Diamond-coated field-effect sensor for DNA recognition — Influence of material and morphology

•C-V characteristics showed order of magnitude higher flat band voltage shifts after DNA hybridization on diamond sensors.•∆ VF (measured at 150 Hz and 1 kHz) showed similar behaviour both for nano- and microcrystalline diamond-coated sensors.•While microcrystalline diamond provided the highest response, nanocrystalline the highest sensitivity to DNA hybridization.

The influence of nanocrystalline (< 20 nm grains) and microcrystalline (around 100 nm grains) diamond thin film morphology on the capacitance–voltage (C–V) characteristics of diamond-coated field-effect SiN sensors was characterized with respect to DNA recognition. DNA was grafted via –OH surface termination. The sensor materials and surfaces were characterized by scanning electron microscopy, Raman Spectroscopy, fluorescence microscopy, XPS, and contact angle measurements. The C–V characteristics exhibited generally an order of magnitude higher flat band voltage shifts (∆ VF) after complementary DNA hybridization for both types of diamond-coated sensors (160 ÷ 300 mV) compared to reference SiN sensor without diamond layer (11 mV), even if incomplete DNA denaturation and ∆ VF fluctuations (60 mV) were accounted for. While microcrystalline diamond provides the highest response, nanocrystalline diamond provides the highest sensitivity. An explanation based on interfacial charges is proposed.

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