Abstract:Graphene has been intensively studied for applications to high-performance sensors, but the sensing characteristics of graphene devices have varied from case to case, and the sensing mechanism has not been satisfactorily determined thus far. In this review, we describe recent progress in engineering of the defects in graphene grown by a silica-assisted chemical vapor deposition technique and elucidate the effect of the defects upon the electrical response of graphene sensors. This review provides guidelines fo… Show more
“…It has been thought that the donor level, such as the O vacancy, is too deep to be ionized and generate free electrons at room temperature, although the ionization energy of the defect is largely suppressed for O vacancies at the surface [44]. Because the BSO film has an expanded lattice volume and an electron-doped electronic structure, it is very likely that the high concentration of O vacancies induces the peak within the band gap and the resulting donated free electrons play an important role in the applications that use BSO, such as a chemical sensor [45] and buffer layer [46]. Therefore, to study the energy of the in-gap state, the nature of the intrinsic defects in the newaly emerging TCO candidate BSO must be understood.…”
Transparent BaSnO 3 thin films have been proposed as an alternative transparent conducting oxide (TCO). Although bulk synthesis and high-quality fabrication of epitaxial films are well established, there are still unsolved aspects about their electronic structure, such as the direct or indirect nature and the size of the band gap. We investigated the electronic structure of epitaxial BaSnO 3 thin films using in situ angle-resolved photoemission spectroscopy. We directly measured an indirect band gap of 3.7 eV, a value compatible with those of previous reports, but we also identified additional in-gap states at −1.6 eV below the conduction band minimum that we attribute to intrinsic defects, mainly oxygen vacancies.
“…It has been thought that the donor level, such as the O vacancy, is too deep to be ionized and generate free electrons at room temperature, although the ionization energy of the defect is largely suppressed for O vacancies at the surface [44]. Because the BSO film has an expanded lattice volume and an electron-doped electronic structure, it is very likely that the high concentration of O vacancies induces the peak within the band gap and the resulting donated free electrons play an important role in the applications that use BSO, such as a chemical sensor [45] and buffer layer [46]. Therefore, to study the energy of the in-gap state, the nature of the intrinsic defects in the newaly emerging TCO candidate BSO must be understood.…”
Transparent BaSnO 3 thin films have been proposed as an alternative transparent conducting oxide (TCO). Although bulk synthesis and high-quality fabrication of epitaxial films are well established, there are still unsolved aspects about their electronic structure, such as the direct or indirect nature and the size of the band gap. We investigated the electronic structure of epitaxial BaSnO 3 thin films using in situ angle-resolved photoemission spectroscopy. We directly measured an indirect band gap of 3.7 eV, a value compatible with those of previous reports, but we also identified additional in-gap states at −1.6 eV below the conduction band minimum that we attribute to intrinsic defects, mainly oxygen vacancies.
“…Recently, various textile-based hybrid nanomaterials have been extensively investigated for applications as next-generation wearable and flexible electronics that include solar cells, − field effect transistors (FETs), − nanogenerators, − and various sensors − due to their flexible and human-friendly characteristics. Among these textile-based electronics, strain and pressure sensors in particular have attracted attention because they can be practically used to measure the physical and physiological activities of humans.…”
Wearable strain-pressure sensors for detecting electrical signals generated by human activities are being widely investigated because of their diverse potential applications, from observing human motion to health monitoring. In this study, we fabricated reduced graphene oxide (rGO)/single-wall carbon nanotube (SWCNT) hybrid fabric-based strain-pressure sensors using a simple solution process. The structural and chemical properties of the rGO/SWCNT fabrics were characterized using scanning electron microscopy (SEM), Raman, and X-ray photoelectron spectroscopy (XPS). Complex networks containing rGO and SWCNTs were homogeneously formed on the cotton fabric. The sensing performance of the devices was evaluated by measuring the effects of bending strain and pressure. When the CNT content was increased, the change in relative resistance decreased, while durability was significantly improved. The rGO/SWCNT (0.04 wt %) fabric sensor showed particularly high mechanical stability and flexibility during 100 000 bending tests at the extremely small bending radius of 3.5 mm (11.6% bending strain). Moreover, the rGO/SWCNT fabric device exhibited excellent water resistant properties after 10 washing tests due to its hydrophobic nature. Finally, we demonstrated a fabric-sensor-based motion glove and confirmed its practical applicability.
“…Owing to a larger area duty ratio at the same area of the conductive channel, the conductivities of the c-GNM-based devices were found to be higher than those of the r-GNM-based devices. Compared to GNRs [ 38 ] or other GNMs [ 39 ] that were reported before, our c-GNM and r-GNM samples can deliver a higher current owing to their large area and uniform size. Fig.…”
In recent years, graphene nanomesh (GNM), a material with high flexibility and tunable electronic properties, has attracted considerable attention from researchers due to its wide applications in the fields of nanoscience and nanotechnology. Herein, we have processed large-area, uniform arrays of rectangular graphene nanomesh (r-GNM) and circular graphene nanomesh (c-GNM) with different neck widths by electron beam lithography (EBL). The electronic properties of those high-quality GNM samples have been characterized systematically. Electrical measurements illustrated that top-gated field effect transistors with different neck widths of the GNM possessed different Ion/Ioff ratios. In particular, the devices based on r-GNM with a neck width of 30 nm were found to possess the largest Ion/Ioff ratio of ~ 100, and the band gap of the r-GNM was estimated to be 0.23 eV, which, to the best of authors’ knowledge, is the highest value for graphene ribbons or a GNM with a neck width under 30 nm. Furthermore, the terahertz response of large-area r-GNM devices based on the photoconductive effect was estimated to be 10 mA/W at room temperature. We also explored the practical application of terahertz imaging, showing that the devices can be used in a feasible setting with a response time < 20 ms; this enables accurate and fast imaging of macroscopic samples.
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