Kataev, Vladimir F.

Lunin, Leonid S.

Ratushnyj, V. I.

Digitale Bibliothek Thüringen

  PROCEEDINGS 11-15 September 2006      FACULTY OF ELECTRICAL ENGINEERING AND INFORMATION SCIENCE    INFORMATION TECHNOLOGY AND ELECTRICAL ENGINEERING - DEVICES AND SYSTEMS, MATERIALS AND TECHNOLOGIES FOR THE FUTURE      Startseite / Index: http://www.db-thueringen.de/servlets/DocumentServlet?id=12391 51. IWK Internationales Wissenschaftliches Kolloquium International Scientific Colloquium Impressum  Herausgeber: Der Rektor der Technischen Universität llmenau  Univ.-Prof. Dr. rer. nat. habil. Peter Scharff  Redaktion: Referat Marketing und Studentische Angelegenheiten  Andrea Schneider   Fakultät für Elektrotechnik und Informationstechnik  Susanne Jakob  Dipl.-Ing. Helge Drumm  Redaktionsschluss: 07. Juli 2006  Technische Realisierung (CD-Rom-Ausgabe):  Institut für Medientechnik an der TU Ilmenau  Dipl.-Ing. Christian Weigel  Dipl.-Ing. Marco Albrecht  Dipl.-Ing. Helge Drumm  Technische Realisierung (Online-Ausgabe):  Universitätsbibliothek Ilmenau    Postfach 10 05 65  98684 Ilmenau  Verlag:   Verlag ISLE, Betriebsstätte des ISLE e.V.  Werner-von-Siemens-Str. 16  98693 llrnenau   © Technische Universität llmenau (Thür.) 2006  Diese Publikationen und alle in ihr enthaltenen Beiträge und Abbildungen sind urheberrechtlich geschützt. Mit Ausnahme der gesetzlich zugelassenen Fälle ist eine Verwertung ohne Einwilligung der Redaktion strafbar.   ISBN (Druckausgabe): 3-938843-15-2 ISBN (CD-Rom-Ausgabe): 3-938843-16-0  Startseite / Index: http://www.db-thueringen.de/servlets/DocumentServlet?id=12391  51st Internationales Wissenschaftliches Kolloquium Technische Universität Ilmenau  September 11 – 15, 2006  L.S. Lunin, V.I. Ratushnyj, V.F. Kataev    Measurement of magnetic field influence on thermal electromotive force in micro and nano semi-conductor films without creation of temperature gradient    Process of charging thermoelectric capacitor which represents system of metal - semiconductor - isolator - metal, from a constant source of a voltage applied through resistor R, occurrence of the thermal electromotive force in such system and influence on this process of a magnetic field is considered. Change of the thermal electromotive force and coefficient Peltier in a cross magnetic field is measured. For measurement of thermal electromotive force and its change it is necessary to create a  temperature gradient that is not always convenient, especially if researched samples represent a thin film or a plate. Creating difference of temperatures even in 1 degree in such case is extremely difficult as the gradient of temperatures turns out very big because of subtlety of a sample. Therefore real difference of temperatures appears to be shares of degree which makes measurements of temperature difference difficult and strongly influences measurement accuracy. So thermal electromotive force measurement without creating temperature gradient represents an actual task. Let's examine a charge of the thermoelectric condenser which is system of metal - semiconductor-isolator-metal powered from a constant source of a voltage applied through resistor R. The equation describing this process is: 0321UUuuudtduRC kCCC +=+++, (1) Where 323121321CCCCCCCCCC ++= , С2, С3 - capacity between metal and the semiconductor, formed because of the electric field penetrating into the semiconductor, С1 - capacity of interelectrode space where isolator is, uC1 = φ1’ - φ 0’, uC2 = φ0’ - φ0, uC3 = φ1 - φ1’ change of potential on Сi. If there is used an enough low-ohm conductor (with conductivity more 0,1 ohm-1 x cm-1) than electric field penetration depth into the semiconductor does not exceed the 100-th shares of micron, and thickness of a dielectric film gets out within the limits of several micron, so С1 < < C2 and C1 < < C3. In a same way 3121 CCCCuuuu >>>> , . Then, designating uuC ≈1  and 323121321CCCCCCCCCC ++= , we can compile an equation for a condenser voltage: 0UUudtduRC k +=+ (2) The solution for the equation (2) is:  0UUAetu kRCt++= −)( . (3) At the initial moment of time the condenser is not charged, therefore 010=Cu kCC Uuu =+ 23 00 , and, kUu =)(0 as 321 CCC uuuu ++= . Then  kk UUUA =++ 0 , A =-U0 and  kRCtUeUtu +−= − )()( 10 . (4) Current flowing through the condenser is RCteRUi−= 0, and energy of the charged condenser is CUUUUCUCUdteRUUdteRUeUudiW kkRCtkRCtRCtC 2221 0200 0 0020000+=+=+−== ∫ ∫ ∫∞ ∞ ∞ −−−)(, (5) Where: 220CU is the energy received by the condenser from a voltage source, СU0Uk - the energy absorbed from an environment because of the charge current direction is chosen in a way that metal-semiconductor contact electrons pass from metal into the semiconductor. At a direction of a current when electrons pass from metal in the semiconductor, they should overcome the potential barrier equal to a energy difference between Fermy level and a bottom of a conductivity zone. Only the "fast electrons" are able for this. Therefore only "cold" electrons remain in contact and it is cooled. When the current goes in an opposite direction, electrons pass from the semiconductor in metal. As electron energy in the semiconductor becomes more than in metal electrons give a part of the energy to a crystal lattice when transiting , and transition is heated up. This phenomenon is known as effect Peltier, and Peltier factor П is equal to a contact potential difference [5] (П=Uk). The energy allocated on the resistor is ∫∞ ==02022CURdtiWR . (6) In [1-5] it is shown, that external fields (magnetic, electromagnetic emission, a field of mechanical deformations) can change thermal electromotive force. Therefore UkА = Uk + ∆Uk (З), where A - key parameter of an external field (for a magnetic field it is an induction of a magnetic field B, for electromagnetic emission - intensity of emission on frequency of maximal absorption I, for deformations it is S, where S is relative deformation). For example, the magnetic field changes a ratio of fast and slow electrons in a current because fast electrons dissipate on thermal fluctuations of a crystal lattice less, than slow electrons, i.e. fast electrons quantity depending on size of a magnetic field in a current is increased, that increases Peltier factor  П = αТ= Uk, and thermal electric force α = α0 [1+сα(ηHB)2] (where α0 is thermal electromotive force) consequently. In absence of a magnetic field, сα - the factor depending on character of electron dispersion (at dispersion on thermal photons with сα ≈ 0,154), ηH  - Hall mobility of electrons in the semiconductor. Because time of electron dispersion on thermal photons has the order of size 10-11с [4] than at each change of a magnetic field new equilibrium distribution of electrons will be established also at this time. It means, that change α and Uk will occur to delay 10-11с, and this delay can be neglected, if a time constant of condenser charge is RC > > 10-11c. If while charging thermoelectric condenser it is placed in an external field, then CUUUW kAC 22 020 +=. (7) When carrying out the charged condenser from external field (А=0) its energy will not change, as external fields of non-electric origin can not change a condenser charge when it's opened, and the capacity is not supposed to change under external fields influence. For example, the magnetic field can not make work on charging the condenser because the magnetic field varied in time (as it's deenergizing) derivates a vortical electric field which, in turn, derivates vortical currents only in electrodes of the condenser, not changing its charge. Hence, energy of the condenser in absence of external field (В=0) is  00 ≠= = CACA WW , I.e.: 2222 0202kAk UUUCUUUC+=+, (8) Where U is a voltage on metal electrodes of the thermoelectric condenser: kAkk UUUUUU 020 2+++−= .. (9) Obviously that if U0=0, U=0, and if U0 > > UkА, UkU ≈ U0 + ∆U, ∆U=UkA-Uk. Thus measuring a voltage on the condenser in an external field and in its absence it is possible to determine the amount of ∆U, i.e. change of Peltier factor under action of an external field. When temperature is known, it is possible to determine specific thermal electromotive force. We have developed and made installation for measurement of change from a magnetic field. It was established, that at room temperature in crystals of indium antimonide thermal electromotive force and Peltier factor in a cross magnetic field with an induction of 0,2 Т changes unless on 5 %.  References: [1] Ure Ronald W. The theory of materials for thermoelectric and thermomagnetic devices. TNIER, t.51, № 5,1963, 702 - 717. [2] Gadjilaev M. Thermal electromotive force InSb in cross quanting magnetic field. News of high Schools, Physics, № 3,1993. [3] Gadjilaev M. Thermal electromotive force n-InSb in a cross magnetic field and at the big temperature gradient, t.34,5th ed, 2000 [4] Weldock. Thermophotoelectric transformation of energy, TNIER, t.51, 697 - 702 [5] Karapet'jan G.J., Kataev V.F., Ratushnyj V.I., Sysoev I.A. "Influence of a magnetic field on size of thermal electromotive force in semiconductors" Works of the international scientific and technical conference. "Mechanical engineering and technosphere on a boundary of XXI century" (September, 11-17, 2000 Sevastopol), 34-35.   Authors: Professor, Dr. Sc. Science L.S. Lunin Dipl.-Ing. V.F. Kataev Dr.-Ing. V.I. Ratushniy South Russian State Technical University 132, Prosveshcheniya St, Rostov Region, Novocherkassk, 346428, Russia Tel. (86352) 2-33-44 Fax (86352) 2-84-63 E-mail: natu@novoch.ru 

Measurement of magnetic field influence on thermal electromotive force in micro and nano semi-conductor films without creation of temperature gradient

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Measurement of magnetic field influence on thermal electromotive force in micro and nano semi-conductor films without creation of temperature gradient

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