Mariusz Pluska

Occurrence of tin pest on the surface of tin‐rich lead‐free alloys

Purpose – The purpose of this paper is to investigate tin pest formation in lead‐free alloys.Design/methodology/approach – Samples of Sn99.5Ag3.0Cu0.5, Sn99Cu1 and Sn98Cu2 alloys were prepared in four different forms. The first group was prepared using traditional PCB technology and a hand soldering method. The next group of samples was composed of as‐received ingots of these alloys. To check the impact of mechanical treatment on the transformation process, additional cold‐worked and cold‐rolled samples were prepared (30 kN). All samples were placed initially either at −18°C or at −65°C for low temperature storage testing. Visual observations, scanning electron microscopy observations and X‐ray diffraction analysis were performed to identify the transformation process. Additional samples were prepared using a force of 75 kN and placed in a chamber at a temperature of −30°C for long‐term testing.Findings – The detectable symptoms of tin pest in samples subjected to mechanical processing with 1 and 2 wt.% o...

Room temperature, single mode emission from two-section coupled cavity InGaAs/AlGaAs/GaAs quantum cascade laser

Room temperature, single mode, pulsed emission from two-section coupled cavity InGaAs/AlGaAs/GaAs quantum cascade laser fabricated by focused ion beam processing is demonstrated and analyzed. The single mode emission is centered at 1059.4 cm−1 (9.44 μm). A side mode suppression ratio of 43 dB was achieved. The laser exhibits a peak output power of 15 mW per facet at room temperature. The stable, single mode emission is observed within temperature tuning range, exhibiting shift at rate of 0.59 nm/K.

Measurement of Magnetic Field Distorting the Electron Beam Direction in Scanning Electron Microscope

The magnetic field that is generated by different electric devices in an environment of a scanning electron microscope (SEM) causes the direction of the electron beam to become distorted and, consequently, registered images to become distorted. This paper describes a method for a measurement of the magnetic field affecting the direction of the electron beam. It consists of the analysis of SEM images that are registered for several distances between the final aperture of an electron column and a specimen. Means of the measurement of a constant and a periodic magnetic field are explained. The presented examples show the results of the measurement of the constant field that is generated by coils that are placed either inside or outside the microscope chassis. The results are compared with the ones obtained using a reference magnetometer. In the presented method, a direct magnetic field influence on the electron beam is separated from any other influences. Also, the magnetic field nonuniformity along the electron beam path is considered. The current investigations enable the magnetic field compensation and test the shielding efficiency of the SEM chassis.

Dependence of cathodoluminescence on layer resistance applied for measurement of thin-layer sheet resistance

The dependence of spatially and spectrally resolved cathodoluminescence in a scanning electron microscope on resistances in semiconductor structures, especially on the layer resistance, is reported. This previously unstudied dependence is utilized for thin‐layer sheet‐resistance measurement. The method is illustrated by an assessment of lateral confinements in semiconductor‐laser heterostructures.

Identification of electron beam vibration sources by separation of magnetic distortion from electric distortion on scanning electron microscope imaging

Different types of distortions in scanning electron microscopy require different methods of their elimination, and therefore influence of these types on particular elements of the SEM system should be known. The proposed method allows for separation of the direct influence of the magnetic field on the electron beam in the SEM chamber from its influence in the SEM column and from the distortions generated in the SEM scanning block. For this purpose, a series of distorted images is registered for several working distances (between the final aperture of the electron column and the specimen) and for several energies of the electrons. Magnitudes of the distortions are measured on these images. For each applied electron energy, the dependence of the results versus the working distance is approximated with the second‐order polynomial function. The analysis of the polynomial coefficients allows for the separation of the above‐mentioned kinds of distortions. The presented method enables a selection of the most efficient solution to the distortions reduction. It utilizes the SEM itself and does not need any additional equipment.

Separation of image-distortion sources and magnetic-field measurement in scanning electron microscope (SEM)

The electron-microscope image distortion generated by electromagnetic interference (EMI) is an important problem for accurate imaging in scanning electron microscopy (SEM). Available commercial solutions to this problem utilize sophisticated hardware for EMI detection and compensation. Their efficiency depends on the complexity of distortions influence on SEM system. Selection of a proper method for reduction of the distortions is crucial. The current investigations allowed for a separation of the distortions impact on several components of SEM system. A sum of signals from distortion sources causes wavy deformations of specimen shapes in SEM images. The separation of various reasons of the distortion is based on measurements of the periodic deformations of the images for different electron beam energies and working distances between the microscope final aperture and the specimen. Using the SEM images, a direct influence of alternating magnetic field on the electron beam was distinguished. Distortions of electric signals in the scanning block of SEM were also separated. The presented method separates the direct magnetic field influence on the electron beam below the SEM final aperture (in the chamber) from its influence above this aperture (in the electron column). It also allows for the measurement of magnetic field present inside the SEM chamber. The current investigations gave practical guidelines for selecting the most efficient solution for reduction of the distortions.

A method for the tin pest presence testing in SnCu solder alloys

Purpose – The purpose of this study is to develop a testing method for tin pest in tin – copper (SnCu) alloys. Tin pest is the allotropic transformation of white β-tin (body-centered tetragonal structure) into gray α-tin (diamond cubic structure) at temperatures < 13.2°C. Design/methodology/approach – Bulk samples of Sn99Cu1 weight per cent (purity, 99.9 weight per cent) were cast in the form of roller-shaped ingots with a diameter of 1.0 cm and a height of 0.7 cm. The samples were then divided into four groups. The first group included samples artificially inoculated with α-tin powder. The second group was inoculated in the same way as the samples from the first group but additionally subjected to mechanical pressing. The third group of ingots was only subjected to mechanical pressing. The fourth group of samples consisted of as-received roller-shaped ingots.All samples were divided into two groups and kept either at −18°C or at −30°C for the low-temperature storage test. For tin pest identification, a v...

Tin Pest and Tin Oxidation on Tin-Rich Lead-Free Alloys Investigated by Electron Microscopy Methods

Soldering of joints in electronic circuits is performed in all branches of electronic industry. At temperatures below 13.2°C, an allotropic transformation of white β-tin into gray α-tin called tin pest may occur, leading to the degradation of mechanical properties or even a total disintegration of the alloy. Presence of some chemical elements in the alloy can inhibit the transformation, while other can promote it, e.g. a significant Pb addition prevents the transformation. However, the Restriction of Hazardous Substances Directive adopted by the European Union since 2006, limits Pb amount to 0.1 wt.%, leading to tin pest phenomenon in tin rich materials. The energy dispersive X-ray spectroscopy (EDXS) in scanning electron microscope was performed on samples of tin-rich lead-free alloys subjected to accelerated low temperature stress and after months of storage at -18 °C showed the tin pest occurrence. Much higher oxygen content in EDXS spectrum was revealed at old regions of transformed α-tin than at new α-tin and non-transformed β-tin regions. The tin pest oxidation is much accelerated in comparison to β-tin and can finally lead to the consuming of the whole tin in deteriorated places by the tin oxide.

Quantitative Measurement of Electromagnetic Distortions in Scanning Electron Microscope (SEM)

Image deformations caused by electromagnetic interference (EMI) are ones of the most frequent undesirable effects in practical scanning electron microscopy. They usually appear, even although the place chosen for a microscope system fulfills EMI conditions, as periodic deformation of vertical edges of an observed specimen. Available, but still very expensive methods for decreasing their influence are shielding and electromagnetic field compensation. The other approach is digital image processing for its correction. However, elimination of the distortions (with hardware or software methods) would be more effective, when their influence on particular elements of microscope system are known or predictable. Current investigations ascertained in which sections of an electron microscope column the geometric deformations are generated, enabled separation of magnetic field influence on electron beam deflection system and its direct influence on electron beam and finally led to obtain a method for quantitative measurement of magnetic field which penetrates the microscope chamber and the electron gun column. The method uses scanning electron microscope itself and was verified by comparing its results with the ones obtained using alternative magnetic field meter.

Detrimental nonlocality in luminescence measurements

Luminescence studies are used to investigate the local properties of various light-emitting materials. A critical issue of these studies is presented that the signals often lack all advantages of luminescence-studies of high locality, and may originate from an extended spatial region of even a few millimeters in size or the whole sample, i.e., places other than intended for investigation. This is a key problem for research and development in photonics. Due to this nonlocality, information indicating defects, irregularities, nonuniformities and inhomogeneities is lost. The issue refers to typical structures with a strong built-in electric field. Such fields exist intentionally in most photonic structures and occur unintentionally in many other materials investigated by applied physics. We reveal [using test samples prepared with focused ion beam (FIB) on an AlGaAs/GaAs laser heterostructure with an InGaAs quantum well (QW)] that nonlocality increases at low temperatures. This is contrary to the widely expe...