高温退火对非晶CNx薄膜场发射特性的影响

采用射频磁控溅射方法在纯N2气氛中沉积了非晶CNx薄膜样品,并在真空中退火至900 ℃.对高温退火引起的CNx薄膜化学成分、键合结构及其场发射特性方面的变化进行研究.用傅里叶变换红外光谱和x射线光电子能谱分析样品的内部成分及键合结构的变化,其中sp2键及薄膜中N的含量与薄膜的场发射特性密切相关.退火实验的结果表明高温退火可以导致CNx薄膜中N含量大量损失,并在薄膜中形成大量sp2键,这些化学成分及键合结构上的变化将直接影响CNx薄膜的场发射特性.与其他温度退火样品相比,750 ℃退火的样品具有最低的阈值电场,显示出较好的场发射特性.     

高温退火处理下SiNx薄膜组成及键合结构变化

采用等离子增强化学气相沉积法, 以氨气和硅烷为反应气体, p型单晶硅为衬底, 低温下(200 ℃)制备了非化学计量比氮化硅(SiN_x)薄膜. 在N₂氛围中, 于500–1100 ℃范围内对薄膜进行热退火处理. 室温下分别使用Fourier变换红外吸收(FTIR)光谱技术和X射线光电子能谱(XPS)技术测量未退火以及退火处理后SiN_x薄膜的Si–N, Si–H, N–H键键合结构和Si 2p, N 1s电子结合能以及薄膜内N和Si原子含量比值R的变化. 详细讨论了不同温度退火处理下SiN_x薄膜的FTIR和XPS光谱演化同薄膜内Si, N, H原子间键合方式变化之间的关系. 通过分析FTIR和XPS光谱发现退火温度低于800 ℃时, SiN_x薄膜内Si–H和N–H键断裂后主要形成Si–N键; 当退火温度高于800 ℃时薄膜内Si–H和N–H键断裂利于N元素逸出和Si纳米粒子的形成; 当退火温度达到1100 ℃时N₂与SiN_x薄膜产生化学反应导致薄膜内N和Si原子含量比值R增加. 这些结果有助于控制高温下SiN_x薄膜可能产生的化学反应和优化SiN_x薄膜内的Si纳米粒子制备参数. 关键词： x薄膜')" href="#">SiN_x薄膜 Fourier变换红外吸收光谱 X射线光电子能谱 键合结构     

含氮氟化类金刚石(FN-DLC)薄膜的研究：(Ⅳ)氮掺杂对薄膜结构的影响

不同条件下，在单晶硅基片上沉积了含氮氟化类金刚石(FN-DLC)薄膜.原子力显微(AFM)形貌显示，掺N后，薄膜变得致密均匀.傅里叶变换吸收红外光谱(FTIR)表明，随着r(r=N₂/［N₂+CF₄+CH₄］)的增大薄膜中C—H键的逐渐减少，C〖FY=,1〗N和C≡N键含量逐渐增加.X射线光电子能谱(XPS)的C1s和N1s峰拟合结果发现，N掺入导致在薄膜中出现β-C₃N₄和a-CN_x(x=1,2,3)成分.Roman散射谱的G峰向高频方向位移和峰值展宽等证明：随着r的增大，薄膜内sp²键态含量增加. 关键词： 氟化类金刚石膜 键结构 氮掺杂     

类富勒烯纳米晶CNx薄膜及其场致电子发射特性

利用微波等离子体增强化学气相沉积技术制备出了CN_x薄膜,并利用x射线光电子能谱、x射线衍射、扫描电子显微镜和Raman光谱等测试手段对所制备的CN_x薄膜的微结构和成分进行了分析.研究了其场致电子发射特性.发现薄膜的结构和场发射特性与反应系中的甲烷、氮气及氢气的流量比有关,当甲烷、氢气及氮气流量比为8/50/50 sccm时,制备的薄膜具有弯曲层状的纳米石墨晶体结构（类富勒烯结构）和很好的场发射特性.场发射阈值电场降低至1.1V/μm.当电场为5.9V/μm时,平 关键词： 类富勒烯 x薄膜')" href="#">CN_x薄膜 场致电子发射 微波等离子体增强化学气相沉积     

含氮氟化类金刚石(FN-DLC)薄膜的研究：(Ⅰ) sp结构与化学键分析

以CF₄，CH₄和N₂为源气体，利用射频等离子体增强化学气相沉积法，在不同功率下制备了含氮氟化类金刚石膜.用俄歇电子能谱、拉曼光谱、X射线光电子能谱和傅里叶变换红外光谱对薄膜的电子结构和化学键进行了表征，并结合高斯分峰拟合方法分析了薄膜中sp²，sp³结构比率.结果表明，制备的薄膜属于类金刚石结构，不同沉积功率下，薄膜内的sp²/sp³值在2.0—9.0之间，随着沉积功率的增加薄膜内sp²的相对含量增加.膜内主要有C—F_x(x=1，2)，C—C，C=C和C≡N等化学键.沉积功率增加，C—C基团增加，膜内F的浓度降低，C—F基团减少，薄膜的关联加强，稳定性提高. 关键词： 含氮氟化类金刚石膜 sp结构 化学键结构 射频功率     

类金刚石和碳氮薄膜的电化学沉积及其场发射性能研究

利用电化学方法在室温下成功地沉积了类金刚石(DLC)薄膜和非晶CN_x薄膜，并 对制备条件进行了讨论.通过扫描电子显微镜、傅里叶变换红外光谱技术，分析了薄膜的表面形貌和化学结合状态.场发射测量结果表明：DLC膜和非晶CN_x的开启场分别为88和 10V/μm；并且在23V/μm的电场下，DLC膜和非晶CN_x膜的发射电流密度分别达到10 和037mA/cm². 关键词： 电化学沉积 类金刚石薄膜 x薄膜')" href="#">CN_x薄膜 场致电子发射     

不同氮源制备CNx纳米管薄膜及其低场致电子发射性能

采用高温热解法，分别以氯化铵(NH₄Cl)和乙二胺(C₂H₈N₂)为氮源在洁净的硅片上沉积生长CN_x纳米管薄膜.利用扫描电子显微镜、高分辨率透射电子显微镜和拉曼光谱对CN_x纳米管进行形貌观察和表征.结果显示不同氮源制备出的CN_x纳米管薄膜的洁净度、有序度以及纳米管的结构明显不同.热解乙二胺(C₂H₈N₂)/二茂铁(C₁₀H₁₀Fe)制备出的结晶度较低的“竹节状” 结构CN_x纳米管平行基底表面有序生长，而且低场致电子发射性能优越,开启电场1.0V/μm，外加电场达到2.89V/μm时发射电流密度为860μA/cm². 关键词： x纳米管')" href="#">CN_x纳米管 高温热解 “竹节状”结构 场致发射     

高能氮离子轰击对四面体非晶碳膜的表面改性和摩擦系数影响的研究

利用过滤阴极真空电弧技术制备了sp³键含量不小于80%的四面体非晶碳(ta-C)膜.利用冷阴极潘宁离子源产生不同能量的氮离子对制备的ta-C薄膜进行轰击,通过X射线光电子能谱和原子力显微镜对薄膜表面结构与形貌进行分析研究.研究表明,随着氮离子的轰击能量的增大,薄膜中的CN键结构略有增大,形成了轻N掺杂;同时,在薄膜表层发生了sp³键结构向sp²键结构的转化;薄膜的表面粗糙度在经过氮离子轰击后从0.2 nm减小至0.18 nm,然后随着轰击能 关键词： 四面体非晶碳 X射线光电子能谱 摩擦系数     

N离子注入对金刚石膜场发射特性的影响

不同剂量的N离子被注入到化学气相沉积金刚石膜内，研究了表面结构及场发射特性的变化.Raman谱和x射线光电子能谱分析表明，N离子的注入破坏了金刚石膜表面原有的sp3结构，并在膜内形成大量的sp2 C—C 和sp2 C—N 键.样品的场发射测试显示N离子的注入显著提高了金刚石膜场发射特性，膜的场发射阈值电场从注入前的18 V/μm下降到注入后的4 V/μm.金刚石膜场发射特性的提高归因于N离子注入后膜内sp2 C键含量的增加和体内缺陷带的形成，这些变化能改变膜的表面功函数，提高Feimi能级，降低电子隧穿表面的能量势垒. 关键词： 场致电子发射 N离子注入 金刚石膜 热丝化学气相沉积     

射频溅射法制备3C-SiC和4H-SiC薄膜

利用射频溅射法在Si衬底上制备了SiC薄膜，并利用x射线衍射（XRD）和红外（IR）吸收谱对薄膜的结构、成分及化学键合状态进行了分析.XRD结果表明，低温制备的SiC薄膜为非晶相，而在高温下（＞800℃），薄膜呈现4HSiC和3CSiC结晶相.IR谱显示，溅射制备薄膜的吸收特性主要为Si—C键的吸收.此外，还利用原子力显微镜对薄膜的表面形貌进行了研究，并研究了样品的场发射特性. 关键词： 射频溅射 SiC薄膜 结构 表面形貌 场发射     

Effect of N2 ambient annealing on the field emission properties of HfNxOy thin films

HfN_xO_y thin films were deposited on Si substrates by direct-current sputtering. The influence of N₂ ambient annealing on the morphology, structure and field emission properties of the HfN_xO_y thin films was studied systematically. Scanning electron microscopy indicates that both the as-deposited and the annealed films are composed of nanoparticles, and the particle sizes of these films do not change much before and after annealing. Atomic force microscopy shows that the surface of the as-deposited films is smooth while that of the annealed films becomes rough, with many protrusions. X-ray diffraction patterns demonstrate that the as-deposited films are amorphous while the samples annealed at over 500 °C are polycrystalline. It is found that the field electron emission properties of the annealed films are better than those of the as-deposited films. The film annealed at 800 °C shows the best field emission properties. The mechanism for the improvement of the field electron emission property of the annealed thin films is also discussed. PACS 73.61.-r; 79.70.+q; 81.05.-t     

碳、碳氮和硼碳氮纳米管场发射性能的比较研究

采用高温热解法在860℃分别制备出了碳、碳氮和硼碳氮纳米管，提纯后利用丝网印刷工艺分别将它们制备成薄膜，并测试了它们的场发射性能.结果表明：碳纳米管、碳氮纳米管和硼碳氮纳米管薄膜的开启电场分别为2.22，1.1和4.4V/μm，当电场增加到5.7V/μm时，它们的电流密度分别达到1400，3000μA/cm²和小于50μA/cm².碳和碳氮纳米管薄膜的场增强因子分别为10062和11521.可见，碳氮纳米管的场发射性能优于碳纳米管，而硼碳氮纳米管的场发射性能比前两者要差.解释了这三种纳米管场发射性能差别的原因. 关键词： 碳纳米管 碳氮纳米管 硼碳氮纳米管 场发射     

Annealing effects on the bonding structures, optical and mechanical properties for radio frequency reactive sputtered germanium carbide films

The effects of thermal annealing in vacuum on the bonding structures, optical and mechanical properties for germanium carbide (Ge_1−xC_x) thin films, deposited by radio frequency (RF) reactive sputtering of pure Ge(1 1 1) target in a CH₄/Ar mixture discharge, are investigated. We find that there are no significant changes in the bonding structure of the films annealed below 300 °C. The fraction of Ge-H bonds for the film annealed at temperatures (T_a) above 300 °C decreases, whereas that of C-H bonds show a decrease only when T_a exceeds 400 °C. The out-diffusion of hydrogen promotes the formation of Ge-C bonds at T_a above 400 °C and thus leads to a substantial increase in the compressive stress and hardness for the film. The refractive indices and optical gaps for Ge_1−xC_x films are almost constant against T_a, which can be ascribed to the unchanged ratios of Ge/C and sp²-C/sp³-C concentrations. Furthermore, we also find that the excellent optical transmission for an antireflection Ge_1−xC_x double-layer film on ZnS substrate is still maintained after annealing at 700 °C.     

Bonding configurations in amorphous carbon and nitrogenated carbon films synthesised by femtosecond laser deposition

The effect of nitrogen addition and laser fluence on the atomic structure of amorphous carbon films (a-C) synthesized by femtosecond pulsed laser deposition has been studied. The chemical bonding in the films was investigated by means of X-ray photoelectron (XPS) and Raman spectroscopies. XPS studies revealed a decrease in the sp³ bonded carbon sites and an associated increase in the N-sp²C bonding sites with increasing nitrogen content in the CN_x films. An increase in laser fluence from 0.36 to 1.7 J/cm² led to a rise in sp³C sites. These results were further confirmed by Raman spectroscopy. The I_D/I_G ratio increased monotonically and G line-width decreased with the increase of nitrogen content in the films indicating a rise in either the number or the size of the sp² clusters. Furthermore a visible excitation wavelength dependence study established the resonant Raman process in a-C and CN_x films. PACS 81.05.Uw; 81.15.Fg; 82.80     

Role of carbon in the formation of hard Ge1−xCx thin films by reactive magnetron sputtering

We have deposited germanium carbide (Ge_1−xC_x) films on Si(1 0 0) substrate via radio-frequency (RF) reactive magnetron sputtering in a CH₄/Ar mixture discharge, and explored the effects of carbon content (x) on the chemical bonding and hardness for the obtained films. We find that x significantly influences the chemical bonding, which leads to a pronounced change in the hardness of the film. To reveal the relationship between the chemical bonding and hardness, first-principles calculations have been carried out. It is shown that as x increases from 0 to 0.33, the fraction of sp³ C-Ge bonds in the film increases at the expense of Ge-Ge bonds, which promotes formation of a strong covalently bonded network, and thus enhances the hardness of the film. However, as x further increases from 0.33 to 0.59, the fraction of sp³ C-Ge bonds in the film gradually reduces, while that of sp³ C-H and graphite-like sp² C-C bonds increases, which damages the compact network structure, resulting in a sharp decrease in the hardness. This investigation suggests that the medium x (0.17<x<0.40) is most favorable to the preparation of hard Ge_1−xC_x films due to the formation of dominant sp³ C-Ge bonds.     

Effect of ECR-assisted microwave plasma nitriding treatment on the microstructure characteristics of FCVA deposited ultra-thin ta-C films for high-density magnetic storage applications

There are higher technical requirements for protecting layer of magnetic heads and disks used in future high-density storage fields. In this paper, ultra-thin (2 nm thickness) tetrahedral amorphous carbon (ta-C) films were firstly prepared by filtered cathodic vacuum arc (FCVA) method, then a series of nitriding treatments were performed with nitrogen plasma generated using electron cyclotron resonance (ECR) microwave source. Here it highlighted the influence of nitrogen flow and applied substrate bias voltage on the structural characteristics of ta-C films during the plasma nitriding process. The chemical compositions, element depth distribution profiles, physical structures and bonding configurations of plasma-nitrided ta-C films were investigated by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and UV-vis Raman spectroscopy. The experimental results show that the carbon nitride compounds (CN_x) are formed in nitrogenated ta-C films in which the N content and its depth distribution depends on bias voltage to large extent rather than N₂ flow. The N content of nitrogenated ta-C films can reach 16 at.% for a substrate bias of −300 V and a N₂ flow of 90 sccm. With increasing nitrogen content, there is less G peak dispersion and more ordering of structure. Furthermore, appropriate nitriding treatment (substrate bias: −100 V, N₂ flow: 150 sccm) can greatly increase the fraction of sp³ and sp³C-N bonds, but the values begin to fall when the N content is above 9.8 at.%. All these indicate that suitable ECR-assisted microwave plasma nitriding is a potential modification method to obtain ultra-thin ta-C films with higher sp³ and sp³C-N fractions for high-density magnetic storage applications.     

Annealing effects on the structure and electrical characteristics of amorphous Er2O3 films

Amorphous Er 2 O 3 films are deposited on Si (001) substrates by using reactive evaporation.This paper reports the evolution of the structure,morphology and electrical characteristics with annealing temperatures in an oxygen ambience.X-ray diffraction and high resolution transimission electron microscopy measurement show that the films remain amorphous even after annealing at 700 C.The capacitance in the accumulation region of Er 2 O 3 films annealed at 450 C is higher than that of as-deposited films and films annealed at other temperatures.An Er 2 O 3 /ErO x /SiO x /Si structure model is proposed to explain the results.The annealed films also exhibit a low leakage current density (around 1.38 × 10 4 A/cm 2 at a bias of 1 V) due to the evolution of morphology and composition of the films after they are annealed.