bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterisation of multilayer materials using a position-sensitive atom probe
Authors: Mackenzie RAD , Smith G D W , Cerezo A. , Liddle J A , Grovenor CRM , Hetherington M G 
Published: June 2020

The position sensitive atom probe (POSAP), described briefly elsewhere in these proceedings, permits both chemical and spatial information in three dimensions to be recorded from a small volume of material. This technique is particularly applicable to situations where there are fine scale variations in composition present in the material under investigation. We report the application of the POSAP to the characterisation of semiconductor multiple quantum wells and metallic multilayers.The application of devices prepared from quantum well materials depends on the ability to accurately control both the quantum well composition and the quality of the interfaces between the well and barrier layers. A series of metal organic chemical vapour deposition (MOCVD) grown GaInAs-InP quantum wells were examined after being prepared under three different growth conditions. These samples were observed using the POSAP in order to study both the composition of the wells and the interface morphology. The first set of wells examined were prepared in a conventional reactor to which a quartz wool baffle had been added to promote gas intermixing. The effect of this was to hold a volume of gas within the chamber between growth stages, leading to a structure where the wells had a composition of GalnAsP lattice matched to the InP barriers, and where the interfaces were very indistinct. A POSAP image showing a well in this sample is shown in figure 1. The second set of wells were grown in the same reactor but with the quartz wool baffle removed. This set of wells were much better defined, as can be seen in figure 2, and the wells were much closer to the intended composition, but still with measurable levels of phosphorus. The final set of wells examined were prepared in a reactor where the design had the effect of minimizing the recirculating volume of gas. In this case there was again further improvement in the well quality. It also appears that the left hand side of the well in figure 2 is more abrupt than the right hand side, indicating that the switchover at this interface from barrier to well growth is more abrupt than the switchover at the other interface.
XTEM analysis of buried layer structure of silicon-on-insulator materials
Authors: Rushan Ni , Chenglu Lin 
Published: June 2020

It Is well known that a buried silicon nitride or silicon oxide layer in silicon can be formed by high dose >150 KeV nitrogen or oxygen implantation into single crystal silicon followed by high temperature annealing. This is one of the techniques to produce silicon-on-insulator (SOI) structures which is promising for a variety of potential application in VLSI, high-voltage devices, high density CMOS circuits and possibly 3-dimensional integration, etc. The main concern is how to produce a buried dielective layer with good insulating properties and with a high quality single crystal silicon overlayer on it.In this paper the microstructures of buriea silicon nitride and silicon oxide layer of the SOI materials formed by N+ or O+ implantation in single-crystal silicon are studied oy means of cross-sectional transmission electron microscopy (XTEM) and infrared (IR) absorption measurements.
Formation of AlGaAs by ion beam mixing of Al films on GaAs
Authors: Deol R.S. , Kamil E.A. , Homewood K.P. , Kobayashi T. 
Published: June 2020

There is considerable interest in the use of ion implantation for material synthesis. The synthesis of AlGaAs by dual implants of As+ and Al+ into GaAs followed by rapid thermal annealing (RTA) has been reported recently. In this paper results relating to the formation of AlxGa1-xAs by depositing thin Al films on GaAs substrates and irradiating with arsenic ions followed by RTA are presented.Aluminium layers of 580Å or 650Å in thickness were deposited onto liquid encapsulated Czochralski (LEC) grown samples of semi-insulating <100> GaAs. The deposition was done using pure aluminium on a heated filament at a chamber pressure of ∽10−6 Torr with the thickness being measured using a talystep. Subsquently As+ implants were performed at room temperature using an energy of 150, 200 or 300 keV and a dose of 3x1016 or 1x1017 cm−2. The implantation energy was selected to ensure that the projected depth exceeded the thickness of the Al overlayer employed.
Nanostructure of semiconductor quantum dots in a borosilicate glass matrix by complementary use of HREM and AEM
Authors: Kim M.J. , Liu L.C. , Risbud S.H. , Carpenter R.W. 
Published: June 2020

When the size of a semiconductor is reduced by an appropriate materials processing technique to a dimension less than about twice the radius of an exciton in the bulk crystal, the band like structure of the semiconductor gives way to discrete molecular orbital electronic states. Clusters of semiconductors in a size regime lower than 2R {where R is the exciton Bohr radius; e.g. 3 nm for CdS and 7.3 nm for CdTe) are called Quantum Dots (QD) because they confine optically excited electron- hole pairs (excitons) in all three spatial dimensions. Structures based on QD are of great interest because of fast response times and non-linearity in optical switching applications.In this paper we report the first HREM analysis of the size and structure of CdTe and CdS QD formed by precipitation from a modified borosilicate glass matrix. The glass melts were quenched by pouring on brass plates, and then annealed to relieve internal stresses. QD precipitate particles were formed during subsequent "striking" heat treatments above the glass crystallization temperature, which was determined by differential thermal analysis.
The use of Scanning Tunneling Microscopy in combination with Scanning Electron Microscopy in the fabrication and imaging of microstructures
Authors: Gómez-Rodríguez J.M. , A.M. Baró 
Published: June 2020

In the last few years, Scanning Tunneling Microscopy (STM), has proven to be a powerful and versatile technique to investigate the topographic and electronic structure of metals and semiconductors with an unprecedent vertical (0.01 nm) and lateral (0.2 nm) resolution. In this paper we are interested in the use of STM to study surfaces having microfabricated structures in the nanometer range, particularly those produced by the STM tip itself.In order to study these samples we have used an STM integrated into a commercial Scanning Electron Microscope (SEM). This allows to address two problems which limit the operation of STM: (i) the limited STM scanning range (1-10 μm) which makes difficult the localization of microstructures on the sample; (ii) the undetermined size and shape of the STM probing tip.Our STM/SEM combination has been described in detail earlier. In short, it consists of an STM placed on the sample stage of a commercial SEM allowing the simultaneous operation of both microscopes.
Magnetic micro structure evaluation by means of electron beam measuring techniques
Authors: Steck M. 
Published: June 2020

The trend to micro miniaturization of magnetic devices with structure dimensions in the sub micrometer range at present necessitates more and more test techniques with a high spatial resolution. The electron beam techniques have been proved to be particularly suitable even ensuring high quality and reliability of these devices.In principle, two different types of measurement can be distinguished. In the sample-hitting type, the e-beam hits the sample and interacts with certain magnetic properties of the specimen. Two categories can be divided: reflection mode and transmission mode. In reflection mode, secondary electrons (SE) and back scattered electrons (BSE) are created by the primary beam. These SE change their trajectories due to the magnetic micro field at the specimen’s surface yielding to different signals at the detector. This contrast is very well known as magnetic contrast type 1. Magnetic contrast type 2 uses the change in the BSE-generation volume due the internal magnetization of the sample. A very new and promising technique is secondary electron microscopy with polarization analysis (SEMPA). SEMPA analyses the SE-spin which depends on the direction of magnetization in the magnetic domains. In reflection mode, SEMPA offers the best spatial resolution (sub-0.1 μm) up to now.
The utilisation of electron-beam damage for the study of beam spreading in synthetic polymers
Authors: Haunton K. M. , Vesely D. 
Published: June 2020

The knowledge of beam spreading is important for determination of spatial accuracy and volume calculation in quantitative X-ray analysis. It is also useful for determination of best conditions for electron beam lithography with high line resolution. The theoretical modelling of beam spreading is difficult as for example the Monte Carlo simulation is very demanding on computer time and many simplifications have to be made. The validity of the theoretical results must therefore be verified experimentally.In this work some new techniques are utilised for evaluation of the spatial distribution of the deposited energy in synthetic polymers, namely the formation of isolated and conjugated double bonds, revealed by staining and by fluorescent microscopy.Thick samples of PVC, PS and PMMA were coated with about 10 nm of carbon and exposed to an electron beam of 75 - 200 keV for different lengths of time. A Hitachi 700H transmission electron microscope (TEM) was operated in the scanning (STEM) mode. Currents of lxl0−9A and 2x10−10A were used. The stationary beam was convergent or parallel.
SEM-EDXA study of bronze/carbon steel interface in relation with adhesion measurements
Authors: de Castellar M.D. , Tura J.M. , Traveria A. , Pujadas J. 
Published: June 2020

Water atomized bronze formed the basis of the powder metallurgy coating. The grain size distribution, its morphology and internal porosity have been previously investigated. The largest bronze particles have a very irregular shape. It becomes more spherical when the granulometry decreases. Figure 1 shows an image of a bronze particle.The XPS analysis of the grain surface revealed a composition of Cu°/CuO being 87/13 and Sn°/SnO2 14.3/87.5. Powders with smallest granulometry show a deeper oxide layer. This is probably due to the larger specific surface shown by these particles.The substrate was sintered carbon steel with 1.75 % Ni, 1 % Cu and 0.5 % Mo as minoritary elements.An optimization of the layer substrate bond strength was carried out. A shear stress was applied on the coating and the force required to detach it from the substrate was measured. Cross sections of the samples obtained in every sintering cycle were observed by SEM.
Butyl rubber slurry formation: Cold-stage SEM study
Authors: Ban L. L. , Powers K. W. , Wang H-C 
Published: June 2020

Poly(isobutylene-co-isoprene) or butyl rubber was invented in 1937 and has been used in many technologically important applications during the ensuing years. Its physical properties such as air-retention encouraged its uses in tire inner tubes, and played an important part in the tubeless tire development. The halogenated derivative is now predominantly used in tubeless radial tires.Butyl rubber is made by a slurry polymerization process with aluminum chloride catalyst at -95°C in methyl chloride diluent. Typical reactor runs only last from 18-60 hours because of fouling of the reactor. Fouling and agglomeration occur because only weak electrostatic repulsion forces exist, but recent patents describe the use of block copolymer stabilizer agents which create steric (entropic) repulsion forces between slurry polymer particles and preventTo better understand the mechanism of reactor fouling, a method was developed to collect samples from within the reactor.
Crystal chemistry of calcium oxalate formed in plants
Authors: Ishii Yuuko , Takiyama Kazuyoshi 
Published: June 2020

Calcium oxalate crystals, which were produced in plants to protect protoplasm from the toxic action of oxalic acid formed by metabolism, were observed with an optical microscope. In the present investigation, calcium oxalate crystals isolated from many plants were studied from the viewpoint of crystal chemistry.Leaves of spinach, begonia, begonia lucerna, garden sorrel, goose foot, camellia, tea-plant, agave, et al., stem of aloe, and barks of cherry-tree, plum-tree, fir, camphor-tree et al. were used in the investigation. Plants were cut into small pieces and pulverized in water with a food blender. The mixture was filtered through gauze and water was sprinkled onto the residue. Many small crystalline particles sank in the filtrate. Particles were carefully gathered into a beaker. Dried particles were observed with a scanning electron microscope(SEM) and analyzed with an X-ray diffraction(XRD).
Microstructure of resistance spot welding of maraging steels
Authors: Neuman I. , Dirnfeld S.F. , Minkoff I. 
Published: June 2020

Experimental work on the spot welding of Maraging Steels revealed a surprisingly low level of strength - both in the as welded and in aged conditions. This appeared unusual since in the welding of these materials by other welding processes (TIG,MIG) the strength level is almost that of the base material. The maraging steel C250 investigated had the composition: 18wt%Ni, 8wt%Co, 5wt%Mo and additions of Al and Ti. It has a nominal tensile strength of 250 KSI. The heat treated structure of maraging steel is lath martensite the final high strength is reached by aging treatment at 485°C for 3-4 hours. During the aging process precipitation takes place of Ni3Mo and Ni3Ti and an ordered solid solution containing Co is formed.Three types of spot welding cycles were investigated: multi-pulse current cycle, bi-pulse cycle and single pulsle cycle. TIG welded samples were also tested for comparison.The microstructure investigations were carried out by SEM and EDS as well as by fractography. For multicycle spot welded maraging C250 (without aging), the dendrites start from the fusion line towards the nugget centre with an epitaxial growth region of various widths, as seen in Figure 1.
An EM study of carbides in double austenitized AISI M2 high-speed steel
Authors: Ögel Bilgehan , Tekin Erdoĝan 
Published: June 2020

Multiple austenitization is not a conventional heat treatment process in tool steel industry and has only recently attracted some attention. Several workers who studied multiple austenitized high speed steels reported a fine carbide precipitation in the matrix of double austenitized specimens. However, the metallography of this precipitation is not well documented and needs further investigation. In this study, the microstructure of AISI M2 high speed steel and the effect of double austenitization on carbide distribution is investigated using SEM.The heat treated specimens were prepared by conventional metallographic methods for SEM examination. Polishing with diamond paste gave better results as much less carbides were extracted from their sites. Picral was used as an etchant.It is known that in M2 steels, undissolved carbides are either M6C or MC type. However, in the present investigation some of the massive undissolved M6C carbides contained small dark regions within them (Fig.l). X-ray mapping for W, Mo and V of such a carbide has shown that it is mainly a M6C carbide,whereas the dark regions on it is rich in vanadium implying that these regions represent V4C3(Fig.2).
Precipitation at the transformation interface of pearlite in steel
Authors: Khalid F. A. , Edmonds D. V. 
Published: June 2020

The austenite/pearlite growth interface in a model alloy steel (Fe-1lMn-0.8C-0.5V nominal wt%) is being studied in an attempt to characterise the morphology and mechanism of VC precipitation at the growth interface. In this alloy pearlite nodules can be grown isothermally in austenite that remains stable at room temperature thus facilitating examination of the transformation interfaces. This study presents preliminary results of thin foil TEM of the precipitation of VC at the austenite/ferrite interface, which reaction, termed interphase precipitation, occurs in a number of low- carbon HSLA and microalloyed medium- and high- carbon steels. Some observations of interphase precipitation in microalloyed low- and medium- carbon commercial steels are also reported for comparison as this reaction can be responsible for a significant increase in strength in a wide range of commercial steels.The experimental alloy was made as 50 g argon arc melts using high purity materials and homogenised. Samples were solution treated at 1300 °C for 1 hr and WQ. Specimens were then solutionised at 1300 °C for 15 min. and isothermally transformed at 620 °C for 10-18hrs. and WQ. Specimens of microalloyed commercial steels were studied in either as-rolled or as- forged conditions. Detailed procedures of thin foil preparation for TEM are given elsewhere.
Microstructural evolution of a nickel-based superalloy
Authors: Monteiro Waldemar A. , Dos Santos Ingrid A. 
Published: June 2020

Superalloys are indispensable for the superior perfomance and efficien of jet engine turbine disks,turbine blades,combustors,roket shells and many other devices and components used in various industries, in Cluding nuclear, space and aeronautics.Over the last thirty years,nickel-base superalloys has undergone more structural studies than any other superalloy as a result of attempts to correlate its properties to microstructure and heat treatment. To avoid contradictory or inconsistent findings, it is also necessary a carefully microstructural observation of the employed starting materials. In the present paper,we report morphologies relating to the as cast , forged and heat-treated Ni-base superalloy by transmission and scanning electron microscopy. This superalloy contain intermettallic compounds and carbides. The alloy in study was an as cast and also forged Ni-Fe based superalloy with the following chemical composition:
Effect of titanium addition on a Ni-Al-Co alloy
Authors: Lin L. S. , Levan G. W. , Russell S. M. , Law C. C. 
Published: June 2020

AEM examinations of a NiAlCo alloy of composition Ni-29 at.% Al-21 at.% Co after room temperature compression show that the microstructure consists of a twinned tetragonal matrix (L10, marked A in Figure 1a) and ordered fcc gamma prime precipitates (L12, marked B in Figure 1a) along grain boundaries. The compressive yield strengths of this alloy at room temperature and 760°C are 754 MPa and 163 MPa respectively. It also has superior room temperature ductility as compared to binary NiAl. An addition of 5 at.% Ti at the expense of Ni was made to this alloy in order to increase the yield strengths. The quarternary alloy shows compressive yield strengths of 976 MPa and 403 MPa at room temperature and 760°C, respectively, indicating that the Ti addition is having the desired effect.Comparison of the microstructures of the two alloys after room temperature compression (Figures la and lb) shows that the Ti containing alloy has a smaller grain size. X-ray diffraction data indicate that the gamma prime volume fraction increases from 10% to 20% as the result of the Ti addition. Titanium was also found to stabilize the B2 matrix (marked A in Figure lb) as no tetragonal L10 phase was found. All precipitates along grain boundaries were identified by micro-diffraction to be gamma prime.
Effect of hafnium addition on a Ni-Al-Co Alloy
Authors: Lin L. S. , Levan G. W. , Russell S. M. , Law C. C. 
Published: June 2020

Recent efforts at P&W have shown that the addition of cobalt to binary NiAl results in an appreciable increase in room temperature ductility. One version of this ternary alloy, designated VIM A, has a composition of Ni-30 at.% Al-35 at.% Co. The addition of 0.5 at.% Hf to this alloy (designated VIM AH) results in an improvement in yield strength at 760°C. Room temperature properties were not found to be significantly affected by the Hf addition. This discussion will focus on the microstructures of alloys VIM A and VIM AH and their relationship to the mechanical properties observed in compression at room temperature and 760°C.The addition of hafnium reduced the grain size of VIM AH alloy. After room temperature compression, both alloys show an ordered bcc (B2) matrix and precipitates which are distributed primarily along grain boundaries. These precipitates were identified by microdiffraction to be ordered fcc (L12) gamma prime for VIM A and hexagonal (A3) for VIM AH.
Microstructrures of the rapidly solidified Nd2Co14B alloys
Authors: He L.L. , Li J.H. , Ye H.Q. 
Published: June 2020

It is known that the Nd2Co14B compound belongs to the Nd2Fe14B-type crystal structure ( 2:14 phase ), and has higher values of coercivity Hci and Cruie temperature Tc of about 1000K. The properties of this compound are sensitive to cooling velocity. In this presentation, we will study the chemical twins and other defects in the phases formed at different cooling velocities. Two kinds of rapidly solidified samples were examined: No.l with low cooling velocity of about 102-103 °C/s and No.2 with high cooling velocity of about 105-106 °C/s. The foils prepared by ion thinning were observed in a JEOL-200CX microscope for high resolution imaging.The main phase in the sample No. 1 was the 2:14 phase. The electron diffraction analysis demonstrated that the lattice parameter of this phase was a=0.88 nm, c=1.21 run with the space group P42/mΩm ( the insert in fig.l ).
Characterization of silicon carbide platelet-reinforced alumina
Authors: Alexander K. B. , Becher P. F. , Waters S. B. 
Published: June 2020

The incorporation of silicon carbide whiskers into ceramic matrices has been shown to result in significant increases in toughness, strength, resistance to thermal shock, slow crack growth, and creep. The health hazards associated with the handling of silicon carbide whiskers, however, can be considerable. Silicon carbide platelets are therefore being considered as an alternative to whiskers for reinforcing ceramic composites.The silicon carbide platelets used in this study were supplied by Alcan International Ltd. The platelets varied from 1 to 5 μm in thickness and 5 to 45 μm in diameter. Sumitomo alumina powder was mixed with the platelets and the composites were fabricated by hot-pressing in vacuum at 1600°C for 1.5 h. The resultant composites had the platelet faces oriented primarily perpendicular to the hot-pressing axis. Specimens containing 7 vol% SiC platelets had a fracture toughness of 6.6 MPa m½, which is about the same value as observed for alumina of equivalent grain size containing 7 vol% SiC whiskers. Considerable porosity was observed in specimens with platelet volume fractions larger than 7 vol%.
AEM-investigation of ceramic coatings on hard metals
Authors: Warbichler P. , Hofer F. 
Published: June 2020

To improve their working life, hard metal tools are coated with ceramic protective coatings by means of chemical vapour deposition (CVD). Generally, several layers are deposited, e.g. titaniumcarbide, titaniumnitride, titaniumcarbonitride and aluminiumoxide with thicknesses ranging from some 10 nm to some μm.The understanding of mechanical properties of the coatings is dependent on gaining a knowledge of both the interfaces and the structure of the coatings involved. The coating properties are, in turn, dependent on the coating deposition parameters. A detailed understanding of the influence of these parameters on the mechanical and chemical properties of the multilayer/substrate combination is therefore required.The structure and morphology of the multilayer coatings have been already investigated by using optical and scanning electron microscopy (SEM), whereas transmission electron microscopy (TEM) was hitherto only applied to the study of single TiC or Al2O3coatings.For TEM-investigations cross-sections must be taken through the multilayer coating and the cemented carbide substrate. In our investigations, a method of preparation described by Newcomb et al.