| Abstract
| - The optical and electrochemical properties of transparent,boron-doped diamond thin film, deposited on quartz, arediscussed. The films were deposited by microwave-assisted chemical vapor deposition, for 1−2 h, using a 0.5%CH4/H2 source gas mixture at 45 Torr and 600 W ofpower. A high rate of diamond nucleation was achievedby mechanically scratching the quartz. This pretreatmentleads to the formation of a continuous film, in a shortperiod of time, which consists of nanometer-sized grainsof diamond. The thin-film electrode was characterized bycyclic voltammetry, atomic force microscopy, and UV−visible absorption spectrophotometry. The film's electrochemical response was evaluated using Ru(NH3)63+/2+ in1 M KCl, Fe(CN)63-/4- in 1 M KCl, and chlorpromazine(CPZ) in 10 mM HClO4. The film exhibited a low voltammetric background current and a stable and activevoltammetric response for all three redox systems. Theoptical transparency of the polycrystalline film in thevisible region was near 50% and fairly constant between300 and 800 nm. The optical and electrical propertieswere extremely stable during 48-h exposure tests invarious aqueous (HNO3, NaOH) solutions and nonaqueous (e.g., chlorinated) solvents. The properties were alsoextremely stable during anodic and cathodic potentialcycling in harsh aqueous environments. This stability isin stark contrast to what was observed for an indium-doped tin oxide thin film coated on quartz. The spectroelectrochemical response (transmission mode) for CPZwas studied in detail, using a thin-layer spectroelectrochemical cell. Thin-layer voltammetry, potential step/absorption measurements, and detection analytical figuresof merit are presented. The results demonstrate thatdurable, stable, and optically transparent diamond thinfilms, with low electrical resistivity (∼0.026 Ω·cm) laterally through the film, can be deposited on quartz.
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