bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conductivity Measurement
Authors: Wentworth Stuart M. 
Published: October 2003

Abstract
A material's conductivity, (or the inverse property, resistivity) relates to its ability to conduct electricity. In metals, conduction of electricity is tantamount to conduction of electrons, which depends on charge density and on scattering of the electrons by the crystal lattice (phonons) or by lattice imperfections. In semiconductors, conductivity is determined by the number of available charge carriers (electrons or holes) and the carrier mobilities. Because of the different mechanisms for conductivity, its dependence on temperature also differs. Conductivity increases with increasing temperature for semiconductors (more carriers are generated) and it decreases with increasing temperature for metals (more scattering by the lattice). Conductivity also depends on physical structure. In crystals, the crystal type and orientation affect conductivity because the electronic structure is intimately tied to the crystal structure. The size of the crystallites (grains) in polycrystalline materials is also important as it affects the scattering of carriers, and, at very small sizes may also affect electronic structure.
The accurate determination of a material's conductivity can be critical for understanding material composition or device performance. The method used to determine conductivity depends on whether the material is a bulk sample or a thin film. This article begins with a section on bulk measurements.
In the second section, two thin‐film approaches are presented which are most frequently used in semiconductor characterization: four‐point probing and the Van der Pauw method.
In the third section measurement approaches are presented that offer the possibility of measurements without damaging the material. These approaches are not as well developed as the contact approaches described in the first two sections. Specialized equipment is required, and accuracy can be rather limited.
The fourth section briefly describes the most common microwave techniques that can be employed to determine conductivity information at high frequencies. Expensive test equipment is required for these approaches, along with specialized test apparatus to probe or hold the samples. The conductivity is not directly measured, but is typically extracted from loss tangent determination.
Some general characteristics for the methods described in these four sections are listed.
Deep‐Level Transient Spectroscopy
Authors: Tin Chin‐Che 
Published: October 2003

AbstractDefects are responsible for many different characteristic properties of a semiconductor. They play a critical role in determining the viability of a given material for device applications. The identification and control of defects have always been among the most important and crucial tasks in materials and electronic device development. The performance and reliability of devices can be significantly affected by only minute concentrations of undesirable defects. Since the determination of the type and quality of defects in a material depends on the sensitivity of a characterization technique, the challenge in materials characterization has been to develop detection methods with improved sensitivity.Deep‐level transient spectroscopy (DLTS) probes the temperature dependence of the charge carriers escaping from trapping centers formed by point defects in the material. This technique is able to characterize each type of trapping center by providing the activation energy of the defect level relative to one of the energy band edges and the capture cross‐section of the traps. It can also be used to compute the concentration and depth profile of the trapping centers.The spectroscopic nature of DLTS is a key feature that provides both convenience and sensitivity.Deep‐level transient spectroscopy has been widely used for many different semiconductors. This technique has distinguished itself in contributing to the resolution of many defect‐related problems in several technologically important semiconductors such as silicon, the Group III to V and II to VI compounds, and alloys. Many variations of basic DLTS have also been developed for improved sensitivity and for more specialized applications in device structures different from the normalp‐nor Schottky barrier diodes.Deep‐level transient spectroscopy is not able to determine the chemistry or the origin of a defect. Deep‐level transient spectroscopy data should therefore be used in conjunction with other techniques. A successful study of defects requires the concerted efforts of many researchers using various characterization techniques in order to derive a more accurate and consistent picture of the defect structure of a given material.
Carrier Lifetime: Free Carrier Absorption, Photoconductivity, and Photoluminescence
Authors: Linnros Jan , Grivickas Vytautas 
Published: October 2003

AbstractThe charge carrier lifetime is one of the most important parameters characterizing a semiconductor. This is mainly for two reasons: (1) the carrier lifetime determines the performance of devices while, at the same time, (2) it is a sensitive measure of material quality and cleanliness. Carrier lifetime may impact device operation directly, such as by affecting the turn‐off speed of a diode or a thyristor operating at high injections or the leakage current of a pn‐junction. Carrier lifetime may also affect operation indirectly. Thus, a high carrier lifetime is desirable in many cases, whereas a low lifetime favors specific applications. Furthermore, for optically active devices, one is interested in radiative recombination, and other recombination mechanisms must be suppressed to enhance quantum efficiency.This article reviews the theory and common concepts in carrier‐lifetime measurement methodology and focuses on a few important and general techniques used to characterize lifetime in semiconductor materials. Thus, device lifetime characterization methods have been left out. The our aim here is to present basic principles of the methods, methodology, and associated difficulties, such that the reader will be able to critically analyze data provided by the methods and to perform simple measurements using the techniques. Also, a selection guide is provided to direct users to the most appropriate method for their specific needs.The three methods described in this article are free carrier absorption (FCA), photoconductivity (PC), and photoluminescence (PL).Free carrier absorptionis not of widespread use but is a very general tool applicable to most semiconductor materials and also to devices. It provides an exceptional advantage, as different geometries and very different injection regimes can be realized, and therefore many different materials and recombination mechanisms may be characterized. It is used here to illustrate many common concepts in lifetime measurement methods.Photoconductivityis one of the few standard methods used both for wafer fabrication quality monitoring and for clean‐room process monitoring.Photoluminescenceis a particularly useful method for characterizing direct‐band‐gap semiconductors, but has also been applied to indirect band‐gap materials. The PL method has also become the workhorse when small volumes must be analyzed, such as in thin‐film studies, for quantum‐well characterization, or for the rapidly expanding field of semiconductor nanostructures.The article commences with a review of the carrier‐lifetime concept and various recombination mechanisms, also illustrating some major difficulties affecting lifetime characterization, such as trapping and surface recombination. Brief outlines of the different techniques and their fundamental principles of operation are given. The three different techniques are described in detail. A selection guide is provided for the different lifetime applications.
Capacitance–Voltage (C‐V) Characterization Of Semiconductors
Authors: Barnes Peter 
Published: October 2003

Abstract

Hillibrand and Gold first described the use of capacitance‐voltage (C‐V) methods to determine the majority carrier concentration in semiconductors. C‐V measurements are capable of yielding quantitative information about the diffusion potential and doping concentration in semiconductor materials. The technique employs
pn
junctions, metal‐semiconductor (MS) junctions (Schottky barriers), electrolyte‐semiconductor junctions, metal‐insulator‐semiconductor (MIS) capacitors, and MIS field effect transistors (MISFETSs). The discussions here emphasize
pn
junctions and Schottky barrier techniques.

C‐V measurements yield accurate information about doping concentrations of majority carriers as a function of distance (depth) from the junction. The major competing technique to C‐V measurements is the Hall effect which, while yielding added information about the carrier mobility, requires difficult, time‐consuming procedures to determine carrier‐depth profiles. In fact, C‐V profiling and Hall measurements can be considered complementary techniques.
In concert with deep‐level transient spectroscopy, C‐V measurements can quantitatively describe the free carrier concentrations together with information about traps. Defects appearing as traps at energies deep within the forbidden gap of a semiconductor can add or remove free carriers. The same Schottky diode can be used for both C‐V measurements and DLTS measurements. The C‐V apparatus and the DLTS apparatus are often a “bundled” setup.
C‐V profiling to determine the doping profile of the mobile majority carriers in a semiconductor is a powerful quantitative technique. Some precautions must be taken, especially in dealing with multiple layered structures such as high‐to‐low doping levels, quantum wells, and the presence of traps. Major considerations and precautions to be taken in dealing with C‐V profiling data acquisition and reduction are also covered in the ASTM standard. The cost of assembling a C‐V profiling apparatus will range between six thousand dollars for a simple, single temperature, manual apparatus to sixty thousand dollars for a fully automated apparatus. C‐V profiling used in concert with deep‐level transient spectroscopy to identify traps, as well as with Hall effect, to address transport mechanisms, provides a powerful set of tools at reasonable cost.
Characterization of

pn

Junctions
Authors: Baca Albert G. 
Published: October 2003

Abstract
The pn junction of a semiconductor material forms part of many commercially important devices such as bipolar junction transistors (BJTs), heterojunction bipolar transistors (HBTs), junction field‐effect transistors (JFETs), and various kinds of diodes (e.g., Zener, rectifying, laser, light emitting). Semiconductor engineers routinely use the current‐voltage (I–V) measurement technique both for the design of semiconductor devices and for yield or process checks during manufacture. The I–V measurement technique is also considered to be a method in materials research because it is used to characterize semiconductor materials and processes used to create these materials. The pn junction I–V technique is useful in materials research because complementary techniques often do not definitively answer whether the material quality is sufficiently good to operate as required in a semiconductor device. The technique can definitely be used on pn junctions present in state‐of‐the‐art semiconductor devices, but in most materials research laboratories, diodes with large feature sizes and considerably simplified sample preparation are preferred for rapid turnaround and lower equipment cost. The technique is most often used when the purpose of characterizing the material is for fabrication of pn junction devices such as BJTs, HBTs, JFETs, and diode structures for a number of applications, including semiconductor lasers and light‐emitting diodes. In that case, the method can be used primarily as a measure of material quality in a device application or as routine intermediate process characterization during device fabrication.
Magnetism and Magnetic Measurements
Authors: Chien C.L. , Xiao G. 
Published: October 2003

Abstract
This article introduces the sections on magnetism and magnetic measurements. Magnetism and magnetic materials have a long and illustrious history. Lodestone (a variety of magnetite) was the first magnetic material of technological importance—which often means military importance as well—due to its seemingly mystical power of seeking direction, a feat which never fails to fascinate a first‐time observer. Lodestones were known to the ancient Egyptian, Greek, and Chinese civilizations, and possibly others. About 2600 B.C., lodestone was instrumental in winning a decisive battle for the first emperor of China, fought in a dense fog against the invading barbarians.
The subject that we generally call magnetism began with the observation that some minerals, such as magnetite, could attract each other and certain other minerals. However, a fundamental understanding of magnetism had to await the advent of quantum mechanics and special relativity in the 20th century.
Today, magnetism enters many aspects of our lives, far beyond just compasses and refrigerator magnets. Magnetic materials and magnetic phenomena inconspicuously appear in many complex devices, for example, theft‐prevention systems in department stores, magnetic recording disks and read heads in the ubiquitous computers and cellular phones, and in magnetic resonance imaging apparatus. Some of the more exciting new developments are the spintronic devices, which are on the verge of becoming realities. These new devices are based on the spin properties of electrons, as opposed to charge alone, as in conventional electronics.
The subject of magnetism is inseparable from electrical charges, their translational motion and their angular momenta. The articles in this category cover magnetic fields and properties, measurement of magnetic fields and their effect on materials behavior.
Generation and Measurement of Magnetic Fields
Authors: Schneider‐Muntau Hans J. , Coey J.M.D. , Kuhns Phil , Rubin Larry , Schott Christian 
Published: October 2003

AbstractIn basic science areas, such as semiconductor physics, superconductivity, structural biology, and chemistry, magnetic fields are used as a powerful tool for analysis of matter because they can change the physical state of a system. In the presence of a magnetic field, the angular momenta (spins), the orbital motion of charged particles, and therefore the energy of the investigated physical system, are altered. One must realize, however, that the size of the induced effects are very modest compared to other physical quantities.The use of magnetic fields and their effects on matter are based on a few micro‐ and macroscopic principles. These principles are utilized not only in basic science areas but also for significant industrial applications, and most of them are also employed to measure magnetic fields. These include the following: Magnetization of nuclei and its decay; induced currents; force on moving charged particles(“Lorentz force”); magnetization; and energy content.Magnetic fields can be generated by magnets created from hard magnetic materials and by electromagnets. Permanent magnets offer a simple, fast, and cost‐effective way to provide small‐volume fields.Permanent magnetsare being employed for MRI applications, accelerator storage rings, and wiggler magnets. Dimagnetism, antiferromagnetism, and ferromagnetism are explained.
Magnetic Moment and Magnetization
Authors: McHenry Michael E. 
Published: October 2003

Abstract

The intrinsic magnetic properties of materials refer to

the origin, magnitude, and directions of atomic magnetic dipole moments;

the nature of the interaction between atomic magnetic dipole moments on neighboring atoms in the solid;

whether these result in collective magnetic phenomena; and

the resulting temperature dependence of the magnetization.

Materials exhibiting collective magnetic response possess additional intrinsic magnetic properties, including the strength of the coupling of magnetic moments to one another and to crystallographic directions, magnetoelastic coupling coefficients, and the temperature(s) at which magnetic phase transformations occur. The intrinsic magnetic properties of species at surfaces and interfaces are known to be distinctly different from those of the bulk in many cases. In this articles the theory of intrinsic magnetic properties, specifically of dipole moment and magnetization, as well as theory and examples of collective magnetic response are achieved.
Theory of Magnetic Phase Transitions
Authors: McHenry Michael E. , Laughlin David E. 
Published: October 2003

Abstract

The existence of magnetic order (collective magnetism) appearing in materials below a particular ordering temperature (e.g., the Curie temperature,
T
C
, or the Neel temperature,
T
N
) points to a class of physical phenomena which are described as
magnetic phase transition
s. The thermodynamics of these phase transitions can be described by energy functions (expressed in terms of intensive or extensive variables), in terms of magnetization − temperature (
M
−
T
) phase diagrams, or in terms of critical exponents that describe the variation of thermodynamic properties (as a function of the order parameter) as the ordering temperature is approached. In this article, the thermodynamics of magnetic ordering transitions, the order of the transitions, critical exponents, and thermodynamic variables are described. Magnetic phase transitions within the framework of the mean field or
Landau theory of phase transitions
with discussion of several magnetic equations of state are presented.
Thermomagnetic Analysis
Authors: McHenry Michael E. 
Published: October 2003

Abstract

The most common method of measuring magnetic ordering temperatures is through the use of
thermomagnetic analysis
techniques. These techniques rely on methods previously described. In essence, thermomagnetic analysis involves sensitive measurement of a magnetic dipole moment in a zero or an applied field as a function of temperature. The components of the system therefore include an appropriate magnetometer. Superconducting quantum interference device (SQUID), vibrating‐sample, and Faraday‐balance magnetometers are commonly used in the field. Large axial fields can be applied using a superconducting solenoid; smaller axial fields can be applied using wound‐metal solenoids. Transverse fields can be applied using split‐coil superconducting solenoids or electromagnets. Measurement of the temperature dependence of magnetic properties requires careful design of the sample chamber and methods for heating and cooling, as well as accurate thermometry for monitoring temperature. Measurement of magnetic transitions of the types described in the other articles may entail the measurement of magnetic properties at temperatures ranging from cryogenic to ∼1100°C (the
T

c

of elemental Co).

The data illustrated in the figures in this article, probing magnetic phase transitions, were taken using either a SQUID magnetometer or a vibrating sample magnetometer. An abbreviated discussion of these systems is given.
The principle of operation of a vibrating sample magnetometer (VSM) is based on placing a magnetic sample in a uniform magnetic field. The sample dipole moment is made to undergo a periodic sinusoidal motion at a fixed frequency using a transducer drive head to vibrate a sample rod.
The term SQUID is an acronym for superconducting quantum interference device. The principles of operation of a typical SQUID magnetometer system for measuring a sample are briefly summarized.
Techniques to Measure Magnetic Domain Structures
Authors: Celotta R.J. , Unguris J. , Kelley M.H. , Pierce D.T. 
Published: October 2003

AbstractCritical to understanding the magnetic properties and the technological application of magnetic materials is the ability to observe and measure magnetic domain structure. The measurement challenge is quite varied. Magnetic fluids can be used to decorate and make simple domain structures visible while highly sophisticated electron microscopy‐based methods may be needed to explore and image nanometer‐scale magnetic phenomena. No one method will solve all of the important domain imaging problems. For that reason, the bases of all the important methods and the practical implications of each are discussed.For purposes of comparison, several important characteristics of each domain imaging technique are briefly summarized.There are several general comments that apply to every domain imaging method discussed in this article. First, each method is related either to a sample's magnetization or to the magnetic field generated by that magnetization. The former observation is of great usefulness in understanding or developing new materials, and the latter is of practical importance in devices. Second, all of the methods are limited to the topmost few micrometers of the sample, and are therefore dominated by magnetic structure related to the surface. None provide the domain structure of the interior of a thick sample where bulk magnetic microstructure is fully developed. Third, all of the methods require smooth, clean, damage‐free surfaces. In general, the surfaces need to have at least the equivalent of a mirror polish, otherwise, topography and surface stress will affect the measurement to varying degrees. Fourth, correlations exist between several of the parameters in each technique we describe. For example, it may not be possible to achieve the ultimate sensitivity specified at the highest resolution possible. Finally, almost all of the techniques use digital signal acquisition and can benefit from the use of modern image processing tools.Expanded discussions of the basis of each technique, its practical aspects, sample preparation required, possible sample modifications, and problems that are specific to the technique described are given. Each section contains references to more complete treatments of the technique and recent examples of its use.