Yunsong Di

Effect of ion bombardment on the field emission property of tetrapod ZnO

The influences of ion bombardment on the field emission performance of tetrapod ZnO nanostructures are reported. As the scanning electron microscopy images and photoluminescence spectrum show, the tips of the field emitters are destroyed and the surface state of the field emitters is also changed after the ion bombardment. The ion bombardment has a considerable effect on the field emission properties of the tetrapod ZnO field emitters. After Ar+ ion bombardment with the energy of 3 keV and the ion current of 0.05 μA for 30 min, the turn-on field increases about 63% and the threshold field increases about 77%, respectively. There are two main reasons for the variation in field-emission property: (1) the decrement of the field enhancement factor β, which is caused by the variation in morphology of field emitter; (2) the increment of work function φ, which is caused by the changed concentration of the surface oxygen vacancy.

Large and stable emission current from synthesized carbon nanotube/fiber network

In order to obtain a large and stable electron field emission current, the carbon nanotubes have been synthesized on carbon fibers by cold wall chemical vapor deposition method. In the hierarchical nanostructures, carbon fibers are entangled together to form a conductive network, it could provide excellent electron transmission and adhesion property between electrode and emitters, dispersed clusters of carbon nanotubes with smaller diameters have been synthesized on the top of carbon fibers as field emitters, this kind of emitter distribution could alleviate electrostatic shielding effect and protect emitters from being wholly destroyed. Field emission properties of this kind of carbon nanotube/fiber network have been tested, up to 30 mA emission current at an applied electric field of 6.4 V/μm was emitted from as-prepared hierarchical nanostructures. Small current degradation at large emission current output by DC power operation indicated that carbon nanotube/fiber network could be a promising candidate for field emission electron source.

A New Triode Structure With a Carbon Nanotube Cathode

A new field-emission triode with a carbon nanotube (CNT) cathode is proposed in this paper. This triode consists of three glass plates: the first one represents the cathode plate, which has an array of holes to which the CNTs are applied by printing; the second plate is mounted below the cathode plate and contains the gate electrodes; and the third one is the anode. The electric field generated by the anode voltage penetrates into the CNT cathode area, which allows a rather low gate voltage to modulate the field-emission current. Simulation and experimental results show the modulation feasibility of this kind of triode structure.

P1–39: Large current emission from CNTs synthesized by a local heating CVD method

A local heating chemical vapor deposition method is used to synthesize carbon nanotubes onto a metal substrate. Compared with normal thermal chemical vapor deposition, this method can provide faster growth rate, more nodes can be formed onto the carbon nanotubes, and emission sites can be increased largely. A maximum current over 100mA was obtained from carbon nanotubes emitter layer with emission area is about 0.7cm2. This method provides an effective way to fabricate carbon nanotubes into a vacuum electronic device to realize large current emission from a cold cathode instead of a thermionic cathode.

High performance field emission of silicon carbide nanowires and their applications in flexible field emission displays

In this paper, a facile method to fabricate the flexible field emission devices (FEDs) based on SiC nanostructure emitters by a thermal evaporation method has been demonstrated. The composition characteristics of SiC nanowires was characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED) and energy dispersive X-ray spectrometer (EDX), while the morphology was revealed by field emission scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The results showed that the SiC nanowires grew along the [111] direction with the diameter of ∼110 nm and length of∼30 μm. The flexible FEDs have been fabricated by transferring and screen-printing the SiC nanowires onto the flexible substrates exhibited excellent field emission properties, such as the low turn-on field (∼0.95 V/μm) and threshold field (∼3.26 V/μm), and the high field enhancement factor (β=4670). It is worth noting the current density degradation can be controlled lower than 2% per hour during the stability tests. In addition, the flexible FEDs based on SiC nanowire emitters exhibit uniform bright emission modes under bending test conditions. As a result, this strategy is very useful for its potential application in the commercial flexible FEDs.In this paper, a facile method to fabricate the flexible field emission devices (FEDs) based on SiC nanostructure emitters by a thermal evaporation method has been demonstrated. The composition characteristics of SiC nanowires was characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED) and energy dispersive X-ray spectrometer (EDX), while the morphology was revealed by field emission scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The results showed that the SiC nanowires grew along the [111] direction with the diameter of ∼110 nm and length of∼30 μm. The flexible FEDs have been fabricated by transferring and screen-printing the SiC nanowires onto the flexible substrates exhibited excellent field emission properties, such as the low turn-on field (∼0.95 V/μm) and threshold field (∼3.26 V/μm), and the high field enhancement factor (β=4670). It is worth noting the current density degradation can be controlled lower than 2% per hour...

Stratified carbon film for large current emission synthesized by a local heating CVD method and its growth mechanism

In order to fulfill the requirements of large current field emission, a kind of stratified carbon film has been synthesized by local heating chemical vapor deposition method. In this stratified structure, carbon fibers with the diameter of more than 500nm have been formed and intertwined with each other as conductive net; carbon nanotubes with the diameter about less than 30nm can be synthesized around the fibers as the field emitters. From the scanning electron microscopy pictures, we can see that the main growth process of carbon fiber is top-down mode, while carbon nanotubes were synthesized on the body of carbon fiber with defect growth mechanism. Field emission tests show that this kind of structure with low turn-on field and large current emission ability.

Effect of outgassing on the field emission property of screen-printed CNTs

To study the mechanism of current degradation of a cold cathode, the outgassing measurement of a field emission diode with screen-printed CNTs cathode has been taken with a quadrupole mass spectrometer (QMS) in an ultra-high vacuum (UHV) system. It was found that the H2, CO2, and CO were outgassed from the diode during the working process. The field emission properties of the cold cathode, such as turn-on field, threshold field and the emission current density, were largely related to the pressure of the outgases. From the outgassing experimental results, the relations between the emission current degradation and the outgassing of field emission devices have been found.

Outgassing of tetrapod ZnO nanostructures and its infliuence on the field-emission preformance

In this work outgassing characteristics of a screen-printed ZnO cathode during the field emission process are studied and plausible outgassing effects on the field emission property of the ZnO cathode are proposed.

Improved emission uniformity of printed carbon nanotubes by adding graphene conductive network

In this paper, we use graphene as conductive layer to improve the field emission properties of CNTs. The metallic nature of graphene and its low contact resistance with metal electrode give a small voltage drop both along the graphene and at the graphene/metal interface. This means that the supply of electrons from the electrode to the emitters is sufficient.

Field emission and other electron sources fabrication of dielectric layer in a novel triode structure CNT-fed

A new triode structure for printable carbon nanotube field emission displays is described in this paper. In the structure, silver paste is printed on the surface of a metal mesh and acts as the gate electrode. Between the gate and the metal mesh is a dielectric layer. MgO film and MgF/sub 2/ film are deposited on the surfaces of the mesh and the funnels by evaporation. A voltage applied on the metal mesh, the primary electrons emit from the CNT cathode and bombard on the surface of the metal mesh with initial energy. The secondary electrons and backscatters are generated. Because of the low energy of the secondary electrons, the gate can control the emission current easily. Therefore the range of the modulate voltage can be withdrawn. The dielectric layer on the surface of the metal mesh must be compact, otherwise silver paste will penetrate in after firing and under high voltage, breakdown of the insulator materials will occur by surface flashover. This paper reports the fabrication process of dielectric layer and the preparation of the materials.