Using fence post designs to speed the atomic layer deposition of optical thin films

Atomic layer deposition (ALD) at this time is much slower than conventional optical thin-film deposition techniques. A more rapid ALD process for SiO(2) has been developed than for other ALD materials. A fence post design for optical thin films has thin layers of high-index posts standing above a broad low-index ground. If a design for ALD can be predominantly composed of SiO(2) layers with thin high-index layers, the deposition times can be correspondingly shortened, and it is shown that the required performance can still be nearly that of more conventional designs with high- and low-index layers of equal thickness. This combination makes the ALD benefits of conformal coating and precise thickness control more practical for optical thin-film applications.     

Glass fibre-reinforced supersulphated cement

The strength properties of alkali-resistant glass fibre-reinforced super-sulphated cement (ssc) have been studied for periods of up to five years in comparison with a similar material made from ordinary Portland cements (opc) and have given very encouraging results. In natural weathering the cement matrix is affected by carbonation in an adverse way but still the composites made from a commercial ssc retain values of rupture modulus, direct tensile strength and Izod impact strength which are superior to those of grc made from opc after five years. The effect of carbonation can be minimized by providing the composite with a protective layer of sand/cement mortar.The properties of a grc component - a hollow fence post made from supersulphated cement - have also been studied and when coated with a layer of sand/cement mortar, retained a significant proportion of its initial strength and toughness. A new method for testing the fence posts is described.     

Surface modification of carbon post arrays by atomic layer deposition of ZnO film

The applicability of atomic layer deposition (ALD) process to the carbon microelectromechanical system technology was studied for a surface modification method of the carbon post electrodes. A conformal coating of the ALD-ZnO film was successfully demonstrated on the carbon post arrays which were fabricated by the traditional photolithography and subsequent two-step pyrolysis. A significant Zn diffusion into the underlying carbon posts was observed during the ALD process. The addition of a sputter-deposited ZnO interfacial layer efficiently blocked the Zn diffusion without altering the microstructure and surface morphology of the ALD-ZnO film.     

Calculation of film thickness for dip coated antireflective films

Antireflective films require an accurate film thickness to be able to perform optimally. The ideal thickness on most films is a quarter wavelength optical thickness (QWOT). The physical thickness of the QWOT film depends on the refractive index of the material that is being used. Each layer of the antireflective coating will have different optimal conditions for applying the film. When using the dip coating method, these conditions are withdrawal speed and concentration of solution.When using the currently accepted equations derived by Yang et al. to calculate the film thickness an error of 31.7% was noted when compared with the experimentally measured film thickness. Realising that the refractive index of the film plays a role in determining the thickness of the film, the equations were modified to take refractive index into account. Once this was taken into account, the calculated film thickness deviated from the measured film thickness by 8.7%. This error can be attributed to experimental errors which involve temperature and concentration fluctuations.     

基于CCD的金属薄板印刷墨层厚度在线检测研究

目的根据金属薄板印刷质量控制的发展趋势和金属薄板印刷的特点,提出了基于CCD机器视觉的金属薄板印刷机墨层厚度在线检测系统。方法通过实验获取信号条的墨层厚度d与实时图片的RGB值,分析由RGB值推得的亮度L*、饱和度和色调角hab与墨层厚度间的对应关系;通过极限学习机(ELM)对亮度、饱和度、色调角与墨层厚度数据进行回归拟合,建立墨层厚度预测模型。结果墨层厚度d与L*,和hab之间存在显著的对应关系。拟合的平均相对误差为2.27%,最大相对误差为7.33%,测量误差低于8%。结论较好地实现了在线墨层厚度检测,具有很好的实际应用价值。     

Synthesis of TaZnO thin films using combinatorial magnetron sputtering and its electrical, structural and optical properties

The structural, electrical, and optical properties of tantalium zinc oxide (TaZnO) thin films grown using combinatorial magnetron sputtering system were investigated. To explore the effects of film thickness and post annealing treatment on the properties of the films, we have fabricated TaZnO sample libraries having different thicknesses and carried out post annealing treatment. Sample libraries fabricated at room temperature showed the resistivity ranged 2.1 to approximately 7.1 x 10(-3) Omega cm, while the films post annealed at 200 degrees C under 1 mTorr exhibited the resistivity as low as 1.2 x 10(-3) Omega cm. XRD measurements revealed that the film structure was strongly depended on the film thickness, showing that the structure was changed from amorphous to polycrystalline with increasing the film thickness. Furthermore, it was found that figure of merit (0TC), which was determined by T% and Rs of the TaZnO films, showed maximum value as the films with a thickness of 230 nm was post-annealed at 200 degrees C under vacuum of 1 mTorr.     

Simple orientational control over cylindrical organic-inorganic block copolymer domains for etch mask applications

Bottom-up patterning methodologies, predicated on chemical self-assembly, have the potential to transcend limitations associated with more traditional lithographies. By controlling the domain orientation of a cylinder-forming organic-inorganic block copolymer, poly(styrene-block-ferrocenyldimethylsilane), it is possible to straightforwardly fabricate massive arrays of either nanoscale dots or wires out of a film composed of a wide variety of materials. In the work reported here, orientational control is achieved by manipulating the polymer film thickness in concert with the annealing treatment. For films much thinner than the equilibrium periodicity of the microdomains, the cylinders spontaneously orient themselves perpendicular to the substrate. Films with thickness close to the equilibrium periodicity exhibit the more common in-plane orientation following thermal annealing. Solvent annealing leads to an in-plane orientation for the full range of film thicknesses studied. As a demonstration of the effectiveness of this method, semiconductor substrates were patterned with arrays of posts and wires, respectively, using the same starting polymeric material as the etch mask. Compatibility of this polymer with various substrate materials is also demonstrated.     

一种基于波段比值法的海面厚油膜评估方法

激光诱导荧光(LIF)技术是目前较为有效的海面溢油探测技术之一,然而基于该技术的油膜厚度反演算法目前仅适用于薄油膜(≤20μm)。鉴于此,建立了一种基于LIF技术利用油膜荧光信号评估较厚油膜厚度的双波段比值模型,利用油膜荧光光谱的波形特性反演油膜厚度并论证了该算法的适用范围。实验数据得出,当油膜较薄时反演结果误差较大,随着油膜厚度增加误差逐渐降低,当油膜荧光信号趋于饱和时,误差较大且随油膜厚度的增加而快速变大。实验结果表明,该算法可以有效评估200~1400μm范围内的海面溢油油膜的厚度,并可以利用油膜荧光信号的测量相对误差评估该算法的适用范围。     

Terahertz ionization of highly charged quantum posts in a perforated electron gas

"Quantum posts" are roughly cylindrical semiconductor nanostructures that are embedded in an energetically shallower "matrix" quantum well of comparable thickness. We report measurements of voltage-controlled charging and terahertz absorption of 30 nm thick InGaAs quantum wells and posts. Under flat-band (zero-electric field) conditions, the quantum posts each contain approximately six electrons, and an additional ~2.4 × 10(11) cm(-2) electrons populate the quantum well matrix. In this regime, absorption spectra show peaks at 3.5 and 4.8 THz (14 and 19 meV) whose relative amplitude depends strongly on temperature. These peaks are assigned to intersubband transitions of electrons in the quantum well matrix. A third, broader feature has a temperature-independent amplitude and is assigned to an absorption involving quantum posts. Eight-band k·p calculations incorporating the effects of strain and Coulomb repulsion predict that the electrons in the posts strongly repel the electrons in the quantum well matrix, "perforating" the electron gas. The strongest calculated transition, which has a frequency close to the center of the quantum post related absorption at 5 THz (20 meV), is an ionizing transition from a filled state to a quasi-bound state that can easily scatter to empty states in the quantum well matrix.     

Multi-layered PZT/polymer composites to increase signal-to-noise ratio and resolution for medical ultrasound transducers

Increasing transducer bandwidth and signal-to-noise ratio (SNR) is fundamental to improving the quality of medical ultrasound images. In previous work, the authors have proposed the use of multi-layer 1-3 PZT/epoxy composites to increase both but have encountered significant fabrication challenges. These difficulties include making the bond thickness between the layers extremely small relative to the ultrasound wavelength and aligning the posts of the composite to increase the coupling coefficient. The authors have routinely achieved a bond thickness of less than 5 mum but aligning the posts is more complicated. Finite element (PZFlex; Weidlinger, Assoc., New York, NY and Los Altos, CA) simulations show that the pulse-echo SNR and bandwidth degrade significantly with misalignment of the posts. Alignment of greater than 90% of the post pitch (i.e., tolerance of 10 to 20 mum) is required to obtain significant increases in SNR and bandwidth relative to conventional transducer arrays. This will be a difficult tolerance for large-scale production. Thus, the authors have developed a multi-layer composite hybrid array that will not require post alignment. This structure consists of a layer of 5 MHz 1-3 composite material on top of conventional 5 MHz PZT, which will provide greater SNR relative to conventional composites and increased bandwidth over multi-layer PZT. PZFlex simulations show that for a 2 MHz linear array element, the 2 layer hybrid structure increases the pulse-echo SNR by 7.5 dB over that from a single layer PZT element. Even without a matching layer, an increase in the -6 dB pulse-echo fractional bandwidth from 22% for the PZT element to 35% for the hybrid element was also predicted. Experimentally, in a 32 element array, the authors achieved an increase of 5.2 dB in SNR and an increased -6 dB bandwidth from 23 to 30%. In vitro and in vivo images showed corresponding improvements.     

Computation of resonant frequency of annular microstrip antenna loaded with multiple shorting posts

Shorting post loaded annular microstrip antenna is of considerable interest. Recent works have presented formulations for annular microstrip patch with a shorting post located at the centre of a circular disc, thereby converting the structure to an annular ring with a centre shot. A theoretical formulation for multiple post loading (up to ten posts) of an annular patch is presented. The posts are located away from the centre of the patch and are thin in diameter with respect to the diameter of the ring. The formulation accurately predicts resonant frequency. For an accurate formulation, the shorting posts have been considered as inductive impedances at the frequency of interest. It is shown that for a short loaded ring, TM₀₁ is the dominant mode. The simple tool presented can be suitably modified to incorporate switching diodes or varactor diodes.     

改进遗传算法在CMP终点检测的应用

提出了一种基于反射法的化学机械抛光(CMP)在线终点判定方法。首先通过改进的单纯形混合遗传算法(GA),对SiO₂薄膜的膜厚与折射率进行了拟合,再以200～1200nm波段内反射率平均值作为特征值,得到了不同膜厚条件下的反射率平均值参照表。以实时反射率与预设膜厚反射率的差方和、特征值大小及其变化趋势这2个条件作为CMP终点判定条件。实验结果表明:混合算法拟合膜厚平均相对误差小于0.21%,折射率平均相对误差小于1.07%;特征值计算速度快,满足在线动态抛光的时间要求。     

油膜厚度超声测量方法及实验研究

根据垂直入射超声波在3层介质中传播的相关理论,给出了基于超声波反射系数油膜厚度测量的谐振模型和弹簧模型,在此基础上进行实验测试。设计并制作了基于STC单片机的信号发生控制器电路,编写了脉冲串波形、频率和个数控制程序,对给定油膜厚度的试件进行了超声测量。结果表明：通过测量超声波反射系数可间接获得机械结构中。油膜厚度,并且测量误差基本保持在5%的范围内。     

光学薄膜的误差灵敏度和允差分析

实际生产出的薄膜的光学特性和理论计算得到的光学特性常常存在差别,这些差别的来源有多种,诸如理论模型假设时忽略的一些因素;薄膜久置引起的薄膜结构改变或吸潮、污染;制造过程中的制造误差(光学监控系统引起的薄膜厚度和折射率的误差)等.针对各种误差的来源有相应的改善方法.本文就光学监控系统引起的薄膜厚度和折射率的误差进行分析,同时提出膜系的允差分析,以尽量减小由于监控设备引起的误差,最后介绍了实际生产的计算机优化监控程序.     

用于标定镀膜机的膜厚样板的制备和测量

镀膜在国民经济生活中得到广泛应用。影响镀膜性能的一个主要参数是膜层在整个基片上的厚度均匀性。利用挡板在基片上多个区域沉积台阶,测量台阶高度的差值用于分析膜厚的均匀性。通过集成非接触聚焦式测头的纳米测量机进行测量,针对镀膜产品上各个特殊的曲面台阶,以参差平方和为标准,用基底无台阶区域的曲线模型拟合台阶底部曲线,参考ISO 5436-1：2000的台阶评价方法,对镀膜基片上多台阶进行了评价。该方法可以用于镀膜机的验收。     

Applicability of X-ray fluorescence spectroscopy as method to determine thickness and composition of stacks of metal thin films: A comparison with imaging and profilometry

In this work the applicability of X-ray fluorescence spectroscopy (XRF) for fast, accurate and non-destructive determination of the thickness of a variety of single-layer and multi-layer metal thin films deposited on glass and silicon is investigated. Data obtained with XRF is compared with information from profilometry and images from scanning electron microscopy (SEM). Whereas thickness determinations based on profilometry and cross-sectional SEM-imaging have restrictions with respect to thickness of metal stacks or hardness of the metals, XRF has no such limitations. Moreover, XRF can discriminate between sublayers in a multi-layer film, and can also be utilized for compositional analysis and density estimations. Good agreement between thickness data obtained with XRF, profilometry and SEM-images is found, under the justifiable assumption that the density of sputter-deposited and evaporated thin films is ca. 5% below that of bulk metals. Similar XRF-results are found for non-patterned areas (64 mm² metal) as well as lithographically patterned areas containing a series of small metal lines (total metal surface ca. 8 mm²). As a consequence, it is concluded that XRF is a versatile technique for analysis, verification, control or evaluation of the thickness, density or (elemental) composition of thin metal film line-patterns, during their fabrication as well as prior or post to applications.     

Prediction of thin film thickness of field emission using wavelet neural networks

Based on wavelet transforms extracting characteristic features from experimental data, the wavelet neural network (WNN) is used as an elementary model to study the characteristics of field emission from thin films. The WNN model is trained with learning samples of thin film thickness. The function mappings that the trained WNN model contains are the very ones that thin film thickness varies with characteristic parameters of field emission. A predicting model on thin film thickness of field emission is obtained. The data of thickness of diamond thin films is used to test this model. The results show that the absolute value of the relative error is within 2.98%, and the well-trained WNN model possesses good forecasting characteristics.     

Sensitivity of the thermocapillary method of thickness determination for transparent liquid films on horizontal absorbing substrates

We present data on the sensitivity of a new method of determining the thicknesses of thin films on flat horizontal substrates, based on the measurement of a stationary thermocapillary response. In the range of film thicknesses exceeding the thermocapillary rupture thickness by no more than 10 μm, the error of the film thickness determination is no greater than 1–2 μm. By increasing the power of the laser beam inducing the thermocapillary convection from 3.5 to 16.5 mW, it is possible to keep the relative error of measurement within 5% in the range of film thicknesses from 150 to 1000 μm for liquids with viscosities within 0.8–5.6 cSt.     

Differential laser trigonometry for measuring the oil film thickness on water

A differential laser trigonometry method is presented for measurement of the oil film thickness on a water surface. The thickness of an oil film can be obtained with two off-plane displacements to a benchmark plane obtained by the imaging spot displacement and the configuration parameter of the imaging system subtracted. The method has been tested in the laboratory via the examination of diesel oil and petroleum films. An experimental system setup has been developed, by which the maximum measurable thickness is 12?mm and the average measurement error is 6.05?µm. The results show that the method presented is feasible, and applicable to dynamic online measurement of oil film thickness of oil spills on the sea surface.