One of the ways to create highly sensitive gas sensors based on graphene is to modify graphene by forming nanometer-sized channels in it. In this work, ion beam etching was used for these purposes. The necessary doses of Ga+ focused ion beam (FIB) were found to etch graphene. Several different structures based on modified graphene have been manufactured and investigated. A method for manufacturing graphene structures with a width of less than 10 nm by Ga+ FIB has been found. Also, high conductivity for structures of nanogap with polyaniline (PANi) was found, which can be used as selective gas sensing structures. The paper presents the responses of structures with nano-channel of PANi between modified graphene electrodes to different concentrations of ammonia and water.
Two-dimensional transition metal dichalcogenides (TMDC) and MoS2 in particular are promising materials as sensitive layers for gas sensing due to room operation temperature, high sensitivity, low dimensions, vast methods of selectivity alteration, etc. MoS2 response to toxic gases exposure depends on applied electric field that expands capabilities of resistive detection techniques, therefore, requires in-depth study. We fabricated a back-gated MoS2 based field-effect transistor (MoS2-FET) with standard photolithography technique on Si/SiO2 substrate. AFM microscopy confirmed the single layer nature of MoS2 flakes by cross-section featuring a thickness of 0.7 nm. Raman spectroscopy revealed A1g and E12g modes position at 403.5 cm-1 and 382 cm-1 respectively. The mobility in the absence of passivation was about 10-1 cm2 V−1s−1. MoS2-FET exhibits room-temperature NH3 sensing with resistive response to 200 ppm exposure of about ~60%, signal-to-noise ratio about 8, and response/recovery time about 100 s.
In this work, we consider the formation of a sensor layer 100 nm thick based on platinum-doped tin oxide. We investigated the method of forming an oxide film using magnetron sputtering Sn and Pt in Ar+O2 plasma. Using X-ray diffraction, it was found that the film consists of nanoscale particles with a metal core. The average size of the nanoparticles forming the film was from 47 to 74 nm The characteristics of the film were measured during additional oxidation in the temperature range from 300 to 700 °C. Thanks to annealing, the resistance of the sensor layer can be varied from 10 kΩ to 100 MΩ at a detection temperature of 300 °C The optimized film has been tested to detect ethanol, acetone, and ammonia at streams of 50, 100, 150 ppm.
In this article a new approach to graphene oxide spray deposition is demonstrated. Developed spray methodic allows to fabricate uniform low thickness graphene oxide coatings on a wide range of substrates without surface hydrophilization. A comparison of films obtained by spray a spin coating methods is given. The perspectives of industrial application of developed method for production of graphene oxide bio- and gas sensors are considered. Results of graphene oxide films local reduction performed by 1030 nm continuous CO2 laser engraver and 445 nm solid-state laser are presented. Features and difficulties of thin graphene oxide films reduction are discussed.
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