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Fig. 5. Schematic representation of electrochemical annealing. Differently oriented domains are represented by differently oriented line patterns, and the dashed line refers to the boundary of the original domain.(1) Upon application of a cathodic potential, -E, monolayer dissolution begins at the domain boundary. (Z), (3) If the cathodic potential is applied for an amount of time sufficient for complete domain dissolution, subsequent application of an anodic potential leads to growth of the surrounding monolayer with no new nucleation occurring where the original domain existed, thus affording a nominally defect-free film. (4) If a small island remains after domain dissolution, upon potential reversai monolayer growth occurs at the edges of the island and the surrounding terrace. In this case, the newly formed domain boundary has a smaller perimeter than before dissolution. (5) Continued potential cycling results in eventual disappearance of the smaller domain. ExperimentalAtomic force microscopy experiments were performed using a Digital Instruments, Inc. Nanoscope 111 scanning probe microscope and Si3N4 cantilevers (quoted spring constant of 0.06 N m-'). A piezoelectric scanner with a maximum lateral scanning range of 15 pm x 15 pm was used for imaging. All images shown were obtained in lateral force mode, at tip scan rates ranging from 2 to 10 Hz. Data were collected using Digital Instruments Nanoscope 111 version 4.1 software and were low-pass filtered once. Image analysis was performed with the Nanoscope I11 and with NIH Image version 1.59b2 (available by anonymous FTP at zippy.nimh.nih.gov) software.Electrodeposition of the monolayers was performed in acetonitrile solutions containing 0.5 mM ET (Aldrich) and 2 mM tetrabutylammonium triiodide (n-Bu4N'13e). The n-Bu4N'13e was prepared by addition of 5 g (0.01354 mol) n-Bu4N'Ie (Aldrich) to 120 ml of 1.7 M KI (Aldrich), followed by addition of 3.44 g of 12. The resulting dark brown solution and deep purple oil layer was stirred at 70 "C for approximately 10 min and allowed to cool to room temperature, resulting in the formation of dark black solids which were filtered, collected and rinsed with distilled water. Recrystallization from hot methanol and drying in vacuo afforded black plate-like crystals of TBAI3.Electrodeposition was performed in an AFM fluid cell (Digital Instruments) equipped with ports for fluid entry and exit. Freshly cleaved, highly oriented pyrolytic graphite (HOPG) was used as the substrate and working electrode, and platinum counter and quasi-reference electrodes were inserted through the outlet port of the fluid cell. Potential cycling was performed by applying a square wave with a homemade function generator. Potential limits were chosen based on the potential at which monolayer deposition and dissolution was observed in the scanning region. Typically, deposition first occurred at approximately 650 mV vs. AglAgCI, with the monolayer remaining stable at 620 mV. The potential was cycled at approximately 620 f 75 mV, with the anodic poten...

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A modified profile method for determing the vertical deposition (or/and exhalation) fluxes of NO, NO2, ozone, and HN03 in the atmosphere surface layer is presented. This method is based on the generally accepted niicrometeorological ideas of the transfer of momentum, sensible heat and matter near the Earth's surface and the chemical reactions among these trace gases. The analysis (aerodynamic profile method) includes a detailed determination of the micrometeorological quantities (such as the friction velocity, the fluxes of sensible and latent heat, the roughness length and the zero plane displacement), and of the height-invariant fluxes of the composed chemically conservative trace gases with "group" concentrations c 1 = NO + NO2 + HNO3, c 2 = NO2 +O3 + 3/2 . HNO3, and c 3 = NO - O3 - 1/2 . HNO3. The fluxes of the "individual" species are finally determined by the numerical solution of a system of coupled nonlinear ordinary differential equations for the concentrations of ozone and HN O3 ("decoding" method). The parameterization of the fluxes is based on the flux-gradient relationships in the turbulent region of the atmospheric surface layer. The model requires only the vertical profile data of wind velocity, temperature and humidity and concentrations of NO, NO2, ozone, and HNO3. The method has been applied to vertical profile data obtained at Jülich (September 1984) and collected in the BIATEX joint field experiment LOVENOX (Halvergate, U.K., September 1989)