Measurement technique for the thermal properties of thin-film diaphragms embedded in calorimetric flow sensors

In diaphragm-based micromachined calorimetric flow sensors, convective heat transfer through the test fluid competes with the spurious heat shunt induced by the thin-film diaphragm where heating and temperature sensing elements are embedded. Consequently, accurate knowledge of thermal conductivity, thermal diffusivity, and emissivity of the diaphragm is mandatory for design, simulation, optimization, and characterization of such devices. However, these parameters can differ considerably from those stated for bulk material and they typically depend on the production process. We developed a novel technique to extract the thermal thin-film properties directly from measurements carried out on calorimetric flow sensors. Here, the heat transfer frequency response from the heater to the spatially separated temperature sensors is measured and compared to a theoretically obtained relationship arising from an extensive two-dimensional analytical model. The model covers the heat generation by the resistive heater, the heat conduction within the diaphragm, the radiation loss at the diaphragm’s surface, and the heat sink caused by the supporting silicon frame. This contribution summarizes the analytical heat transfer analysis in the microstructure and its verification by a computer numerical model, the measurement setup, and the associated thermal parameter extraction procedure. Furthermore, we report on measurement results for the thermal conductivity, thermal diffusivity, and effective emissivity obtained from calorimetric flow sensor specimens featuring dielectric thin-film diaphragms made of plasma enhanced chemical vapor deposition silicon nitride.     

Metallic thin-film thermocouple for thermoelectric microgenerators

A new metallic thin-film thermocouple orientated towards thermoelectric microgenerators has been developed. It consists of a 3 μm thick NiCr/SiO₂/Sb multilayer structure sputter deposited onto a thermally oxidized silicon substrate. A relative Seebeck coefficient of _ab = 76 μV K⁻¹ and an optimal figure of merit of z_ab = 0.08 × 10⁻³ K⁻¹ have been measured for this material combination. Both parameters are very close to the theoretical values.     

Three-dimensional thin-film Li-ion microbatteries for autonomous MEMS

Autonomous MEMS require similarly miniaturized power sources. In this paper, we present the first working three-dimensional (3-D) rechargeable Li-ion thin-film microbattery technology that is compatible with MEMS requirements. The technology has been developed, and full 3-D cells have been manufactured on both glass and silicon substrates. Our 3-D microbatteries have a sandwich-like structure of conformal thin-film electrodes, electrolyte and current collectors. The films are deposited sequentially on all available surfaces of a perforated substrate (e.g., silicon or a glass microchannel plate or "MCP") using wet chemistry. The substrate has thousands of high-aspect ratio holes per square cm, thereby providing more than an order of magnitude increase in surface area per given footprint (original 2-D substrate area). The full 3-D cell consists of a Ni cathode current collector, a MoO/sub y/S/sub z/ cathode, a hybrid polymer electrolyte (HPE) and a lithiated graphite anode that also serves as anode current collector. One 3-D cell with a roughly 1-/spl mu/m-thick cathode ran at C/10 to 2C charge/discharge rates and room temperature for 200 cycles with 0.2% per cycle capacity loss and about 100% Faradaic efficiency. The cell exhibited a capacity of 2 mAh/cm/sup 2/, about 30times higher than the capacity of a similarly built planar (2-D) cell with the same footprint and same cathode thickness.     

Image processing plume fluence for superconducting thin-film depositions

Process control is a crucial element in all deposition techniques. It is especially elusive in the versatile and efficient deposition technique known as pulsed-laser-deposition (PLD). PLD produces a plume of highly energetic components which is directed onto a suitable substrate for growing required films. Image processed plume emissions from a YBa₂Cu₃O_{7 − x} target are in situ monitored at 553.5 nm to determine two-dimensional spatial information about the plume. Simultaneously, time-of-flight (TOF) information also at 553.5 nm is gathered from two positions along the plume path. Manual and fuzzy-logic based regulation of laser beam energy based on this TOF feedback has resulted in improved film quality and reproducibility. Imaging of the plume under various deposition conditions, both with and without process control, will help to improve the understanding of changing environmental conditions on the plume characteristics growth and quality.     

A finite volume scheme for cardiac propagation in media with isotropic conductivities

A finite volume method for solving the monodomain and bidomain models for the electrical activity of myocardial tissue is presented. These models consist of a parabolic PDE and a system of a parabolic and an elliptic PDE, respectively, for certain electric potentials, coupled to an ODE for the gating variable. The existence and uniqueness of the approximate solution is proved, and it is also shown that the scheme converges to the corresponding weak solutions for the monodomain model, and for the bidomain model when considering diagonal conductivity tensors. Numerical examples in two and three space dimensions are provided, indicating experimental rates of convergence slightly above first order for both models.     

航空发动机用薄膜热电偶研制

针对航空发动机涡轮叶片表面温度测试的迫切需求,采用薄膜沉积工艺,能够在Ni基高温合金表面制备热电性能较好的中温K型(NiCr/NiSi,<600℃)、高温R型(Pt—13%Rh/Pt,<900℃)、超高温(ITON/Pt,<1 100℃; In ON/ITON,> 1 200℃)等薄膜热电偶。薄膜热电偶由NiCr Al Y过渡层、热生长Al_2O_3层、Al_2O_3绝缘层、功能层和Al_2O_3保护层构成。通过静态标定结果分析,其塞贝克系数分别达到38. 26,10. 60,78. 60,123. 10μV/℃,在恶劣环境下具有良好的稳定性和一致性,使用寿命均大于10 h。     

Pyroelectric thin-film sensor array

Pyroelectric thin-film point detectors and 1 × 12 arrays have been fabricated and characterized. They consist of sol-gel-deposited PZT thin-film elements on micromachined Si₃N₄/SiO₂ membranes. The measured current and voltage response as a function of modulation frequency of a 1 × 12 array element is compared with finite-element calculations. Voltage responsivities of almost 3000 V W⁻¹ in vacuum and 800 V W⁻¹ in air have been achieved for 0.4 mm × 0.9 mm elements. Some point detectors have been completely packaged and correct operation in a movement detection system has been demonstrated.     

Assessment of testing methodologies for thin-film vacuum MEMS packages

In this paper, a summary of the most relevant failure mechanisms of thin-film vacuum microelectromechanical systems (MEMS) packages and existing testing techniques will be presented. Then, based on analytical models for thin-film vacuum MEMS packages (volume in the order of 10E−11 l), a feasibility study on options for thin-film vacuum MEMS package testing will be presented. This feasibility study leads to new insights and suggestions for future thin-film vacuum MEMS package testing.     

Machine vision algorithms for automated inspection thin-film disk heads

Machine vision algorithms and a supporting architecture that were integrated in a fully automated prototype system for disk head inspection are presented. Some specific methods are elaborated on, including the computation of the Hough transform and multicode masks in pipeline architectures, object segmentation in textured backgrounds, and matching of extracted defects with inspection specifications. Extensive experimental results are given.<>     

Pin-on-disk wear study on thin-film disks for contact recording systems

The main subjects to be solved for realizing contact recording systems are the reduction of head wear and head vibration. To reduce head wear, we investigated pin wear on various thin-film disk surfaces. We compared the effects of roughness of disk surfaces and molecular weight (MW) of lubricants. The results showed that the pin wear became larger as the lubricant MW became smaller or the disk roughness became large. In addition, we found the tape burnishing of disk surfaces was effective in pin wear reduction. From above, we developed sliding condition models on thin-film disks.     

Yield strength of thin-film parylene-C

For the first time, the yield strength of thin-film parylene-C is measured from membrane load-deflection experiments and surface profile analysis. To do so, the onset pressure which causes plastic deformation of the membrane is first experimentally measured. Then a new 2-step displacement model, together with the energy minimization technique [1], is developed to convert the onset pressure to the yield strength on the pre-stressed parylene membrane under a uniform pressure loading. The results depict a Yield Strength of 59 MPa (or 0.012 of strain) for thin-film parylene-C in comparison to 55 MPa reported by parylene vendor (measured from large samples) [2]. To double check with the result, the balloon model [3] is further used to compare with the stress value from our model at the center of parylene membranes and good agreements are obtained. This work is supported by the NSF Center for Neuromorphic Systems Engineering (CNSE) at Caltech.     

薄膜微量热计的信号采集与处理模块设计

薄膜微量热计是测量亚微米厚度薄膜热动力学特性的重要手段,针对薄膜微量热计的脉冲扫描量热测试方法改进了系统的信号采集与分析模块。微量热计原始信号经高精度仪用放大电路后,由高速数据采集卡采集送入PC机;采用LabVIEW软件编写的控制程序并采用Matlab软件实现数据的分析处理。对加载了70 nm厚度In薄膜的微量热计进行热容测试,观测到了In薄膜的熔化峰和熔点,表明系统具有足够高的信噪比和检测灵敏度。     

Research on electrostatic actuator polymer thin-film for controlling light scattering phenomena

The purpose of this paper is based on micro fabrication technology, while integrating planar waveguide technology and the scattering phenomenon generated by electro-statically actuator thin film, to develop a 2-dimensional display technology capable of being cleared and re-displayed. For thin film displacement, the restoration of inward elasticity needs to be overcome. During thin film displacement, attraction due to suction occurs when coming into contact with light waveguide; electrostatic force and elastic force are restored and mutually balanced, causing display to light up. On the other hand, when input voltage is released, electrostatic force stops and thin film is restored to original position, causing display to darken. The design structure uses SU-8 as supporting posts, and PDMS as the electrostatic thin film suspended above the glass substrate (light waveguide). The experimental results show that a waveguide with an electrode length of 250 μm (sub-pixel length), a micro-post height of 27 μm, and a PDMS film thickness of 16 μm requires an actuator voltage of 314 V; and a micro-post height of 27 μm, and a PDMS film thickness of 8 μm requires an actuator voltage of 189 V. Thus, with an arrayed micro-electrode design, electronic paper and panels with large color display area could be manufactured.     

基于薄膜压力传感器的矫形鞋垫个性化定制方法

矫形鞋垫对治疗足部疾病和足部引起的生物力疾病有显著的疗效。借助3D打印技术,矫形鞋垫能够高效、便捷地被制造出来。鞋垫加厚厚度的变化对患者足底疼痛点位置、足底局部集中力影响很大,严重影响矫正效果,鉴于适合患者行走的3D打印矫形鞋垫的设计模型需要有其足底的几何模型和受力数据,但是现有的模型参数设定大多依赖于医生的经验来量化其大小,为此本文提出了通过穿戴足底压力检测装置获取患者的足底压力数据,依据压力中心轨迹的位置与大小计算矫形鞋垫局部加厚厚度,经过个性化定制流程,可以较科学地实现矫正目标。     

薄膜热电偶动态建模方法

以薄膜热电偶动态补偿设计为背景,应用离散小波分析方法对实验数据进行了预处理,提出了基于自适应线性神经网络的薄膜热电偶辨识方法,建立了传感器的动态模型,通过试验数据的交叉检验,证明所采用的方法能获得理想的辨识效果。     

Single-layer thin-film transistor analysis and design

A set of direct current (DC) analytical equations is formulated for the analysis and design of a single-layer thin-film transistor (TFT). For a specified TFT structure, drain current is calculated as a function of drain and gate voltage (taking the source as ground) according to the Enz, Krummenacher, Vittoz (EKV) compact model. One model parameter function is required to implement this EKV-based equation, that is, drift mobility as a function of gate voltage. Drift mobility is evaluated as a consequence of accumulation layer electrostatics assessment of the TFT structure specified. In order to implement the model, three semiconductor properties (low-frequency (static) relative dielectric constant, free electron concentration, and maximum (no trapping) mobility), two structure properties (insulator capacitance density and TFT width-to-length ratio), and one physical operating parameter (temperature) must be specified. Optimal TFT mobility performance is achieved when the thickness of the semiconductor channel layer is constrained to be less than 2.22 times the channel layer Debye length such that “short-base” TFT operation obtains. Additionally, higher mobility TFT performance is obtained by selecting a channel layer with a small electron effective mass, reducing channel layer trap density, reducing channel layer thickness, reducing the free electron concentration, and/or increasing gate capacitance density.     

Fabrication of piezoelectric multilayer thin-film actuators

In this study, we fabricated multilayer ceramics (MLCs) composed of multilayered Pb(Zr,Ti)O₃ (PZT) piezoelectric thin films with internal electrodes and evaluated their dielectric and piezoelectric properties. The stack of PZT ferroelectric layers (550 nm) and SrRuO₃ (SRO, 80 nm) electrodes were alternatively deposited on Pt/Ti-coated silicon-on-insulator substrates by radio-frequency magnetron sputtering. The MLCs composed of one, three, and five PZT layers were fabricated by the alternate sputtering deposition of PZT ferroelectric layers and SRO electrodes through the movable shadow mask. The capacitances of MLCs were proportionally increased with the number of PZT layers, while their relative dielectric constants were almost same among the each MLC. The MLCs exhibited symmetric and saturated P–E hysteresis loops similar to the conventional PZT thin films. We estimated that the piezoelectric properties of MLCs by FEM simulation, and confirmed that the effective transverse piezoelectric coefficients (d _31,eff ) increased with the number of PZT layers. The piezoelectric coefficients calculated to be d _31,eff  = ?2964 pC/N at 25 PZT layers, which is much higher than those of conventional single-layer piezoelectric thin films.     

Modeling the growth of thin-film surfaces

Simulation of the growth of thin-film surfaces is considered. A brief review of the existing approaches and models is made. An original model of the growth of thin-film surfaces is proposed, which comprises a stochastic cellular automat and enables one to study the influence of the substrate temperature and the deposition rate and time on the parameters characterizing the morphology of the surface. The results of the modeling are compared with the data of atomic-force microscopy of experimentally produced thin films.     

A new dynamic hydrogen reference electrode for applications in thin-film sensor systems

The realization and applicability of a new dynamic hydrogen reference electrode (DHRE) within an electrochemical microcell for sensor applications is reported. The electrodes are fabricated in thin-film technology and fixed within a flow-through device. An experimental setup for accurate electrochemical potential measurements is described. Smooth platinum, platinized platinum and pHEMA coated electrodes are investigated with regard to their initialization behavior, stability, reproducibility and interference with electrolytes. It is found that platinized platinum DHREs show excellent stability and reproducibility. For uncoated electrodes, the electrochemical potential is established within seconds. The potential is independent of the pH value within the range of pH 4–10. Interference with sulfate and phosphate is observed. Thus, the platinized platinum DHRE is well suited for bioanalytical sensor applications, where the pH value is buffered and the concentrations of the disturbing anions are constant or very low.