Non-destructive Measurement Technique Research Articles

Surface Roughness Measurement Using Laser Speckle Statistical Analysis

Abstract This work represents a noncontact nondestructive technique for surface roughness measurement. The technique is based on investigating the statistical properties of the speckle patterns that are developed whenever a surface is illuminated with a highly coherent light source such as a laser. The main objective is to correlate the sizes of the speckles with their light intensities to the surface roughness and profile. Different statistical approaches and correlation analysis have been implemented. Spatial data analysis, or variogram analysis, has been used to develop the relationship between observations taken at various locations. Among the other advantages of such an approach, this technique is simple to implement and suitable for operation in a manufacturing environment.

Investigations on possibilities of inline inspection of high aspect ratio microstructures

LIGA is the basic idea of promising developments for the manufacturing of microelectromechanical system parts containing high aspect ratio microstructures. Aim of the work is a brief discussion of the starting-points for inline process inspection within a direct LIGA technology using deep X-ray lithography for the production of micromechanical gear wheels with critical dimensions of ∼35 μm width at ∼1 mm height as well as to show methodic and technical measuring possibilities. Firstly, results of the determination of residual solvent content distribution within ultra-thick SU-8 films are shown obtained from refracted near field optical measurements. Furthermore, the capability of X-ray computer tomographic imaging is discussed and measurements for the determination of the three-dimensional shape of high aspect ratio microstructures are practically demonstrated with microscopic and interferometric optical methods. Finally, first results demonstrate the potential of the optical coherence tomography for several further important measurement tasks, among others, e.g. for the imaging of the distribution of mechanical stress at the resist–substrate interface. The results show that much information which is essential in the LIGA process can be achieved with recently available measurement methods. However, further development of non-destructive measurement techniques would be desirable for an effective inline process control of mass production of micromechanical parts.

Measurement of critical current density of YBCO film by a mutual inductive method using a drive coil with a sharp iron core

Recent developments in high-temperature superconductors have facilitated the production of high critical current and large-area films by the PLD method or MOD method. Nondestructive measurement techniques for high quality films are of great importance to estimate superconducting properties, such as the critical current density, JC. The inductive method using the third-harmonic voltage component, V3, is a promising technique for the measurement of the properties of JC. On inductive determination of JC for high-JC thin films and thicker films (thickness d ⩾ 0.1 mm), the drive coil must generate a magnetic field sufficiently large to break the complete field shielding of the film. Therefore, we investigated a mutual inductance technique using a drive coil with a sharp ferromagnetic core for investigation of the JC of the PLD–YBCO film. As a result, an abrupt nonlinear increase in the voltage across the pick-up coil was detected after magnetic full penetration of the film, and the threshold of the drive current Ith was suppressed to 0.23–0.28 times as compared with that measured by the inductive method using the third-harmonic voltage, V3. FEM analysis indicated the diameter of the excitation field region to be 0.6 mm in the case of a 0.4 mm ϕ iron core. The E–J characters measured by the mutual inductive method as a function of frequency agreed well with those measured by the inductive method using V3.

Effect of initial resist thickness on residual layer thickness of nanoimprinted structures

Quantification and control of the residual layer thickness is a critical challenge facing nanoimprint lithography. This thickness must be known to within a few nanometers, yet there are very few nondestructive measurement techniques capable of extracting such information. Here we describe a specular x-ray reflectivity technique that can be used to not only quantify the thickness of the residual layer with sub-nm resolution, but also to extract the pattern height, the line-to-space ratio, and relative linewidth variations as a function of the pattern height. This is illustrated through a series of imprints where the initial film thickness is varied. For films with sufficient resist material to fill the mold, complete pattern filling is observed and the residual layer thickness is directly proportional to the initial film thickness. When there is insufficient resist material in the film to completely fill the patterns in the mold, a finite residual layer thickness of approximately 50–100Å is still observed.

Grain-scale processes governing shear band initiation and evolution in sands

A variety of experimental techniques have been used to advance understanding of strain localization phenomena in sands. However, all of these methods have fallen short in characterizing the evolution of the grain-scale processes that necessarily control shear band formation and growth in sands. This paper presents results of application of the non-destructive displacement measurement technique of digital image correlation (DIC) to measure two- and three-dimensional surface displacements on plane strain and axisymmetric sand specimens over short time steps. The abundance of local displacement data, high level of accuracy, and nearly continuous (spatially and temporally) record of displacement evolution afforded by the DIC technique has finally enabled a means to quantify local displacements to particulate-scale intensity. The data have been used to evaluate the local displacement mechanisms leading to the triggering of the formation of persistent shear bands, the timing of shear band formation with regard to the achievement of peak stress, and the character of displacements within fully formed shear bands. Insights are offered regarding the relation between strain localization and global stress–strain behavior, and the ensuing interpretations of shear banding as a hardening or softening phenomenon. Comparison of behavior between plane strain and triaxial tests offer additional perspective on the influences of three-dimensional stresses and boundary conditions on shear banding. The results further shed light on the micro-deformation mechanisms (i.e. buckling columns) responsible for the observed local strain non-uniformities that characterize “steady-state” shear band evolution.

A Nondestructive Technique for Local Measurement of Dielectric Loss in Substrates of Integrated Circuits at Microwaves

A device for nondestructive measurements of dielectric loss in substrates of integrated circuits and film materials in a local 2-mm-diameter zone has been developed. The main element of the device is a coaxial resonator with a measurement hole at its end and a clamp for dielectric substrates in the form of a cylindrical waveguide that is evanescent for measurement frequencies. In such a system, emission of electromagnetic waves from the measurement hole is absent, although the phenomenon of emission is characteristic of a coaxial resonator with a hole to which a dielectric is applied. The absence of radiation loss simplifies the determination of the loss tangent for dielectric substrates. A formula for calculations and a measurement technique in the range of 10 GHz are presented.

Index Profile of Radial Gradient Index Lens Measured by Imaging Ellipsometric Technique

A simple three-intensity imaging ellipsometric technique is proposed for measurement of the refractive index profile (RIP) of a radial gradient index (GRIN) lens. According to our numerical analysis, the improved ellipsometric parameters measured by this method are valid as long as the azimuth deviation of the polarizer is less than 3°. A BK7 glass and a radial GRIN lens were measured. A fairly flat refractive index surface profile was obtained for the glass within a 0.3% error. The on-axis refractive index of the radial GRIN lens and its RIP are well fitted to the specifications provided by the manufacturer. Instead of the refracted-ray method, we provide a reflective and nondestructive measurement technique for measurement of the gradient index of a flat surface.

Development of Nondestructive Measurement Technique for Fruits Sugar Content with Near-Infrared Laser Diodes Operating at Three Different Wavelengths

A new measurement technique based on three near-infrared laser diodes is proposed for non-destructive evaluation of sugar content in fruits. A parameter γ, which is independent of the optical path length is considered, such that γ=ln (Ri/Rk)/ln (Ri/Rk), where the values of reflectance Ri, j, k represent the ratio of values of diffuseli ght power reaching to two receiving fibers corresponding to different wavelengths λi, j, k.Based on a simulation with a modeled-apple, it was found that there are optimum combinations among three wavelengths for which the correlation between the parameter γ and the sugar content of fruit becomes sufficiently high. The sugar content of apples was also measured experimentally with an accuracy of 0.63 Brix, by employing three laser diodes with wavelengths of 911, 936 and 1055 nm. The measurements clearly show the usefulness of the proposed technique.

Development of non-destructive Young's modulus measurement techniques in non-oriented CeF3 crystals

For a reliable mechanical assembly of scintillating crystals for the application to radiographic systems such as Positron Emission Tomographer (PET) and high-energy physics calorimeters (e.g. in CMS at CERN LHC), the evaluation of the monocrystal elastic constant (Young's modulus) is needed. Its knowledge is also essential in the photoelastic analysis for the determination of residual stresses. In this work non-destructive techniques based on elastic wave propagation are tested. They differ in the mechanical excitation device: instrumented hammer, traditional ultrasonic probes and laser-generated ultrasound. We have analysed three non-oriented cerium fluoride crystal samples produced for scintillation applications. Finally, we have validated the experimental results comparing them with the elastic constant calculated by using the stiffness matrix.

Multi-wavelength all optical measurement for the characterization of recombination process in thin mc-Si samples

A contactless, all-optical and non-destructive technique for simultaneous measurement of minority carrier recombination lifetime and surface recombination velocity, at low injection level, in multi-crystalline silicon samples is presented. Being contactless and non-destructive with respect to the surface to be analyzed, the method does not need any surface treatment to be applied and therefore is suitable for routine lifetime characterization in solar cell fabrication processes.

Cross sectional area measurement of tendon and ligament in vitro: a simple, rapid, non-destructive technique

The structural properties of tendons and ligaments are integral to their ability to function effectively in vivo and are determined from both the geometrical form and material properties. Many studies of tendon and ligament include a mechanical assessment of the structure in vitro. However, to determine the material properties of the constituent tissues it is necessary to measure cross-sectional area (CSA). Problems associated with this include damage to the structure, inaccurate values for non-uniform shapes, labour intensive techniques or requirement of expensive equipment. We describe a non-destructive technique for measurement of tendon and ligament CSA based on that of Race and Amis (J. Biomech. 29 (1996) 1207). The modified technique uses aqueous rapid curing alginate dental impression paste, digital photography and computerised image analysis. This technique is quick and simple to carry out and provides accurate values (within 0.8%) for CSA which are reproducible (coefficient of variation=1.42%). The technique is non-destructive and can be used on specimens with an irregular shape.

A Nondestructive Electrical Test Structure to Monitor Deep Trench Depth for Automated Parametric Process Control

A novel nondestructive measurement technique is proposed to electrically monitor the depth of a trench etched in silicon for the purpose of process control in a manufacturing environment. A simple bipolar npn transistor can be constructed, the gain of which is shown to relate to the trench depth. The ratio of the injected emitter current to the captured collector current has demonstrated the ability to resolve variations in trench depth of less than 0.2 /spl mu/m. The proposed structure is studied using two-dimensional simulations and experiments. A case study of two different silicon reactive ion etch tools is offered to demonstrate the effectiveness of the proposed technique.

The characterisation of work-hardened austenitic stainless steel by NDT micro-magnetic techniques

It is accepted that the work-hardening of austenitic stainless steels during machining or cold-working results in two main products: the appearance of α′-martensite and increased dislocation densities within the host material. In machining, this results in many difficulties (poor surface finish, poor machinability and high tool wear). Non-destructive sensing is essential in today's high volume production environments because of its ease of use, speed and non-invasive sensing. Non-destructive magnetic measurement techniques have been employed to characterise the work-hardening of an austenitic stainless steel grade (SS404) due to room-temperature plastic tensile loading. These techniques include the use of magnetic Barkhausen noise, ferromagnetic phase measurement and coercivity measurement. It was found that the dislocation density, rather than the α′-martensite phase, to be the cause of material work-hardening. It is suggested that the use of coercivity measurement is a useful quantitative and non-destructive method for characterising work-hardening of the studied alloy in relation to the amount of its plastic deformation (work-hardening).

Measurement of the thermophysical properties of an NPL thermal conductivity standard Inconel 600

Flash methods have become one of the most commonly used techniques for measuring the thermal diffusivity and thermal conductivity of various kinds of solids and liquids such as metals, carbon materials, ceramics, and polymers. Easy sample preparation, small sample dimensions, fast measurement times, and high accuracy are only some of the advantages of this nondestructive measurement technique. However, the accuracy of measurement and level of uncertainty of the resulting data are becoming increasingly important for countless industrial applications. Instruments must be analyzed to determine the uncertainty of the system at different temperatures and application ranges. One way of checking the accuracy of the results is to cross-check the unit with certified reference materials. However, there is a lack of standard materials for thermal diffusivity/thermal conductivity all over the world. Furthermore, for some available standards, the thermophysical properties are known only over a limited temperature range. Here we report thermophysical property measurements on an NPL certified thermal conductivity standard, Inconel 600. Tests were carried out between -125 and 1000°C. A DIL 402 C pushrod dilatometer was employed to determine the thermal expansion and density change of the material. The specific heat was measured by differential scanning calorimetry. The thermal diffusivity was measured with the laser flash technique. The measured data were used to determine the thermal conductivity of the material.

Separation of bulk lifetime and surface recombination velocity by multiwavelength technique

A contactless, all-optical and non-destructive technique for simultaneous measurement of minority carrier recombination lifetime and surface recombination velocity, at low injection level, in silicon samples is presented. Being contactless and non-destructive with respect to the surface to be analysed, the method is appealing for routine lifetime characterisation.

Measuring the Sugar Content of Apples and Apple Juice by Near Infrared Spectroscopy

The sweetness of apples is usually measured by destructive inspection, which is time-consuming. As an alternative, a rapid instrument with high accuracy is very desirable. This paper reports an application using the NIR method to measure the sugar content of apples quantitatively. Samples containing mainly water showed that it was possible to measure the sugar content of fruit using the second derivative treatment (the background is removed) of the nearinfrared absorption spectrum. Measurements of the sugar content of four varieties of apples had correlation coefficients of 0.94 or more and a standard error of prediction (SEP) of 0.546°Bx at most. In the two kinds of apple juice, we obtained a SEP value of 0.439°Bx at most and correlation coefficients of 0.97 or more. We also found that 912 nm was an important wavelength for determining sugar content for both apples and juice. These results were in good agreement with calibrated values. NIR spectroscopy is a non-destructive measurement technique, and there is value in utilizing it for samples that are mainly water. Biotechnology applications are expected.

17th Symposium on Non-Destructive Measurement Techniques

17th Symposium on Non-Destructive Measurement Techniques

Nondestructive measurement of resistivity in bulk In xGa 1− xAs crystals

By using a nondestructive resistivity measurement (NDRM) technique, which is based on a Fourier analysis of charge response in a metal–insulator–semiconductor–metal (MISM) structure, the resistivity in bulk In x Ga 1− x As crystals has been measured. Two-dimensional (2-D) distribution map measured in a sample sliced along the growth direction in a graded composition ingot of In x Ga 1− x As crystal showed that the resistivity gradually decreased from 10 8 to 10 5 Ω cm with the increase of indium composition except in the seeding region. It was also found that there were inhomogeneous distributions of resistivity in the seeding region due to the diffusion of Si from the GaAs seed crsytal. Since the inhomogeneous distribution of resistivity reflects the growth conditions such as temperature distribution and melt flow, the nondestructive measurement of resistivity by the NDRM technique is useful for evaluating not only the crystal quality but also the growth technique in bulk In x Ga 1− x As crystals.

Infrared spectroscopic ellipsometry—a new tool for characterization of semiconductor heterostructures

Spectroscopic ellipsometry (SE) for infrared wavelengths is presented as a novel technique for contactless and nondestructive measurement of free-carrier and crystal-structure properties of complex semiconductor heterostructures for device applications. Infrared (IR)-active lattice vibrations and LO phonon–plasmon coupled modes dominate the infrared dielectric response of semiconductor materials. Analysis of ellipsometry data from 2 to 33 μm can precisely determine thin-film dielectric functions (DF) without numerical Kramers–Kronig analysis and thus provides information on phonon mode frequencies and broadening parameters, static dielectric constants, and free-carrier parameters, even for films with thicknesses only a fraction of the probing wavelengths. Alloy composition, film strain, and crystal quality of sample constituents in thin-film heterostructures can be derived. An infrared dielectric function database, which was established by analysis of simple heterostructures, is used for the investigation of complex device structures. As an example, we demonstrate the characterization of a laser diode (LD) structure based on group-III-nitride materials, where information such as concentration and mobility of free carriers in the n- and p-type regions, thickness, alloy composition, and quality of device constituents are accessible.

核融合炉内外におけるトリチウムの回収技術 3.水素同位体科学研究センターにおける最近のトリチウム研究

Recently developed techniques for nondestructive measurement of tritium, separation of hydrogen isotopes, and decontamination of tritium-contaminated materials at the Hydrogen Isotope Research Center (HRC) in Toyama University were introduced. As a nondestructive measuring technique for high level tritium, β-ray-induced X-ray spectrometry (BIXS) was applied to the evaluation of elemental, oxidized, and ad/absorbed tritium, and it was concluded that this technique is fairly available for determination of tritium in gaseous, liquid, and solid states. A new separation technique by gas chromatography using the Pd-based alloy was proposed, which can be operated near room temperature. Performance of the present separation technique was examined by using a mixture of H, D, and T species. Finally, an example of the thermal behavior of tritium absorbed in stainless steel type 316 was shown.