Stable zinc oxide field emitter-based backlight unit for liquid crystal display

A zinc oxide ZnO field emitter-based backlight unit for liquid crystal display with a gated structure is fabricated by screen-printing processes.The measured anode field emission current density reaches 0.62 mA/cm2 when the applied gate voltage is 570 V.Part of the anode current is contributed by the secondary electron emission which is excited from the MgO layer inside the gate apertures on the gate plate. The average emission current density and luminance are 0.47 mA/cm2 and 1 250 cd/m2 respectively with a fluctuation of about 10% during the 1 000 min measurement.By a finite element method calculation the gated structure shows a good electron beam focusing property. The driving performance of the backlight unit is characterized by SPICE simulation tools and measured by the oscilloscope. Stable field emission line-by-line scanning and fast response characteristics of the backlight unit indicate its promising application in the liquid crystal displays.

Degradation of the Emission Current from the Field Emitter Caused by Ion Bombardment

In field emission devices, the emission current sometimes degrades with the time. The mechanism of the current degradation is complicated. In this paper, a program is used to simulate the movement of the electron beam from a field emitter. According to the current distribution and the trajectories of the primary electron beam, it is shown that the residual gas is ionized and the ion pairs are generated. The trajectories of the positive ions are simulated. With the different locations and kinetic energy of i...

Experimental study of negative capacitance in LEDs

The experimental study on negative capacitance（NO） of various light-emitting diodes（LEDs） is presented. Experimental result shows that all LEDs display the NO phenomenon. The voltage modulated electroluminescence（VMEL） experiment confirms that the reason of negative capacitance is the strong recombination of the injected carriers in the active region of luminescence. The measures also verify that the dependence of NO on voltage and frequency in different LEDs is similar. NO phenomenon is more obvious with higher voltage or lower frequency.

Enhanced Efficiency and Durability of Organic Electroluminescent Devices by Doping in Emitting Layer

Remarkable improvement in efficiency and stability has been observed in a doped organic electroluminescence device, which consists of a hole-transport layer, an electron-transport layer and a luminescent layer. The hole-transport layer is a N,N’-bis(3-methyphenyl)-N,N’-diphenylbenzidine film. The doped emitting layer consists of 8-(quinolinolate)-aluminum as the host and rubrene as the emission dopant. The doped device demonstrated a brightness in excess of 40 000 cd/m 2 and the maximum external quantum efficiency of 3.4%, which is about six times and four times respectively greater than those of the undoped device. For no packaged deviced, a luminance half-life on the order of about 230 h has been achieved under a constant current density of 15 mA/cm 2, starting at 500 cd/m 2 at the room temperature.

Theoretical Study on Field Emission Patterns of the Nanotube

The distributions of the electrical potential and field have been given from Maxwells field equations.The results show that there exists very strong electric field intensity on the tip of the nanotube,and the intensity decays rapidly as the distance increases away from the tip. The strong electric field intensity on the tip is consistent with the low threshold voltage under the electric field emission from a nanotube. The calculation also revealed that the higher the aspect ratio is,the stronger the electric field intensity on the tip of the nanotube will be,if the distance and voltage between the cathode and the anode do not change, which predicts the lower threshold voltage under the field emission.

Ultra-Thin Double-Walled Carbon Nanotubes： A Novel Nanocontainer for Preparing Atomic Wires

Double-walled carbon nanotubes （DWCNTs） with high graphitization have been synthesized by hydrogen arc discharge. The obtained DWCNTs have a narrow distribution of diameters of both the inner and outer tubes, and more than half of the DWCNTs have inner diameters in the range 0.6-1.0 nm. Field electron emission from a DWCNT cathode to an anode has been measured, and the emission current density of DWCNTs reached 1 A/cm2 at an applied field of about 4.3 V/~tm. After high-temperature treatment of DWCNTs, long linear carbon chains （C-chains） can be grown inside the ultra-thin DWCNTs to form a novel C-chain@DWCNT nanostructure, showing that these ultra-thin DWCNTs are an appropriate nanocontainer for preparing truly one-dimensional nanostructures with one-atom-diameter.

Behaviors of field emitters under pulsed voltages

In this paper we described our study of the behaviors of field emitters driven by square-wave voltages. We observed phenomena under pulsed voltages that generally do not manifest themselves under direct-current voltages. We interpreted these phenomena with the cathode and anode combined treated as equivalent to a resistor and a condenser in series connection. First,because of the delay caused by the charging process of the condenser, the waveform of the voltage across the cathode-anode gap was remarkably distorted. Second, the resistor led to considerable attenuation in field emission, which was clearly observable within each pulse and became more dramatic with increasing repetition frequency of the pulses. Furthermore, the field emission currents under direct-current voltages were lower than those under pulsed voltages. This disparity is attributed to rising resistance in the circuit with rising temperature. We also discussed the restrictions that the waveform distortion and current attenuation could impose on potential field emitter applications.

Highly sensitive detection of mercury（Ⅱ） ions with few-layer molybdenum disulfide

Two-dimensional （2D） layered transition metal dichalcogenide （TMD） materials （e.g., MoS2） have attracted considerable interest due to their atomically thin geometry and semiconducting electronic properties. With ultrahigh surface to volume ratio, the electronic properties of these atomically thin semiconductors can be readily modulated by their environment. Here we report an investigation of the effects of mercury（II） （Hg^2＋） ions on the electrical transport properties of few-layer molybdenum disulfide （MoS2）. The interaction between Hg^2＋ ions and few-layer MoS2 was studied by field-effect transistor measurements and photoluminescence. Due to a high binding affinity between Hg2. ions and the sulfur sites on the surface of MoS2 layers, Hg^2＋ ions can strongly bind to MoS2. We show that the binding of Hg^2＋ can produce a p-type doping effect to reduce the electron concentration in n-type few-layer MoS2. It can thus effectively modulate the electron transport and photoluminescence properties in few-layer MoS2. By monitoring the conductance change of few-layer MoS2 in varying concentration Hg2~ solutions, we further show that few-layer MoS2 transistors can function as highly sensitive sensors for rapid electrical detection of Hg^2＋ ion with a detection limit of 30 pM.