a-SixC1−x:H thin films with subnanometer surface roughness for biological applications

Abstract

The characterization of a-SixC1−x:H thin films by plasma-enhanced chemical vapor deposition with high hydrogen dilution for biological applications is addressed. A root mean square roughness less than 1 nm was measured via atomic force microscopy for an area of 25 μm2. Structural analysis was done using Fourier transform infrared spectroscopy in the middle infrared region. It was found that under the deposition conditions, the formation of Si–C bonds is promoted. Electrical dark conductivity measurements were performed to evaluate the effect of high hydrogen dilution and to find the relation between carrier transport properties and the structural arrangement. Conductivities of the order of 10−7 to 10−9 S/cm at room temperature for methane–silane gas flow ratio from 0.35 to 0.85 were achieved, respectively. UV-visible spectra were used to obtain the optical band gap and the Tauc parameter. Optical band gap as wide as 3.55 eV was achieved in the regime of high carbon incorporation. Accordingly, deposition under low power density and high hydrogen dilution reduces the roughness, improves the structure of the network, and stabilizes the film properties as a greater percentage of carbon is incorporated. The biofunctionalization of a-SixC1−x:H surfaces with NH2-terminated self-assembled monolayers was obtained through silanization with 3-aminopropyltrimethoxysilane. This knowledge opens a window for the inclusion of these a-SixC1−x:H thin films in devices such as biosensors.

Biofunctionalization Process of a-SiC:H Surfaces Applied to an Interdigitated Microelectrode Array to Detect Enterotoxigenic Escherichia coli

“…1 by comparing with the S0 spectrum corresponding to the a-SiC:H thin films. These peaks are according with a previous work [10]. The low occurrence of the peak at 1200 cm -1 indicates that the majority of O-C2H6 terminal groups were hydrolyzed during the process.…”

“…Then the samples were rinsed with anhydrous toluene and methanol, consecutively. Finally, the samples were dried in an oven at 110 °C for 1 h, removing water and forming siloxane bonds [10].…”

Detection of Salmonella enterica on silicon substrates biofunctionalized with anti-Salmonella IgG, analyzed by FTIR spectroscopy

“…Functional groups as carbonyl or amine can interact with the functionalities of the inorganic phase (Castruita-de León et al, 2018). In Figure 4 and 5, spectra of functionalization with 3-APTMS and GTA on cSi and aSi are observed, comparing both materials similar spectra were obtained, this because FTIR technique is used to confirm the presence of functional groups but it does not indicate structure of the material; unlike aSiCH (Figure 6) where a different spectrum was gotten; in all cases, it can be observed in untreated substrates spectra bands related to Si-O stretching vibration modes at 616 cm −1 and 1100 cm −1 (bond generated by the interaction of the substrate surface with oxygen present in the environment, previous activation), Si-H (640 cm −1 wagging mode and 2000 cm −1 stretching vibration modes), Si-H 2 (2090 cm −1 stretching vibrational modes); specifically bands related to Si-C bonds (750-780 cm −1 ) in stretching mode were observed in aSiCH (Herrera-Celis et al, 2015). For the functionalization process with 3-APTMS, silanes are bound through the formation of a Si-O-Si bond between treated surface and silanol groups (Yamaura et al, 2004;Taylor et al, 2000;Liu et al, 2005).…”

Interdigitated Microelectrode Arrays Based on Non-Cytotoxica-SixC1-x:H forE. coliDetection

“…The corresponding peaks were those at 640 cm −1 , 770 cm −1 and 1000 cm −1 for Si-H n wagging, Si-C stretching and CH n wagging, respectively. 29 The deconvolution of the FTIR data was done by fitting Gaussian curves using the tool Fit Multi-peaks in OriginPro 8 (OriginLab Corporation, MA, USA).…”

“…After that, the samples were rinsed separately with anhydrous toluene and methanol, and dried in an oven at 110 • C for 1 h, removing any water and forming siloxane bonds. 40 Next the silanized samples were dipped in a 2.5% solution of glutaraldehyde (GA) (Sigma-Aldrich, #G7651) in phosphate buffer (PB) solution (Sigma-Aldrich, #63238) for 1 h at 25 • C and 350 rpm. This was followed by rinsing the samples with phosphate buffered saline (PBS, pH 7.4).…”