An in situ characterization technique for electron emission behavior under a photo-electric-common-excitation field: study on the vertical few-layer graphene individuals

Abstract

The in situ characterization on the individuals offers an effective way to explore the dynamic behaviors and underlying physics of materials at the nanoscale, and this is of benefit for actual applications. In the field of vacuum micro-nano electronics, the existing in situ techniques can obtain the material information such as structure, morphology and composition in the process of electron emission driven by a single source of excitation. However, the relevant process and mechanism become more complicated when two or more excitation sources are commonly acted on the emitters. In this paper, we present an in situ nano characterization technique to trigger and record the electron emission behavior under the photo-electric-common-excitation multiple physical fields. Specifically, we probed into the in situ electron emission from an individual vertical few-layer graphene (vFLG) emitter under a laser-plus-electrostatic driving field. Electrons were driven out from the vFLG’s emission edge, operated in situ under an external electrostatic field coupled with a 785 nm continuous-wave laser-triggered optical field. The incident light has been demonstrated to significantly improve the electron emission properties of graphene, which were recorded as an obvious decrease of the turn-on voltage, a higher emission current by factor of 35, as well as a photo-response on-off ratio as high as 5. More importantly, during their actual electron emission process, a series of in situ characterizations such as SEM observation and Raman spectra were used to study the structure, composition and even real-time Raman frequency changes of the emitters. These information can further reveal the key factors for the electron emission properties, such as field enhancement, work function and real-time surface temperature. Thereafter, the emission mechanism of vFLG in this study has been semi-quantitatively demonstrated to be the two concurrent processes of photon-assisted thermal enhanced field emission and photo field emission.

A tunable photo-electric co-excited point electron source: low-intensity excitation emission and structure-modulated spectrum-selection

“…Second, electrons pumped into the vacuum may be confined to a nano or even atomic scale by the nano-cold-cathode materials employed. Third, the electron emission yield and quantum efficiency are believed to be significantly improved, with the assistance of applied electrostatic field 30,31 and plasmon-enhanced nearfield 32,33 that may exist, and simultaneously the driving power consumption for the cathode and device are greatly reduced. These advantages are particularly important for point electron sources, where the performance demand of electron beam from an individual emitter is extremely high, such as low energy spread, high brightness and low energy consumption.…”

“…), 19,37,38 and carbon-based materials (carbon nanotubes, graphene, diamond, etc.). 15,20,31 Among them, tungsten (W) shows advantages of high electric and thermal conductivities, excellent high-temperature stability, as well as large-current and high-current-density output properties. W needle is one of the most traditional and widely used cathode materials.…”

“…W needle cathode has been demonstrated to show an emission current of pA to nA driven by a femtosecond laser pulse. 31,39,40 In addition, W needle cathode has been demonstrated to exhibit tunable electron emission behavior and spatial distribution by the interactions among light excitation, biased voltage, and emitter geometry. 41 However, most results obtained so far were based on a high-intensity and large-size femtosecond laser.…”

Self-Assembly Vertical Graphene-Based MoO3 Nanosheets for High Performance Supercapacitors

“…Graphene stands out among carbon-based electrode materials due to its good electrical conductivity and large specific surface area formed by folds [19][20][21][22]. For such a Nanomaterials 2022, 12, 2057 2 of 13 two-dimensional nanostructure, the semi-metallic property is favorable to unimpeded electron transport and rapid electrochemical reaction kinetics, and the unique layered architecture provides adequate transmission paths for ions and electrons.…”