多层模型计算椭偏法测量的SiO2/Si超薄膜厚度

采用不同的光学模型对厚度为6 nm,密度为2.2 g/cm3的理想SiO2薄膜理论曲线进行了拟合,得到了薄膜厚度的计算结果随所采取的薄膜密度变化的规律:选用更大的薄膜密度值进行拟合计算会得到更小的厚度结果,其趋势近似线性.参考GIXRR方法测量得到的薄膜物理结构的结果,给出了优化的拟合计算模型(薄膜密度为2.4 g/cm3、表面粗糙度为0.4 nm、界面粗糙度为0.3 nm),对于热氧化法制备的厚度小于10 nm的SiO2超薄膜,使用此模型进行拟合计算,可以得到比常规模型更为准确的厚度结果.采用优化的模型拟合了期望厚度为2,4,6,8,10 nm的SiO2超薄膜的SE实验曲线,得到的厚度结果分别为2.61,4.07,6.02,7.41,9.43 nm,与传统模型计算结果相比,分别降低了13.8%,10.3%,8.1%,7.3%和6.6%.     

X射线反射法分析ZnO基薄膜的厚度、密度和表面粗糙度

采用X射线反射法(XRR)测试了在SiO_2玻璃衬底上磁控溅射沉积的单层ZnO基薄膜的反射强度,得到了反射强度随掠入射角变化的曲线;讨论了薄膜厚度、密度和表面粗糙度与反射曲线的关系,最后通过拟合XRR曲线获得了所制备薄膜的厚度、密度和表面粗糙度分别为55.8 nm,5.5 g·cm~(-3)和1.7 nm,与利用XRR数据直接计算出的薄膜厚度56.2 nm仅相差0.4 nm,表面粗糙度也与AFM测试的结果基本相符。可见XRR能无损伤、精确且快速地测试薄膜试样的厚度、密度和表面粗糙度等参数。     

纳米尺度氧化铪薄膜膜厚标准物质的研制

研制了氧化铪(HfO2)层厚度名义值分别为1nm、5nm、10nm的3种氧化铪薄膜膜厚标准物质,采用溯源至SI长度和角度基准的纳米薄膜厚度校准装置为标准物质候选物定值.研究建立了具有普适性的四层拟合模型,基于该模型对不同厚度的氧化铪薄膜的测量曲线进行了拟合,这是拟合结果准确可靠的基础.氧化铪薄膜膜厚标准物质具有良好的均...     

表面波方法表征纳米多孔SiO2薄膜机械特性的对准技术

超声表面波方法表征薄膜材料机械特性的过程是将理论计算的色散曲线与实验所得的色散曲线进行拟合,获得所测薄膜样品的杨氏模量值．因此,实验信号的有效性是获得准确结果的最重要因素．双端压电传感探头的设计确保了实验测试条件与理论计算模型的一致性,从而进一步增加了测定结果的准确性．应用此技术对纳米多孔SiO2薄膜的机械性能进行了测定,当其膜密度为1．15g/cm^3时,拟合出的杨氏模量值为1．5GPa．分析结果还表明影响拟合结果准确性的实验因素主要是压头的位置与平头表面波的角度偏差．     

纳米尺度HfO_2薄膜的光谱椭偏模型建立

为了建立厚度为1 nm左右HfO_2超薄膜的光谱椭偏测量方法,采用掠入射X射线反射技术进行国家/地区实验室间比对认证,其膜厚准确量值作为参比值,建立了HfO_2超薄膜的光谱椭偏结构拟合模型。研究了HfO_2超薄膜的光谱椭偏色散模型和拟合参数,最后确定了拟合色散模型为Tauc-Lorentz 3,拟合光谱范围为3.45~4.35 eV,表面污染层孔隙比例为60:40。     

LaAlO3/BaTiO3超晶格薄膜界面结构分析

通过研究发现,利用激光分子束外延技术生长的LaAlO3/BaTiO3超晶格薄膜具有良好的电学性能,其剩余极化可达到25μc/cm2.性能决定于结构,因此本文分析研究了LaAlO3/BaTiO3超晶格薄膜的界面结构.首先通过高能电子衍射技术在薄膜生长过程中对各层的生长及界面状况进行观测,再通过小角X射线衍射曲线及其计算机拟合曲线进一步确定超晶格薄膜的界面及结构参数,如界面的粗糙度、单层厚度等.通过研究发现,由于晶格之间的差异,LaAlO3/BaTiO3超晶格薄膜中LaAlO3和BaTiO3层的生长过程及微结构存在着一定的差异.     

溶剂蒸汽辅助制备超薄PVP栅介质膜及性能研究

使用溶剂蒸汽辅助制备超薄PVP栅介质膜,得到了低漏电流密度(E=1 MV/cm时,为1.12×10-9A/cm2;E=2 MV/cm时,为5.42×10-9A/cm2)、膜厚为10 nm的超薄PVP栅介质膜,其单位面积栅电容达到了566 nF/cm2。此外,AFM测试表明溶剂蒸汽辅助退火使薄膜表面粗糙度由0.36 nm降到了0.21 nm,空间电荷限制电流法(SCLC)的分析结果表明薄膜体内陷阱密度减少了26%。     

X射线反射法和椭圆偏振法结合测量热处理溶胶-凝胶ZrO2薄膜的结构和光学参数

采用溶胶-凝胶法在硅片基底上制备ZrO2薄膜,在150℃～750℃范围内不同温度下进行热处理,研究了热处理对膜层结构和光学性能的影响。X射线反射用于膜层厚度和界面粗糙度分析,结果表明热处理温度由150℃升至750℃,膜层厚度由常温状态下的112.3nm减小到34.0nm,表面和界面粗糙度均小于2nm。以X射线反射法测得的膜层厚度为初始值,对椭圆偏振仪的测量结果进行拟合,得到不同温度的膜层折射率,结果表明热处理温度为550℃时膜层折射率达到最大值。X射线反射作为直接的膜层厚度测试手段,所得结果为准确分析椭偏光谱提供了参考。     

纳米多孔二氧化硅薄膜的制备及其光学性质研究

以正硅酸乙酯(TEOS)为先驱体，采用溶胶-凝胶法，结合旋转涂胶和超临界干燥等工艺，在硅片上制备了纳米多孔SiO2薄膜。XRD和AFM表明该SiO2薄膜为无定形态，具有多孔网络结构，表面均匀平整，其SiO2基本粒子和孔隙的直径为30～40nm。利用椭偏光谱仪测量了SiO2薄膜在波长245～1650nm的椭偏光谱，采用Si／cauchy／rough结构模型对该光谱进行了拟合，获得了SiO2薄膜的厚度和光学常数。SiO2薄膜的厚度为500～1100nm；折射率为1．13～1．21；孔隙率为56％～70％；介电常数为1．9～2．3。     

LaAlO3/BaTiO3超晶格薄膜的生长及结构分析

采用激光脉冲分子束外延技术,在(100)取向的SrTiO3 单晶基片上成功外延生长了LaAlO3/Ba TiO3 超晶格薄膜。在超晶格薄膜生长过程中,采用高能电子衍射技术(RHEED)对LaAlO3/BaTiO3 超晶格薄膜的生长过程以及平面晶格变化进行了分析。通过对超晶格薄膜中各层RHEED衍射条纹的分析计算发现超晶格薄膜存在一个临界厚度,其值约为 17nm,当超晶格薄膜的厚度小于该临界厚度时,晶格畸变在逐渐增加,当厚度超过该临界厚度时,晶格畸变因弛豫现象的产生而逐渐减小。超晶格薄膜中不同层的RHEED衍射条纹的差别说明了由于不同应力的作用使超晶格薄膜中LAO层和BTO层表面粗糙度不同。     

Controlling the crystallinity and roughness of atomic layer deposited titanium dioxide films

The surface roughness of thin films is an important parameter related to the sticking behaviour of surfaces in the manufacturing of microelectomechanical systems (MEMS). In this work, TiO2 films made by atomic layer deposition (ALD) with the TiCl4-H2O process were characterized for their growth, roughness and crystallinity as function of deposition temperature (110-300 degrees C), film thickness (up to approximately 100 nm) and substrate (thermal SiO2, RCA-cleaned Si, Al2O3). TiO2 films got rougher with increasing film thickness and to some extent with increasing deposition temperature. The substrate drastically influenced the crystallization behaviour of the film: for films of about 20 nm thickness, on thermal SiO2 and RCA-cleaned Si, anatase TiO2 crystal diameter was about 40 nm, while on Al2O3 surface the diameter was about a micrometer. The roughness could be controlled from 0.2 nm up to several nanometers, which makes the TiO2 films candidates for adhesion engineering in MEMS.     

基于PECVD方法制备的透明硅氧烷（SiOxCyHz）阻隔薄膜特性研究

柔性、透明的高阻隔性薄膜在有机太阳能薄膜电池、柔性有机发光二极管、电子纸和真空绝热板等领域都有需求。采用对电极辊结构的等离子体增强化学气相沉积方法,卷对卷的方式在聚酯(PET)基膜上,以硅醚(HMDSO)为单体,氧气(O₂)为反应气体,制备了柔性硅氧烷(SiOxCyHz)薄膜。研究了膜厚,氧气/单体比例、压力等参数对透水率(WVTR)的影响规律、测试了膜层的组分、透射光谱、应力等特性。研究结果表明,透水率随硅氧烷薄膜厚度增大而减小,随氧气/单体比例增大而减小,随压力减小而增大。500 nm厚的硅氧烷薄膜透水率低于5×10^-3g/(m²·day),可见光谱段(380-760 nm)透光率达到88.6%,表面粗糙度为1.8 nm,薄膜应力随薄膜厚度增加显著增大。     

Spectrographic ellipsometry study of a liquid crystal display substrate consisting of thin films of SiO2, polyimide and indium tin oxide on glass

Variable angle spectrometric ellipsometry at room temperature is used to determine thin film parameters of substrates used in liquid crystal displays. These substrates consist of sequential thin films of polyimide (PI), on indium tin oxide (ITO),on SiO₂ deposited on a glass backing approximately 1.1 mm thick. These films were studied by sequentially examining more complex systems of films (SiO₂, SiO₂-ITO, SiO₂-ITO-PI). The SiO₂ layer appears to be optically uniform and flat. The ITO film is difficult to characterize. When this surface film's lower surface is SiO₂ and upper surface is an air-ITO-interface it is found that including surface roughness and variation of the optical properties with ITO thickness in the model improved the fit; suggesting that both phenomena exist in the ITO films. However, the surface roughness and graded nature of optical properties could be not determinable by ellipsometry when the ITO is coated with a polyimide film. The PI films are ellipsometrically flat and over the wavelength range from 500 to 1400 nm the real refractive index of polyimide films varying in thickness between 25 and 80 nm is well modeled by a two-term Cauchy model with no absorption. The ellipsometric thickness of the ITO layer is the same as the profilometric thickness; however, the ellipsometric thickness of the polyimide layers is roughly 10 nm larger than that obtained from the profilometer. These final observations are consistent with the literature.     

Localized CO2 laser annealing induced dehydrogenation/ablation and optical refinement of silicon-rich silicon dioxide film with embedded si nanocrystals

CO2 laser annealing induced effects of dehydrogenation, Si nanocrystal precipitation, ablation, and optical refinement in PECVD grown SiO1.25 film are investigated. Dehydrogenation shrinks SiO1.25 thickness by 40 nm after annealing at laser intensity (Plaser) of 4 kW/cm(2) for 1.4 ms. As Plaser increases to 6 kW/cm(2), the photoluminescence (PL) red-shifts to 806 nm due to the size enlargement of Si nanocrystals, while a reduced optical bandgap energy from 3.3 to 2.43 eV and an enlarged refractive index from 1.57 to 1.87 are also observed. Transmission electron microscopy analysis reveals that the randomly oriented Si nanocrystals exhibit an average diameter of 5.3 nm and a volume density of 1.9 x 10(18) cm(-3). CO2 Laser ablation initiates at intensity higher than 7 kW/cm(2), which introduces numerous structural defects with a strong PL at 410 nm. Such an ablation inevitably leads to a blue-shifted optical bandgap energy from 2.43 to 2.76 eV as Plaser enlarges from 6 to 12 kW/cm(2) are concluded.     

Ellipsometry of thin films of copper phthalocyanine

Ellipsometric measurements have provided qualitative information on the optical properties of CuPC films deposited on a thin gold layer substrate. Detailed interpretation was complicated by variations in the density of the deposited layers and the surface roughness of the substrate. Films less than 100 nm thick can be satisfactory represented by a single homogeneous isotropic layer. Thicker films appear to be equivalent to an isotropic inner layer and an anisotropic outer layer, where the latter results from bulk deposition of CuPC with the molecules in a predominant orientation to the surface. Reasonable agreement has been obtained between film thicknesses measured by weighing and by ellipsometry, assuming a single homogeneous anisotropic film for thickness in excess of 150 nm.     

Behavior of pentacene initial nucleation on various dielectrics and its effect on carrier transport in organic field-effect transistor

The influence of dielectric surface energy on the initial nucleation and the growth of pentacene films as well as the electrical properties of the pentacene-based field-effect transistors are investigated. We have examined a range of organic and inorganic dielectrics with different surface energies, such as polycarbonate/SiO2, polystyrene/SiO2, and PMMA/SiO2 bi-layered dielectrics and also the bare SiO2 dielectric. Atomic force microscopy measurements of sub-monolayer and thick pentacene films indicated that the growth of pentacene film was in Stranski-Kranstanow growth mode on all the dielectrics. However, the initial nucleation density and the size of the first-layered pentacene islands deposited on different dielectrics are drastically influenced by the dielectric surface energy. With the increasing of the surface energy, the nucleation density increased and thus the average size of pentacene islands for the first mono-layer deposition decreased. The performance of fabricated pentacene-based thin film transistors was found to be highly related to nucleation density and the island size of deposited Pentacene film, and it had no relationship to the final particle size of the thick pentacene film. The field effect mobility of the thin film transistor could be achieved as high as 1.38 cm2Ns with on/off ratio over 3 x 10(7) on the PS/SiO2 where the lowest surface energy existed among all the dielectrics. For comparison, the values of mobility and on/off ratio were 0.42 cm2Ns and 1 x 10(6) for thin film transistor deposited directly on bare SiO2 having the highest surface energy.     

Optical properties of electrochemically deposited ZnO thin films on colloidal crystal film of SiO2 microspheres

The optical properties of electrochemically deposited ZnO thin films on colloidal crystal film of SiO2 microspheres structures were studied. Colloidal crystal film of SiO2 microspheres were self-assembled by evaporation using SiO2 in solution at a constant 0.1 wt%. ZnO in thin films was then electrochemically deposited on to colloidal crystal film of SiO2 microspheres. During electrochemical deposition, the content of Zn(NO3)2 x 6H2O in solution was 5 wt%, and the process's conditions were varied between of 2-4 V and 30-120 s at room temperature, with subsequent heat-treatment between 200 and 400 degrees C. A smooth surface and uniform thickness of 1.8 microm were obtained at 3 V for 90 s. The highest PL peak intensity was obtained in the ZnO thin film heat-treated at 400 degrees C. The double layered ZnO/SiO2 colloidal crystals showed clearly better emission properties than the SiO2/ZnO and ZnO structures.     

Characterization on pulsed laser deposited nanocrystalline ZnO thin films

Nanocrystalline zinc oxide thin films were deposited on glass and silicon substrates by using pulsed laser deposition at different laser energy densities (1.5, 2, and 3 J/cm²). The film thickness, surface roughness, composition, optical and structural properties of the deposited films were studied using an α-step surface profilometer, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), optical transmittance, and X-ray diffraction (XRD), respectively. The film thickness was calculated as 244 nm. AFM analysis shows that the root-mean-square roughness increases with increasing laser energy density. XPS analysis shows that the interaction of zinc with oxygen atoms is greatly increased at high laser energy density. In the optical transmittance spectra, a shift of the absorption edge towards higher wavelength region confirms that the optical band gap increases with an increase in laser energy density. The particle size of the deposited films was measured by XRD, it is found to be in the range from 7.87 to 11.81 nm. It reveals that the particle size increases with an increase in laser energy density.