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[IEEE 2019 24th Microoptics Conference (MOC) - Toyama, Japan (2019.11.17-2019.11.20)] 2019 24th Microoptics Conference (MOC) - Study of Plasmonic Nanolasers with Graphenea??Metal Interaction
摘要： We report the design, fabrication, and proof-of-concept characterization of an X-ray generator for improved X-ray absorption imaging that uses a nanostructured field emission cathode as the electron source and a microstructured transmission anode as the X-ray generating structure. Field emission cathodes consume less power, respond faster, and tolerate lower vacuum than the thermionic cathodes used in conventional X-ray generators. The use of a transmission anode, instead of a conventional reflection anode, allows filtering of the background radiation (bremsstrahlung) while allowing efficient generation of X-ray at lower voltages by exciting atomic shell transitions, resulting in emission of X-ray with narrow spectral linewidth for sharper imaging of biological tissue. The fabricated field emission cathode contains arrays of self-aligned and gated silicon field emitters. The field emission cathodes turn on at bias voltages as low as 25 V, and their gates transmit almost 100% of the electrons to the anode. The cathodes produce per-emitter electron currents in excess of 2 μA (current density >2 A/cm2) at a bias voltage of 80 V. A desktop rig is built to generate X-ray with a field emission cathode and transmission anode. Using the facility, we obtained X-ray absorption images of several objects. The images clearly show details under 500 μm in size, as well as soft tissue and fine bone structures without using contrast agents.
关键词： medical imaging,Field emission,X-ray generation
更新于2025-09-19 17:13:59
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Field emission enhancement of composite structure of ZnO quantum dots and CuO nanowires by Al2O3 transition layer optimization
摘要： In this paper, ZnO quantum dots (QDs)-CuO nanowires (NWs) heterostructure was synthesized by a mild solution method. The Al2O3 transition layer were deposited on CuO NWs by surface modification engineering using atomic layer deposition (ALD) to increase the nucleation probability of ZnO QDs. The field emission properties of the composites were investigated. The results reveal that the CuO@Al2O3/ZnO QDs ternary heterostructures have the turn-on field of 2.82 V/μm and the field emission enhancement factor of 5798, which are superior to that of ZnO QDs-CuO NWs and pure CuO NWs. The improvement of field emission performance is mainly attributed to the decrease of the electron transport barrier at the interface and the increase of the oxygen vacancies, making it easier to transport electrons to ZnO QDs. The use of amorphous Al2O3 in the transition layer also effectively alleviates the lattice mismatch between ZnO QDs and the substrate. This study provides an effective method for enhancing the field emission performance of the core-shell nanomaterial device.
关键词： transition layer,field emission,composite structure,ZnO quantum dots
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Performance and Degradation Evaluation of PV Modules on the Substring Level by an In-Situ Electronic Device
摘要： We report silicon ?eld emitter arrays (FEAs) that demonstrate current densities >100 A/cm2 at gate–emitter voltages <75 V. These are the highest current densities reported for a semiconductor FEA, and approach the current densities of Spindt-type metal cathodes. We achieved these results using a new device structure that employs high-aspect-ratio silicon nanowire current limiters in series with each emitter tip to address the major failure mechanisms in FEAs. These current limiters mitigate emitter tip failure due to joule heating thus allowing for higher reliability. We employed a novel fabrication process to produce small gate apertures (≈350 nm) that are self-aligned to the ?eld emitter tip enabling device operation at >100 A/cm2 with gate-to-emitter voltages that are less than 75 V. These FEAs demonstrate performance that has the potential to enable smaller, more ef?cient, and high-power vacuum electronics.
关键词： FEAs,nanowires,Field emission arrays,silicon FEAs,silicon tips,silicon nanowire current limiters
更新于2025-09-19 17:13:59
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Cobalt ferrite decorated multiwalled carbon nanotubes as the electrode for efficient field electron emission
摘要： In the present study, Cobalt Ferrite (CF) nanoparticles with different weight concentrations were successfully decorated on Multi-Walled Carbon nanotubes (MWCNT) using a simple glycol assisted chemical route. The physicochemical and electronic properties of CF decorated MWCNTs (MWCNT-CF) were accomplished with the help of different techniques such as X-ray Diffraction (XRD), Raman Spectroscopy, Transmission Electron Microscopy (TEM), X-ray Photo-electron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR). Further, the effect of CF concentration on Field Emission (FE) characteristics of MWCNT-CF is investigated. The FE studies revealed that, CF decorated MWCNT emitter (MWCNT-CF; 1:1) exhibits lower turn on (0.52 V/μm, at 10 μA/cm2) and threshold fields (0.62 V/μm, at 100 μA/cm2) in contrast to pristine CF, MWCNT, and MWCNT-CF (1:0.5 and 1:2). Interestingly, from the MWCNT-CF (1:1) emitter, very high emission current density ~ 10408 μA/cm2 has been extracted at a relatively lower applied field of 1.18 V/μm. The enhancement in FE characteristics of MWCNT-CF emitters is attributed to lowering of work function measured from the UPS analysis and increased number of emitting sites. The results imply that very high current density field emitters can be fabricated using a simple strategy based on the decoration of MWCNT’s with CF nanoparticles.
关键词： Reflux,Cobalt Ferrite,Multiwalled Carbon Nanotubes,Field Emission,Nanoparticles
更新于2025-09-19 17:13:59
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Field emission enhancement of PbS colloidal quantum dot-decorated single-walled carbon nanotubes
摘要： Herein, a simple and effective PbS colloidal quantum dot (CQD) decoration method for single-walled carbon nanotube (SWNT) is demonstrated. By dipping the SWNT film into a CQD dispersion followed by a solid-state ligand exchange, CQDs were successfully decorated onto the wall of SWNT without compromising a narrow size distribution. Spectroscopic studies suggested that (1) the CQD decoration and subsequent ligand exchange process did not alter the chemical nature of the SWNT framework and (2) there was a charge (electron) transfer process from the PbS CQD to the SWNT. Field emission (FE) characteristics of the CQD-decorated SWNT films revealed that FE enhancement was indeed established from SWNTs with a moderate degree of CQD decoration, while those with excessive decoration (coating) exhibited notable FE suppression. Horizontal current-voltage measurements with perpendicular-directional external electric field modulation suggested that electron supplement of SWNT from PbS CQD was pronounced as the amount of decorated CQDs increased. Based on the experimental results, we proposed a new mechanism demonstrating FE enhancement of a CQD/SWNT heterostructure.
关键词： Charge transfer,Field emission,Single-walled carbon nanotubes,Quantum dots,Ligand-exchange
更新于2025-09-16 10:30:52
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Effect of Affinity Discontinuity on Heterojunction p-i-n Solar Cell Performance
摘要： We report the design, fabrication, and proof-of-concept characterization of an X-ray generator for improved X-ray absorption imaging that uses a nanostructured field emission cathode as the electron source and a microstructured transmission anode as the X-ray generating structure. Field emission cathodes consume less power, respond faster, and tolerate lower vacuum than the thermionic cathodes used in conventional X-ray generators. The use of a transmission anode, instead of a conventional reflection anode, allows filtering of the background radiation (bremsstrahlung) while allowing efficient generation of X-ray at lower voltages by exciting atomic shell transitions, resulting in emission of X-ray with narrow spectral linewidth for sharper imaging of biological tissue. The fabricated field emission cathode contains arrays of self-aligned and gated silicon field emitters. The field emission cathodes turn on at bias voltages as low as 25 V, and their gates transmit almost 100% of the electrons to the anode. The cathodes produce per-emitter electron currents in excess of 2 μA (current density >2 A/cm2) at a bias voltage of 80 V. A desktop rig is built to generate X-ray with a field emission cathode and transmission anode. Using the facility, we obtained X-ray absorption images of several objects. The images clearly show details under 500 μm in size, as well as soft tissue and fine bone structures without using contrast agents.
关键词： medical imaging,Field emission,X-ray generation
更新于2025-09-16 10:30:52
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Synthesis of Lithography Free Micro-Nano Electron Field Emitters Using Pulsed KrF Laser Assisted Metal Induced Crystallization of Thin Silicon Films
摘要： Hydrogenated amorphous thin silicon films (a-Si:H) deposited on metal coated glass substrates were investigated to analyze the effect of a novel processing technique called Laser Assisted Metal Induced Crystallization (LAMIC) on their electron field emission (FE) properties. Post-surface characterization of the processed films showed increased surface roughness and the presence of uniformly spaced “island-like” micro-nano structures on the surface of metal coated backplane samples. Best FE results were obtained from samples sputtered with a thin layer of Aluminum (Al) on top and cross laser annealed at 190 mJ/cm2 (y-axis) and 100 mJ/cm2 (x-axis). FE measurements indicate a low turn-on electric field of less than 16 V/mm with emission currents in the order of 10?6 A. FE results were found to be particularly dependent on the laser fluence and the surface morphology exhibited very high discharge resistance. Oxidation of the films was observed to deteriorate their FE characteristics, thereby increasing the emission threshold to 36 V/mm. Diode configured field emission display prototypes are fabricated to exemplify their potential as cold cathode emitters.
关键词： excimer laser crystallization,electron field emission,metal induced crystallization,micro-nano emitters,Hydrogenated amorphous silicon
更新于2025-09-16 10:30:52
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Field emission property of vertically aligned nitrogen-doped multi-walled carbon nanotubes produced by chemical vapor deposition
摘要： Vertically aligned nitrogen-doped multi-walled carbon nanotubes (N-MWNTs) were synthesized by the chemical vapor deposition (CVD) at 900 °C using imidazole mixed with ferrocene as carbon and nitrogen sources, and catalyst, respectively. The effects of ammonia (NH3) and hydrogen (H2) flow rates on the growth of N-MWNTs were investigated (hereafter referred to A-N-MWNTs and H-N-MWNTs, respectively). Transmission electron microscopy (TEM) revealed the bamboo-like structure of the N-MWNTs, in which the separation between individual bamboo compartments decreased with increasing nitrogen concentration in N-MWNTs. X-ray photoelectron spectroscopy (XPS) analysis results supported that the nitrogen concentrations in N-MWNTs is 0.55 at.%, whereas A-N-MWNTs and H-N-MWNTs with the flow rate at 10 standard cubic centimeters per minute (sccm) (10A-N-MWNTs and 10H-N-MWNTs, respectively) showed 1.14 and 4.06 at.%, respectively. We found that the optimal conditions for the highest nitrogen-doped multi-walled carbon nanotubes (MWNTs) was a flow rate of NH3 and H2 at 10 sccm. Results from field emission measurements indicated that the turn-on fields of N-MWNTs, 10A-N-MWNTs and 10H-N-MWNTs were 6.7, 4.3 and 3.1 V/μm, respectively, while the field enhancement factors (β) were 5230, 10,805 and 20,390, respectively. Furthermore, the current density of N-MNWTs increased with increasing the nitrogen atoms in MWNTs. The results support that field emission based on N-MWNTs is a good emitter with low turn-on field and large field enhancement factor. Nitrogen doping in MWNTs makes them attractive candidates as high-performance field emitters.
关键词： Field emission,Nitrogen-doped multi-walled carbon nanotubes,Chemical vapor deposition
更新于2025-09-12 10:27:22
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Field emission characteristics of CNT film emitters according to emission tip shapes
摘要： We fabricated carbon nanotube (CNT) field emitters using a CNT film, which indicated the point-type CNT film emitter, and evaluate field emission properties of the CNT field emitter in the triode configuration. The CNT film emitters showed good emission properties such as the low turn-on field, the high emission current and emission stability. We also investigated field emission properties of the CNT film emitter by adjusting the angle of tip of the CNT film.
关键词： field emission,triode structure,point-type field emitter,Carbon nanotubes field emitter
更新于2025-09-10 09:29:36
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Graphene paper as an emitter for low-power X-ray sources
摘要： Carbon materials are known to be one of the most suitable platforms for the development of cold electron emitters. Here we explore field emission (FE) performance of so-called graphene paper that is a micrometer-thick foil obtained by stacking chemically exfoliated graphene layers. We find, that shaped into triangular form, graphene paper exhibits competitive FE characteristics, such as high-current density stable in time, and low threshold fields. In addition, we study the degradation of such graphene-based emitters under high emissions currents and discuss possible application for a transmission-type X-ray source.
关键词： field emission,graphite emitter,x-ray source
更新于2025-09-10 09:29:36