Auger and X-ray photoelectron spectroscopic and electrochemical characterization of titanium thin film electrodes

Auger (AES) and X-ray photoelectron spectroscopic (XPS) characterizations of electrochemically oxidized titanium are described. Surface oxides on thin (200–250 Å) vacuum deposited titanium films were formed under conditions of linear potential scan in 1 N KClO₄, 1 N HClO₄ and 1 N H₂SO₄. Current/voltage, capacitance/voltage and surface conductance/voltage relationships confirmed the irreversible formation of the surface oxide at thickness of 20–30 Å/V, for low applied potentials. Post moretem analysis of the thin films by AES and XPS indicated a mixture of metal and metal oxides (TiO₂, Ti₂O₃, TiO) on each surface, with the higher oxide states predominating on the electrochemically oxidized films. Observation of the L_IIIM_2,3M_4,5, N(E) signal shape in the Auger spectra of the potentially oxidized oxidized films showed a suboxide TiO-like surface rather than an TiO₂ surface state. Deconvolution of the $\text{Ti}\text{(2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext><mtext>,\; </mtext><mtext>3</mtext><mtext>2</mtext>}}\text{)}\text{XPS}$ spectra confirmed the coexistence of multiple oxidation states of Ti during electrochemical or atmospheric oxidation of the films. Ion sputtering of each surface was used to characterize the subsurface metal/metal oxide composition and to correlate the oxygen to metal atomic ratio with electrochemical pretreatment.