Abstract
Glassy carbon (GC) thin film was successfully deposited via thermal pyrolysis of ethanol vapor by means of chemical vapor deposition at 1000 °C without any catalysis. The Raman spectra of the grown GC film showed typical peaks of D1, G, and 2D1 including derivative peaks of D2 band and a combinational peak of D1 + G that indicates the film is glassy carbon. XPS analysis of the C 1s core showed the deposited films have carbon atoms consisting of an almost sp2 binding structure. A picture of the cross-sectional transmission electron microscope showed the stacking layers of a disordered carbon have a turbostratic layer with a few nanometers graphitic domain, about 13 nm estimated by Raman spectra. Two types of pH sensor were fabricated. One is a GC based field-effect transistor with a top gate of a solution (GC-FET), and the other is a GC extended gate electrode connected to commercial Si FET (GC-EGFET). The average pH sensitivity of GC-FET and GC-EGFET is 21.5 mV/pH and 26.5 mV/pH, respectively, which are comparable for graphene-based solution gating pH sensors that have appeared in the recent literature.
Highlights
Glassy carbon (GC) is a technologically important material and the GC electrodes have been widely used due to their excellent properties including strong corrosion resistance, chemical inertness, thermal stability and a structure impermeable to both gases and liquids, wide electrochemical potential window, electrocatalytic activity for redox reactions, good electrical conductivity, good biocompatibility, and low fabrication costs [1,2,3,4]
We demonstrate a solution-gated GC film field-effect transistor (FET) and an extended gate FET using the same device structure to evaluate the electrical characteristics for the GC film
The film deposited for 10 min and 30 min is essentially uniforms, the domains of the GC for 60 min are larger and the surface looks bumpier in the atomic force microscope (AFM) images, but the field emission scanning electron microscope (FE-SEM) images are looked smooth surface
Summary
Glassy carbon (GC) is a technologically important material and the GC electrodes have been widely used due to their excellent properties including strong corrosion resistance, chemical inertness, thermal stability and a structure impermeable to both gases and liquids, wide electrochemical potential window, electrocatalytic activity for redox reactions, good electrical conductivity, good biocompatibility, and low fabrication costs [1,2,3,4]. Pyrolysis carbon shows a structure with a microstructure composed of both graphitic and amorphous, the electrical resistivity is still high for the sensing electrodes [12] The latter technique has several issues to overcome such as uniformity of dispersed ink, removing the dispersant, and a cost of fabrication ink [19]. GC processed using CVD exhibits several advantages, including good electrical and chemical properties, a large area deposition resulting in low cost fabrication This technique has advantages of the large scales, the simple process, and a low cost compared with preceding graphene and SWCNTs. A large-scale GC film across an entire substrate contrasts with the conventional micromechanical exfoliated graphene which graphene is prepared in the form of small flakes [20]. Our experiments indicate the potential of this new glassy carbon film-based device in pH sensing applications
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