镍硅颗粒膜的表面传导电子发射特性

本文提出采用镍硅颗粒薄膜作为表面传导电子发射显示的发射体材料,通过光刻和磁控溅射在两电极(10μm间隙)之间制备30 nm厚的镍硅颗粒膜。施加三角波电压进行电形成工艺,并测试了器件的电学特性。获得主要结果有,在器件阳极电压2000 V和器件阴极电压13 V的作用下,可以重复探测到稳定的器件发射电流,并且随器件阴极电压的增加而明显增加,最大的发射电流达到了1.84μA(共18个单元);电形成过程中,单个发射体单元的薄膜电阻从13Ω增加到10913Ω;通过对器件发射电流的Fowler-Nordheim结分析,可以确定电子发射机理属于场致电子发射。     

冷轧钢表面硅锆复合膜的制备及其耐腐蚀性能

纯硅烷膜耐腐蚀性能不理想,经掺杂改性处理后可得到改善。以硝酸锆掺杂1,2-双(三甲氧基硅基)乙烷(BTMSE),在冷轧钢基体表面制备了无机/有机复合硅烷膜。采用电化学技术及硫酸铜点滴试验对比考察了复合硅烷膜与纯硅烷膜的耐腐蚀性能。结果表明:相比于纯硅烷膜,锆盐掺杂硅烷复合膜的腐蚀电位、极化电阻明显增大,腐蚀电流密度明显降低,耐腐蚀性能提高;硝酸锆在金属表面形成了含有ZrO2+的夹杂化合物层,起到物理阻隔作用,进而提高了硅烷膜的耐腐蚀性能。     

Co~(2+)掺杂聚苯胺复合薄膜的电化学合成及抗腐蚀性能的研究

在含有苯胺(PANI)、硝酸(HNO3)和硝酸钴[Co(NO3)2·6H2O]的溶液中,采用循环伏安法(CV)在不锈钢基底表面制备PANI/Co2+复合薄膜。利用傅里叶红外光谱(FT-IR)、X射线衍射(XRD)等手段对其结构和形貌进行表征。在0.5mol/L H2SO4中,通过循环伏安测试(CV)、交流阻抗(EIS)、塔菲尔(Tafel)曲线对PANI/Co2+复合薄膜的耐腐蚀性能进行了研究。结果表明,不锈钢表面覆盖掺杂态聚苯胺膜后,其腐蚀电位比纯聚苯胺膜时提高,可以显著降低腐蚀电流密度,并且Co2+浓度会影响掺杂态膜的耐腐蚀性。     

纳米多孔硅的电化学制备及性能研究

纳米多孔硅是一种潜在的化学和生物传感材料,本文采用电化学腐蚀法制备纳米多孔硅。采用SEM技术分析多孔硅的表面形貌,研究了腐蚀条件对多孔硅的孔隙率、厚度、I-V特性的影响。结果表明,多孔硅的孔隙率随着腐蚀电流密度和腐蚀时间的增加而呈线性增大趋势;其厚度随着腐蚀电流密度的增加而近似呈线性增大趋势,随腐蚀时间的成倍增加而显著增大;其I-V特性表现出非整流的欧姆接触。     

图案化厚膜多孔硅制备与表征

图案化多孔硅是微电子、微机械、光电子器件的重要组成部分.实验以含Si3N4保护层的光刻单晶硅片为基底,采用电化学阳极氧化法制备图案化厚膜多孔硅,分析阳极氧化前后Si3N4保护层表面形貌变化特征和光刻尺寸对图案化多孔硅宽度、膜层厚度的影响规律,表征图案化多孔硅的结构、组成与发光性能.结果表明,氧化前Si3N4保护层局部区域出现枝晶,阳极氧化后形成不均匀孔状结构;制备的图案化多孔硅膜厚62～83μm,其横向扩展程度和膜层厚度均随光刻尺寸增大呈减小趋势;图案化多孔硅微结构含大量不规则裂纹和硅柱,新鲜制备的表面含Si-Hx键,其光致发光峰值波长650nm.     

专利技术

一种氮氧化物气体传感器元件的制备方法申请(专利)号:201210400849.9公开(公告)日:2013-03-27申请(专利权)人:天津大学摘要:本发明公开了一种氮氧化物气体传感器元件的制备方法,步骤为:(1)对n型单面抛光的单晶硅片进行清洗;(2)采用双槽电化学腐蚀法在硅片的抛光表面制备孔径尺寸在50~200 nm的硅基孔洞有序多孔硅,腐蚀液为6%~8%的氢氟酸水溶液,施加的腐蚀电流密度为115~135mA/cm2,腐蚀时间为5~25 min;(3)再将多孔硅置于超高真空对靶磁控溅射设备的真空室,制备基     

多孔硅气体传感器的制备及其气敏性能的研究

以P+型硅片为基底,利用双槽电化学腐蚀方法制备不同孔隙率的多孔硅(Porous Silicon),介绍多孔硅气体传感器的原理和优点,通过SEM和AFM对PS薄膜的表面形貌进行分析,研究不同孔隙率条件下PS薄膜的气敏灵敏特性.结果表明:随着孔隙率的增加,PS薄膜的响应/恢复时间不断减小,薄膜对空气中较低浓度的NO2(体积分数为0.1×10-6～6×10-6)具有优异的敏感特性和响应特性.     

Fe(V)-MCM-48的合成、表征和催化性能的研究

制备了不同硅铁(钒)比的中孔分子筛Fe(V)-MCM-48,通过XRD、红外(IR)、氮气吸附-脱附和透射电镜(TEM)等分析手段对产物进行结构表征并研究了样品对苯羟基化制备苯酚的催化性能。结果表明,金属离子掺杂量以及制备过程中原料的加入顺序都对样品结构有很大影响。在适量金属掺杂量下,通过先加金属盐后加硅源的方法得到具有完好MCM-48型中孔特征结构的Fe(V)-MCM-48。以Fe-MCM-48或V-MCM-48为催化剂,双氧水作氧化剂,详细考察了金属掺杂量、催化剂用量和反应时间对苯羟基化反应的影响。结果表明,在70℃下反应时间6h时,苯/双氧水摩尔比为1:5,催化剂用量0.1g时,Fe-MCM-48(n(Si)/n(Fe)=40)和V-MCM-48(n(Si)/n(V)=20)具有较高的催化活性,苯的转化率分别为9.5%和9.7%。     

AZ31镁合金基Cu-MOF-SA超疏水膜的制备及其耐腐蚀性能研究

腐蚀是影响镁及其合金大规模应用的关键技术难题之一,因可有效隔离金属基底与腐蚀介质的直接接触,从而降低腐蚀速率,制备超疏水表面成为提高镁合金耐蚀性的有效途径。通过一步电沉积方法,在AZ31镁合金基底上成功制备了铜-金属有机骨架-硬脂酸(Cu-MOF-SA)超疏水膜,并对超疏水膜的耐腐蚀性、化学稳定性和耐热性进行了综合研究。结果表明,表面的水接触角可达158°,超疏水膜覆盖的试样在3.5%NaCl溶液中表现出良好的耐腐蚀性能,相比AZ31镁合金基底,其腐蚀电位正移了0.24 V,腐蚀电流密度降低了1个数量级。在pH值为1～14的溶液中浸润24 h后,超疏水膜的水接触角仍可达135°以上,浸泡在pH=1的溶液24 h的超疏水膜的腐蚀电位比AZ31镁合金基底高0.21 V。在20～90℃空气中保温24 h后,超疏水膜的水接触角仍保持在154°以上,80℃下保温24 h后其腐蚀电位比AZ31镁合金基底的高0.22 V,腐蚀电流密度比AZ31镁合金基底的小1个数量级。结果表明,本研究制备的Cu-MOF-SA疏水膜具有良好的超疏水性和耐腐蚀性。     

笼网型空心阴极氩气放电特性研究

采用高功率脉冲电源,研究了氩气气氛下工作气压、脉冲电压和频率等参数对笼网型空心阴极放电特性的影响,并对等离子体发射光谱进行了分析。结果发现:在脉冲电压增加到一定程度,脉冲电流随时间呈指数型(n1)激增。提高工作气压、脉冲频率及脉冲电压,笼型空心阴极放电增强。脉冲峰值电流随气压和脉冲电压的升高而增大,但随频率增大呈现降低趋势。光谱分析表明,氩气笼型空心阴极放电主要物种是Ar*和Ar+粒子,随脉冲电压、工作气压及频率的增大,Ar*和Ar+粒子数量增多。     

Effects of porous silicon morphology on ballistic electron emission

Porous silicon ballistic electron emission source with a structure of metal/porous silicon/Si/metal is obtained by anodization, rapid thermal oxidation, and sputtering. The microstructures of porous silicon layers are characterized by means of scanning electron microscope. The results show that disordered pores are formed at anodization current densities of 15 mA/cm2, 30 mA/cm2, and 45 mA/cm2 for 5 min, respectively. However, straight pores are formed at anodization current densities of 60 mA/cm2, and 75 mA/cm2 for 5 min, respectively. The electron emission characteristic of porous silicon ballistic electron emission sources is measured in vacuum. The results show that electrons emitted into the vacuum from the porous silicon samples with disordered pores. Under a bias condition, injected electrons from the substrate are accelerated by the strong electric field on the surfaces of the Si nanocrystallites in disordered pores, and then emitted into the vacuum through Pt film. However, no electron emission is observed in porous silicon samples with straight pores. It attributes to the lack of Si nanocrystallites in straight pores. So there is not accelerating tunnels enough for electrons. According to disordered or straight pores, we can estimate whether PS samples emit electrons or not.     

Highly ordered hexagonally arranged nanostructures on silicon through a self-assembled silicon-integrated porous anodic alumina masking layer

A combined process of electrochemical formation of self-assembled porous anodic alumina thin films on a Si substrate and Si etching through the pores was used to fabricate ideally ordered nanostructures on the silicon surface with a long-range, two-dimensional arrangement in a hexagonal close-packed lattice. Pore arrangement in the alumina film was achieved without any pre-patterning of the film surface before anodization. Perfect pattern transfer was achieved by an initial dry etching step, followed by wet or electrochemical etching of Si at the pore bottoms. Anisotropic wet etching using tetramethyl ammonium hydroxide (TMAH) solution resulted in pits in the form of inverted pyramids, while electrochemical etching using a hydrofluoric acid (HF) solution resulted in concave nanopits in the form of semi-spheres. Nanopatterns with lateral size in the range 12-200?nm, depth in the range 50-300?nm and periodicity in the range 30-200?nm were achieved either on large Si areas or on pre-selected confined areas on the Si substrate. The pore size and periodicity were tuned by changing the electrolyte for porous anodic alumina formation and the alumina pore widening time. This parallel large-area nanopatterning technique shows significant potential for use in Si technology and devices.     

Al-assisted Anodic Etched Porous Silicon

The photoluminescence (PL) properties and the surface morphologies of the porous silicon (PS) prepared from the wafers whose front sides were coated with or without Al film were studied. Furthermore, the Fourier Transforms Infrared (FTIR) and the Raman spectra were carried out. By introducing the Al film onto the front side of the wafer before the anodic etching, the surface morphology of the PS was quite different from that of conventional PS, which can be explained by the formation mechanism of the PS. The different PL properties of the PS may be attributed to the discrepancy in the structural configuration of the samples.     

Effect of electroless etching parameters on the growth and reflection properties of silicon nanowires

Vertically aligned silicon nanowire (Si NW) arrays have been fabricated over large areas using an electroless etching (EE) method, which involves etching of silicon wafers in a silver nitrate and hydrofluoric acid based solution. A detailed parametric study determining the relationship between nanowire morphology and time, temperature, solution concentration and starting wafer characteristics (doping type, resistivity, crystallographic orientation) is presented. The as-fabricated Si NW arrays were analyzed by field emission scanning electron microscope (FE-SEM) and a linear dependency of nanowire length to both temperature and time was obtained and the change in the growth rate of Si NWs at increased etching durations was shown. Furthermore, the effects of EE parameters on the optical reflectivity of the Si NWs were investigated in this study. Reflectivity measurements show that the 42.8% reflectivity of the starting silicon wafer drops to 1.3%, recorded for 10 μm long Si NW arrays. The remarkable decrease in optical reflectivity indicates that Si NWs have a great potential to be utilized in radial or coaxial p-n heterojunction solar cells that could provide orthogonal photon absorption and enhanced carrier collection.     

Luminescent Properties of Porous Si Passivated by Diamond Film and DLC Film

Surface passivation methods for porous Si (PS) surfaces, i.e., depositing diamond film or diamond-like carbon (DLC) film on PS surfaces, were attempted. Two emission bands, weak blue band and strong red band existed in the PL spectrum of diamond film coated on PS, were discovered by the photoluminescence measurements. The luminescent mechanism and stability were discussed. The results indicated that diamond film may stabilize the PL wavelength and intensity of PS, and therefore could become a promising passivation film of porous Si. The PL properties of PS coated by DLC films, including hydrogenated diamond like carbon (DLC:H) film and nitrogen doped DLC film (DLC:N) were also studied in this paper. The DLC films may stabilize the PL of PS, but the photoluminescent intensity was obviously weaker than that of diamond film coated PS.     

Blue luminescence from porous layers produced by metal-assisted chemical etching on low-doped silicon

Photoluminescent porous layers were formed on highly resistive p-type silicon by a metal-assisted chemical etching method using K₂Cr₂O₇ as an oxidizing agent. A thin layer of Ag is deposited on the (1 0 0) Si surface prior to immersion in a solution of HF and K₂Cr₂O₇. The morphology of the porous silicon (PS) layer formed by this method as a function of etching time was investigated by scanning electron microscopy (SEM). It shows that the surface is formed by macropores filled with microporous silicon. The porous layers were characterized by backscattering spectrometry (BS) as a function of etching time in random and channelling mode. Channelling spectra show that the porous layer remains crystalline after etching. On the other hand, random and channelling spectra show that the deposited silver diffuses into the pore. Luminescence from metal-assisted chemically etched layers was measured. It was found that the PL intensity increases with increasing etching time. This behaviour is attributed to increase of the density of the silicon nanostructure. Finally, the PL spectra show two peaks of emission at 450 and 600 nm.     

Morphology and microstructure at different scales of porous silicon prepared by a nonconventional technique

In this work we present first results concerning the detailed structure of porous silicon (PS) layers prepared by a new method using a vapour-etching (VE)-based technique. Studies of the photoluminescence properties of VE-based PS show that the visible emission occurs at high energies as compared with PS prepared by conventional techniques. To understand the VE-based PS features, we need to point out the PS microstructure throughout its general morphology. For this purpose a microscopy multiscale study was done. Scanning, conventional transmission, and high-resolution transmission electron microscopes were employed. The investigations were made on PS films prepared from moderately and heavily doped n- and p-type silicon. SEM images show that VE-based PS layers are essentially formed of clusters like interconnected structures. TEM studies show that these clusters are composed of nanocrystallites with different shapes. The effect of the doping type of the starting Si substrate on the characteristics of the PS layers was examined (thickness, porosity, behavior). Pore propagation was found to depend on doping type. The crystallinity of the PS layers was also locally studied in depth.     

Optical and microstructural investigations of porous silicon

Raman scattering and photoluminescence (PL) measurements on (100) oriented n-type crystalline silicon (c-Si) and porous silicon (PS) samples were carried out. PS samples were prepared by anodic etching of c-Si under the illumination of light for different etching times of 30, 60 and 90 min. Raman scattering from the optical phonon in PS showed the redshift of the phonon frequency, broadening and increased asymmetry of the Raman mode on increasing the etching time. Using the phonon confinement model, the average diameter of Si nanocrystallites has been estimated as 2.9, 2.6 and 2.3 nm for 30, 60 and 90 min samples, respectively. Similar size of Si crystallites has been confirmed from the high resolution transmission electron microscopy (HRTEM). Using 2TO phonon mode intensity, we conjectured that the disordered Si region around the pores present in 30 min PS dissolved on etching for 90 min. The photoluminescence (PL) from PS increased in intensity and blue shifted with etching time from 2.1–2.3 eV. Blue shifting of PL is consistent with quantum confinement of electron in Si nanocrystallites and their sizes are estimated as 2.4, 2.3 and 2.1 nm for 30, 60 and 90 min PS, respectively which are smaller than the Raman estimated sizes due to temperature effect. Unambiguous dominance of quantum confinement effect is reported in these PS samples.     

Synthesis of ultra-small silicon nanoparticles by femtosecond laser ablation of porous silicon

We report a detailed study on the synthesis of ultra-small (1–10 nm) colloidal silicon nanoparticles (Si NPs) by ablating porous silicon (pSi) in acetone using femtosecond laser pulses. Porous silicon is considered as a target material for ablation because it contains a large number of light emitting silicon nanoparticles. The pSi samples were prepared by anodic etching of silicon in aqueous HF solution for different etching current densities. Transmission electron microscope measurements confirmed the successful formation of well-isolated spherical silicon nanoparticles. The average size of spherical NPs were estimated to be ~7.6, ~7, and ~6 nm when anodic etching current densities of 5, 10, and 20 mA/cm² were used respectively for preparing pSi targets. The crystallinity of these Si NPs was confirmed by selective area electron diffraction and Raman spectroscopy measurements. The observed blue shift in the absorption and emission spectra are attributed to reduction in the average particle size with increase in etching current density. These Si NPs may be useful for fabricating low-dimensional microelectronic compatible photonic devices.     

二氧化硅纳米颗粒的反应离子刻蚀及其在硅纳米针尖制备中的应用

系统地研究了硅衬底上二氧化硅纳米颗粒的反应离子刻蚀（R IE）过程,并在此基础上制备了可用于场发射的硅纳米针尖阵列.首先,采用改进的蒸发法在硅衬底上实现二氧化硅纳米颗粒的单层密排结构,再采用典型的刻蚀二氧化硅的RIE技术同时刻蚀硅衬底和二氧化硅纳米颗粒,在对纳米颗粒尺寸随刻蚀进行而改变的电镜照片分析的基础上,获得了相应的二氧化硅纳米颗粒刻蚀模型,计算得到横向和纵向的刻蚀速率;当刻蚀后的二氧化硅纳米颗粒从衬底上脱落后,进一步对硅衬底的刻蚀可以得到锐利的硅纳米针尖阵列,初步的实验结果表明,所制备的硅纳米针尖具有较好的场发射特性.