Photo-lithographic patterning of biomimetic molecularly imprinted polymer thin films onto silicon wafers

This investigation describes the design and synthesis of molecularly imprinted polymers (MIPs) as patterned thin films, based on molecular modelling of functional monomer-template interactions and validation by NMR-spectroscopy. Several MIP thin films were prepared from a solution containing the template N-boc-l-phenylalanine and functional acrylic monomers at varying ratios with a cross-linker and initiator in a porogenic solvent. This solution was then spin-coated onto 3-(trimethoxysilyl)propyl methacrylate-functionalised silicon wafers and subsequently the film was photo-polymerised. After template extraction, the film thickness and topography of a methacrylic acid MIP was characterised with atomic force microscopy. A 4-vinylpyridine-MIP thin film was then made by depositing the pre-polymerisation solution on top of the methacrylic acid MIP by spin-coating. Photo-lithographic etching through a gold grid and extraction of non-polymerised solution from under the gold mask yielded a grid-patterned surface, in which two different MIPs alternate with dimensionality at the micro- or submicro-meter scale. Selectivity differences between the two MIP surfaces towards fluorescent template analogue N-dansyl-l-phenylalanine were documented using fluorescence microscopy. This side-by-side comparison on the same thin film allows fast and cost-effective assessment of the two very different MIP selectivities towards various biomolecules.     

Functional networks models for rapid characterization of thin films: An application to ultrathin polycrystalline silicon germanium films

Optimal performances of thin film devices such as those of micro/nano-electromechanical systems like sensors and actuators are possible with accurate and reliable characterization techniques. Such techniques can be enhanced if predictive models are constructed and deployed for production and monitoring. This paper presents functional networks as a novel modeling approach for rapid characterization of thin films such as thickness, deposition rate, resistivity and uniformity based on 8 deposition parameters. The functional network (FN) models were developed and tested using 154 experimental data sets obtained from ultrathin polycrystalline silicon germanium films deposited by Applied Materials Centura low pressure chemical vapour deposition system. The results showed that the proposed FN models perform excellently for all the outputs with minimum and maximum regression coefficients of 0.95 and 0.99, respectively. To further demonstrate the robustness of these models, several trend analyses were conducted. The performance statistics indicates that the mean percentage error for the model, based on the deposition rate, lies between 0.3% and 0.8% for silane, germane, diborane flow rates and pressure. For these deposition variables, the probability or p-value at a significance level of 0.01 implies that no significant difference exists between the means of the predicted and the measured values. The results are further discussed in light of physics of the CVD process.     

Electrostatic microresonators from doped hydrogenated amorphous and nanocrystalline silicon thin films

This paper reports on the fabrication and characterization of flexural electrostatic microresonators based on doped thin-film hydrogenated amorphous and nanocrystalline silicon processed at temperatures below 110/spl deg/C using surface micromachining on glass substrates. The microelectromechanical structures are bridges made of either phosphorus-doped hydrogenated amorphous silicon (n/sup +/-a-Si:H) deposited by plasma-enhanced chemical vapor deposition (PECVD) or boron-doped hydrogenated nanocrystalline silicon (p/sup +/-nc-Si:H) deposited by hot-wire chemical vapor deposition (HWCVD). The microbridges, which are suspended over an aluminum (Al) gate electrode, are electrostatically actuated and the mechanical resonance is detected in vacuum using an optical detection method. The resonance frequency and energy dissipation mechanisms involved in thin-film silicon based microresonators are studied as a function of the geometrical dimensions of the structures. Resonance frequencies up to 36 MHz are observed and a Young's modulus of 147 GPa is extracted for n/sup +/-a-Si:H, and of 165 GPa for the p/sup +/-nc-Si:H films. Quality factors as high as 5000 and 2000 are observed for the n/sup +/-a-Si:H and p/sup +/-nc-Si:H resonators, respectively, and are limited by surface losses. The effect on the resonance frequency and quality factor of depositing a metal layer on the thin-film silicon structural layer is studied.     

Surface impedance of silicon substrates and films

It is shown that at microwave–millimeterwave frequencies and for DC resistivities below ρ⁺=(2πf_τε₀ε_L)⁻¹ silicon should be regarded as a lossy metal characterized by resistivity, skin depth, and surface impedance, while at higher resistivities it may be regarded as a lossy dielectric characterized by a lattice dielectric constant (ε_L=11.7) and loss tangent. The sheet resistance defined as a ratio of DC resistivity to film thickness is not an adequate parameter to characterize the films at microwave frequencies. The surface impedance of a thin semiconductor film is complex with both real and imaginary parts strongly dependent on frequency, DC resistivity of substrate and film, substrate thickness, and the presence of a ground plane on the backside of the substrate. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 433–440, 1998     

Electron emission from polymer films under electric‐field influence

Abstract— This paper presents the field‐emission characteristics of a polymer‐covered tungsten‐spike cathode. The emission images obtained from a field‐emission microscope together with the electron energy distribution and Fowler‐Nordheim curves compared with those of a typical tungsten cathode are presented.     

Coding coarse grained polymer model for LAMMPS and its application to polymer crystallization

We present a patch code for LAMMPS to implement a coarse grained (CG) model of poly(vinyl alcohol) (PVA). LAMMPS is a powerful molecular dynamics (MD) simulator developed at Sandia National Laboratories. Our patch code implements tabulated angular potential and Lennard-Jones-9-6 (LJ96) style interaction for PVA. Benefited from the excellent parallel efficiency of LAMMPS, our patch code is suitable for large-scale simulations.This CG-PVA code is used to study polymer crystallization, which is a long-standing unsolved problem in polymer physics. By using parallel computing, cooling and heating processes for long chains are simulated. The results show that chain-folded structures resembling the lamellae of polymer crystals are formed during the cooling process. The evolution of the static structure factor during the crystallization transition indicates that long-range density order appears before local crystalline packing. This is consistent with some experimental observations by small/wide angle X-ray scattering (SAXS/WAXS). During the heating process, it is found that the crystalline regions are still growing until they are fully melted, which can be confirmed by the evolution both of the static structure factor and average stem length formed by the chains. This two-stage behavior indicates that melting of polymer crystals is far from thermodynamic equilibrium. Our results concur with various experiments. It is the first time that such growth/reorganization behavior is clearly observed by MD simulations.Our code can be easily used to model other type of polymers by providing a file containing the tabulated angle potential data and a set of appropriate parameters.

Program summary

Program title: lammps-cgpvaCatalogue identifier: AEDE_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDE_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: GNU's GPLNo. of lines in distributed program, including test data, etc.: 940 798No. of bytes in distributed program, including test data, etc.: 12 536 245Distribution format: tar.gzProgramming language: C++/MPIComputer: Tested on Intel-x86 and AMD64 architectures. Should run on any architecture providing a C++ compilerOperating system: Tested under Linux. Any other OS with C++ compiler and MPI library should sufficeHas the code been vectorized or parallelized?: YesRAM: Depends on system size and how many CPUs are usedClassification: 7.7External routines: LAMMPS (http://lammps.sandia.gov/), FFTW (http://www.fftw.org/)Nature of problem: Implementing special tabular angle potentials and Lennard-Jones-9-6 style interactions of a coarse grained polymer model for LAMMPS code.Solution method: Cubic spline interpolation of input tabulated angle potential data.Restrictions: The code is based on a former version of LAMMPS.Unusual features.: Any special angular potential can be used if it can be tabulated.Running time: Seconds to weeks, depending on system size, speed of CPU and how many CPUs are used. The test run provided with the package takes about 5 minutes on 4 AMD's opteron (2.6 GHz) CPUs.References:

[1]

D. Reith, H. Meyer, F. Müller-Plathe, Macromolecules 34 (2001) 2335-2345.

[2]

H. Meyer, F. Müller-Plathe, J. Chem. Phys. 115 (2001) 7807.

[3]

H. Meyer, F. Müller-Plathe, Macromolecules 35 (2002) 1241-1252.

     

TiNi (shape memory) films silicon for MEMS applications

TiNi shape memory alloy in thin film form is an excellent candidate for MEMS microactuation. Using RF sputter deposition, thin films of TiNi (51.7 at% Ti-48.3 at% Ni) have been formed on silicon substrates and produced shape memory behavior at approximately 60°C. Films were amorphous when deposited and were subsequently annealed at 515°C for 30 min. to crystallize the shape memory microstructure. Excellent adherence was achieved onto silicon, SiO₂ and poly-silicon surfaces. Microfabrication was used to create TiNi diaphragms, which exhibited useful shape memory microactuation and other desirable mechanical properties. The diaphragms recovered greater than 2% strain when heated through the phase transformation temperature, providing a maximum work density of at least 5×10⁶ J/m ³. This work density is higher than that of any other type of microactuation     

Evaluation of plasma deposited silicon nitride thin films for microsystems technology

Plasma deposited silicon nitride thin films were deposited at temperatures between 150/spl deg/C and 300/spl deg/C. Diagnostic microstructures were fabricated from the thin films using bulk micromachining, and the strain was calculated from optical measurement of postbuckling deflection. The results indicate that the residual strain of the thin films is dominated by film-substrate thermal mismatch, with the coefficient of thermal expansion monotonically increasing with decreasing deposition temperature. Metal-insulator-metal devices of variable area were also fabricated to measure the dielectric constant, which was shown to be independent of deposition temperature. The importance of these results to microsystems technology (MST) was briefly discussed.     

平板图案的跟踪及其在增强现实中的应用

介绍一种实时的基于单摄像机的平板图案跟踪算法。该算法可以在增强现实应用中用于摄像机定位和虚拟物体的放置。针对跟踪中由运动模糊和目标较小所引起的跟踪失败情况做出了讨论,提出结合使用LK跟踪算法和基于匈牙利算法的角点匹配来解决这些问题。还提出使用基于约束的非线性优化来降低噪声对摄像机方位计算的影响。实验结果表明,该算法能够在复杂情况下,可靠地跟踪目标图案,获取准确平滑的摄像机定标结果。     

Planar CMOS compatible process for the fabrication of buried microchannels in silicon, using porous-silicon technology

This work presents a new method for the fabrication of buried microchannels, covered with porous silicon (PS). The specific method is a two-step electrochemical process, which combines PS formation and electropolishing. In a first step a PS layer with a specific depth is created at a predefined area and in the following step a cavity underneath is formed, by electropolishing of silicon. The shape of the microchannel is semi-cylindrical due to isotropic formation. The method allows accurate control of the dimensions of both PS and the cavity. The formation conditions of the PS layer and the cavity were optimized so as to obtain smooth microchannel walls. In order to obtain stable structures the area underneath the PS masking layer was transformed into n-type by implantation, taking advantage of the selectivity of PS formation between n- and p-type silicon. With this technique, a monocrystalline support for the PS layer is formed on top of the cavity. Various microchannel diameters with different thickness of capping PS layer were obtained. The process is CMOS compatible and it uses only one lithographic step and leaves the surface of the wafer unaffected for further processing. A microfluidic thermal flow sensor was fabricated using this technology, the experimental evaluation of which is in progress.     

基于关联规则挖掘的生化企业数据分析及其应用研究

生物化工产品的工业生产,要求有合适的生产环境,由于生产过程的复杂性,掌握适宜的生产环境较为困难.数据挖掘是从现有数据中找规律,可以从历史数据中,找出关联模式,从而获取对决策目标有利的生产环境条件.本文针对生物化工(生化)企业生产的数据特征,基于关联规则挖掘,分析生化企业生产数据,同时结合目前大多数关联规则挖掘算法的数据模型要求,重点论述了环境因子和环境因子数据项的关系,提出将原始数据指标分割成数据项,及分割后的数据项合并为决策目标的方法.由于生化企业生产决策目标的确定性,提出了具有确定性决策项时关联规则挖掘的优化算法,可快速地挖掘感兴趣的频繁数据项集.在此基础上,开发了具有数据预处理(环境指标分割)、关联知识发现、结果生成的应用系统,对系统做了初步试验和分析,从系统输出的结果中,可以辅助企业进行生产环境的优化.研究表明,用关联规则挖掘分析生化企业数据是有效的.     

Anelasticity and damping of thin aluminum films on silicon substrates

A new dynamic measurement system has been developed to investigate damping in thin metal films. This system includes a vacuum chamber, in which a free-standing bilayer cantilever sample is vibrated using an electrostatic force, and a laser interferometer to measure the displacement and velocity of the sample. With this equipment, internal friction as low as 10/sup -5/ in micrometer thick metal films in a temperature range from 300 to 750 K can be measured. Free-standing cantilevers with different frequencies have been fabricated using well-established integrated circuit (IC) fabrication processes. The cantilevers consist of thin metal films on thicker Si substrates, which exhibit low damping. From measurements of internal friction of Al thin films at various temperatures and frequencies, it is possible to study relaxation processes associated with grain boundary diffusion. The activation energy calculated from the damping data is 0.57 eV, which is consistent with previous research. This value suggests that the mechanism of internal friction in pure Al films involves grain boundary diffusion controlled grain boundary sliding. A model to describe these damping effects has been developed. By deriving an expression for the diffusional strain rate using a two-dimensional (2-D) Coble creep model, and modifying the conventional standard linear solid model for the case of bending, it is possible to give a good account of the observed damping.     

Micro porous polymer foil for application in evaporation cooling

A novel bionic cooling system for photo voltaic (PV)-cells based on a micro porous evaporation polymer foils is developed and the cooling mechanism is demonstrated. The foil consists of a two layer permanent resist on a silicon substrate with an evaporation pore diameter of 35 μm. Evaporation rates of the porous cooling area exceed those of bulk water by about three orders of magnitude. A homogeneous cooling effect on the PV front side of 4.2 K at an environment temperature of 55 °C and 45 % RH is proved. The developed fabrication is transferable to large scale mass production.     

Photochromic films prepared by vacuum co-deposition of polymer and spiropyrans

Photochromic polymer thin films have been prepared by vacuum co-deposition of PTFE and several spirocompounds. Their photochromic properties were studied with the use of the spectral-kinetic method. A number of positive properties for application of these films were found.     

InP dies transferred onto silicon substrate for optical interconnects application

We bonded quantum well InP dies on a photonic layer transferred on silicon CMOS processed wafer using direct molecular bonding. This approach is suitable for new applications, viz., photonics on silicon, 3D packaging and integrated sensors. The chips are diced from a bulk substrate and bonded directly onto a silicon substrate without any organic nor metallic adhesive layer. A thin silicon dioxide layer can be added on both assembled surfaces to enhance bonding quality. After bonding, the dies can mechanically be thinned down to 20 μm and chemically etched. The InAsP quantum well stack of the InP dies keeps its optoelectronics features and performances after being transferred onto a silicon substrate.     

Fabrication of ceramic microcomponents and microreactor for the steam reforming of ethanol

Ceramics have several advantages over other materials in MEMS, such as heat resistance, hardness, corrosion resistivity even in harsh environments, chemical inertness for biological applications and catalytic activity of surfaces and so on. For these advantages ceramic microstructures will be very potentially useful in microsystem, especially in microreactor. A novel method for the high aspect ratio micro ceramic structures fabrication based on deep X-ray lithography and lost-mold technique is developed. By using this method, ceramic microreactors have been successfully fabricated. The ceramic microreactor consists of 14 identical microchannels in parallel, each with typical dimensions of approximately 300 μm in width, 400 μm in height and 20 mm in length. The Ni film catalyst with thickness of 300 nm is uniformly coated through sputtering process. The steam reforming of Ethanol into hydrogen on the ceramics microreactor was studied at temperatures between 500 and 700°C. The microreactors have been characterized by studying of C₂H₆O conversion, H₂ selectivity, and product stream composition.     

Single‐layered retardation films with negative wavelength dispersion birefringence made from liquid‐crystalline monomers

Organic light‐emitting diode displays have a cathode composed of a layer of highly reflective metal. Reflection of external light from this layer can be suppressed with a broadband quarter‐wave plate. Although various types of quarter‐wave plate retardation films have been prepared by copolymerizing, mixing, or laminating multiple polymers, ideal wavelength dispersion has not been achieved with thin retardation films because of their relatively low birefringence and the complexity of the procedure required manufacturing them. In this study, we developed (i) new liquid‐crystalline monomers with negative wavelength dispersion birefringence that we used to obtain thin, single‐layered retardation films suitable for coating and (ii) retardation films with different molecular alignments. We found that the monomers showed high solubility and high regularity of molecular alignment, with less damage to the substrate and alignment films. We also investigated the wavelength dispersion and thermal stability of the films. We succeeded in developing retardation films that had a homeotropic alignment or a hybrid alignment with negative wavelength dispersion. These alignments can be used to obtain antireflection films with an improved viewing angle for organic light‐emitting diode displays or next‐generation thin displays.     

硅尖的制备及在传感器技术中的应用

介绍了硅尖的制备及其在传感器技术中的应用。硅尖的制备方法可与现代IC工艺兼容且易削尖,故比其它材料微尖更实用。硅尖的应用随着制备工艺的改进与其它相关技术的进步必将得到新的开发。     

The influence of the silicon dioxide barrier films on the laser ablation destruction of the glass composites with the films drown from the sols

The laser ablation destruction of the composites with nano dimensional oxide one- or two-layers films drown from the sols on a glass substrate has been studied. It has been shown that the laser ablation destruction threshold energy density depends on the number and chemical composition of the layers and the drawing velocity. The ablation threshold energy density of the two-layer composites finds out mainly a tendency to decrease at the 3.8 mm/s drawing velocity, but at the 5.8 mm/s one—to increase that can be explained by the films thickness decreasing and the low-melting components from the glass substrate diffusion due to the barrier films diminishing.