Flexible contact stamp for electrical conductivity measurements of a soft matter

In this communication, a simple homemade four probe conductivity setup has been presented to measure the electrical conductivity of molecularly grafted and passivated solid surfaces. Setup was also extended for the temperature dependent conductivity measurements by designing a small furnace using nichrome heating element. The importance of prepared setup lies in its easy designing ability, portability and reliability to measure the conductivity of soft matters. Setup was designed for four probe conductivity measurements which can be used for two probes conductivity measurements also, depending upon the requirements under investigation. Setup was tested using its four probes for electrochemically grafted indium tin oxide surfaces with thiol containing organic molecules and trichloroethylene passivated Si surface. It was found very sensitive even for observing small changes in current–voltage values whereas recorded curves were quite reproducible.     

Development of an improved Kelvin probe force microscope for accurate local potential measurements on biased electronic devices

An improved setup for accurate near‐field surface potential measurements and characterisation of biased electronic devices using the Kelvin Probe method has been developed. Using an external voltage source synchronised with the raster‐scan of the KPFM‐AM, this setup allows to avoid potential measurement errors of the conventional Kelvin Probe Force Microscopy in the case of in situ measurements on biased electronic devices. This improved KPFM‐AM setup has been tested on silicon‐based devices and organic semiconductor‐based devices such as organic field effect transistors (OFETs), showing differences up to 25% compared to the standard KPFM‐AM lift‐mode measurement method.     

Development of fast-response portable NDIR analyzer using semiconductor devices

In this paper, a novel fast response NDIR analyzer (FRNDIR), which uses an electrically pulsed semiconductor emitter and dual type PbSe detector for the PPM-level detection of carbon dioxide (CO₂) at a wavelength of 4.28 μm, is described. Modulation of conventional NDIR energy typically occurs at 1 to 20 Hz. To achieve real time highspeed measurement, the new analyzer employs a semiconductor light emitter that can be modulated by electrical chopping. Updated measurements are obtained every one millisecond. The detector has two independent lead selenide (PbSe) with IR band pass filters. Both the emitter accuracy and the detector sensitivity are increased by thermoelectric cooling of up to —20 degrees C in all semiconductor devices. Here we report the use of semiconductor devices to achieve improved performance such that these devices have potential application to CO₂ gas measurement and, in particular, the measurement of fast response CO₂ concentration at millisecond level.     

Modal analysis and experimental research into improved centering–leveling devices

Centering–leveling devices are often used together with rotary tables to improve measuring process in various fields of metrology. The most important factor of measurement quality – accuracy – is affected by numerous external and internal factors. To ensure the optimum quality of measurements, several factors have to be well known and thus taken into account in the final measurement to minimize their influence. Analysis of structural dynamics provides data on sensitivity as well as an appropriate method to verify the analytical model. The paper deals with an analysis of structural dynamics of a plain structure centering–leveling device by performing appropriate modal analysis. The experimental setup for vibration monitoring and measurement principle underpinning the work is described in the paper. Measurement results of table dynamics as well as a comparison of theoretical and experimental modal shapes are discussed.     

Experimental characterization of low-frequency noise in power MOSFETs for defectiveness modelling and technology assessment

In this work we analyse the applicability of low-frequency (LF) noise measurement in order to study the defectiveness in the gate oxide of power MOSFETs (Metal–Oxide–Semiconductor Field-Effect Transistors). To this purpose, we implement a low-noise experimental set-up, which is able to measure, in particular, the flicker (“1/f”) contribution to the drain noise current of the device under test, with high accuracy in terms of noise floor and the adequate bias system flexibility required by the application. First, we show how these measurements can be used to empirically detect the physical model and related compact expressions, which best describe the source of 1/f-like fluctuations in this type of devices. Then, according to the selected physical model, the defect density in the gate oxide is extracted. In order to validate the proposed methodology, experimental data are reported and discussed in the case of power U-MOSFETs.     

Ultrahigh vacuum-compatible fabrication and electrical characterization systems for environmentally sensitive metal oxide semiconductor capacitors

We describe an integrated, ultrahigh vacuum system for metal oxide semiconductor (MOS) device fabrication and characterization. This system is advantageous for electrical property measurements on electronic devices with environmentally sensitive materials and is especially important as device dimensions approach the nanoscale. Without exposure to atmosphere, MOS capacitors were fabricated by evaporatively depositing gate metal on molecular-beam-epitaxy (MBE) grown dielectrics through a shadow mask in an UHV electrode-patterning chamber. Finished devices were transferred in UHV to an in situ UHV electrical characterization probe station. We obtained excellent agreement between air-ambient ex situ and in situ probe station measurements with less than 0.3% systemic error for frequencies from 20 Hz to 1 MHz. We have successfully measured MOS capacitors with sensitivity to a density of interface states of 1x10(10) states cm(-2) eV(-1). These measurements show 0.5% systematic error for measurement frequencies from 20 Hz to 1 kHz and less than 0.1% from 1 kHz to 1 MHz. The integrated system presented here is one where complex, MBE-grown MOS heterostructures can be synthesized and tested rapidly to explore new field-effect-device physics and functionality.     

Experimental determination of the propagation of wireless signals on board a cruise ship

The characterization of the wireless channel on board a cruise ship is considered by means of frequency domain measurements of received power and propagation attenuation. This electromagnetic environment is rather new and is characterized by abundance of reflecting and diffracting elements, so that a significant difference with respect to more common residential and office environments was found. The measurement setup is simple and easy to position and operate; the measurement results were validated by comparison with another independent measurement setup. The results indicate that the power losses for corridors are not a power law of distance, due to scattering; even in large environments such as restaurant halls the presence of reflecting and scattering objects and installations largely affects the received power.     

A Technique for Measuring Low-Frequency Current Noises in Semiconductor Gas Sensors

A technique and laboratory setup for measuring the low-frequency current noise of semiconductor gas-sensitive structures in a spectral range of 0.001–100 Hz are described. The setup allows noise measurements at sample temperatures of 20–450°C at various compositions of the gas phase and different bias voltages of the transport current. A method for selecting the bias-voltage value and a technique for preparing samples for noise measurements that appreciably increases (by 20–50%) the reproducibility of measurement results are described. An example of studying the noise of gas sensors based on SnO₂–Pt–Pd in a neutral medium (argon), atmospheric air, and a mixture of air and acetone vapors is presented.     

PMetro: Measurement of urban aerosols on a mobile platform

PMetro is an innovative time/space resolved urban aerosol monitoring and data management system. The core of the monitoring system is a customized optical particle counter (OPC) integrated on a cabin of the metro urban transport system in Perugia (Central Italy). This peculiar arrangement and setup allow regular, real-time measurement of aerosol particles on a well defined path through the city all over the day. The performances of the prototype OPC system have been customized and finally inter-compared with those of similar commercial devices placed at fixed points along the metro line. Data from the mobile system are integrated with environmental measurements from fixed monitoring stations along the metro path in order to attain models of the evolution of urban aerosol pollutants.     

Microwave band on-chip coil technique for single electron spin resonance in a quantum dot

Microwave band on-chip microcoils are developed for the application to single electron spin resonance measurement with a single quantum dot. Basic properties such as characteristic impedance and electromagnetic field distribution are examined for various coil designs by means of experiment and simulation. The combined setup operates relevantly in the experiment at dilution temperature. The frequency responses of the return loss and Coulomb blockade current are examined. Capacitive coupling between a coil and a quantum dot causes photon assisted tunneling, whose signal can greatly overlap the electron spin resonance signal. To suppress the photon assisted tunneling effect, a technique for compensating for the microwave electric field is developed. Good performance of this technique is confirmed from measurement of Coulomb blockade oscillations.     

Error analysis in high-accuracy digital measurements

Knowledge of the upper limits of errors in digital sampling is very important in high-accuracy measurements, for these errors are significant elements for establishing measurement quality. In this paper, we carefully go through the theoretical background necessary for an in-depth understanding of the main sources of errors in high-accuracy measurement of harmonic components. We assess the significance of each error source both qualitatively and quantitatively, and also the efficiency of error-reduction strategies. Theoretical results are backed by simulations and also experimental results obtained with digitally sampled data. We discuss the aliasing- and integration-error interplay due to the lowpass filtering performed prior to digital sampling. We also discuss the non-causal integration model often assumed for sampling devices, e.g., digital voltmeters, and how the correction term shall be used with periodical signals in practical measurement setups.     

高压电流互感器小信号校验设备的应用与分析

针对高压电流互感器小信号校验设备的应用,进行试验性地检测、应用和分析。针对发现的问题,提出解决的办法,使高压电能计量装置的基建验收和现场检定工作能够高效、便捷、可靠开展,为此种设备的推广应用提供规范和依据。     

A setup for measurements of free-electron lifetime in a gas phase

A setup for measuring the lifetime of free electrons in a neutral buffer gas that contains an electronegative impurity is described. This setup is intended for prompt diagnostics of carcinogenicity of chemical compounds and consists of an ionization chamber with laser photoionization of the cathode, a gas system, and a system for collection and processing of experimental data based on an HBJI45 amplitude-to-digital converter. The techniques for preparing the tested gaseous mixtures and processing the experimental results are described. The results of measurements of the lifetimes and calculated free-electron capture constants for a CO₂ + O₂ calibrating mixture and mixtures of CO₂ with organic molecules are presented. The setup allows measurements of the lifetimes of free electrons in mixtures in the range 0.5–70 μs at measurement errors of 0.2–6%, respectively, and study of two or three potentially carcinogenic substances a week.     

Concepts for validating intelligent process measurements

With increased automation, operational validation is vital for effective control, maintenance and management of industrial plants and processes. Validation should be traceable, starting from the interface to the process up to the highest level of operations. At present, validation is focused at the systems level and current methods are based on condition monitoring, and fault detection and isolation techniques using functional, analytical and hardware redundancy. With the focus at the systems level, redundancy methods exploit integration and fusion of information from multiple measurement devices, and thus tend to disregard validation of the operation of the individual devices themselves. Transducers and sensors provide an interface to the process and produce measurement information. Validation of the measurement output from a sensor is imperative in situations where the cost of redundancy may be prohibitive. This paper presents concepts for validating measurements made with intelligent devices. The proposition is that an intelligent device should provide both measurement and condition information. The condition information should be used to assess the validity of the measurement by identifying metrics which describe the sensor and process conditions, respectively. This is the lowest level of validation because it occurs at the interface with the process being monitored. The information required for this level of validation can be obtained by utilizing all the components of the signal produced by a sensor, providing that the sensor has a wide frequency response. An example of a validation approach which follows from this argument is briefly described.     

Atmospheric visibility and Angström exponent measurements through digital photography

This paper presents a low-cost system for the measurement of atmospheric visibility. The measurement setup is composed by a consumer digital camera which is controlled by a computer. The camera acquires photos of the landscape that include natural dark objects. Then the computer calculates the atmospheric visibility based on the apparent contrast, against the background, of these dark objects through the Lambert–Beer law. Two different approaches are proposed so that the system is able to measure the atmospheric visibility both under normal and low visibility conditions. The use of the three color channels of the camera allows the measurement of the extinction coefficient at different wavelengths along with the Angström exponent which is an important parameter in the classification of atmosphere aerosols.Measurements performed with the developed system are presented and include the atmospheric visibility, the extinction coefficient and the Angström exponent. The results presented correspond to the measurements performed along a week that included a desert dust event. This event dramatically reduced the atmospheric visibility due to the desert dust particles. Angström exponent measurements were performed with another instrument for comparison. Finally, an uncertainty analysis of the measured atmospheric visibility is presented.     

Semiconductor devices "from inside"

Operation of any semiconductor device can be presented by unique configuration of the electrical field (potential) and charge (doping) distribution within the device. More specifically, the status of operation is described by the quasi-Fermi energy (QFE) profile across the device. Visualization of the dynamic operation of the device and quantitative measurements of the QFE profile is provided by differential voltage contrast (DVC), which is a modification of the secondary electron imaging in a scanning electron microscope (SEM). The DVC consists of storing two images of a tested semiconductor device. Exposed to the electron beam is a cross section, for example, of a field effect transistor (FET). The first image, covering the entire inside of the FET from source to drain, is taken when the device is not biased. The second image of the same area is taken when the transistor is biased. The secondary electron signal is enhanced or retarded by actual distribution of a potential across the tested device. Subtraction pixel by pixel of the two carefully aligned images removes morphologic contrast from the screen, takes away surface features and contamination of the sample, and reveals the contribution of the electrical field to the changes of contrast. The calibration procedure allows measurement of the potential distribution with a precision of 0.05 V. The first derivative of a potential profile provides for distribution of the electrical field and the second derivative gives the doping profile across the tested device. A variety of semiconductor devices such as p-n junctions, Zener diodes, MOSFET's, MESFET's, solar cells and optical detectors, quantum well lasers, etc., were tested. Videotaping of the tested devices allows us to observe the changes in the electrical field and charge distribution as the device operates in a wide range of electrical or optical signals.     

Determining the thermal generation rate of minority charge carriers at semiconductor-ultrathin oxide interfaces

A simple proximate method for determining the generation rate G _s of electron-hole pairs in metal-ultrathin oxide-semiconductor (MOS) structures is proposed. This method is based on measurements of dynamic current-voltage characteristics of MOS structures in the region of deep depletion of the semiconductor surface and on the comparison of these data to a quasi-equilibrium volt-farad characteristic (VFC) of an ideal MOS structure. This approach to determining G _s from the value of the structure capacitance is insensitive either to a shift of the VPC, which is caused by the presence of built-in charges, or a recharge of localized electron states in the oxide and at the Si-SiO₂ interface. The proposed technique also allows one to take the influence of a tunneling current through an insulator on the measurement results into account. The algorithm was tested in studies of generation and annihilation processes of centers of generation of electron-hole pairs in n-Si-based MOS structures with an ultrathin (≅4 nm) oxide.     

C-V measurements of micron diameter metal-oxide-semiconductor capacitors using a scanning-electron-microscope-based nanoprobe

The C-V electrical characterization of microstructures on a standard probe station is limited by the magnification of the imaging system and the precision of the probe manipulators. To overcome these limitations, we examine the combination of in situ electrical probing and a dual column scanning electron microscope/focused ion beam system. The imaging parameters and probing procedures are carefully chosen to reduce e-beam damage to the metal oxide semiconductor capacitor device under test. Estimation of shunt capacitance is critical when making femtofarad level measurements. C-V measurements of micron size metal-oxide-silicon capacitors are demonstrated.     

Salinity and flow regime independent multiphase flow measurements

For oil production fields, there is a need for downhole measurements of the gas/water/oil multiphase flow. In extreme conditions a relatively simple, robust, and non-intrusive system will be appropriate. A measurement setup that combines multiple gamma beam (MGB) and dual modality densitometry (DMD) measurements, would be able to determine the gas volume fraction (GVF) independently of the flow pattern, and monitor changes in water salinity. MGB measurements of gamma-ray transmission along multiple sections across the oil pipe will provide information on the flow pattern. Whereas the DMD principle will give information on changes in salinity from a combination of transmission and scattering gamma-radiation measurements. In this work we present the results from MGB and DMD measurements of a multiphase flow with high-speed gamma-ray tomograph measurements as reference for the flow pattern. The MGB measurements should enable us to distinguish between stratified or wavy/slug and annular or slug flow. Flow patterns with several minor components distributed evenly over the measurement cross section, like bubble flow, will be interpreted as homogeneous flow. The DMD measurements can be used to monitor salinity changes of the water component for intervals where the GVF is low and the water cut of the liquid is high. Combined with other gauges for water cut measurements, the MGB and DMD measurement setup should improve the multiphase flow measurements, and enable increased oil/gas recovery and production water monitoring.     

Wavelength-encoded optical psychrometer for relative humidity measurement

In this article an optical psychrometer, in which temperature measurements are performed by means of two fiber Bragg grating sensors used as dry-bulb and wet-bulb thermometers, is introduced. The adopted design exploits both the high accuracy of psychrometric-based relative humidity measurements with acknowledged advantages of wavelength-encoded fiber optic sensing. Important metrological issues that have been addressed in the experimental work include calibration of the fiber Bragg grating temperature sensors, evaluation of response time, sensitivity, hysteresis, linearity, and accuracy. The calibration results give confidence that, with the current experimental setup, measurement of temperature can be done with an uncertainty of +/- 0.2 degrees C and a resolution of 0.1 degrees C. A detailed uncertainty analysis is also presented in the article to investigate the effects produced by different sources of error on the combined standard uncertainty uc(U) of the relative humidity measurement, which has been estimated to be roughly within +/-2% in the range close to saturation.