表面形貌特殊的碳纳米管薄膜及其场发射增强

采用磁控共溅射法在Si片表面镀NiTi膜作为碳纳米管生长的催化剂,制备出表面形貌特殊的碳纳米管薄膜,如"丘状"和"星状"的表面微结构。通过扫描电子显微镜对碳纳米管薄膜的形貌进行表征,采用二极管形式测试了碳纳米管薄膜的场发射性能。实验结果表明,这两种碳纳米管薄膜都具有优异的场发射性能,10μA/cm~2时的开启电场分别仅为1.02 V/μm和1.15 V/μm,在外加电场为2.4 V/μm时的电流密度分别达到4.32 mA/cm~2和6.88 mA/cm~2。通过场发射FN的曲线计算得到的场发射增强因子分别为10113和6840。这两种碳纳米管薄膜优异的场发射性能与其表面的微结构有关。表面的粗糙结构增强了部分碳纳米管的局域电场,易于发射电子。     

非晶碳和碳纳米管混合薄膜的场发射性能

利用微波等离子体化学气相沉积法在不锈钢衬底上直接合成非晶碳和碳纳米管混合薄膜.采用氢气和甲烷作为反应气体,流量分别为100和16sccm.沉积室内的压强为5.0kPa.利用场发射扫描电镜(SEM)和喇曼谱(Raman)对制备的薄膜的结构和形貌进行了分析.场发射实验在5×10-5Pa的真空下进行.实验结果表明:制备的非晶碳和碳纳米管混合薄膜开启电场较低,仅有0.9V/μm;在电场为3.7V/p.m时电流密度达到4.0mA/cm2,发射点密集,分布均匀.表明此种材料是一种优良的场发射冷阴极材料.     

碳纳米管薄膜的电泳沉积及其场发射性能研究

利用电泳沉积法在铝片上制备了碳纳米管薄膜冷阴极。通过扫描电镜、Raman光谱观察分析了表面形貌和结构,并对场发射性能进行了测试。经过研磨处理的碳纳米管薄膜样品,开启电场为2V／μm,当电场强度为4V／μm时电流密度达到2600μA／cm^2,发光点密度大于10^4／cm^2。     

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。     

非晶氮化硼薄膜的场致电子发射研究

利用脉冲激光沉积 (PLD)技术在镀钛的陶瓷衬底上制备出了非晶态氮化硼薄膜 ,借助于X射线衍射(XRD)、扫描电子显微镜 (SEM )及Raman光谱分析了该薄膜的结构 ,并研究了薄膜场致电子发射特性 ,阈值电场为4 6V μm ,当电场为 9V μm时 ,电流密度为 5 0 μA cm2 。     

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。     

Field Electron Emission from Diamond—like Carbon Films

A low turn-on field electron emission from diamond-like carbon films has been observed for the first time to author‘s knowledge,Carbon films were prepared by micowave plasma chemical vapor deposition(CVD).Special pretreatment ceramic substrates were used.The characteristics of the film have been identified by using X-ray diffraction(XRD),and Raman spectrum.The field emission experiment has been performed in a vacuum chamber with a base pressure of about 10^-5Pa.The turn-on field of 1.2V/μm,and the current density of 1.25 mA/cm^2 at electric field of 6V/μm were obtained.     

单晶纳米硅薄膜的制备及其场发射特性

用小电流、特殊配比溶液的电化学阳极腐蚀法在p型、〈100〉晶向、0.01Ω·cm电阻率的硅片制备了大面积纳米硅薄膜.通过SEM,TEM,XRD和Raman光谱技术分析薄膜颗粒的微细结构.实验结果表明该纳米硅薄膜由直径为10～20nm,晶向一致的颗粒紧密排列而成,具有很好的物理化学稳定性.系统研究了薄膜结构特征和溶液配比、腐蚀时间、腐蚀电流密度的关系.成功观察到该薄膜具有很好的场发射特性,在0.1μA/cm2电流密度下,其开启电场为3V/μm,接近碳纳米管的1.1V/μm.     

脉冲激光沉积非晶碳-聚酰亚胺复合薄膜的场致电子发射研究

利用脉冲激光沉积技术制备出非晶碳-聚酰亚胺复合薄膜,并观察到其场发射阈值场强(4V/μm)比类金刚石薄膜(>12V/μm)有较大的降低,最大发射电流密度为1.2mA/cm~2.利用透明导电薄膜阳极技术可观察电子在薄膜阴极表面的发射位置.并对该复合薄膜的场电子发射机理进行了初步探讨.实验表明该复合薄膜有可能作为一种新型的场发射冷阴极材料.在平面显示器件中得到应用.     

Field electron emission from amorphous CNx:B films

CN_x:B thin films were prepared on titanium coated ceramic substrate by pulsed laser deposition technique (PLD). The microstructure of the film was examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The analyses indicate that the deposited samples are amorphous CN_x:B thin films. Field electron emission characteristics of amorphous CN_x:B thin films were measured in a vacuum chamber with a base pressure of about 3.2×10⁻⁵ Pa. The turn-on field of the film was 3.5 V/μm. The current density was 60 μA/cm² at an electric field of 9 V/μm. The experimental results indicate that this film could be a promising material applicable to cold cathodes.     

非晶碳/Mo_2C混合膜冷阴极FED发光显示

对Al2O3陶瓷衬底进行粒度为W20的金刚砂机械抛光,采用磁控溅射方法镀过渡层Mo,对其表面进行Nd∶YAG激光刻蚀处理。最后在微波等离子体增强化学汽相沉积(MPCVD)反应腔中在一定条件下沉积了薄膜,反应气体为CH4和H2。从样品的Raman谱可以看出薄膜有非晶碳成分。样品XRD谱线中有比较明显的晶态Mo2C衍射峰。所制备的样品为非晶碳/Mo2C混合结构薄膜。在高真空室中测量了样品的场发射特性,其开启场强为0.55V/μm,在1.8V/μm电场下测得样品的场发射电流密度为6.8mA/cm2。由样品CCD照片观察其发射特性可以看出,样品发射点密度随场强的增大而增加,发射点比较均匀。同时计算样品在2.2V/μm场强下样品发射点密度大于103/cm2。实验表明该薄膜是一种好的场致电子发射体。     

Influence of annealing temperature on field emission from tetrapod-shaped ZnO-whisker films obtained by screen printing

Tetrapod-shaped zinc oxide whisker-film emitters were fabricated on indium tin oxide glass substrates using a screen-printing method. The influence of annealing temperature on field emission of tetrapod-whisker ZnO-based emitters was investigated. X-ray diffraction and scanning electronic microscopy were applied to characterize the structure and the surface morphology of the deposited films. It was found that ZnO-based emitters annealed at 250 °C have the best field emission properties with the lowest turn-on field of 2.6 V/μm at a current density of 1 μA/cm², the lowest threshold field of 5.2 V/μm at a current density of 1 mA/cm² and high field emission enhancement factor of 4129. Moreover, films with homogeneous, fine and dense light spots with low emission current fluctuation of 1.7% were obtained from samples annealed at 250 °C.     

MOCVD生长的SiC衬底高迁移率GaN沟道层AlGaN/AlN/GaN HEMT结构

用MOCVD技术在高阻6H-SiC衬底上研制出了具有高迁移率GaN沟道层的AlGaN/AlN/GaN高电子迁移率晶体管(HEMT)结构材料,其室温和80K时二维电子气迁移率分别为1944和11588cm2/(V·s),相应二维电子气浓度为1.03×1013cm-2;三晶X射线衍射和原子力显微镜分析表明该材料具有良好的晶体质量和表面形貌,10μm×10μm样品的表面粗糙度为0.27nm.用此材料研制出了栅长为0.8μm,栅宽为1.2mm的HEMT器件,最大漏极饱和电流密度和非本征跨导分别为957mA/mm和267mS/mm.     

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.     

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.     

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。     

Improvement of the field emission properties of carbon nanotubes by CNT/Fe_3O_4 composite electrophoretic deposition

A simple CNT/Fe_3O_4 composite electrophoretic deposition method to improve the field emission cathode properties of carbon nanotubes(CNTs) is proposed.It is found that CNT/Fe_3O_4 composite electrophoretic deposition leads to better field emission performance than that of single CNT electrophoretic deposition.The result is investigated using SEM,J-E and FE.After the process,the turn-on electric field decreases from 0.882 to 0.500 V/μm at an emission current density of 0.1 mA/cm~2,and the latter increase...     

碳纳米管场发射冷阴极的低温制备及场发射性能

利用纳米银的低温熔接性和良好导电性,研究了以纳米银取代传统的有机粘结剂和导电银浆制备CNTs场发射冷阴极的新工艺.将CNTs、纳米银、粘性松油醇和有机溶剂混合研磨后涂敷在镀Cu玻璃基片上,250℃烧结30min后,纳米银颗粒之间互相熔接,将周围的CNTs粘结成为整体膜,形成了表面平整、导电性和场发射性能良好的CNTs阴极.测量了不同纳米银掺入量的CNTs阴极的场发射性能,结果表明:当CNTs:Ag质量比率为1:1时,CNTs阴极具有最好的场发射性能,阈值电场为4.9V/μm,当电场强度为5.7V/μm时,场发射电流密度为41mA/cm2.纳米银比例过大,烧结后CNTs被熔接的银膜覆盖,高电压时场发射电流明显下降,而纳米银掺入量太少则会导致CNTs阴极的附着力和导电性变差.     

Preparation, characterization and oxide CMP performance of composite polystyrene-core ceria-shell abrasives

To improve their chemical mechanical polishing (CMP) performance, composite polystyrene-core ceria-shell (PS/CeO₂) abrasives were synthesized by in-situ chemical precipitation. The as-synthesized PS/CeO₂ composite microspheres samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and zeta potential analysis. Oxide CMP performance of the PS/CeO₂ composite abrasives was investigated by atomic force microscopy (AFM). The results indicate that PS/CeO₂ composite abrasives with a core-shell structure are obtained successfully. The particle size of as-prepared PS/CeO₂ composite particles is about 140 nm, and the PS microspheres are uniformly coated by CeO₂ nanoparticles. The surface of thermal oxide film polished by PS/CeO₂ composite abrasives has lower topographical variations and surface roughness than that polished by CeO₂ nanoparticles. After polished by composite abrasives, root-mean-square roughness of wafer within 5 μm × 5 μm area is 0.331 nm, and material removal rate can reach 484.5 nm/min.     

不锈钢衬底的预处理条件对碳纳米管薄膜场发射性能的影响

在不同预处理条件的不锈钢衬底上,利用微波等离子体化学气相沉积(MWPCVD)方法从甲烷和氢气的混合气体中沉积碳纳米管薄膜,并对其场发射性能进行了研究.实验发现,不锈钢衬底的机械抛光和酸洗,能降低碳纳米管膜的开启场强,增大它的发射电流密度.在场强为6.25V/μm时,衬底未处理样品的电流密度为1.2mA/cm2,而衬底抛光的样品和衬底抛光又酸洗的样品的电流密度分别达到3.2和2.75mA/cm2.衬底只需机械抛光,而不需要酸洗,就能改良碳纳米管膜的场发射性能.