Direct observation of hydration of TiO2 on Ti using electrochemical AFM: freely corroding versus potentiostatically held conditions

Hydration of titanium/titanium oxide surfaces under freely corroding and po tentiostatically held conditions has been characterized using electrochemic al atomic force microscopy (EC AFM). In contrast to conventional high vacuu m techniques. AFM enables measurement of morphological surface structure in the in situ hydrated state. Electrochemical probes in the imaging environm ent further enable acquisition of electrical characteristics during AFM ima ging. Experiments were performed on etched, electropolished commercially pu re titanium. As noted by direct observation and corroborated by power spect ral density (Fourier analysis) measurements. oxide domes cover the titanium surface and grow laterally during hydration. Applied potential altered the growth rate. Under open circuit potential conditions, growth proceeded app roximately six times faster than under a -1 V applied voltage (1098 +/- 52 nm(2)/min +/- versus 184.84 +/- 19 nm(2)/min). Film growth increased electr ical resistance and lowered interfacial capacitance based on step polarizat ion impedance spectroscopy tests. (C) 2001 Elsevier Science B.V. All rights reserved.