Optical and Electrochemical Properties of Optically Transparent, Boron-Doped Diamond Thin Films Deposited on Quartz

Abstract

The optical and electrochemical properties of transparent, boron-doped diamond thin film, deposited on quartz, are discussed. 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 of power. A high rate of diamond nucleation was achieved by mechanically scratching the quartz. This pretreatment leads to the formation of a continuous film, in a short period of time, which consists of nanometer-sized grains of diamond. The thin-film electrode was characterized by cyclic voltammetry, atomic force microscopy, and UV-visible absorption spectrophotometry. The film's electrochemical response was evaluated using Ru(NH3)6(3+/2+) in 1 M KCl, Fe(CN)6(3-/4-) in 1 M KCl, and chlorpromazine (CPZ) in 10 mM HClO4. The film exhibited a low voltammetric background current and a stable and active voltammetric response for all three redox systems. The optical transparency of the polycrystalline film in the visible region was near 50% and fairly constant between 300 and 800 nm. The optical and electrical properties were extremely stable during 48-h exposure tests in various aqueous (HNO3, NaOH) solutions and nonaqueous (e.g., chlorinated) solvents. The properties were also extremely stable during anodic and cathodic potential cycling in harsh aqueous environments. This stability is in stark contrast to what was observed for an indium-doped tin oxide thin film coated on quartz. The spectroelectrochemical response (transmission mode) for CPZ was studied in detail, using a thin-layer spectroelectrochemical cell. Thin-layer voltammetry, potential step/ absorption measurements, and detection analytical figures of merit are presented. The results demonstrate that durable, stable, and optically transparent diamond thin films, with low electrical resistivity (approximately 0.026 omega x cm) laterally through the film, can be deposited on quartz.

New Horizons in Spectroelectrochemical Measurements: Optically Transparent Carbon Electrodes

“…In the other architecture, a thin film is deposited on an optically transparent substrate; for example, a diamond/quartz OTE (24,26). This OTE is analogous to a thin film of ITO on quartz and has an electric resistivity of ~10 S/cm, an optical transparency of ~50% at 300-800 nm, a working-potential window of ≥3V in aqueous media, stable voltammetric background currents and optical properties over a wide potential range, and relatively rapid electron-transfer kinetics for a number of redox systems without conventional pretreatment.…”

“…strated on the optically active redox systems ferri/ferrocyanide and methyl viologen with a freestanding diamond disk OTE (22). This was followed by work on the optically active redox molecule chlorpromazine with a diamond/quartz OTE (24).…”

Characterization of Optical and Electrical Properties of Transparent Conductive Boron-Doped Diamond thin Films Grown on Fused Silica

“…Currently, diamond devices are used in high power electronics [2], diamond diodes [3], high-power switches [4] or high-frequency devices, such as transistors [5]. However, the most common use of BDD materials is for electrodes in electrochemistry [6][7][8] or spectroelectrochemistry [9]. The electrodes of this type have a good chemical and electrochemical stability even in highly aggressive media, a long lifetime and a wide potential window for the water discharge.…”

“…They suggest that an area of the high conductivity density correlates with a high boron doping level along with electrical conductivity heterogeneity of boron-doped poly-/microcrystalline diamond surfaces. Stotter et al [9] investigated an optical transmittance in the UV-VIS range and absorbance with a spectro-electrochemistry method based on measurements using an optical transparent BDD electrode with a maximum 50% transmittance on quartz. These results showed that the optical and electrical properties were extremely stable during 48-h exposure tests in various aqueous (HNO3, NaOH) solutions and non-aqueous (e.g.…”

“…These parameters are critical for developing integrated optical sensors [26,27], transparent electronics [28] and opto-electrochemical bio-sensing devices [29,30].…”