Enhanced electron emission from phosphorus-doped diamond-cladsilicon field emitter arrays

Undoped and phosphorus (P)-doped diamond-clad Si field emitter arrays have been successfully fabricated using microwave plasma chemical vapor deposition (MPCVD) technology. The electron emission from the blunt diamond-clad microtips are much higher than those for the pure Si tips with sharp curvature due to a lower work function. Furthermore, the characteristics of emission current against applied voltage for the P-doped diamond-clad tips show superior emission at lower field to the undoped ones. After the examination of Auger electron spectroscopy (AES) and electrical characteristics of as-grown diamond, such a significant enhancement of the electron emission from the P-doped diamond-clad tips is attributed to a higher electron conductivity and defect densities     

Simulation and design of field emitter array

Some simulation results about potential, field strength, and emitting current density of cone-shaped emitter arrays are presented. Several important design features about the field emitter array are discussed. The most striking feature is that if one wants to obtain more current from the field emitter array in a given device area, there is a limit to the density of the emitter array due to the emitter tip field strength lowering effect, which is a result of the interaction from nearby surrounding tips. If one reduces the tip radius to increase the field strength a higher current density is compensated by a reduced effective emitting area; therefore, to obtain the highest emitter current for a certain set of designed emitter array geometric parameters a corresponding optimal tip radius needs to be determined     

Effect of diamond-like carbon coating on the emissioncharacteristics of molybdenum field emitter arrays

We have studied the electron emission characteristics of Mo field emitter arrays (FEAs) using a diamond-like carbon (DLC) film deposited by a layer-by-layer technique using plasma enhanced chemical vapor deposition. The turn-on voltage was lowered from 55 to 30 V by a 20 nm thick hydrogen-free DLC coating and maximum emission current was increased from 166 to 831 μA. Also the gate voltage required to get the anode current of 0.1 (μA/emitter) decreases from 77 to 48 V. Furthermore, the emission current from DLC coated Mo FEAs is more stable than that of noncoated Mo FEAs     

Optimization of electron beam focusing for gated carbon nanotube field emitter arrays

We fabricated gated field emitter arrays with a novel focusing structure of electron beams, where the focusing electrode concentrically surrounded each gate hole. Carbon nanotube emitters were screen printed inside an amorphous-Si concave well far below the gate. It was theoretically and experimentally verified that the concave well structure effectively focused the emitted electron beams to their designated phosphor pixels by modulating focusing gate voltages. For the vacuum packaged field emission displays with the pixel specification fitting high-definition televisions, color reproducibility of approximately 71% was achieved at the brightness of 400 cd/m/sup 2/.     

Rate equation of current degradation of the Spindt-type field emitter array

The degradation rate of the emission current of the Spindt-type field emitter arrays in the display environment has been measured. The relative degradation rate is found to be a function of the square of emission current and proportional to the anode bias (voltage). A life model is presented that leads to development of an analytical rate equation of emission current degradation. Based on this model, there is a steady-state level at which the emission current is stable. The steady-state emission current depends on anode bias, background pressure in the package and cleanliness of anode and cathode surfaces. Experimental results are consistent with the rate equation derived from the model. Since the model does not include any material and process that make the cathode, it could probably apply to any field emission cathodes.     

Uniform electron emission from a nitrogen-doped diamond-basedelectron emitter fabricated by the sintering technique

A nitrogen (N)-doped diamond-based electron emitter has been fabricated by the sintering technique prior to the chemical vapor deposition process in order to improve the uniformity. There are no spatial differences in reflective electron energy loss spectra (REELS) from the diamond-based electron emitter, suggesting that uniform surface conditions are obtained. The uniform electron emission from the obtained electron emitter is confirmed through emission current vs anode voltage characteristics measurements. It seems that the uniformity of the emitter surface results in uniform electron emission from the diamond electron emitter     

Improvement of electron emission efficiency and stability bysurface application of molybdenum silicide onto gated poly-Si fieldemitters

As an approach to improve electron field emission and its stability, molybdenum (Mo) silicide formation on n⁺ polycrystalline silicon (poly-Si) emitters has been investigated. Mo silicide was produced by direct metallurgical reaction, namely, deposition of Mo and subsequent rapid thermal annealing. The surface morphologies and emission properties of Mo-silicided poly-Si (Mo-polycide) emitters have been examined and compared with those of poly-Si emitters. While anode current of 0.1 μA per tip could be obtained at the gate voltage of 82 V from poly-Si emitters, the same current level was measured at 72 V from Mo-polycide emitters. In addition, the application of Mo silicide onto poly-Si emitters reduced the emission current fluctuation considerably. These results show that the polycide emitters can have potential applications in vacuum microelectronics to obtain superior electron emission efficiency and stability     

激光在硅基底沉积类金刚石膜的光学应用

研究了氧气氛和掺硅对类金刚石(DLC)膜性能的影响机理.采用飞秒激光烧蚀石墨靶材,通过氧气氛、掺硅和离轴平移旋转等技术,在硅基底上镀制出比传统工艺透过率、硬度、附着力和稳定性等性能更优的无氢DLC膜.实验验证了随着氧气氛压强的增大,样片透过率先增大后减小,存在一个最佳气压(2 Pa).并且掺硅有助于改善DLC膜的性能,掺硅量也存在一个最佳值.在3-5 μm波段,正面镀DLC膜、背面镀普通增透膜的硅红外窗口的平均透过率≥91.7%,DLC膜的纳米硬度高达40～50 GPa.且通过军标规定的高温、低温、湿热、盐雾、重摩擦等环境实验.满足光学窗口工程应用的要求.     

利用场发射扫描电镜的低电压高性能进行材料表征

场发射扫描电子显微镜（FESEM）是一种高分辨扫描电镜,在材料分析中得到广泛应用。尤其是良好的低压高空间分辨性能和低压下良好的SE像相互结合使用,使SEM应用范围得到扩展。     

外场下等离子体中波的增强和带电粒子流的加速

在不考虑碰撞机制的情况下,研究了外加高频电磁场(泵波)下等离子体中Langmuir波和离子声波的增强以及带电粒子流的加速.基于流体力学方程,推导了描述等离子体参量不稳定性的振动方程,进一步得到描述带电粒子流加速的数学表达式和有质动力的数学表达式.结果表明,在等离子体参量不稳定性的激发过程中,Langmuir波和离子声波得以增强以及带电粒子流由于泵波与Langmuir波(离子声波)的耦合而加速;有质动力的产生是由于泵波与Langmuir波(离子声波)的耦合而且它是参量不稳定过程的策动力,另外有质动力不仅存在高频分量,还存在低频分量.     

Study on the vacuum breakdown in field emission of a nest array of multi-walled carbon nanotube/silicon nanoporous pillar array

A composite structure, a nest array of multi-walled carbon nanotubes/silicon nanoporous pillar array (NACNT/Si-NPA), with good field emission properties, was synthesized through growing CNT on Si-NPA by thermal chemical vapor deposition. In order to make full use of its good field emission properties, the vacuum breakdown behavior accompanied with field emission from NACNT/Si-NPA was investigated. The results revealed that a positive feedback of field emission and resulted Joule heat ignited a small portion of protruding emitters, which caused spark discharge, destroyed the anode and generated a large amount of heat. The thermal runaway ultimately resulted in the destruction of substrate and vacuum breakdown.     

Investigation of growth properties of patterned and aligned carbon nanotubes for field emitter

We demonstrate the use of microstructures as an inducement for the growth of patterned and aligned carbon nanotubes (CNTs) during thermal chemical vapor deposition process. The growth of individual nanotube lines of vertical-standing 8-10 μm length can be controlled in almost any directions. In directions of approximate 90°, 60°, 45° or 0° relative to substrate surface, kinds of aligned CNTs patterns were synthesized. We also show that the flow of carrier gas and apical dominance like plant growth are the main factors of patterning CNTs, which indicates that the distribution of electric field can be controlled and the shielding effects can be weakened. The result establishes a method of patterned and aligned nanotubes, which is well suited for ordered arrays of CNTs field emitters. The field emission currents were observed to be fairly reproducible ranging from 375 to 1000 V and field emission measurements show a low turn-on field (1.25 V/μm).     

Analysis of efficiency limitations in high-low emitter back surface field silicon solar cells

Analytical and numerical models have been used to analyse the electrical behaviour of HLE-BSF n+-n-p-p+ silicon solar cells. It is shown that this structure should have lower open-circuit voltage values than the simple HLE solar cell due to the recombination current in the p+ region. Back surface passivation is proposed as a means to improve the Voc, that can be as high as 650 mV.     

Analysis of emitter efficiency enhancement induced by residualstress for in situ phosphorus-doped polysilicon emitter transistors

This paper analyzes the enhancement of emitter efficiency in in situ phosphorus-doped polysilicon (IDP) emitter transistors, whose polysilicon emitter is crystallized from an in situ phosphorus-doped amorphous Si film. There are two factors that enhance the emitter efficiency of the IDP emitter. One is a potential barrier at the LDP/substrate interface produced by residual stress in the IDP layer. The other is a very thin oxide layer at the interface, which prevents epitaxial growth at the interface. We have distinguished between the emitter efficiency enhancement due to each of these two factors by analyzing the characteristics of three types of IDP emitter in which the residual stress and the thin oxide layer at the interface are controlled differently. We found that the potential barrier due to the residual stress increases the emitter efficiency from about two times to about eight times depending on the emitter size, and that the thin oxide layer at the interface increases the emitter efficiency by about three times     

碳纳米管场致发射阴极浆料的研制

通过筛选阴极浆料中的载体、不同种类的粘结剂和添加剂,开发出具有优良场致发射性能的大面积、低成本丝网印刷复合阴极浆料并烧结制成阴极。结果表明:在电场强度为3.2V/μm下其电流密度约为42×10–3A/cm2,场发射均匀性很好,二极管型发光板发光亮度为625cd/m2。该阴极适用于制作大面积的CNT-FED阴极和液晶显示器的背光源。     

Field electron emission of multiwalled carbon nanotubes and carbon nanofibers grown from Camphor

Vertically aligned carbon nanofibers (CNF) and multiwalled carbon nanotubes (MWCN) were synthesized from camphor by catalytic thermal chemical vapor deposition on Co and Co/Fe thin films (for CNF) and on silicon substrates using a mixture of camphor and ferrocene (for MWCN). CNF and MWCN were studied by scanning and transmission electron microscopy, visible Raman spectroscopy, X-ray diffraction in order to get insight into the microstructure and morphology of these materials. Field electron emission study indicates turn-on field of about 1.52, 2.3 and 4.3 V/μm for MWCN, Co/CNF and Co/Fe/CNF films, respectively; and threshold field of about 2.48, 3.1 and 6 V/μm, respectively. Our study indicates a better performance for field electron emission compared with some of the earlier published reports which might be due to higher aspect ratio, good graphitization and suitable density.     

Stable field emission from planar-gate electron source with MWNTs by electrophoretic deposition

A planar-gate electron source with multi-wall carbon nanotubes (MWNTs) has been successfully fabricated by conventional magnetron sputtering, lithography and electrophoretic deposition (EPD). The optical microscopy showed that he MWNTs purified in H₂SO₄/HNO₃ solution were selectively deposited on cathode. High resolution transmission electron microscopy (HRTEM) images and Raman spectra demonstrated that some MWNTs was destroyed and generated some defect. Field emission results indicated that the emission current of this triode structure is completely controlled by gate voltage. The turn-on voltage of electrophoretic deposited MWNTs cathode at current density of 1 μA/cm² was lower than that of screen printed MWNTs cathode besides better emission uniformity. In addition, the emission current fluctuation was less than 3% for 400 min. All the results indicate that the fabricated electron emission source has a good field emission performance and long lifetime.     

A novel fabrication process of a silicon field emitter array withthermal oxide as a gate insulator

We have successfully developed a fabrication process of a silicon field emitter array with a gate insulator formed by Si₃N₄ sidewall formation and subsequent thermal oxidation. This process overcomes some problems in the conventional fabrication, such as high etch rate, low breakdown field, and gate hole expansion arising from evaporation of gate oxide. Therefore, we could improve process stability and emission performance, and also reduce gate leakage current. The optimum process conditions were determined by process simulations using SUPREM-4. The turn-on voltage of the fabricated field emitters was approximately 38 V. An anode current of 0.1 μA (1 μA) per tip was measured for a 625-tip array at the gate bias of 80 V (100 V), and the gate current was less than 0.3% of the anode current at those emission levels     

Field emission characteristics of an oxidized porous polysilicon field emitter using the electrochemical oxidation process

The field emission characteristics of an oxidized porous polysilicon (OPPS) were investigated with Pt/Ti multilayer electrode using the electrochemical oxidation (ECO) process. A Pt/Ti multilayer electrode, using ECO, showed highly efficient and stable electron emission characteristics; moreover, it can be applied to large area of a glass substrate with a low temperature process. Electron emission characteristics were improved with O₂ annealing at 600 °C after the ECO process. It was found that forming a high quality oxide layer from the ECO-formed SiO₂ was crucial in improving electron emission characteristics. The Pt/Ti OPPS field emitter, which was annealed at 600 °C for 5 h, showed an efficiency of 3.81% at