Invisible Defects Research Articles

Three-dimensional X-ray topographic characterization of synthesized diamond crystals

Synthesized diamond crystals grown at high temperatures and high pressures were characterized by three-dimensional X-ray topography. The diffraction planes and wavelength of the monochromatic X-rays used were (004), {111}, and , and 0.0521 nm, respectively. Images of lattice defects in diamond crystals were reconstructed from a stack of about 300 X-ray limited projection topographs using the image processing software Image-J. The three-dimensional structures and nature of lattice defects were identified on the basis of the reconstructed topographs. The pyramidal shape of the four-part stacking fault generated from the seed crystal was identified using the dependence of visible or invisible defect images with diffraction planes. The sector boundary between the [001] and [111] growth directions was also first observed by three-dimensional topography. The image of the sector boundary did not show any dependence on diffraction planes.

Darboux–Crum transformations, Jordan states and PT-symmetry

We describe how Darboux–Crum transformations with Jordan states provide an useful method for the design of complex optical systems. We focus in the construction of PT-symmetric models with features like invisible periodic defects and vanishing reflection coefficient. Some illustrative examples are discussed.

Generation mechanism of large-size invisible defects on Si epitaxial wafers

The new Si epitaxial (epi) defects not seen in scanning electron microscope (SEM) measurements were investigated. Morphologies of these defects were measured by atomic force microscope (AFM) but source of defect was not found in transmission electron microscope (TEM) measurements. In order to find the origin of the invisible defect, we observed the morphological changes of the various substrate defects after epi growth process. Most of the defects were removed during hydrogen (H2) baking and hydrogen chloride (HCl) etching steps, but some particles survived. Among the survived defects, it was confirmed that the non-metallic particles having 200nm or more were the origin of the invisible epi defects.

Rail Track Irregularity Detection Method Based on Computer Vision and Gesture Analysis

In this paper, rail track irregularity detection system based on computer vision and SVD analysis is proposed and located in the train's operator cabin near the front. Images are captured by FLEA3 camera of Point-Grey, and vibration signals are collected by sensor device MPU6050 integrating 3-axis accelerometer and 3-axis gyroscope. Root mean square of gray-scale threshold Pulse Coupled Neural Network (RMS-PCNN) is used for segmentation of the rail track's image in a single loop, and the improved coupled map lattice(CML) is used for filtering the image and signifying the rail track. After perspective, the track radius can be fetched by analysis of regression. Vibration signal filtered by SVD-unscented Kalman filter(UKF) can reflect the wagon movements. In unscented Kalman filter, Cholesky is replaced by SDV in UT(unscented transform), which can solve negative definite matrix caused by covariance matrix on account of calculation error and round-off error. Also numerical stability is improved under the guarantee of filtering accuracy and the same complexity level of algorithm based on SVD-UKF. Looking up the radius record table, the corresponding threshold in gyroscope signal can be selected, and Compared to the super elevation, the invisible irregularity defects of rail bed will be found out.

Efficient defect identification of soft failures induced by device local mismatch for nano-scale SRAM yield improvement

As the device size continues shrinking to nano-scale region, tiny defects induced device local mismatch in SRAM array becomes a major yield limiter. It is often quite time consuming and challenging to identify such kind of invisible defects through conventional FA techniques. This paper presents an efficient methodology on device local mismatch fault isolation with the combination of test features, advanced Electrical Failure Analysis (EFA) and Physical Failure Analysis (PFA) techniques. A successful case study involving this advanced methodology will be also discussed.

Characterization of mono-ethylene-glycol based industrial polyurethanes samples by fast-neutron radiography and neutron tomography

A complicated structural organization of polyurethanes may have a strong influence on the materials functional properties. Under particular conditions such as mechanical and thermal loading and aging, it leads to the material degradation, even in fresh-prepared bulk polymers and especially if defects are present in the material. Unwanted bubbles can be observed, which form during the expansion of the mixture during its chemical reaction and remain present in the final product. These macro-, micro- and nano-bubbles influence the material's performance. In this work, neutron radiography and tomography have been adopted to characterize at a macro-scale level the bulk of commercially available polyurethane samples, obtained from dissimilar- mixture ratios with different densities and branching levels as well as from different zones of the production mould. The characterisation allowed an estimation of the different dense materials - as they are used, e.g., in soles of shoes - as well as the invisible defects like pores and cracks, responsible for the materials fracture by mechanical loading. The obtained information are expected to be useful for various industrial sectors such as automotive and footwear industry. It will be completed by applying SANS, which has already proved to characterize the microstructure of the bulk-polymer with respect to nano-pores, micro-cracks and their arrangement in the polymer matrix.

Critical invisible defect detection system of thin film transistor panels using Kelvin probe force microscopy

In this paper, a novel method that can perform measurements of the contact potential difference (CPD) between a tip and a thin film transistor (TFT) panel using the Kelvin probe force microscopy (KPFM) is proposed for inspection of critical invisible defects on TFT panels. In this application, the surface potential of a TFT panel is inferred from the electrostatic interaction force between a tip and a TFT panel induced by the electric field. The experimental results are given to illustrate that the KPFM provides a novel and feasible way to detect the most critical invisible defects on TFT panels.

Defect Detection of Fiberglass Composite Laminates (FGCL) with Ultrasonic A-Scan Signal Measurement

Fiberglass composite laminates are widely used in many industries, due to its advantages of high specific strength and high specific modulus. Invisible defect such as delamination and inclusion may cause composite structural failure. Therefore, several research on ultrasonic testing for composite material defect detection have been done for the past few years. However, improper parameter setup may lead to significant error to determine the behavior of defects. In this paper, the intensive study on defect detection with ultrasonic single crystal immersion transducer has been conducted. In general, the defects detection thru acquired signal is determine the behavior of defects through the certain ultrasonic parameter setup such as sound velocity, pulse width, gain, sampling rate and transducer distance with specimen surface. Furthermore, an A-scan signal interpretation for FGCL defect detection is demonstrated and illustrated. This research is focusing on for FGCL with maximum thickness up to 10 mm in ambient temperature. The result shows an appropriate ultrasonic parameter will result better signal interpretation analysis.

Between invisible defects and visible impact: the life experiences of adolescents and young adults with congenital heart disease.

To describe the life experiences of adolescents and young adults with congenital heart disease. Owing to medical advances, most children with congenital heart disease are expected to survive into adulthood. The transitional development from adolescence to adult is the critical period for fostering self-care. Descriptive phenomenological study. Thirty-five patients of 15-24 years old with congenital heart disease were recruited from paediatric cardiology clinics by purposive sampling. They were individually interviewed between October 2012-February 2013 using a semi-structured interview guideline and joined adult congenital heart disease clinics at two medical centres in northern Taiwan. The data were analysed using descriptive phenomenological method developed by Giorgi. The essence of the life experience of adolescents and young adults with congenital heart disease involves a dynamic process of moving between invisible defects and coexistence with the disease. Six themes emerged: (1) invisible defects: the existence of imperfect understanding; (2) conflict: interpersonal frustrations; (3) imbalance: the loss of self-balance; (4) suffering: increasing anxiety; (5) encounters: meeting needs; and (6) coexistence: positive coping strategies. As patients with congenital heart disease transition from adolescence into adulthood, they must learn about their disease, overcome frustration and anxiety and develop self-care strategies for coexisting with congenital heart disease. Results of this study may serve as clinical care guidelines for adolescents and young adults with congenital heart disease and give a reference for developing transitional intervention strategies.

Invisible surface defects in a tight-binding lattice

Surface Tamm states arise in one-dimensional lattices from some defects at the lattice edge and their energy generally falls in a gap of the crystal. The defects at the surface change rather generally the phase of propagative Bloch waves scattered off at the lattice edge, so that an observer, far from the surface, can detect the existence of edge defects from e.g. time-of-flight measurements as a delay or an advancement of a Bloch wave packet. Here we show that a special class of defects can sustain surface Tamm states which are invisible, in a sense that reflected waves acquire the same phase as in a fully homogeneous lattice with no surface state. Surface states have an energy embedded into the tight-binding lattice band and show a lower than exponential (algebraic) localization. Like most of bound states in the continuum of von Neumann - Wigner type, such states are fragile and decay into resonance surface states in presence of perturbations or lattice disorder. The impact of structural lattice imperfections and disorder on the invisibility of the defects is investigated by numerical simulations.

Microfocus X-ray printed circuit board inspection system

In order to solve the problem of digital radiography for printed circuit board (PCB) defect inspection, a new inspection system for PCB defect inspection with high resolution X-ray is proposed and implemented in this paper. The influence of the focus size of X-ray source on imaging formation is analyzed to get the best geometrical magnification. Moreover, the relationship between the resolution of intensifier and geometrical magnification is presented by analyzing the performance of MCP-X intensifier, which results in calculating the comprehensive resolution of this system. The experiment result indicates that the measurements on defect character is achieved by inspection software, and the defect analysis accuracy on ball grid array (BGA) solder joint of circuit board achieves minimum resolution of 0.03mm. As a result, this system succeeds in implementing invisible solder joint defect inspection on BGA.

Scattering contrast of X-ray radiation

It is experimentally established that, in the majority of cases, the X-ray radiation scattered on different constituent parts of a weakly absorbing object provides sufficient information on inner structure, different types of structural inhomogeneities, and morphological characteristics, such as shapes, sizes, and location of invisible defects of the object. In this study, a new method for investigation of the inner structure of noncrystalline materials is developed. The method is based on recording of the scattered X-ray radiation. It is demonstrated that the image contrast, formed by the X-ray radiation scattered on weakly absorbing objects, can be considerably higher than the absorption contrast.

Methodology and Application of the Detection of Invisible Defect by Voltage Contrast Inspection

The study aimed at the detection of non-visual defects of poly gate CT leakage at dense logic area by voltage-contrast (VC) inspection. At the same time, some new steps after N-type plus (NP) source drain (S/D) implantation of front-end-of-the-line (FEOL) was proposed and compared to detect poly gate CT leakage at the dense logic area. The cause of t`he poly gate CT leakage was the extreme tiny poly footing which was too small to be detected by the optical system. The PG leakage was obviously impacted by poly etch process and the step height between active area (AA) and shallow trench isolation (STI). The poly gate CT leakage defects were solved by inline controlling to reduce the step height between AA and STI and optimizing poly etch process. Furthermore, the application extended the VC inspection from just middle-end-of-the-line to FEOL of semiconductor technology.

鋼板表面凹凸欠陥の低角入射条件における光学的特性と欠陥検査への応用

Concave and convex defects on steel sheets sometimes become problem in steel production line. These defects are usually invisible because their height or depth is as small as surface roughness of steel sheets. Therefore they could be detected by human inspection only after grinding steel surface using grindstone. This paper describes optical characteristics of such kinds of defects on steel sheets with certain roughness, especially on low-angle light incident condition, and proposes optical inspection system utilized “Magic mirror” phenomenon with low angle laser incidence to detect these defects without grinding. The on-line inspection system has been built and proved to have the capability to detect such kinds of invisible defects.

ART2 알고리즘을 이용한 세라믹 영상에서의 결함 검출

세라믹 소재 영상은 사람의 육안으로 판단하기 힘든 내부 기공이나 균열, 이물질 등의 결함들이 존재한다. 본 논문에서는 사람의 육안으로 검출하기 힘든 세라믹 소재로 이루어진 파이프 용접부에 있는 결함을 확인하기 위해 ART2 알고리즘을 이용하여 세라믹 영상에서 결함을 검출하는 방법을 제안한다. 비파괴 검사는 본질에 손상이 전혀 가지 않는 검사 방법이기 때문에 소재의 결함 검출에 대해서는 적절한 방법이다. 따라서 본 논문에서는 Ends-In Search Stretching 기법을 적용하여 명암 대비를 강조하고, 명암 대비가 강조된 영상에서 삼각형 타입의 소속 함수를 이용한 퍼지 이진화 기법을 적용한 후, 임의의 패턴 입력에 대해서도 효과적으로 특징을 분류하는 개선된ART2 알고리즘을 적용하여 결함 영역을 검출한다. 제안된 방법을 세라믹 소재 영상을 대상으로 실험한 결과, 기존의 방법보다 효율적으로 결함이 검출되는 것을 확인하였다. There are invisible defects by naked eyes in ceramic material images such as internal stomata, cracks and foreign substances. In this paper we propose a method to detect and extract such defects from ceramic pipe weld zone by applying ART2 learning. In pre-processing, we apply Ends-in Search Stretching to enhance the intensity and then perform fuzzy binarization with triangle type membership function followed by enhanced ART2 that interacts with random input patterns to extract such invisible defects. The experiment verifies that this proposed method is sufficiently effective.

Organosilica functionalized zeolitic imidazolate framework ZIF-90 membrane for CO2/CH4 separation

The separation of CO2/CH4 is reported by using 3-aminopropyltriethoxysilane (APTES) modified zeolitic imidazolate framework ZIF-90 membrane. The as-prepared ZIF-90 membrane was modified by APTES based on an imine condensation reaction between the free aldehyde groups of the ZIF-90 frameworks and the amino groups of APTES. After APTES modification, the morphology, purity and crystallinity of the ZIF-90 membrane keep unchanged. Attributing to both pore mouth narrowing and sealing of invisible intercrystalline defects of the polycrystalline ZIF-90 layer, the separation performances of the APTES-modified ZIF-90 membrane are remarkably enhanced. For the separation of equimolar CO2/CH4 mixture at 225°C and 1bar, a CO2 permeance of 1.26×10−8 molm−2s−1Pa−1 and a CO2/CH4 selectivity of 4.7 are obtained, which is of promising in the potential application of CO2 separation and removal.

Combining wet etching and real-time damage event imaging to reveal the most dangerous laser damage initiator in fused silica

A reliable method, combining a wet etch process and real-time damage event imaging during a raster scan laser damage test, has been developed to directly determine the most dangerous precursor inducing low-density laser damage at 355 nm in fused silica. It is revealed that ~16% of laser damage sites were initiated at the place of the scratches, ~49% initiated at the digs, and ~35% initiated at invisible defects. The morphologies of dangerous scratches and digs were compared with those of moderate ones. It is found that local sharp variation at the edge, twist, or inside of a subsurface defect is the most dangerous laser damage precursor.

Fast, exact and non-destructive diagnoses of contact failures in nano-scale semiconductor device using conductive AFM

We fabricated a novel in-line conductive atomic force microscopy (C-AFM), which can analyze the resistive failures and examine process variance with an exact-positioning capability across the whole wafer scale in in-line DRAM fabrication process. Using this in-line C-AFM, we introduced a new, non-destructive diagnosis for resistive failure in mobile DRAM structures. Specially, we focused on the self-aligned contact (SAC) process, because the failure of the SAC process is one of the dominant factors that induces the degradation of yield performance, and is a physically invisible defect. We successfully suggested the accurate pass mark for resistive-failure screening in the fabrication of SAC structures and established that the cause of SAC failures is the bottom silicon oxide layer. Through the accurate pass mark for the SAC process configured by the in-line C-AFM analyses, we secured a good potential method for preventing the yield loss caused by failures in DRAM fabrication.

Evaluation of the similarities and differences in response patterns to the Pediatric Quality of Life Inventory and the Child Oral Health Impact Scores among youth with cleft

To examine (a) the pattern of responses to a generic health-related quality of life (HRQL) measure (Pediatric Quality of Life Inventory--PedsQL) and an oral health-related quality of life (OHRQoL) measure (Child Oral Health Impact Profile--COHIP), and (b) the associations of these scores with surgical recommendation status among youth with cleft. Cross-sectional data (baseline) regarding clinicians' surgical recommendations and quality of life (QoL) measures were examined from an ongoing observational study on treatment outcomes. Approximately one-third of the racially and geographically diverse sample (N = 1,200; mean = 11.6 years) received surgical recommendations to correct either visible (aesthetic) or invisible (functional) defects. Effect sizes were used to quantify differences in QoL based on surgical recommendation and to compare the sensitivity of the PedsQL and COHIP subscales. Using Pearson coefficients, the scores of those recommended for surgery were compared with those without a surgical recommendation. A moderate correlation (0.52) was found between the total scores on the PedsQL and COHIP (p < 0.0001). Subscale correlations between the QoL measures ranged from 0.19 to 0.48 with the strongest correlation between the PedsQL Emotional (r = 0.47) and COHIP Socioemotional Well-being subscale. The effect size for the COHIP Socioemotional Well-being (0.39) was larger than the PedsQL Social/Emotional (0.07/0.11) subscale (Z = 5.30/Z = 4.64, p < 0.0001, respectively), and the total COHIP (0.31) was significantly greater than the total PedsQL scale (0.15, z = 2.65, p = 0.008). A significant relationship was found between generic HRQL, OHRQoL, and surgical needs among youth with cleft with the COHIP having larger effect sizes than the PedsQL among surgical groups.

Development of non-destructive method of detecting steel bars corrosion in bridge decks

One of the most common defects in reinforced concrete bridge decks is corrosion of steel reinforcing bars. This invisible defect reduces the deck stiffness and affects the bridge's serviceability. Regular monitoring of the bridge is required to detect and control this type of damage and in turn, minimize repair costs. Because the corrosion is hidden within the deck, this type of damage cannot be easily detected by visual inspection and therefore, an alternative damage detection technique is required. This research develops a non-destructive method for detecting reinforcing bar corrosion. Experimental modal analysis, as a non-destructive testing technique, and finite element (FE) model updating are used in this method. The location and size of corrosion in the reinforcing bars is predicted by creating a finite element model of bridge deck and updating the model characteristics to match the experimental results. The practicality and applicability of the proposed method were evaluated by applying the new technique to a two spans bridge for monitoring steel bar corrosion. It was shown that the proposed method can predict the location and size of reinforcing bars corrosion with reasonable accuracy.