A. Czerwinski

Deep-ultraviolet Raman investigation of silicon oxide: thin film on silicon substrate versus bulk material

Raman spectroscopy is a powerful experimental technique for structural investigation of silicon based electronic devices such as metal‐oxide‐semiconductor-type structures. It is widely used for characterization of mechanical stress distribution in silicon substrate. However, in the case of Raman measurements of oxide layer on silicon substrate visible excitation makes this technique almost useless. The reason for this difficulty is two-phonon scattering from silicon substrate which masks the signal from oxide layer. Application of deep-ultraviolet (deep-UV) excitation reduces the penetration depth of the radiation into silicon substrate about 30 times. As a result, the simultaneous measurement of one-phonon scattering from silicon substrate and the Raman spectrum of the oxide layer become possible. This work presents the study of thin silicon oxide film on silicon substrate with application of deep-UV Raman scattering. The spectra measured for thin film are compared with reference spectra obtained for bulk material.

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...

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.

Tuning the polarity of charge transport in InSb nanowires via heat treatment

InSb nanowire (NW) arrays were prepared by pulsed electrodeposition combined with a porous template technique. The resulting polycrystalline material has a stoichiometric composition (In:Sb = 1:1) and a high length-to-diameter ratio. Based on a combination of Fourier transform infrared spectroscopy (FTIR) analysis and field-effect measurements, the band gap, the charge carrier polarity, the carrier concentration, the mobility and the effective mass for the InSb NWs was investigated. In this preliminary work, a transition from p-type to n-type charge transport was observed when the InSb NWs were subjected to annealing.

Selective etching of dislocations in GaN and quantitative SEM analysis with shape-reconstruction method

Due to the differences in etch-pit morphologies, chemical etching offers a possibility to determine densities of dislocations in respect to their type. In the present paper we propose a method, which implements a simple shape-from-shading procedure, i.e. with results derived from image brightness dependence on surface slope. It allows estimation of etch-pit depth distributions from scanning electron microscopy micrographs. This method is used to obtain depth distributions from GaN surface after etching in molten KOH-NaOH eutectic mixture. Depth distributions are used to estimate densities of etch-pits related to a given dislocation type. The distributions are compared with dislocation densities determined with transmission electron microscopy.

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.

Transmission electron microscopy study of erbium silicide formation from Ti/Er stack for Schottky contact applications

In this paper, we present results of transmission electron microscopy studies on erbium silicide structures fabricated under various thermal conditions. A titanium cap has been used as a protective layer against oxidation during rapid thermal annealing of an erbium layer in a temperature range of 300–700°C. Both layers (200 nm Ti and 25 nm Er) were deposited by electron‐beam sputtering. The investigations have shown that the transformation of the 25‐nm‐thick erbium into erbium silicide is completed after annealing at 500°C. At higher temperatures, the formation of a titanium silicide layer above erbium silicide is observed. The lowest Schottky barrier has been measured in the sample annealed at 700°C.

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.

New approach to cathodoluminescence studies in application to InGaN/GaN laser diode degradation

Cathodoluminescence (CL) studies are widely applied in semi‐conductor science and technology. However, for structures with a p‐n junction the CL spatial distribution can be strongly affected by internal current flows of the electron beam induced current generated within the structure. This influence is the investigated in application to CL studies of degradation in aged laser diodes with InGaN multiquantum wells.

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...