Hydrogenated Graphene Based Organic Thin Film Transistor Sensor for Detection of Chloride Ions as Corrosion Precursors

Corrosion monitoring and management has been at the center of structural health monitoring protocols due to its damaging effects on metallic structures. Current corrosion prevention and management programs often fail to include environmental factors such as Cl− ions and surface wetness. Early detection of these environmental factors can prevent the onset of corrosion and reduce repair and maintenance-related expenses. There is growing interest in creating solution-processed thin film environmental sensors with high sensitivity to corrosion precursors, low-cost fabrication, and small footprint, rendering them viable candidates for investigation as potential corrosion sensors that could be easily integrated into existing structures and screen printed or patterned directly into surface coatings. In this work, we have implemented C60-based n-type organic thin film transistors (OTFTs) with functionalized graphene oxide for humidity sensing and functionalized graphene nanoparticles for Cl− ion detection, using low-cost solution processing techniques. The reduced graphene oxide (rGO)-coated OTFT humidity sensor is designed for the qualitative estimation of surface moisture levels and high levels of humidity, and it exhibits a relative responsivity for dry to surface wetness transition of 122.6% to surface wetness, within a response time of 20 ms. We furthermore implemented an in-house synthesized hydrogenated graphene coating in conjunction with a second OTFT architecture for Cl− ions sensing which yielded a sensitivity of 4%/ppm to ultrafine ionic concentrations, over an order of magnitude lower than the range identified to cause corrosion in aircraft structures.

Ab-initio simulation of hydrogenated graphene properties

Ab-initio simulation of hydrogenated graphene properties was performed. At present, graphene is considered one of the most promising materials for the formation of new semiconductor devices with good characteristics. Graphene has been the subject of many recent investigations due to its peculiar transport, mechanical and others properties [1]. The chemical modification of graphene named as graphane has recently entered the investigation as a possible candidate to solve problems connected with the lack of a graphene bandgap. Graphane is a compound material consisting of two-dimensional graphene bonded by some atoms of hydrogen. The investigation shows that graphane has the three valley Г-М-K band structure with the Г valley, which has the smallest energy gap between the conductivity zone and the valence zone. The calculation of relative electron masses and non-parabolic coefficients in Г, М and K valleys was performed. Based on the obtained characteristics, it is possible to implement a statistical multi-particle Monte Carlo method to determine the characteristics of electron transfer in heterostructure semiconductor devices. A research on modified graphene structures is important for fundamental science and technological applications in high-speed transistor structures operating in the microwave and very high frequency ranges.

Reversible hydrogenation restores defected graphene to graphene

Graphene as a two-dimensional material is prone to hydrocarbon contaminations, which can significantly alter its intrinsic electrical properties. Herein, we implement a facile hydrogenation-dehydrogenation strategy to remove hydrocarbon contaminations and preserve the excellent transport properties of monolayer graphene. Using electron microscopy we quantitatively characterized the improved cleanness of hydrogenated graphene compared to untreated samples. In situ spectroscopic investigations revealed that the hydrogenation treatment promoted the adsorption ofytyt water at the graphene surface, resulting in a protective layer against the re-deposition of hydrocarbon molecules. Additionally, the further dehydrogenation of hydrogenated graphene rendered a more pristine-like basal plane with improved carrier mobility compared to untreated pristine graphene. Our findings provide a practical post-growth cleaning protocol for graphene with maintained surface cleanness and lattice integrity to systematically carry a range of surface chemistry in the form of a well-performing and reproducible transistor.

MOCVD growth of gallium and indium microparticles for SERS applications

The MOCVD growth of Ga and In microparticles was performed on graphene/SiC substrates. The test of effectiveness of the microparticles grown for SERS was based on the observation of H–Si vibrations on hydrogenated graphene grown on SiC. It was shown by scanning electron microscopy that the Ga or In microparticles grown were in the form of hemispheres with a flat side attached to the substrate. Raman measurements have shown that the effective H–Si SERS signal arises at the edges of the hemisphere microparticles. In addition, it was found that Ga or In microparticles are covered by GaAs or InAs shells, respectively. The presence of GaAs and InAs coverage of metallic microparticles arises from the As contamination of the MOCVD system used for III–V compound growth. However, these coverages do not significantly affect the surface plasmons resonance in the metallic microparticles.