattering of the substrate Ta 4f metallic photoelectrons through ordered TaCl@sub 5@ adlayers. A multilayer formed for TaCl@sub 5@ adsorption on Cu at 130 K, and a single multilayer desorption peak was observed at 275 K. At 300 K, TaCl@sub 5@ dissociatively adsorbed on Cu, and uptake saturated at less than one monolayer, limited by adsorbed Cl ligands. TPD for this adsorption showed Ta@super +@ (m/z 181) and Cu@super +@ (m/z 63) desorption features at 355 and 495 K, respectively. No detectable Ta or Cl was observed by XPS on the Cu surface following TPD, in which the surface temperature reached 900 K.