Addressable gated field emitter arrays (FEAs) have important applications in vacuum microelectronic devices. To fabricate high-performance device, a comprehensive understanding on the field emission characteristics of gated FEAs is necessary, which requires a quantitative analysis method. In this work, a general model based on Fowler-Nordheim (FN) theory has been established to fulfill this blank. It is found that nonlinear FN plot with positive and negative slopes could occur in gated FEAs, which its turning point is related to the proportion of anode and gate field. This provides a way for obtaining the field strengths applied by the anode and gate structures. Besides, the transconductance of the gated FEAs increases exponentially with the total surface field, which indicates that both the anode and gate field need to be increased for achieving a high transconductance device. As a demonstration, the addressable gated ZnO nanowire FEAs using multimicrosize pattern with radius as small as $2.5 ~\mu \text{m}$ have been designed and fabricated. The relationship between the transconductance and anode voltage can be well fitted by using the model, which deduces the proportion of anode and gate field in the device to be about 3:1.

Uniform large-area flat-panel X-ray sources have potential applications in projection imaging. Achieving such a source has remained a challenge. A diagonal 4-in cold cathode flat-panel X-ray source device has been fabricated using ZnO nanowire field emitter arrays. A large-area uniform X-ray emission was produced, and projection imaging with a resolution of more than 5.0 lp/mm was realized. Its projection imaging resolution and its dependence on geometric imaging parameter settings were studied along with the imaging performance of the device. Simulations using the fast ray-tracing algorithm were performed, yielding results consistent with those from experiments. Optimal parameter settings for high-resolution projection imaging using the flat-panel X-ray source are presented. This study has significance in the application of this cold cathode flat-panel X-ray source in X-ray imaging.

Full static x-ray computed tomography (CT) technology has enabled higher precision and resolution imaging and has been applied in many applications such as diagnostic medical imaging, industrial inspection and security screening. In this technique, the x-ray source section is mainly composed of a thermionic cathode and electron beam scanning system. However, they have several shortcomings such as limited scanning angle, long response time and large volume. Distributed and programmable cold cathode (i.e. carbon nanotubes, ZnO nanowires (NWs)) field-emission x-ray sources are expected to solve these problems. However, there have been several long-standing challenges to the application of such cold field emitters for x-ray sources, such as the short lifetime and rigorous fabrication process, which have fundamentally prevented their widespread use. Here, we propose and demonstrate a cold field-emission x-ray source based on a graphene oxide (GO)-coated cuprous sulfide nanowire (Cu2S NW/GO) cathode. The proposed Cu2S NW/GO x-ray source provides stable emission (>18 h at a direct voltage of 2600 V) and has a low threshold (4.5 MV m-1 for obtaining a current density of 1 μA cm-2), benefiting from the demonstrated key features such as in situ epitaxy growth of Cu2S NWs on Cu, nanometer-scale sharp protrusions within GO and charge transfer between the Cu2S NWs and GO layer. Our research provides a simple and robust method to obtain a high-performance cold field emitter, leading to great potential for the next generation of x-ray source and CT.

Addressable nanowire field-emitter arrays (FEAs) show potential for application in vacuum microelectronic devices, and a focusing structure is essential for modulation of the electron beam in FEAs. However, because of the complicated device structure induced by the focusing structure, nanowire integration in such a device is very difficult. To address this issue, a coaxis-gated ZnO nanowire FEA structure with an in-plane focusing gate electrode is proposed. The focusing gate electrode is located in the same plane as the cathode and control gate, and the addressing function is realized using a via structure. The coaxis-gated ZnO nanowire FEAs were fabricated using a four-mask microfabrication process, thus requiring one mask less than traditional focused FEAs. The characteristics of the fabricated ZnO nanowire FEAs were studied, and their addressing and focusing abilities were verified.

Large-area ZnO nanowire field emitter arrays have important applications in flat-panel displays, light sources, photodetectors and X-ray sources, where it is crucial to realize a high field emission current and current density over a large-area. In this paper, large-area ZnO nanowire arrays with various array spacings were prepared by the thermal oxidation technique from patterned Zn film arrays, and their field emission properties were studied. The results show that the Zn array density is related to the nanowire length and population density. A mechanism is proposed wherein the stress-induced process and mass transport process both play key roles in the growth. Herein, ZnO nanowire arrays in a 4.7 x 4.7 cm(2) area exhibited a sufficient quantity of emission sites and diminished field screening effect and a high current of 12.9 mA with a current density of 0.58 mA/cm(2). This work provides useful guidance for optimizing ZnO nanowires and enhancing field emission current performance for large-area ZnO nanowire field emission devices.

Flat panel X-ray source enables the possibility of adaptive X-ray imaging which could achieve close range imaging. In this study, a flat panel X-ray source module based on ZnO nanowire field emitter arrays was fabricated. High resolution projection imaging using the module was achieved, which demonstrated the feasibility of adaptive X-ray imaging using nanowire FEA flat panel X-ray source.

Addressable ZnO nanowire field emitter arrays have potential application in vacuum microelectronic devices. In this study, an under-gate structure ZnO nanowire field emitter arrays were designed and successfully fabricated using microfabrication process. High density patterned ZnO nanowires were used in each pixel to minimized the screen effect and increase the emission current. Modulation of field emission current by the gate voltage was achieved.

In this study, a gated ZnO nanowire field emitter arrays (FEAs) was fabricated for the application of pulsed flat panel X-ray source. The ZnO nanowires were grown using thermal oxidation method and the growth ZnO nanowires in the device structure was optimized by adjusting the oxidation atmosphere. The pulsed response of the FEAs was studied and corresponding X-ray emission was detected.

Polycrystalline gallium oxide thin film was prepared using electron-beam evaporation and a post-annealing treatment. Cathodoluminescent measurement show the gallium oxide thin film has emission peaks ranging from 300 to 650 nm. Using gallium oxide thin film anode, a flat panel UV light source was fabricated by using ZnO nanowires field emitter arrays.

Micron-size-patterned ZnO nanowire field emitters were fabricated by thermal oxidation method. The morphology and population density of the ZnO nanowires grown on the patterns were optimized by adjusting the ambient atmospheric fluidity around patterns during thermal oxidation process. Field emission characteristics of prepared micron-size-patterned ZnO nanowire arrays were measured. The results show large area current ZnO nanowire field emitters with high and stable current could be achieved by using the method reported in this study.