Advanced

Thermoelectric phenomena in low-dimensional semiconductor systems

Larsson, Magnus LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

Denna avhandling behandlar termoelektriska effekter, framförallt i lågdimensionella halvledarsystem. Åtskilliga nya fenomen diskuteras, undersöks och förklaras.



Introduktionsdelen innehåller en sammanfattning för allmänheten på svenska samt en introduktion till termoelektriska effekter på engelska. Detta görs dels med hjälp av en semi-klassisk teoretisk modell, men även en modell baserad på Landauers teori, vilken används då elektrontransporten är ballistisk. Efter introduktionen följer 6 artiklar.



I artikel 1 och 2 undersöks den termoelektriska strömmens riktning, som bestäms av den kemiska potentialens position i förhållande till den kvantmekaniska... (More)
Popular Abstract in Swedish

Denna avhandling behandlar termoelektriska effekter, framförallt i lågdimensionella halvledarsystem. Åtskilliga nya fenomen diskuteras, undersöks och förklaras.



Introduktionsdelen innehåller en sammanfattning för allmänheten på svenska samt en introduktion till termoelektriska effekter på engelska. Detta görs dels med hjälp av en semi-klassisk teoretisk modell, men även en modell baserad på Landauers teori, vilken används då elektrontransporten är ballistisk. Efter introduktionen följer 6 artiklar.



I artikel 1 och 2 undersöks den termoelektriska strömmens riktning, som bestäms av den kemiska potentialens position i förhållande till den kvantmekaniska transmissionsfunktionen. I artikel 3 studeras konduktiviteten i en kvanttråd och vi visar att små hopp i konduktiviteten blir resultatet av växelverkan mellan elektroner och fononer.



Artikel 4 behandlar en kvantring, som inte är i kontakt med någon partikelreservoar. Elektroner och fononer växelverkar i två punkter. Med hjälp av Boltzmann ekvationen bestäms elektronernas fördelningsfunktion i detta icke-jämvikts system. När fononerna inte har samma temperatur kan en elektrisk ström propagera i ringen. I artikel 5 beräknas transmissionfunktionen för fononer i ett supergitter i en riktning vinkelrät mot väx-riktningen. Slutligen i artikel 6 föreslås en ny metod att konstruera ett kylchip som använder sig av både tunnling och termionisk emission av elektroner. (Less)
Abstract
This thesis investigates thermoelectric effects, predominantly in low-dimensional semiconductors. Various novel phenomena are predicted, investigated and discussed.



The introductory part of the thesis contains a summary in Swedish for the general public as well as a general introduction to thermoelectric effects using both a semi-classical theory valid for diffusive electron transport, as well as the Landauer approach valid for ballistic electron systems. After the introduction, six original papers are presented.



In paper 1 and 2 we investigate the thermoelectric current reversal in the presence of potential barriers. The quantum mechanical transmission function in relation to the chemical potential... (More)
This thesis investigates thermoelectric effects, predominantly in low-dimensional semiconductors. Various novel phenomena are predicted, investigated and discussed.



The introductory part of the thesis contains a summary in Swedish for the general public as well as a general introduction to thermoelectric effects using both a semi-classical theory valid for diffusive electron transport, as well as the Landauer approach valid for ballistic electron systems. After the introduction, six original papers are presented.



In paper 1 and 2 we investigate the thermoelectric current reversal in the presence of potential barriers. The quantum mechanical transmission function in relation to the chemical potential determines the sign of the current. This thermopower anomaly does not violate the thermodynamic law.



In paper 3 we predict a substep in the conductance of a quantum wire, due to interaction of the quantum confined electrons and phonons. This substep should be experimentally observable.



Paper 4 deals with a quantum ring, not connected to any particle reservoirs. However, electron-phonon interaction is introduced at two points. Using a Boltzmann-equation approach the non-equilibrium electron distribution is calculated. Furthermore, electric and heat currents appear in the ring whenever the two phonon baths are not of equal temperature. This can be developed into a thermionic couple.



In paper 5 the zone-folding effect of phonons in a superlattice is studied. The transmission function of phonons is calculated via a transfer matrix approach. Surprisingly, it is concluded that the zone folding effect has negligible effect on thermal conductance.



Finally, paper 6 combines quantum mechanical tunneling and thermionic emission into a new cool chip, operable at room temperature. The cooling power and efficiency of such a proposed chip is investigated, and is found very favorable. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Galperin, Yuri, University of Oslo, Department of Physics
organization
publishing date
type
Thesis
publication status
published
subject
keywords
kvantmekanik, relativitet, gravitation, statistisk fysik, termodynamik, Semiconductory physics, Halvledarfysik, thermopower anomaly, thermoelectricity, thermionic couple, zone-folding, cool chip, ballistic, thermionic, Mathematical and general theoretical physics, Matematisk och allmän teoretisk fysik, thermodynamics, statistical physics, relativity, quantum mechanics, klassisk mekanik, classical mechanics
pages
122 pages
publisher
KFS AB
defense location
Sal B, Fysicum. Sölvegatan 14 C 223 62 Lund Sweden
defense date
2005-01-21 10:15
ISBN
91-628-6327-4
language
English
LU publication?
yes
id
7a037415-8398-45b4-af9c-13d079c6d5c1 (old id 544118)
date added to LUP
2007-09-28 11:20:21
date last changed
2016-09-19 08:45:03
@misc{7a037415-8398-45b4-af9c-13d079c6d5c1,
  abstract     = {This thesis investigates thermoelectric effects, predominantly in low-dimensional semiconductors. Various novel phenomena are predicted, investigated and discussed.<br/><br>
<br/><br>
The introductory part of the thesis contains a summary in Swedish for the general public as well as a general introduction to thermoelectric effects using both a semi-classical theory valid for diffusive electron transport, as well as the Landauer approach valid for ballistic electron systems. After the introduction, six original papers are presented.<br/><br>
<br/><br>
In paper 1 and 2 we investigate the thermoelectric current reversal in the presence of potential barriers. The quantum mechanical transmission function in relation to the chemical potential determines the sign of the current. This thermopower anomaly does not violate the thermodynamic law.<br/><br>
<br/><br>
In paper 3 we predict a substep in the conductance of a quantum wire, due to interaction of the quantum confined electrons and phonons. This substep should be experimentally observable.<br/><br>
<br/><br>
Paper 4 deals with a quantum ring, not connected to any particle reservoirs. However, electron-phonon interaction is introduced at two points. Using a Boltzmann-equation approach the non-equilibrium electron distribution is calculated. Furthermore, electric and heat currents appear in the ring whenever the two phonon baths are not of equal temperature. This can be developed into a thermionic couple.<br/><br>
<br/><br>
In paper 5 the zone-folding effect of phonons in a superlattice is studied. The transmission function of phonons is calculated via a transfer matrix approach. Surprisingly, it is concluded that the zone folding effect has negligible effect on thermal conductance.<br/><br>
<br/><br>
Finally, paper 6 combines quantum mechanical tunneling and thermionic emission into a new cool chip, operable at room temperature. The cooling power and efficiency of such a proposed chip is investigated, and is found very favorable.},
  author       = {Larsson, Magnus},
  isbn         = {91-628-6327-4},
  keyword      = {kvantmekanik,relativitet,gravitation,statistisk fysik,termodynamik,Semiconductory physics,Halvledarfysik,thermopower anomaly,thermoelectricity,thermionic couple,zone-folding,cool chip,ballistic,thermionic,Mathematical and general theoretical physics,Matematisk och allmän teoretisk fysik,thermodynamics,statistical physics,relativity,quantum mechanics,klassisk mekanik,classical mechanics},
  language     = {eng},
  pages        = {122},
  publisher    = {ARRAY(0xaf9d088)},
  title        = {Thermoelectric phenomena in low-dimensional semiconductor systems},
  year         = {2005},
}