bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetotransport in Metals and Alloys
Authors: Bass Jack 
Published: October 2003

AbstractElectronic transport properties are fundamental to the classification of materials. The behaviors of the electrical resistivity ρ, the thermal conductivity κ, and the thermopowerSare used to define whether a material is a metal, a semi‐conductor, or an insulator. Studies of how ρ, κ, andSvary with impurity content (alloying), magnetic fieldB, sample size, deformation, etc., provide insight into the nature of current carriers and how they are scattered. Studies of magnetoresistance, the variation of ρ withB, can yield additional information about electronic structure, the current carriers, and their scattering. In systems involving magnetic metals,has technical applications to magnetic sensing and memory. The Hall effect and the thermopowerScan often be used to infer the sign of the charge of the majority current carriers, and the thermal conductivity κ, while closely related to ρ, can manifest differences that contain significant information. The Hall effect in semiconductors also finds use in sensors, but in metals it is smaller and usually of more interest for the physical insight it can provide into both nonmagnetic and magnetic metals. Changes with magnetic field in the thermal conductivity and thermoelectric coefficients of metals are usually small and difficult to measure. They have provided useful information about physical phenomena such as many‐body contributions to thermoelectricity and giant magnetoresistance in granular alloys and magnetic multilayers but are much less studied than the resistivity and Hall effect. Transport and magnetotransport measurements of metals and alloys are made over a wide range of temperatures extending from the lowest achievable temperature to the liquid state.This article focuses on four measured quantities in solid metals and alloys in the presence of a temporally constant and spatially uniform magnetic fieldB—the electrical resistanceR, the Hall resistance, the thermal conductanceK, and the thermopowerS. The basic theory underlying these quantities applies also to liquid metals and alloys. The discussion begins with definitions and general information, including how to relate the measured quantities to the fundamental properties ρ, the Hall coefficient, κ, andS. These are followed by a brief description of the behaviors of ρ, κ, andSin zero magnetic field. Many more quantities than these four can be defined and measured, some of which have provided important information about metals. A few are briefly discussed.
Electrochemical Techniques
Authors: Bocarsly Andrew B. 
Published: October 2003

Abstract
Electrochemistry, in contrast to most materials characterization disciplines, contains a bifurcated methodology having applications both in materials synthesis and as a physical characterization technique. On the one hand, a variety of functional surfaces are prepared electrochemically, for example, the anodization of aluminum, electroetching of semiconductors, and electroplating of metallic films. Similarly, the electrosynthesis of bulk materials such as conducting organic polymers has taken on importance in recent years. On the other hand, electrochemistry has been demonstrated to be of use as a physical characterization technique for the quantification of conducting and semiconducting surfaces. The corrosion properties of metallic surfaces and semiconductor electronic properties are two key areas where electrochemical characterization has had a high impact. In keeping with the central analytical theme of this work, this category limits its focus to the class of electrochemical techniques specifically aimed at characterizing materials and their interfaces (as opposed to synthetic electrochemistry). In some cases, the line between materials synthesis and measurement can become hazy. The field of sensors based on chemically modified electrodes (CMEs) is a good example of this confusion. Often sensors of this type are electrosynthesized and the synthesis parameters represent an important portion of the systems characterization. Cases such as this are included in the topical coverage of these articles.
Semiconductor Photoelectrochemistry
Authors: Anz Samir J. , Fajardo Arnel M. , Royea William J. , Lewis Nathan S. 
Published: October 2003

Abstract
This article discusses methods and experimental protocols in semiconductor electrochemistry. The basic principles that govern the energetics and kinetics of charge flow at a semiconductor‐liquid contact are discussed. The principal electrochemical techniques of photocurrent and photovoltage measurements used to obtain important interfacial energetic and kinetic quantities of such contacts are then described in detail.
After this basic description of concepts and methods in semiconductor electrochemistry, methods for characterizing the optical, electrical, and chemical properties of semiconductors through use of the electrochemical properties of semiconductor‐liquid interfaces are described. The latter part of this unit focuses on methods that provide information primarily on the properties of the semiconductor surface and on the semiconductor‐liquid junction.
In some cases, the semiconductor‐liquid junction provides a convenient method for measuring properties of the bulk semiconductor that can only be accessed with great difficulty through other techniques; in other cases, the semiconductor‐liquid contact enables measurement of properties that cannot be determined using other methods. Due to the extensive amount of background material and the interdisciplinary nature of work in this field, the discussion is not intended to be exhaustive, and the references cited in the various protocols should be consulted for further information.

This article covers the following methods in semiconductor electrochemistry:

Photoconductor/photovoltage measurements

Measurement of semiconductor band gaps using semiconductor‐liquid interfaces

Diffusion length determination using semiconductor‐liquid contacts

Differential capacitance measurements of semiconductor‐liquid contacts

Transient decay dynamics of semiconductor‐liquid contacts

Measurement of surface recombination velocity using time‐resolved microwave conductivity

Electrochemical photocapacitance spectroscopy

Laser spot scanning methods at semiconductor‐liquid contacts

Flat‐band potential measurements of semiconductor‐liquid interface

Time‐resolved photoluminescence spectroscopy to determine interfacial charge transfer kinetic parameters

Steady‐state
J‐E
data to determine kinetic properties of semiconductor‐liquid interfaces.
Scanning Electrochemical Microscopy
Authors: Wipf David O. 
Published: October 2003

AbstractScanning electrochemical microscopy (SECM) is one of a number of scanning probe microscopy (SPM) techniques that arose out of the development of the scanning tunneling and atomic force microscopes. Scanning probe microscopes operate by scanning, or “rastering,” a small probe tip over the surface to be imaged. The SECM tip is electrochemically active, and imaging occurs in an electrolyte solution. In most cases, the SECM tip is an ultramicroelectrode (UME), and the tip signal is a Faradaic current from electrolysis of solution species. Some SECM experiments use an ion‐selective electrode (ISE) as a tip. In this case, the tip signal is usually a voltage proportional to the logarithm of the ion activity in solution. The use of an electrochemically active tip allows an extremely versatile set of experiments, with chemical sensitivity to processes occurring at a substrate surface as an essential aspect.A requirement of SPM techniques is that the signal from the tip must be perturbed in some reproducible fashion by the presence of the surface. One of the two methods used in SECM to provide this signal change is known as the “feedback” mode. Feedback can provide topographic images of either electronically insulating or conducting surfaces.A unique advantage of SECM is the ability to design experiments in which the mediator interacts with the substrate surface to provide chemical and electrochemical activity maps at micrometer and submicrometer resolution.
The Quartz Crystal Microbalance In Electrochemistry
Authors: Arbuckle‐Keil Georgia A. 
Published: October 2003

Abstract
The electrochemical quartz crystal microbalance (EQCM) has found wide acceptance as an analytical tool. Nanogram mass changes that occur on the surface of a quartz crystal can be correlated with the amount of charge passed during an electrochemical process. This technique has been widely reviewed.
That a mass change can be determined from the resonant frequency change of a quartz crystal has been extensively used in vapor deposition techniques for many years. However, the use of the quartz crystal microbalance (QCM) in contact with a liquid during electrochemical studies is more recent. Initial investigations were applied to the underpotential deposition of metals. The EQCM has since been applied to a wide variety of electroactive materials. Examples include conducting polymers, conducting polymer bilayers, redox polymers, charge‐transfer salts, hydrogen uptake by a metal, electrochromic behavior of metal oxide electrodes, polymerization of disulfides, self‐assembled ferrocene‐based monolayers, Prussian blue and nickel ferricyanide.
The fact that the mass change of any electroactive material during any electrochemical change can be evaluated with the EQCM has led to its widespread application. The ability to simultaneously determine the mass and the charge passed during an electrochemical process in an electroactive material is critical for characterization in many instances. For example, the polymerization mechanism of an electrochemically synthesized material can be studied as well as quantifying the amount of ion and/or solvent transport during oxidation/reduction. In addition, recent applications of the QCM include simultaneous QCM and ellipsometry, investigating solvent dynamics in polymer films and determining contact angles and surface tensions.
This article provides a general overview of the EQCM technique and provides details about particular interpretative precautions. The QCM has also been called a thickness‐shear‐mode (TSM) oscillator. Related techniques involve the surface‐acoustic wave and flexural‐plate wave devices.
Reflected‐Light Optical Microscopy
Authors: Connell Richard G. 
Published: October 2003

AbstractReflected‐light microscopes were developed for imaging the surfaces of opaque specimens. Microscopy, regardless of the instrumental technique, has as its sole objective the production of visual images that can be further analyzed by counting measurements to quantify any of a number of microstructural properties including grain size, the volume fractions of phases, count (or identification) of microconstituents or microstructural features such as twins, number of inclusions, surface area of grains and second phases, and more esoteric microstructural measurements such as the total mean curvature of the grain boundary in a given specimen. Quantification of microstructural features may be accomplished by manual counting while viewing the image through the microscope, taking measurements from photographic or digital images, or using a computer for digital image analysis. Obtaining quantitative microstructural information constitutes the specialized field of quantitative microscopy or stereology, based upon geometric and topological considerations and statistics. Stereology is a branch of quantitative microscopy that provides for the inference of three‐dimensional structure information from two‐dimensional measurements.While reflected‐light microscopy alone is not intended for the measurement of material properties, coupled with the techniques of quantitative microscopy it does provide the connecting links among properties, chemical composition, and processing parameters. However, an experienced microscopist can obtain much useful qualitative information related to processing and properties. For instance, one may assess the degree of annealing of a metal or alloy by the amount of the microstructure that appears to consist of recrystallized grains. In a production setting, a microscopist may quickly determine if a material meets specified properties merely by observing the microstructure and judging it on the basis of experience.It is the intent of this article to describe the more common techniques of reflected‐light microscopy, but not to delve into microstructural property measurement. Emphasis is placed on the use of the higher‐power instruments (metallographs), because of the variety of useful illumination modes and image‐forming techniques that are available on these instruments.
Photoluminescence Spectroscopy
Authors: Toney James E. 
Published: October 2003

Abstract
Photoluminescence (PL) spectroscopy is a powerful technique for investigating the electronic structure, both intrinsic and extrinsic, of semiconducting and semi‐insulating materials. When collected at liquid helium temperatures, a PL spectrum gives an excellent picture of overall crystal quality and purity. It can also be helpful in determining impurity concentrations, identifying defect complexes, and measuring the band gap of semiconductors. When performed at room temperature with a tightly focused laser beam, PL mapping can be used to measure micrometer‐scale variations in crystal quality or, in the case of alloys and superlattices, chemical composition.
The information obtainable from PL overlaps with that obtained by absorption spectroscopy, the latter technique being somewhat more difficult to perform for several reasons. First, absorption spectroscopy requires a broadband excitation source, such as a tungsten‐halogen lamp, while PL can be performed with any above‐band‐gap laser source. Second, for thin‐film samples absorption spectroscopy requires that the substrate be etched away to permit transmission of light through the sample. Third, for bulk samples the transmitted light may be quite weak, creating signal‐to‐noise ratio difficulties. On the other hand, absorption spectroscopy has the advantage of probing the entire sample volume, while PL is limited to the penetration depth of the above‐band‐gap excitation source, typically on the order of a micrometer.
The areas of application of PL also overlap somewhat with Raman spectroscopy, but the latter is much harder to perform because of the inherent weakness of nonlinear scattering processes and because of its sensitivity to crystallographic orientation. On the other hand, this sensitivity to orientation gives Raman spectroscopy a capability to detect variations in crystallinity that PL lacks.
There are also more elaborate techniques, such as photoluminescence excitation (PLE), time‐resolved PL, and resonant Raman scattering, but these techniques are more useful for basic scientific investigations than for routine crystal characterization.
Ultraviolet and Visible Absorption Spectroscopy
Authors: Tissue Brian M. 
Published: October 2003

Abstract
Ultraviolet and visible (UV‐Vis) absorption spectroscopy is the measurement of the attenuation of a beam of light after it passes through a sample or after reflection from a sample surface. This article uses the term UV‐Vis spectroscopy to include a variety of absorption, transmittance, and reflectance measurements in the ultraviolet (UV), visible, and near‐infrared (NIR) spectral regions. These measurements can be at a single wavelength or over an extended spectral range. This article provides an overview of the technique and does not attempt to provide a comprehensive review of the many applications of UV‐Vis spectroscopy in materials research. In this regard, many of the references were chosen to illustrate the diversity of applications rather than to comprehensively survey the uses of UV‐Vis spectroscopy. A unifying theme is that most of the measurements discussed in this article can be performed with simple benchtop spectrometers and commercially available sampling accessories.
The UV‐Vis spectral range is approximately 190 to 900 nm. This definition originates from the working range of a typical commercial UV‐Vis spectrometer. This article includes the use of UV‐Vis‐NIR instruments because of the importance of characterizing the NIR properties of materials for lasers, amplifiers, and low‐loss optical fibers for fiber‐optic communications and other applications. Wavelength and energy ranges of the UV‐Vis and related spectral regions are summarized.
Ultraviolet‐visible spectroscopy is one of the more ubiquitous analytical and characterization techniques in science. There is a linear relationship between absorbance and absorber concentration, which makes UV‐Vis spectroscopy especially attractive for making quantitative measurements. Ultraviolet and visible photons are energetic enough to promote electrons to higher energy states in molecules and materials. UV‐Vis spectroscopy is useful to the exploration of the electronic properties of materials and materials precursors in basic research and in the development of applied materials. Materials that can be characterized by UV‐Vis spectroscopy include semiconductors for electronics, lasers, and detectors; transparent or partially transparent optical components; solid‐state laser hosts; optical fibers, waveguides, and amplifiers for communication; and materials for solar energy conversion. The UV‐Vis range also spans the range of human visual acuity of approximately 400 to 750 nm, making UV‐Vis spectroscopy useful in characterizing the absorption, transmission, and reflectivity of a variety of technologically important materials, such as pigments, coatings, windows, and filters.
The use of UV‐Vis spectroscopy in materials research can be divided into two main categories: (1) quantitative measurements of an analyte in the gas, liquid, or solid phase and (2) characterization of the optical and electronic properties of a material.
Raman Spectroscopy of Solids
Authors: Devine Thomas M. 
Published: October 2003

AbstractRaman spectroscopy is based on the inelastic scattering of light by matter and is capable of probing the structure of gases, liquids, and solids, both amorphous and crystalline. In addition to its applicability to all states of matter, Raman spectroscopy has a number of other advantages. It can be used to analyze tiny quantities of material (e.g., particles that are ∼1 μm on edge), as well as samples exposed to a variety of conditions such as high temperature and high pressure and samples embedded in other phases, so long as the surrounding media are optically transparent.Succinctly stated, Raman scattering results from incident radiation inducing transitions in the atoms/molecules that make up the scattering medium. The transition can be rotational, vibrational, electronic, or a combination (but first‐order Raman scattering involves only a single incident photon). In most studies of solids by Raman spectroscopy, the transitions observed are vibrational and these are the focus of this article.
Ultraviolet Photoelectron Spectroscopy
Authors: Hill J.P. 
Published: October 2003

Abstract

Ultraviolet photoelectron spectroscopy (UPS) probes electronic states in solids and at surfaces. It relies on the process of photoemission, in which an incident photon provides enough energy to bound valence electrons to release them into vacuum. Their energy
E
, momentum ℏ
k
, and spin σ provide the full information about the quantum numbers of the original valence electron using conservation laws. Depicts the process in an energy diagram. Essentially, the photon provides energy but negligible momentum (due to its long wavelength λ=2π/|
k
|), thus shifting all valence states up by a fixed energy (“vertical” or “direct” transitions). In addition, secondary processes, such as energy loss of a photoelectron by creating plasmons or electron‐hole pairs, produce a background of secondary electrons that increases toward lower kinetic energy. It is cut off at the vacuum level
E
V
, where the kinetic energy goes to zero. The other important energy level is the Fermi level
E
F
, which becomes the upper cutoff of the photoelectron spectrum when translated up by the photon energy. The difference ϕ =
E
V
‐
E
F
is the work function. It can be obtained by subtracting the energy width of the photoelectron spectrum from the photon energy.

Photoemission is complemented by a sister technique that maps out unoccupied valence states, called inverse photoemission or bremsstrahlung isochromat spectroscopy (BIS). Inverse photoemission represents the reverse of the photoemission process, with an incoming electron and an outgoing photon. The electron drops into an unoccupied state and the energy is released by the photon emission.
Both photoemission and inverse photoemission operate at photon energies in the ultraviolet (UV), starting with the work function threshold at ∼4 eV and reaching up to 50‐ to 100‐eV photon energy, where the cross‐section of valence states has fallen off by an order of magnitude and the momentum information begins to get blurred. At kinetic energies of 1 to 100 eV, the electron mean free path is only a few atomic layers, making it possible to detect surface states as well as bulk states.
Impulsive Stimulated Thermal Scattering
Authors: Rogers John A. , Maznev Alex , Nelson Keith A. 
Published: October 2003

AbstractImpulsive stimulated thermal scattering (ISTS) is a purely optical, non‐contacting method for characterizing the acoustic behavior of surfaces, thin membranes, coatings, and multilayer assemblies, as well as bulk materials . The method has emerged as a useful tool for materials research in part because: (1) it enables accurate, fast, and nondestructive measurement of important acoustic (direct) and elastic (derived) properties that can be difficult or impossible to evaluate in thin films using other techniques; (2) it can be applied to a wide range of materials that occur in microelectronics, biotechnology, optics, and other areas of technology; and (3) it does not require specialized test structures or impedance‐matching fluids which are commonly needed for conventional mechanical and acoustic tests. Further, recent advances in experimental design have simplified the ISTS measurement dramatically, resulting in straightforward, low‐cost setups, and even in the development of a commercial ISTS photoacoustic instrument that requires no user adjustments of lasers or optics. With this tool, automated single‐point measurements, as well as scanning‐mode acquisition of images of acoustic and other physical properties, are routine.ISTS, which is based on transient grating (TG) methods, is a spectroscopic technique that measures the acoustic properties of thin films over a range of acoustic wavelengths. This article, focuses only on ISTS measurement of acoustic motions in thin films. It begins with an overview of other related measurement techniques. It then describes the ISTS acoustic data and demonstrates how it can be used to determine: (1) the stress and flexural rigidity in thin membranes; (2) the elastic constants of membranes and supported films; and (3) the thicknesses of single or multiple films in multilayer stacks.