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This Provisional PDF corresponds to the article as it appeared upon acceptance. Fully formatted PDF and full text (HTML) versions will be made available soon. Developing a theoretical relationship between electrical resistivity, temperature, and film thickness for conductors Nanoscale Research Letters 2011, 6:636 doi:10.1186/1556-276X-6-636 Fred Lacy (fredlacy@engr.subr.edu) ISSN 1556-276X Article type Nano Express Submission date 7 June 2011 Acceptance date 22 December 2011 Publication date 22 December 2011 Article URL http://www.nanoscalereslett.com/content/6/1/636 This peer-reviewed article was published immediately upon acceptance. It can be downloaded, printed and distributed freely for any purposes (see copyright notice below). Articles in Nanoscale Research Letters are listed in PubMed and archived at PubMed Central. For information about publishing your research in Nanoscale Research Letters go to http://www.nanoscalereslett.com/authors/instructions/ For information about other SpringerOpen publications go to http://www.springeropen.com Nanoscale Research Letters © 2011 Lacy ; licensee Springer. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. - 1 - Developing a theoretical relationship between electrical resistivity, temperature, and film thickness for conductors Fred Lacy* 1 1 Electrical Engineering Department, Southern University and A&M College, Pinchback Hall, Rm 428, Baton Rouge, LA, 70813, USA *Corresponding author: fredlacy@engr.subr.edu Email address: FL: fredlacy@engr.subr.edu Abstract Experimental evidence has made it clear that the size of an object can have an effect on its properties. The electrical resistivity of a thin film will become larger as the thickness of that film decreases in size. Furthermore, the electrical resistivity will also increase as the temperature increases. To help understand these relationships, a model is presented, and equations are obtained to help understand the mechanisms responsible for these properties and to give insight into the underlying physics between these parameters. Comparisons are made between experimental data and values generated from the theoretical equations derived from the model. All of this analysis provides validation for the theoretical model. Therefore, since the model is accurate, it provides insight into the underlying physics that relates electrical resistivity to temperature and film thickness. Keywords: Callendar-van Dusen; conductivity; mean free path; nanofilm; resistance temperature detector; temperature sensor; thin film. PACS: 73.61.At; 73.50.Bk; 72.15.Eb; 72.10.d; 63.20.kd. Introduction Nanotechnology is an emerging branch of science that seeks to understand how materials operate and function when at least one of their dimensions is less than 100 nm in size. Through various experimental studies, it is understood that when materials shrink to dimensions on the nanoscale, many of the properties or characteristics that they display in bulk form are no longer valid [1-5]. Mechanical, thermodynamic, electrical, and optical properties have been shown to be altered because of the size difference. The reasons for this change in properties are due to increased surface interactions as well as absorption and scattering effects [1-5]. Several studies have shown that diminishing one of the dimensions Conductors and Insulators Conductors and Insulators Bởi: OpenStaxCollege This power adapter uses metal wires and connectors to conduct electricity from the wall socket to a laptop computer The conducting wires allow electrons to move freely through the cables, which are shielded by rubber and plastic These materials act as insulators that don’t allow electric charge to escape outward (credit: Evan-Amos, Wikimedia Commons) Some substances, such as metals and salty water, allow charges to move through them with relative ease Some of the electrons in metals and similar conductors are not bound to individual atoms or sites in the material These free electrons can move through the material much as air moves through loose sand Any substance that has free electrons and allows charge to move relatively freely through it is called a conductor The moving electrons may collide with fixed atoms and molecules, losing some energy, but they can move in a conductor Superconductors allow the movement of charge without any loss of energy Salty water and other similar conducting materials contain free ions that can move through them An ion is an atom or molecule having a positive or negative (nonzero) total charge In other words, the total number of electrons is not equal to the total number of protons Other substances, such as glass, not allow charges to move through them These are called insulators Electrons and ions in insulators are bound in the structure and cannot move easily—as much as 1023 times more slowly than in conductors Pure water and dry table salt are insulators, for example, whereas molten salt and salty water are conductors 1/7 Conductors and Insulators An electroscope is a favorite instrument in physics demonstrations and student laboratories It is typically made with gold foil leaves from a (conducting) metal stem and is insulated from the room air in a glass-walled container (a) A positively charged glass rod is brought near the tip of the electroscope, attracting electrons to the top and leaving a net positive charge on the leaves Like charges in the light flexible gold leaves repel, separating them (b) When the rod is touched against the ball, electrons are attracted and transferred, reducing the net charge on the glass rod but leaving the electroscope positively charged (c) The excess charges are evenly distributed in the stem and leaves of the electroscope once the glass rod is removed Charging by Contact [link] shows an electroscope being charged by touching it with a positively charged glass rod Because the glass rod is an insulator, it must actually touch the electroscope to transfer charge to or from it (Note that the extra positive charges reside on the surface of the glass rod as a result of rubbing it with silk before starting the experiment.) Since only electrons move in metals, we see that they are attracted to the top of the electroscope There, some are transferred to the positive rod by touch, leaving the electroscope with a net positive charge Electrostatic repulsion in the leaves of the charged electroscope separates them The electrostatic force has a horizontal component that results in the leaves moving apart as well as a vertical component that is balanced by the gravitational force Similarly, the electroscope can be negatively charged by contact with a negatively charged object Charging by Induction It is not necessary to transfer excess charge directly to an object in order to charge it [link] shows a method of induction wherein a charge is created in a nearby object, without direct contact Here we see two neutral metal spheres in contact with one another but insulated from the rest of the world A positively charged rod is brought near one of them, attracting negative charge to that side, leaving the other sphere positively charged This is an example of induced polarization of neutral objects Polarization is the separation of charges in an object that remains neutral If the spheres are now separated 2/7 Conductors and Insulators (before the rod is pulled away), each sphere will have a net charge Note that the object closest to the charged rod receives an opposite charge when charged by induction Note also that no charge is removed from the charged rod, so that this process can be repeated without depleting the supply of excess charge Another method of charging by induction is shown in [link] The neutral metal sphere is polarized when a charged rod is brought near it The sphere is then grounded, meaning that a conducting wire is run from the sphere to the ground Since the earth is large and most ground is a good conductor, it can supply or accept excess charge easily In this case, electrons are attracted to the sphere through a wire called the ground wire, because it supplies a conducting path to the ground The ground connection is broken before the charged rod is removed, leaving the sphere with an excess charge opposite to that of the rod Again, an opposite charge is achieved when ...This Provisional PDF corresponds to the article as it appeared upon acceptance. Fully formatted PDF and full text (HTML) versions will be made available soon. Developing a theoretical relationship between electrical resistivity, temperature, and film thickness for conductors Nanoscale Research Letters 2011, 6:636 doi:10.1186/1556-276X-6-636 Fred Lacy (fredlacy@engr.subr.edu) ISSN 1556-276X Article type Nano Express Submission date 7 June 2011 Acceptance date 22 December 2011 Publication date 22 December 2011 Article URL http://www.nanoscalereslett.com/content/6/1/636 This peer-reviewed article was published immediately upon acceptance. It can be downloaded, printed and distributed freely for any purposes (see copyright notice below). Articles in Nanoscale Research Letters are listed in PubMed and archived at PubMed Central. For information about publishing your research in Nanoscale Research Letters go to http://www.nanoscalereslett.com/authors/instructions/ For information about other SpringerOpen publications go to http://www.springeropen.com Nanoscale Research Letters © 2011 Lacy ; licensee Springer. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. - 1 - Developing a theoretical relationship between electrical resistivity, temperature, and film thickness for conductors Fred Lacy* 1 1 Electrical Engineering Department, Southern University and A&M College, Pinchback Hall, Rm 428, Baton Rouge, LA, 70813, USA *Corresponding author: fredlacy@engr.subr.edu Email address: FL: fredlacy@engr.subr.edu Abstract Experimental evidence has made it clear that the size of an object can have an effect on its properties. The electrical resistivity of a thin film will become larger as the thickness of that film decreases in size. Furthermore, the electrical resistivity will also increase as the temperature increases. To help understand these relationships, a model is presented, and equations are obtained to help understand the mechanisms responsible for these properties and to give insight into the underlying physics between these parameters. Comparisons are made between experimental data and values generated from the theoretical equations derived from the model. All of this analysis provides validation for the theoretical model. Therefore, since the model is accurate, it provides insight into the underlying physics that relates electrical resistivity to temperature and film thickness. Keywords: Callendar-van Dusen; conductivity; mean free path; nanofilm; resistance temperature detector; temperature sensor; thin film. PACS: 73.61.At; 73.50.Bk; 72.15.Eb; 72.10.d; 63.20.kd. Introduction Nanotechnology is an emerging branch of science that seeks to understand how materials operate and function when at least one of their dimensions is less than 100 nm in size. Through various experimental studies, it is understood that when materials shrink to dimensions on the nanoscale, many of the properties or characteristics that they display in bulk form are no longer valid [1-5]. Mechanical, thermodynamic, electrical, and optical properties have been shown to be altered because of the size difference. The reasons for this change in properties are due to increased surface interactions as well as absorption and scattering effects [1-5]. Several studies have shown that diminishing one of This Provisional PDF corresponds to the article as it appeared upon acceptance. Fully formatted PDF and full text (HTML) versions will be made available soon. Developing a theoretical relationship between electrical resistivity, temperature, and film thickness for conductors Nanoscale Research Letters 2011, 6:636 doi:10.1186/1556-276X-6-636 Fred Lacy (fredlacy@engr.subr.edu) ISSN 1556-276X Article type Nano Express Submission date 7 June 2011 Acceptance date 22 December 2011 Publication date 22 December 2011 Article URL http://www.nanoscalereslett.com/content/6/1/636 This peer-reviewed article was published immediately upon acceptance. It can be downloaded, printed and distributed freely for any purposes (see copyright notice below). Articles in Nanoscale Research Letters are listed in PubMed and archived at PubMed Central. For information about publishing your research in Nanoscale Research Letters go to http://www.nanoscalereslett.com/authors/instructions/ For information about other SpringerOpen publications go to http://www.springeropen.com Nanoscale Research Letters © 2011 Lacy ; licensee Springer. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. - 1 - Developing a theoretical relationship between electrical resistivity, temperature, and film thickness for conductors Fred Lacy* 1 1 Electrical Engineering Department, Southern University and A&M College, Pinchback Hall, Rm 428, Baton Rouge, LA, 70813, USA *Corresponding author: fredlacy@engr.subr.edu Email address: FL: fredlacy@engr.subr.edu Abstract Experimental evidence has made it clear that the size of an object can have an effect on its properties. The electrical resistivity of a thin film will become larger as the thickness of that film decreases in size. Furthermore, the electrical resistivity will also increase as the temperature increases. To help understand these relationships, a model is presented, and equations are obtained to help understand the mechanisms responsible for these properties and to give insight into the underlying physics between these parameters. Comparisons are made between experimental data and values generated from the theoretical equations derived from the model. All of this analysis provides validation for the theoretical model. Therefore, since the model is accurate, it provides insight into the underlying physics that relates electrical resistivity to temperature and film thickness. Keywords: Callendar-van Dusen; conductivity; mean free path; nanofilm; resistance temperature detector; temperature sensor; thin film. PACS: 73.61.At; 73.50.Bk; 72.15.Eb; 72.10.d; 63.20.kd. Introduction Nanotechnology is an emerging branch of science that seeks to understand how materials operate and function when at least one of their dimensions is less than 100 nm in size. Through various experimental studies, it is understood that when materials shrink to dimensions on the nanoscale, many of the properties or characteristics that they display in bulk form are no longer valid [1-5]. Mechanical, thermodynamic, electrical, and optical properties have been shown to be altered because of the size difference. The reasons for this change in properties are due to increased surface interactions as well as absorption and scattering effects [1-5]. Several studies have shown that http://jbiol.com/content/8/8/73 Ong and Corces: Journal of Biology 2009, 8:73 Abstract Insulator elements mediate intra- and inter-chromosomal inter actions. The insulator protein CCCTC-binding factor (CTCF) is important for insulator function in several animals but a report in BMC Molecular Biology shows that Caenorhabditis elegans, yeast and plants lack CTCF. Alternative proteins may have a similar function in these organisms. Eukaryotic genomes have developed a variety of strategies for efficiently orchestrating the complex patterns of gene expression required for proper cellular differentiation. Com- parative genome analyses suggest that developmental evolution is largely driven by the increase in the complexity of these expression patterns [1]. Consistent with this hypo- thesis, recent studies indicate that transcription factor- coding genes tend to be under greater positive evolutionary selection compared with other genes [2]. To establish and maintain cell-specific patterns of gene expression, regions of the genome are kept in a silenced state while imme diately adjacent regions are transcriptionally active because of the presence of promiscuous enhancer elements that can act over large distances. Insulators were originally des cribed as DNA regulatory elements that ensure the progress of an accurate transcriptional program by keeping in check communication between enhancers and promo ters and creating boundaries that prevent inappropriate interactions between adjacent chromatin domains. Accu mu lating evidence suggests that these properties of insulators arise from their ability to mediate intra- and inter-chromosomal interactions, which result in the formation of chromatin loops through clustering of multiple insulator sites [3]. Depending on the complexity of the genome, the capability to mediate long-range interactions with other protein complexes may allow insulator proteins to carry out a variety of functions in the nucleus [4]. CCCTC-binding factor (CTCF) is the only known insulator protein necessary for establishing patterns of nuclear architecture and transcriptional control in vertebrates [5]. This protein is also found in invertebrates such as Anopheles gambiae, Aedes aegypti and Drosophila melanogaster [6]. A recent study by Heger et al. in BMC Molecular Biology [7] has shown that the gene encoding CTCF is not present in the genomes of several model organisms, including Saccharomyces cerevisiae, Schizo- saccharo myces pombe, Arabidopsis thaliana and Caeno- rhab ditis elegans. Because of the widespread presence of insulators and the essential role of CTCF in a wide variety of eukaryotic organisms, this absence of the gene in other organisms raises the possibility that other regulatory mechanisms might have evolved to replace the function of this protein. Here, we provide a brief overview of how insulator proteins work in Drosophila and vertebrates, as well as how plants and fungi may have adapted different proteins to accomplish insulator function. We also discuss how insulator proteins such as CTCF may have evolved new functions to handle more complex genomes in animals. Examples of insulator function The mechanisms of insulator function are best understood from analyses of the gypsy element of Drosophila. Gypsy insulator sites are bound by the Suppressor of Hairy-wing protein (Su(Hw)), in a sequence-specific manner. This protein in turn recruits other factors, including centro- somal protein 190 kDa (CP190), Modifier of mdg4 (Mod(mdg4)2.2), topoisomerase I-interacting RS protein (dTopors) and RNA, to form clusters of ‘insulator bodies’ (consisting of these proteins and DNA) with multiple gypsy sites [8] (Figure 1a). Recently, other Drosophila insulator proteins, dCTCF and Boundary element asso cia- ted factor (BEAF), have also been shown to recruit CP190 to specific DNA sites [9], suggesting that loop formation through long-range protein interactions Journal of Physical Science, Vol. 20(1), 75–86, 2009 75 Mechanochemical Synthesis and Characterisation of Bismuth-Niobium Oxide Ion Conductors S.N. Ng * , Y.P. Tan * and Y.H. Taufiq-Yap Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia * Corresponding authors: sinnee83@gmail.com, yptan@fsas.upm.edu.my Abstract: Bismuth niobate solid solutions, Bi x NbO δ (2.5 ≤ x ≤ 6), have been prepared using a mechanochemical method. The solid solutions were also prepared using a solid- state conventional method for comparison purposes. Bi 3 NbO 7 was successfully obtained via a mechanochemical method at a lower synthesis temperature (milled at 1000 rpm for one hour followed by heating at 700 o C for 24 h) than the conventional solid-state method. Electrical properties of the single-phase materials were studied by AC impedance spectroscopy. Further characterization of the materials was carried out using differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The results showed that no thermal changes and phase transitions were observed and all materials were thermally stable. Keywords: bismuth niobate, mechanochemical, solid-state reaction, impedance spectroscopy 1. INTRODUCTION Ionic conductors have provided a fascinating interdisciplinary field of study for over a century. In oxygen ion conductors, current flow occurs by the movement of an oxide ion through the crystal lattice. As well as the intrinsic interest in these materials, there has been a continued drive for their applications in technological devices such as solid oxide fuel cells (SOFCs), oxygen sensors, and many other applications. These entire devices offer the potential of enormous commercial and ecological benefits provided suitable high performance materials can be developed. 1–4 Yittria-stabilized zirconia (YSZ), which is used as the electrolyte in SOFC operates at a temperature around 1000 o C. Thus, high operating temperatures will result in high fabrication costs and also affect the material stability and compatibility and the thermal degradation of the electrolyte itself. Therefore, there is a continuing effort to search for oxide ion conductors that can operate at lower temperature in order to reduce costs. Mechanochemical Synthesis and Characterisation 76 Bismuth oxide, Bi 2 O 3 , is recognized as a good oxide ion conductor due to its crystal structure (fluorite type) and its high ratio of oxygen vacancies. Bi 2 O 3 exists in four polymorphs, which are α, β, γ, and δ. The high-temperature form of bismuth oxide, δ-Bi 2 O 3, which has an oxygen-deficient fluorite-type structure, has been recognized as one of the best solid-state oxide ion conductors due to the high concentration of intrinsic oxygen vacancies. 5 However, δ-Bi 2 O 3 is only stable in a narrow temperature range from 730 o C to its melting point at 824 o C. Below 730 o C, the monoclinic α-Bi 2 O 3 is the stable phase. In order to enhance the stability of the high-temperature and highly conducting δ-phase, it can be doped with transition metal oxides such as Nb 2 O 5 , Ta 2 O 5 , WO 3 or rare-earth oxides. 6–9 Among the many choices of substituting cations in δ-Bi 2 O 3 , Nb 5+ is probably the most frequently used due to its high efficiency in stabilizing the cubic phase at room temperature. 10 Bismuth niobate (Bi 3 NbO 7 ) exists in two crystallographic configurations, a tetragonal (type III) phase and a pseudocubic (type II) phase. The tetragonal phase shows a higher electrical conductivity than the pseudocubic phase. It was suggested that this is associated with the redistribution of the oxygen sublattice (or oxygen vacancies) induced by superstructure ordering in tetragonal Bi 3 NbO 7 , which appears to increase the mobility of free charge carriers and therefore improves the electrical conductivity. The plots of ionic conductivity ... Travoltage Wiggle Johnnie's foot and he picks up charges from the carpet Bring his hand close to the door knob and get rid of the excess charge 5/7 Conductors and Insulators John Travoltage Section... car wax and car tires are insulators. ) Describe how a positively charged object can be used to give another object a negative charge What is the name of this process? 6/7 Conductors and Insulators. . .Conductors and Insulators An electroscope is a favorite instrument in physics demonstrations and student laboratories It is typically made with