四针状纳米ZnO在场致发射显示器的应用研究

以高温气相氧化法制备的四针状纳米ZnO作为场致发射材料,采用浆料印刷和烧结的方法将其制备成场致发射阴极基板.将阴极板和荧光屏封装成5×25.4 mm二极结构的场致发射显示器,进行了场致发射特性实验,实现了稳定的场致电子发射及简单字符显示.该二极结构ZnO-FED的开启场强为1.5 V/μm,当场强为5.3 V/μm时,发射电流密度可达5.11 μA/cm2.通过实验测定场增强因子约为6 772,表现出了好的场致电子发射性能.实验结果表明了四针状纳米ZnO纳米材料是一种很好的场致发射阴极材料.     

在家用微波炉中合成四针状ZnO

将锌粉和石墨粉以一定比例混合放入家用微波炉中,在微波辐照下燃烧生成了白色松软的ZnO膜,将此薄膜用扫描电子显微镜(SEM)、能量损失谱(EDS)、透射电子显微镜(TEM)和X射线衍射光谱(XRD)分析其成分和形貌。结果显示,该ZnO为单晶四针状晶须,晶须直径为20~50nm,分析了它的生长机理并测试其场发射特性,得到该ZnO的开启场强较低为3.88V/μm,相应的电流密度为10μA/cm2,在场强为5.7V/μm时达到最大发射电流密度为0.39mA/cm2。     

热CVD法制备的碳纳米管线阵列的场发射特性

采用半导体光刻技术在硅衬底上获得图形化掩膜,然后用热化学气相淀积(T-CVD)的方法制备了图形化的碳纳米管线阵列,用扫描电镜和拉曼光谱仪对碳纳米管进行了表征.研究了图形化碳纳米管线阵列的场发射特性,并与无图形化处理的碳纳米管薄膜样品的场发射特性进行了比较.当发射电流密度达到10 μA/cm2时,无图形化处理的碳纳米管薄膜、10 μm碳纳米管线阵列以及2 μm碳纳米管线阵列样品的开启电场分别为3 V/μm、2.1 V/μm和1.7 V/μm;而当电场强度达3.67 V/μm时,相应的电流密度分别为2.57 mA/cm2、4.65 mA/cm2和7.87 mA/cm2. 实验结果表明,图形化处理后的碳纳米管作为场发射体,其场发射特性得到了明显的改善.对改善的原因进行了分析和讨论.     

衬底温度对氧化锌薄膜场发射性能的影响

利用射频磁控溅射法制备了不同衬底温度的氧化锌(ZnO)薄膜.研究了其场发射特性,分析了场发射特性和衬底温度的变化关系.实验结果表明, 开启电场随着衬底温度的增加呈先增大后减小的趋势,场发射特性的变化是由于衬底温度的改变引起表面形貌的变化所致.衬底温度为300 ℃时沉积的ZnO薄膜样品粗糙度最小,场发射性能最差,其开启场强为1.7 V/μm,场强为3.8 V/μm时电流密度仅为0.001 97 A/cm2;衬底温度为400 ℃时沉积的ZnO薄膜样品表面粗糙度最大,场发射特性也优于其他薄膜;开启场强为0.82 V/μm, 场强为3.8 V/μm时电流密度稳定在0.03 A/cm2.Fowler-Nordheim(F-N)曲线为直线表明, 电子是在外加电场的作用下隧穿表面势垒束缚发射到真空的.     

石英管型MWPCVD法制备的纳米针状结构碳膜的场发射特性

利用石英管型微波等离子体化学气相沉积装置,在Si基板上制备了具有纳米针状结构的碳膜。场发射特性测试表明,纳米针状结构碳膜具有良好的场发射特性,阈值电场为2.2V/μm,外加电场为9V/μm时,电流密度达到65mA/cm2。利用统计效应修改了Fowler-Nordheim(F-N)模型,成功地解释了在低电场区域的场发射机理。但是利用修改的F-N模型,不能解释高电场区域的电流密度的饱和现象,这将有待于进一步研究。     

氧化钨纳米结构：可控制备及场发射性能

通过简单调控化学气相沉积反应气压制备了形貌尺寸可控的各种非化学计量比氧化钨纳米结构。场发射研究表明W18O49纳米线具有优异的场发射性能。对于10 μA/cm2的发射电流,其开启电压为7.1 V/μm。 实验中测得最高场发射电流密度4.05mA,对应场强为17.2 V/μm。场发射过程中的热蒸发和脱附测试表明该氧化钨纳米线的场发射再现性很高。     

纳米石墨片的制备及场发射特性

将可膨胀石墨粉放入家用微波炉中进行微波辐照,使石墨粉发生燃烧膨胀,将燃烧的产物用无水乙醇超声后旋涂于硅片上,用扫描电子显微镜(SEM)观察其形貌,得到仅几纳米厚的准二维结构的纳米石墨片。对其进行场发射特性测试,结果显示其具有优异的场发射性能,其开启场强为5.9V/μm,对应的电流密度为0.01mA/cm2。在场强为10.25V/μm时,得到最大发射电流密度为5.9mA/cm2。该纳米石墨片制作方法简单、快捷,可成为一种优异的准二维场发射电子源。     

碳纳米球薄膜的场发射特性

利用微波等离子体化学气相沉积法,在Si(100)衬底上制备了碳纳米球薄膜。利用拉曼光谱和场发射扫描电子显微镜研究了薄膜的结构以及表面形貌,表明碳纳米球薄膜是由约2～3μm长、100nm宽的无定形碳纳米片相互缠绕、交织成球状而构成的。在高真空系统中测量了碳纳米球薄膜的场发射特性,结果表明,碳纳米球薄膜具有良好的场发射特性,阈值电场为3.1V/μm,当电场增加到10V/μm时,薄膜的场发射电流密度可达到60.7mA/cm2。通过三区域电场模型合理地解释了碳纳米球薄膜在低电场、中间电场和高电场区域的场发射特性。     

GaN纳米线阵列的电子场发射研究

基于HCl辅助热蒸发GaN粉末的方法制备了纯净的一维GaN纳米线垂直阵列,重点研究了不同生长时间对应不同形貌的GaN纳米结构的电子场发射性能,以及氨气氛围下热退火对GaN纳米线阵列场发射性能的影响,并分析了其影响机理.通过对生长时间分别为20 min,60 min(未退火处理)与60 min(退火处理)的三组样品进行对比,结果显示:生长时间为60 min(未退火处理)的样品,电流密度达到1μA/cm2时的开启电场的值为2.1 V/μm,且获得1 mA/cm2的阈值电流密度也只需要4.5 V/μm的电场.     

金刚石颗粒与硅基底的超声焊接及场发射性能（英文）

采用一种超声焊接工艺,通过施加纳米幅度的超声水平振动将金刚石颗粒牢固地焊接于硅基底表面。在此过程中超声力小于硅所能承受的剪切应力,使硅表面得以发生超声软化进而促成焊接的形成。焊接界面的分析结果表明硅与金刚石颗粒之间的连接不仅仅是机械嵌合,还包括原子之间的键合。当焊接时间为5 s、振幅为500 nm时形成了稳固的纳米焊接。焊接后的金刚石场发射阴极获得了较低的开启场强(电流密度为1μA/cm2时的场强)1.4 V/μm,并且当电场强度达到9.6 V/μm时,可获得到高达1 mA/cm2的电流密度。     

Excellent Field‐Emission Performances of Neodymium Hexaboride (NdB6) Nanoneedles with Ultra‐Low Work Functions

High‐quality NdB₆ nanostructures with a low work function are successfully synthesized via an one‐step catalyst‐free chemical vapor deposition process. Field emission properties of these nanostructures (curve nanowires, short‐straight nanorods, long‐straight nanowires, and nanoneedles) are systematically investigated and found to be strongly affected by the tip morphologies and temperatures. The nanoneedles with sharp tips demonstrate the lowest turn‐on (2.71 V/μm) and threshold (3.60 V/μm) electric fields, as well as a high current density (5.37 mA/cm²) at a field of 4.32 V/μm in comparision with other nanostructures. Furthermore, with an increase in temperature from room temperature to 623 K, the turn‐on field of the nanoneedles decreases from 2.71 to 1.76 V/μm, and the threshold field decreases from 3.60 to 2.57 V/μm. Such excellent performances make NdB₆ nanomaterials promising candidates for application in flat panel displays and nanoelectronics building blocks.     

Co‐synthesis of ZnO–CuO Nanostructures by Directly Heating Brass in Air

ZnO–CuO nanostructures have been simultaneously synthesized by directly heating a CuZn alloy (brass) on a hotplate in ambient conditions. Depending on the Zn concentrations in the brasses, the dominant products transition from CuO nanowires to ZnO nanostructures. By changing the growth temperature and local Zn contents, 1D ZnO nanowires/nanoflakes, 2D ZnO nanosheets, and complicated 3D ZnO networks are obtained. Electron microscopy studies show that the as‐synthesized ZnO nanoflakes and nanosheets are single crystalline. Based on “self‐catalytic” growth, a tip‐growth mechanism for ZnO nanostructures is discussed, in which the Cu in brass plays an important role to confine the lateral growth of ZnO. Finally, the electron field emission from the ZnO–CuO hybrid systems is tested for the demonstration of potential applications.     

Tungsten oxide nanostructures:controllable growth and field emission

正Non-fully oxidized tungsten oxide(WO_(3-x)) nanostructures with controllable morphology were fabricated by adjusting the gas pressure in chemical vapor deposition.The comparative field emission(FE) measurements showed that the obtained W_(18)O_(49) nanowires have excellent FE property.The turn-on field was 7.1 V/μm for 10μA/cm~2 and the observed highest current density was 4.05 mA/cm~2 at a field of 17.2 V/μm.Good electron emission reproducibility was also observed during thermal evaporation and desorption testing.     

图形化氧化锌阵列的制备及其场发射性能研究

为了减小场发射的屏蔽效应,采用图形化技术对氧化锌(ZnO)纳米枝阵列进行调控,并研究图形化ZnO枝阵列的性能。首先采用光刻法在ITO导电玻璃上制备图形化ZnO种子层,再用电沉积法在图形化种子层上生长ZnO纳米枝阵列。利用扫描电子显微镜(SEM)、X射线衍射(XRD)研究所制备的图形化ZnO阵列形貌、结构等,并测试其场发射性能。研究结果表明,制备的图形化ZnO纳米枝是圆阵列,直径为330μm左右,纳米ZnO主干平均直径为400~500nm,发现主干上有一些精细的类似锥状的纳米量级微细枝结构,并且具有良好的场发射性能,开启场强为2.15V/μm,场增强因子为16 109。该图形化生长ZnO阵列阴极的方法是一种能较好改善材料场发射性能的方法,在场发射应用领域表现出较好的前景。     

Growth enhancement and field emission characteristics of one-dimensional 3,4,9,10-perylenetetracarboxylic dianhydride nanostructures on pillared titanium substrate

We have utilized the π–π interactions between 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) molecules and temperature-induced morphology changes to synthesize one-dimensional (1D) nanostructures of PTCDA on a heated (ca. 100 °C) titanium substrate through vacuum sublimation. Because of the pillared Ti structures and the presence of reactive Ti–Cl sites, the titanium substrate played a crucial role in assisting the PTCDA molecules to form 1D nanostructures. The average diameter of the nanofibers deposited on the Ti-CVD substrate, a Ti substrate formed by chemical vapor deposition (CVD), at 100 °C was ca. 84 nm, with lengths ranging from 100 nm to 3 μm. When the PTCDA nanofibers were biased under vacuum, the emission current remained stable. The turn-on electric field for producing a current density of 10 μA/cm² was 8 V/μm. The maximum emission current density was 1.3 mA/cm², measured at 1100 V (E = 11 V/μm). From the slope of the straight line obtained after plotting ln(J/E²) versus 1/E, we calculated the field enhancement factor β to be ca. 989. These results demonstrate the PTCDA nanofibers have great potential for applicability in organic electron-emitting devices.     

A novel complementary N+-charge island SOI high voltage device

A new complementary interface charge island structure of SOI high voltage device (CNI SOI) and its model are presented. CNI SOI is characterized by equidistant high concentration n+-regions on the top and bottom interfaces of dielectric buried layers. When a high voltage is applied to the device, complementary hole and electron islands are formed on the two n+-regions on the top and bottom interfaces. The introduced interface charges effectively increase the electric field of the dielectric buried layer (E1) and reduce the electric field of the silicon layer (Es), which result in a high breakdown voltage (BV). The influence of structure parameters and its physical mechanism on breakdown voltage are investigated for CNI SOI. EI = 731 V/μm and BV = 750 V are obtained by 2D simulation on a l-μm-thick dielectric layer and 5-μm-thick top silicon layer. Moreover, enhanced field E1 and reduced field Es by the accumulated interface charges reach 641.3 V/μm and 23.73 V/μm, respectively.     

锌衬底上直接生长密度可调的氧化锌纳米棒阵列和场发射特性

在锌衬底上制备了取向生长、形貌各异、不同密度的氧化锌纳米棒阵列.研究发现,氧化锌纳米棒在温度低于70℃、适量的碱性溶液、大气压下能够在锌衬底上大规模制备,并且氧化锌纳米棒的直径,在锌衬底上的密度和形貌完全依赖于氢氧化钠和硝酸锌的浓度.场发射测试表明:氧化锌纳米棒阵列开启电场较低(电流密度达1μA/cm2时场强仅为3.8 V/μm),显示了氧化锌纳米棒阵列在场发射方面的潜在应用.     

在硅片上电沉积不同形貌的ZnO纳米结构的研究

采用简单的电化学沉积方法,通过调节电解液浓度和pH值,在硅衬底上实现了ZnO纳米结构的形貌控制。通过X射线衍射、扫描电镜和光致发光谱等表征手段对不同形貌的ZnO纳米结构进行了研究。研究发现,通过调节沉积条件,可以获得纳米棒、纳米簇丛和纳米片等不同形貌的ZnO纳米结构。其中,溶液pH值是纳米ZnO从一维结构到二维结构转变的关键因素。当pH值为12时,所获得的纳米ZnO为二维片状结构。光致发光谱显示二维ZnO纳米片的紫外本征峰相对于一维ZnO纳米棒发生了明显的蓝移,并且可见区的发光峰大大降低。这一结构将在光电器件、传感器等领域有很好的应用前景。     

An Improved Planar Triode With ZnO Nanopin Field Emitters

In this letter, an improved planar triode with ZnO nanopin field emitters has been proposed. Comparison with a conventional planar triode, a layer of ZnO nanostructures is deposited between the cathode and gate electrode. These ZnO nanostructures are used as field emitters. Because both electrodes and ZnO layer can be deposited with screen-printing method, the fabrication process of an improved planar triode is quite simple. As experimental results shown, the turn-on voltage and the threshold voltage are low. The swing voltage is about 120 V when the anode current of a single pixel is 200 nA. A good focus performance is also obtained with a new electrode-pattern in the planar triode.