Characterization of CVD Heavily B‐Doped Diamond Thin Films for Multi Electrode Array Biosensors

Abstract

Nanocrystalline diamond is an excellent material for the fabrication of Multi Electrode Arrays used to monitor the activity of biological cells and tissues. Yet, the overall performances in terms of background noise, electrochemical activity and transparency for fluorescence detection, are difficult to optimize. The aim of this study is to obtain an orientative guide on how to reach a good compromise between the competing properties. For this purpose, several samples of diamond films were produced under a variety of synthesis conditions, to be employed in the fabrication of amperometric Multi Electrode Arrays. After the fabrication, the samples were characterized from a structural, electrical, electrochemical and optical point of view in order to find possible correlations with the parameters adopted in their production.

Towards the insulator-to-metal transition at the surface of ion-gated nanocrystalline diamond films

“…The resulting free holonic density was n h = 3.2 ± 0.5 · 10 20 e + /cm 3 , corresponding to a B-doping concentration of 0.36 ± 0.06 %, and consistent with Ref. [25]. Fig.1b shows a sketch of the EDL device, which was obtained by dicing the NCD film into smaller rectangles (∼ 0.7 × 0.3 cm 2 ), and drop-casting a small amount of conductive silver paste to realize electrical contacts for source (S), drain (D), and four-wire voltage probes (V 1 and V 2 ).…”

“…Nanocrystalline diamond (NCD) films were grown by a two-step Chemical Vapor Deposition (CVD) process on AF32eco high-temperature glass substrates. A detailed description of the growth process has been reported elsewhere [25]. The films consisted of an underlying intrinsic NCD layer (≃ 1 µm) with a B-doped NCD layer (≃ 300 nm) on top, as determined by Scanning Electron Microscopy [25].…”

“…A detailed description of the growth process has been reported elsewhere [25]. The films consisted of an underlying intrinsic NCD layer (≃ 1 µm) with a B-doped NCD layer (≃ 300 nm) on top, as determined by Scanning Electron Microscopy [25]. Fig.1a shows a representative topography image acquired via Atomic Force Microscopy (AFM) in contact mode.…”

Enhancing the Transparency of Highly Electroactive BNCD‐MEAs

“…Previous studies demonstrated the dependency of electrical, electrochemical, and optical characteristics on growing parameters like crystal structure, temperature, and doping density . Furthermore, the selection of transparent carrier materials was a serious limiting factor, mainly due to thermal issues like the softening temperature of glasses or a mismatch of the coefficients of thermal expansion with respect to diamond, in case of sapphire and quartz.…”

“…Previous studies demonstrated the dependency of electrical, electrochemical, and optical characteristics on growing parameters like crystal structure, temperature, and doping density. [35] Furthermore, the selection of transparent carrier materials was a serious limiting factor, mainly due to thermal issues like the softening temperature of glasses or a mismatch of the coefficients of thermal expansion with respect to diamond, in case of sapphire and quartz. Sapphire has a thermal expansion about threefold that of diamond, resulting in an excessive compressive stress on the NCD-film, thus leading to delamination, when it cools down after the CVD process at %800 C. Conversely, quartz has nearly zero thermal expansion coefficient.…”