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Offset Corbino thin film transistor is a good candidate for high voltage thin film transistor (HVTFT) due to the uniform drain electric field distribution benefiting from the circular structure. The physical model of offset Corbino thin film transistor characteristics has yet to be clarified. In this study, Equations are derived to describe the current–voltage relations of Corbino TFT with offset at the drain or source sides. The influence of offset position and parameters on the saturation voltage and the saturation current was described quantitatively. Three-dimensional Computer-Aided Design simulation and experiment results verify the theoretical physical model. Our physical model provides design rules for high voltage offset Corbino TFT when considering the voltage tolerance and saturation current balance. [ABSTRACT FROM AUTHOR]

Field electron emission vacuum photodiode is promising for converting free-space electromagnetic radiation into electronic signal within an ultrafast timescale due to the ballistic electron transport in its vacuum channel. However, the low photoelectric conversion efficiency still hinders the popularity of vacuum photodiode. Here, we report an on-chip integrated vacuum nano-photodiode constructed from a Si-tip anode and a single-crystal CsPbBr3 cathode with a nano-separation of ~30 nm. Benefiting from the nanoscale vacuum channel and the high surface work function of the CsPbBr3 (4.55 eV), the vacuum nano-photodiode exhibits a low driving voltage of 15 V with an ultra-low dark current (50 pA). The vacuum nano-photodiode demonstrates a high photo responsivity (1.75 AW−1@15 V) under the illumination of a 532-nm laser light. The estimated external quantum efficiency is up to 400%. The electrostatic field simulation indicates that the CsPbBr3 cathode can be totally depleted at an optimal thickness. The large built-in electric field in the depletion region facilitates the dissociation of photoexcited electron–hole pairs, leading to an enhanced photoelectric conversion efficiency. Moreover, the voltage drop in the vacuum channel increases due to the photoconductive effect, which is beneficial to the narrowing of the vacuum barrier for more efficient electron tunneling. This device shows great promise for the development of highly sensitive perovskite-based vacuum opto-electronics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Gated Si-tip with on-tip integrated gate-all-around field effect transistor using hyperbolic nano-channel (Hy-GAAFET) for actively controlled field electron emission is presented. Fully IC compatible nano-fabrication procedures were developed to obtain the Hy-GAAFET and the on-tip integration with the Si-tip emitter. The Hy-GAAFET exhibit characteristics of ${I}_{\textit {on}}/{I}_{\textit {off}} =\sim 10$ 4, ${I}_{\textit {sat}} = 0.25 ~\mu \text{A}/\mu \text{m}$ at ${V}_{\textit {gaa}}=-0.4$ V and 20 mV of drain-induced barrier lowering. The emission current of the gated Si-tip can be actively regulated by the Hy-GAAFET gate voltage, i.e., 0.4 pA/mV with an extractor voltage of 53 V and showed a well-optimized current stability. This on-chip integrated device is promising for applications in modern miniature vacuum nano electronics. [ABSTRACT FROM AUTHOR]

Advanced field‐effect transistors (FETs) with nontrivial gates (e.g., offset‐gates, mid‐gates, split‐gates, or multi‐gates) or hybrid integrations (e.g., with diodes, photodetectors, or field‐emitters) have been extensively developed in pursuit for the "More‐than‐Moore" demand. But understanding their conduction mechanisms and predicting current–voltage relations is rather difficult due to countless combinations of materials and device factors. Here, it is shown that they could be understood within the same physical picture, i.e., charge transport from gated to nongated semiconductors. One proposes an indicator based on material and device factors for characterizing the transport and derives a unified and simplified solution for describing the current–voltage relations, current saturation, channel potentials, and drift field. It is verified by simulations and experiments of different types of devices with varied materials and device factors, employing organic, oxide, nanomaterial semiconductors in transistors or hybrid integrations. The concise and unified solution provides general rules for quick understanding and designing of these complex, innovative devices. [ABSTRACT FROM AUTHOR]

High-voltage thin-film transistors (HV-TFTs) with designed field-plates are experimentally demonstrated to work in a wide range of kilo-voltage (kV) and with the tunable breakdown voltages (${V}_{{\mathrm {BD}}}$). The field plates have been placed in different positions and biased at different voltages to investigate how to effectively enhance ${V}_{{\mathrm {BD}}}$. The largest ${V}_{{\mathrm {BD}}}$ is up to 263 % of the case without field plate and reaches 1902.5 V. By monitoring the electric potential at the end of the gated channel (${V}_{1}$), it is revealed that the enhanced ${V}_{{\mathrm {BD}}}$ is associated with a reduced ${V}_{1}$. Therefore, the device breakdown is in fact caused by the breakdown of dielectric near the end of the gated channel in HV-TFTs rather than the destruction of semiconductor near the drain in regular TFTs. This study unveils the breakdown mechanisms of HV-TFTs and provides an effective design route for balancing the breakdown voltages and on-current of the HV-TFTs. [ABSTRACT FROM AUTHOR]

Addressable flat-panel x-ray source has important applications in next-generation low-dose x-ray imaging technology. In this study, a fully vacuum-sealed addressable flat-panel x-ray source has been fabricated using a ZnO nanowire cold cathode. The x-ray source was formed by assembling gated ZnO nanowire field emitters and a molybdenum thin film transmission anode target. Pulsed and addressable x-ray emission was achieved by applying voltages to the extraction gate. Radiation dose rates of 235 nGy/s were achieved when the device was operated at 21 kV anode voltage and 140 V gate voltage. Projection x-ray images of objects were obtained by the flat-panel x-ray source. Our results demonstrated the feasibility of a fully addressable cold cathode flat-panel x-ray source. [ABSTRACT FROM AUTHOR]

Vacuum flat-panel detectors (VFPDs) using a cold cathode and photoconductor have important applications in large-area photodetectors; however, the mechanism for achieving high photoresponsivity must be further explored. In this article, theoretical analysis was performed to examine the electron-bombardment-induced photoconductivity (EBIPC) effect based on the equivalent circuit model. Formulas for photo/dark current were derived, which indicated that carrier multiplication was mainly due to energetic electron bombardment. The theoretical formulas also revealed the carrier multiplication mode inside the photoconductor of VFPDs and the relationship between the responsivity and device parameters. To verify the theoretical results, VFPDs with a ZnS photoconductor and ZnO nanowire cold cathode were studied. The responsivity initially increased and then decreased by increasing the photoconductor thickness. In addition, a broad dynamic range was achieved with a linear dynamic range of 106.02 dB, which was attributed to the efficient collection of carriers induced by EBIPC at the optimized thickness. Our theoretical results were validated by the experimental results and can provide guidance for developing VFPDs based on EBPIC. [ABSTRACT FROM AUTHOR]

Using density functional theory, we investigate the vibrational properties and polarization-resolved Raman spectra of α-PtO2 and obtain the Raman tensor and angle-dependent Raman intensity of α-PtO2. It is found that the polar plot of A1g mode in parallel polarization configuration is useful in identifying the orientation of the crystal. The Raman intensity of the Eg mode is about five times stronger than that of the A1g mode. The Raman intensity is about three times stronger when the wave vector of the incident light is in x or y direction than in z direction. Our work will help the material scientists to characterize the α-PtO2 and to identify its orientation by comparing the experimental spectra with our result. [ABSTRACT FROM AUTHOR]

The thermal runaway of a quasi‐1D (Q1D) field emitter is an important cause of vacuum breakdown, which limits the field emission current density in field emitter arrays (FEAs). Comprehensive knowledge on the self‐heating process of zinc oxide (ZnO) nanowires is important for obtaining a high breakdown field for activating more emitters. This work investigates the self‐heating model of individual ZnO nanowire by considering the thermal field emission current distribution along the nanowire. Theoretical calculations suggest that the thermal field emission distribution along the nanowire can be reflected on the profile of the field emission pattern, which offers a method for determining its temperature. The field emission ring pattern is experimentally observed in the ZnO nanowire, whose intensity profile indicates that the nanowire can be steadily heated above 900 K. Considering the high breakdown field of high‐thermal stability ZnO nanowires, the field emission current density of ≈1.4 mA cm−2 can be achieved using these nanowires in a 3.5‐inch FEA. These findings provide an alternative method for measuring the Q1D field emitter temperature and a guideline for improving the field emission current from large‐scale Q1D FEAs. [ABSTRACT FROM AUTHOR]

Integrated field emission electron sources with low driving voltage are desired for micro/nano vacuum electronics. Herein, we demonstrate the enhanced and stable electron emission from crystalline gold–silver (Au–Ag) alloy nanoparticle capped Si nanowires (SiNWs) and the achieved gated electron sources with low driving voltage (<50 V). Thermally induced self-assembly hemispherical (50–80 nm) crystalline Au–Ag nanoparticles were prepared and used as masks in plasma etching to form vertically aligned high aspect ratio (~14) SiNWs. The nanoparticles were preserved after the etching, forming in situ integrated Au–Ag/Si junctions with each individual SiNWs. The SiNWs with capped nanoparticles possess superior field emission current density (45.80 mA/cm2) and current stability (fluctuation ~6%). A self-aligned process was developed to fabricate gated field emission devices, using the Au–Ag nanoparticle capped SiNWs as cathode. The gated devices showed field emission at low gate voltage (69.52-μA/cm2 at 42.1 V). Experimental and numerical simulation studies demonstrated the Au–Ag/Si contact behaved as space-charge-limited (SCL) Schottky conduction. The idea behind the enhancing and stable emission is that the SCL–Schottky junction undergoes a process of negative feedback and thus suppressed the current and shot-noise from the outstanding SiNWs. Accordingly, more SiNWs were activated and contributed stable and higher field emission current. [ABSTRACT FROM AUTHOR]

We investigate a polarized Raman characterization of Zr2X (X = C, N), excited by two commonly used laser lines with wavelenghts of 532 nm and 633 nm, based on first principle calculations. The Raman spectra of Zr2X has two Raman shift peaks which correspond to the degenerate in-plane vibration mode (Eg) and out-of-plane vibration mode (A1g). Furthermore, we study the polarization angle dependent Raman intensity for both Eg and A1g modes in parallel and perpendicular configurations for these two materials. We found that the polarization angle dependent Raman intensity is isotropic when the laser line is perpendicular to the Zr2X plane. There are either only two maxima, or two maxima larger than the other maxima, in the parallel configuration when the laser line is parallel to the Zr2X plane, which might be useful in identifying the orientation of Zr2X in experiment. The results show that the locations of the maxima of the polarization angle dependent Raman intensity rarely depend on the exciting laser line, except that of the Eg mode of Zr2N. [ABSTRACT FROM AUTHOR]

High-voltage thin-film transistors (HV-TFTs) based on amorphous InGaZnO (a-IGZO) are demonstrated to work in the range of kilo-voltage (kV). The devices feature a high breakdown voltage of over 1.1 kV, on-current of 10.8 $\mu \text{A}$ , and an on/off current ratio over 105. By integrating kV-TFTs with ZnO nanowires, actively controlled field emitters are obtained that exhibit extremely small current fluctuation in the emission current (2.4 % for 3600s). The operating mechanisms of the HV-TFTs are investigated by in-situ measurement of channel potentials and simple equations are derived to describe the current–voltage relations. This study demonstrates the feasibility of using a-IGZO in HV-TFTs that drive large-area field-emitter arrays and provide general understanding and design rules for HV-TFTs designed to drive nanowire field emitters. [ABSTRACT FROM AUTHOR]

We investigated the stability of reduced graphene oxide for oxygen density ranging from 6.25% to 50% with the density functional theory and found the most, the second most, and the third most stable oxygen configurations. The effect of relaxation of lattice on the electronic properties is found to be negligible for low O coverage and crucial for higher O coverage, respectively. The densities of states and the band gaps were calculated. The bandgap is found to be a non-monotonic function of oxygen density, with minima at O/C = 11.1% and 25%. [ABSTRACT FROM AUTHOR]

Silicon (Si) nanostructures may play an important role in future nanoelectronics. Here, arrays of single vertically aligned Si nano-needles (SiNNs) are fabricated and found to exhibit a significant piezoresistance effect under large non-uniaxial strain. The experiments were performed by in situ manipulating of the SiNNs in a scanning electron microscope. The method enables us to determine the piezoresistance effect under the combined action of compressive and tensile strains, which is different from reported works on the piezoresistance effect of Si nanostructures under uniaxial/biaxial strains. This has given rise to an opportunity to further explore the physical origins responsible for the piezoresistance of Si. The relative change in resistivity under the non-uniaxial strain was calculated from the experimental I-V data. The results show that a greater piezoresistance effect can be achieved as compared with that of Si nanowires under uniaxial strain. We propose that the suppression of inter-valley scattering and the change of electron concentration caused by the energy band shift are the main reasons for the large piezoresistance effect. [ABSTRACT FROM AUTHOR]

WO3 nanowire films were prepared by thermal evaporation. The electrochromic properties and relative near infrared absorption mechanism of the films in detail are investigated by electrochemistry, ultraviolet–visible–near infrared spectroscopy, x-ray diffraction spectroscopy, and some theoretical approaches. The studies indicate that WO3 nanowire films show excellent electrochromic properties, including a rapid response time (∼3 s) and a large contrast ratio between the bleached and the colored states. These improvements are due to the loose structure of the films and the small diameter of a single nanowire. It is also shown that a lithium tungsten bronze structure appears when the film is colored, causing two broad absorption bands centering around 920 and 1800 nm. A calculation including the Urbach effect, cation-polaron absorption and large polaron absorption was carried out to interpret the absorbance. A brief discussion of the discrepancy of the transmittance spectrum in the region λ>800 nm between the nanowire film and other traditional films is presented in the end. [ABSTRACT FROM AUTHOR]

The improving of tip-to-tip electron emission uniformity in an array is one of the essential issues for the vacuum microelectronic/nanoelectronic applications. Here, we report the achieving of quasi-saturated ultrahigh arsenic concentration ($\sim 6.7\times 10^{{21}}$ /cm3) at the Si nanotip apex, in the mechanisms of dopant segregation during the thermal oxidation and the limitation of arsenic solubility in Si. The tips with quasi-saturated high-level arsenic concentration possess a well tip-to-tip uniformity in surface work function. The measured work function for the tips in an array with saturated dopant concentration is in a narrow range of 4.347–4.371 eV (~2.1% fluctuation). This merit not only resulted in high emission current density (~418.36 mA/cm2) from the devices at a relatively lower gate voltage but also brought well spatially uniform electron emission in an array. The work inspired vital insight into the interpretation for mechanisms in dopant density control and the improving of emission uniformity of the Si-tip array. It could be used as an essential approach to acquire high-performance Si-based vacuum electronic devices. [ABSTRACT FROM AUTHOR]

Using density functional theory, we investigated the vibrational properties and Raman spectra of pristine blue phosphorene and fluorinated blue phosphorene. The fluorinated blue phosphorene possesses a Dirac cone at the K point (about 310 cm−1). The shape of the Dirac cone remains unchanged under different tensile strains. The Raman tensor and thus angle-dependent Raman intensities of all Raman active modes are calculated for the polarizations of scattered light parallel and perpendicular to that of the incident light. The characteristics of angle-dependent Raman intensities are discussed. Moreover, the polarization direction averaged non-resonant Raman spectra of pristine blue phosphorene and fluorinated blue phosphorene are compared with that of germanene and black phosphorene. [ABSTRACT FROM AUTHOR]

ZnO nanowire field-emitter arrays (FEAs) show great application potentials in large-area vacuum microelectronics devices. However, the electron divergence is an issue which should be addressed. In this paper, ZnO nanowire FEAs with co-planar focus electrode were designed. A four-mask fabrication process and lift-off process were adopted to achieve the integration of focus electrode. The device demonstrated line-addressing and focusing capability with a spacing of 5 mm between anode and cathode, and the linewidth of field-emission images was reduced from 2.25 to 1.35 mm when the focus voltage changed from 50 to −50 V. Besides, line-shaped emission patterns were observed during focusing process, which was attributed to the emission pattern from the ZnO nanowire and the asymmetrical focusing electrical field. [ABSTRACT FROM AUTHOR]

The development of field electron emission materials requires purposeful analytical modeling of structural features. A vertical wedged ordered nanostructure shows better field emission current density because of its in-plane continuity at the top emission edge: Individually, its calculated average current density can be 8.3-26.7 times larger than a tapered nanostructure when its bottom area s increases from 0.5 to 2.5 µm2, can be 2.2-12.7 times as its radius of top curvature r decreases from 65 to 5 nm, and can be 7.3-17.3 times as its length L increases from 0.5 to 5 µm. For an ordered nanostructure array, its average current density can be about 160 times larger than the a reference tapered array when the individual elements are closely aligned. Over three orders of magnitude improvment can be observed when optimal emitter spacing conditions are used. Structural analytical models and numerical simulation prove to be in good correspondence with previously reported experimental data, and may serve as a guide for the design and preparation of field electron emission materials with a clear purpose in the future. [ABSTRACT FROM AUTHOR]

We have investigated the field evaporation of grounded arsenic (As) doped silicon (Si) clusters composed of 52 atoms with density functional theory (DFT) to mimic Si nano structures of hundreds of nanometers long standing on a substrate. Six cluster structures with different As doping concentrations and dopant locations are studied. The critical evaporation electric fields are found to be lower for clusters with higher doping concentrations and doping sites closer to the surface. We attribute the difference to the difference in binding energies corresponding to the different As-doping concentrations and to the doping locations. Our theoretical study could shed light on the stability of nano apexes under high electric field. [ABSTRACT FROM AUTHOR]

The rational design and fabrication of zinc oxide (ZnO) nanowire (NW) lateral field electron emission device and the possible application as a display pixel structure are reported. In the device, the cathode and anode are ranked side-by-side on the same panel. The NW-clusters were controlled to locally grow on the edges of the electrodes with different tilted status, i.e., in angle range of 75^\circ–110^\circ, 0^\circ–110^\circ, and 0^\circ–57^\circ, respectively. The devices with NWs at different tilt-angle showed distinct field electron emission properties. The device with 0^\circ–57^\circ tilted NWs possess the best performance, i.e., an emission current of 9.3 \muA (current density: 6.22 A/cm^2) was obtained at a low cathode-anode (50 \mum in separation) bias of 477 V. Stable cathodoluminescence was observed from the indium titanic oxide anode, suggests a possibility for display application. Mechanisms responsible for the enhanced field electron emission and the related device physics are proposed. Significantly, the low temperature (\sim80^\circC) solution-phase growth of ZnO NWs enables the fabrication of the devices on flexible polyimide substrate, which has also been demonstrated here. This paper opens up possibilities on developing NW-based lateral field electron emission device for vacuum micro/nanoelectronics applications. [ABSTRACT FROM AUTHOR]

The laser-induced doping and fine patterning of luminescent ZnS nanospheres is reported. Monodispersive ZnS nanospheres were synthesized in a large scale (gram-quantity) by a low temperature (70 °C) aqueous method following a self-aggregation and size-limiting process. The nanospheres were in a narrow (60–80 nm) diameter distribution and were formed by aggregated nanocrystals (∼4 nm in diameter). Laser-induced doping to obtain luminescent patterns was realized by performing a laser irradiation (wavelength: 1064 nm) on the films of nanospheres mixed with dopant precursors (i.e. MnCl2 or AlCl3). Patterns on both the flat and highly curved substrates were fabricated. Fine luminescent microarrays with sizes of ∼15 μm were fabricated by further performing a laser-induced “peel-off” on the doped films. Single-element (Mn) doping and dual-element (Al–Cl) co-doping were demonstrated. Strong photoluminescence spectra centered at ∼590 nm and ∼513 nm were attained from the Mn doped and Al–Cl co-doped patterns, respectively, while the corresponding cathodoluminescence revealed a slight blue shift. The formation of a donor–acceptor pair was proposed to interpret the luminescence intensity enhancement of the featured Al–Cl co-doped ZnS. This work provides an approach to produce fine luminescent patterns for application in high resolution displays, multi-color light emitting diodes and X-ray imaging. [ABSTRACT FROM AUTHOR]

Field emission from a MOSFET-controlled ZnO nanowire (NW) cathode is reported. The emission current was modulated in four orders of magnitude (from 0.2 nA to 1.15 \mu\A) by tuning the MOSFET gate voltage from 0.8385 to 1.5255 V. The modulation of the emission current showed an exponential relationship with the MOSFET gate voltage. The MOSFET control can dramatically reduce the emission current fluctuation, i.e., from 61.4% to 3.2%, at a current level of \sim650 nA. The related mechanisms responsible for the improvement on field-emission current stability, the correlation between the vacuum breakdown of the NWs, and the failure of the MOSFET were discussed. The technique combines cold-cathode nanomaterials with mature solid-state technology to produce a reliable cathode in an on-chip form, which shows promising potential for modern vacuum micro-/nanosized electronic device applications. [ABSTRACT FROM AUTHOR]