Evaluation of Thin Film Titanium Nitride Electrodes for Electroanalytical Applications

Abstract

Titanium nitride is a hard and inert conducting material that has yet not been widely used as electrode material for electroanalytical applications although there are highly developed protocols available to produce well adherent micro and nanostructured electrodes. In this paper the possibilities of using titanium nitride thin films for electroanalytical applications is investigated. Scanning electrochemical microscope (SECM) was used for analysis of the redox kinetics of a selected fast redox couple at thin films of titanium nitride (TiN) in different thicknesses. The investigation was carried out by approaching an amperometric ultramicroelectrode (UME) to the TiN film while the soluble redox couple (ferrocenemethanol/ferrociniummethanol) served as mediator in a SECM configuration. The substrate was biased at a potential so that it rereduces the species being produced at the UME, thus controlling the feedback effect. Normalized current -distance curves were fitted to the theoretical model in order to find the apparent heterogeneous standard rate constant (k8) at the sample. The data are further supported by structural investigation of the TiN films using scanning force microscopy and X-ray photoelectron spectroscopy. It was found that the kinetics are little influenced by prolonged storage in air. The heterogeneous standard rate constants in 2 mM ferrocenemethanol were (0.73 AE 0.05) Â 10 À3 cm s À1 for 20 nm TiN thin layer, (1.5 AE 0.2) Â 10 À3 cm s À1 for 100 nm TiN thin layer and (1.3 AE 0.2) Â 10 À3 cm s À1 for 300 nm TiN thin layer after prolonged storage in air. Oxidative surface treatment (in order to remove organic adsorbates) decreased the kinetics in agreement with a thicker oxide layer on the material. The results suggest that their direct use for amperometric detection of reversible redox systems in particular at miniaturized configurations may be advantageous.

Chemical Reaction on Etched TaNO Thin Film as O2 Content Varies in CF4/Ar Gas Mixing Plasma

“…These binding energies are in agreement with the reported values [19]. [19][20][21]. Figure 4 shows the XPS narrow scan spectra for O 1s taken at a 90 o angle.…”

“…3, mono peaks at the binding energy (B. E.) of 26.1 eV and 27.6 eV corresponded to Ta 4f 5/2 and Ta 4f 7/2 as reported by C. Atanassova et. al [18][19][20]. As shown in Fig.…”

“…We could not identify the N 1s peaks from 396 eV to 400 eV. Because the O-F bond is removed during the etching process, the intensity of the N 1s peak did not appear to be nearly that of the Ta 4p 3/2 peak [18][19][20]. The F 1s photoelectron peaks obtained from the etched sample are shown in Fig.…”

“…This lead to an etch rate increase with increasing amounts of O 2 content in the CF 4 /Ar plasma. This shift to higher energy was due to the chemical reaction [20,21].…”

Electrochemical analysis of nanostructured iron oxides using cyclic voltammetry and scanning electrochemical microscopy

“…2 μm thick layer of nanostructured Pt prepared by electrodeposition of Pt within a lyotropic liquid crystal molecular template as previously reported [39,40]. The modified ME was mounted on a SECM instrument running under SECMx software [45]. The SECM used closed loop piezoelectric motors (mechOnics AG, München, Germany) as positioning system and a CHI700 B bipotentiostat (CH Instruments, Austin TX, USA) [46].…”