【作者】 张宇；

【导师】 周灵平； 杨武霖；

【作者基本信息】 湖南大学 ， 材料科学与工程， 2017， 硕士

【摘要】 金刚石薄膜具有良好的化学稳定性、较低的功函数和电子亲和势等优异的物理化学特性,是一种在真空微电子器件和平板显示器等方面有着广阔应用前景的场发射冷阴极材料。因此,对金刚石薄膜组织结构和场发射性能的研究具有重要的学术价值和应用背景。本文在对CVD设备的热丝拉伸装置、热丝与进气口距离以及样品台旋转进行改造的基础上,采用热丝化学气相沉积方法在基底单晶硅(100)表面沉积金刚石薄膜;采用XRD、Rarman和XPS等测试方法表征金刚石薄膜的微观结构,通过EFE和Hall效应测试其电学特性和场发射性能;研究了反应气压、碳源浓度、氩气浓度及金属过渡层对金刚石薄膜微观结构和场发射性能的影响,并对金属过渡层改善微米金刚石薄膜场发射性能的机理进行了详细分析,主要研究结果如下:反应气压、碳源浓度、氩气浓度及金属过渡层对金刚石薄膜的微观结构均有显著的影响。其中碳源浓度对金刚石的晶粒尺寸调控最为明显,随着甲烷浓度的降低,金刚石的晶粒尺寸由纳米量级逐渐变为微米级,在甲烷浓度为2.8%时晶粒尺寸可达到2.35μm;反应气压对膜层沉积速率的影响最显著,膜层沉积速率随着反应气压的降低逐渐增大,在反应气压为1.5 kPa时沉积速率可达6.2 μm/h;氩气浓度的变化和金属过渡层的添加对金刚石薄膜组织结构和相成分有显著的调控影响,使金刚石薄膜中非金刚石相发生明显的变化。通过不同工艺对金刚石薄膜结构的调控,实现了对其场发射性能的优化。在H2/CH4反应体系中,当反应气压为4kPa和甲烷浓度为14.3%时,金属过渡层的引入使微米金刚石/金属/硅复合薄膜的电学性能和场发射性能增强,MCD/W/S i复合薄膜电导率比无过渡层高两个数量级;开启场强为5.4 V/μm,比无过渡层降低了 44%;场发射电流密度在电场强度为8.9 V/μm时可达到1482 μA/cm2。金属过渡层不仅改善膜基界面特性,疏通电子迁移的界面通道,而且使金刚石薄膜内sp2碳含量增加,为电子运输提供更多导电通道,有益于获得更高的场发射电流,进而表现出良好的场发射性能。在H2/CH4/Ar反应体系中制备的纳米金刚石薄膜表现出优异的场发射性能,随着Ar浓度增加,场发射性能显著增强,其中当反应气压为2kPa、甲烷浓度为14.3%、氩气浓度为45.7%时,表现出最优的场发射性能,开启场强低至3.8 V/μm、场发射电流密度在6.5 V/μm时可达2125 μA/cm2。更多还原

【Abstract】 Diamond film has good chemical stability,low work function and electron affinity and other excellent physical and chemical characteristics,and it is a field emission cold cathode material that has a broad application prospect in areas such as vacuum microelectronics devices and graphic displays.Therefore,the study on the microstructure and field emission property of diamond films holds important academic value and application background.Based on the alteration of hot wire drawing device,the distance between the hot filament and the inlet,and the rotation of the sample stage,deposition of diamond thin film by hot filament chemical vapor deposition method in the basement single crystal silicon(100)surface;the microstructure of the diamond films were characterized by XRD,Raman and XPS,and etc.The electrical property and field emission property of the diamond films were characterized by EFE and Hall effects.It studied the influence reaction pressure,carbon source concentration,argon concentration and metal transition layer had on the micro structure and field emission property of the diamond film,and did a detailed analysis on the mechanism of the metal transition layer to improve the field emission property of diamond films.The main results are as below:Reaction temperature,carbon source concentration,argon concentration and metal transition layer all had a significant influence on the microstructure of diamond film,among which carbon source concentration had the most obvious regulation and controlled on the grain size of the diamond.With the decrease of the methane concentration,the grain size was 2.35 μm when the methane concentration was 2.8%;the influence reaction gas pressure had on the deposition rate of the film was the most significant,as deposition rate increases with the decrease of the reaction pressure,and the deposition rate was up to 6.2 μm/h at the reaction pressure of 1.5 kPa;the change of argon concentration and the addition of the metal transition layer had a significant control influence on microstructure and phase composition of the diamond film,which made non-diamond phase change significantly in diamond film.Through different processes controlled the structure of diamond film,achieving its field emission performance optimization,when the reaction gas pressure was 4 kPa,the methane concentration was 14.3%in the H2/CH4 reaction system,metal transition layer optimized electrical properties and field emission properties of micron diamond/metal/silicon composite film,conductivity of MCD/W/Si composite structure of the film was two orders of magnitude higher than the transition layer;open field strength was 5.4 V/μm,which was 44%lower than that of the non-transition layer;field emission current density could reach 1482 μA/cm2 when the electric field intensity was 8.9 V/μm.The metal transition layer could not only improve interface characteristics and clear the interface channel of electron transport,but also increased the content of sp2 in the diamond film,and provided more conductive channels for the electronic transportation,which helped to obtain a higher field emission current,and then good field emission property should present.The nano-diamond films with excellent field emission properties prepared in the H2/CH4/Ar reaction system.With the increase of Ar concentration,the field emission properties was significantly enhanced;when the reaction gas pressure was 2 kPa,the methane concentration was 14.3%and the argon concentration was 45.7%,the diamond film exhibited the best field emission properties;open field was as low as 3.8 V/μm,and current density could achieve 2125 μA/cm2 while electric field intensity was 6.5 V/μm.更多还原