University of Groningen

Induced excitations in some metal oxidesSirbu, Silviu

IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.

Document VersionPublisher's PDF, also known as Version of record

Publication date:2008

Link to publication in University of Groningen/UMCG research database

Citation for published version (APA):Sirbu, S. (2008). Induced excitations in some metal oxides. s.n.

CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).

Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.

Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.

Download date: 13-01-2021

Induced Excitations In SomeMetal Oxides

Silviu Sirbu

Zernike Institute PhD thesis series 2008-24ISSN 1570-1530ISBN 978-90-367-3003-7

The work described in this thesis was performed in the research group Optical CondensedMatter (part of the Zernike Institute for Advanced Materials) at the University of Gronin-gen, The Netherlands. This work is part of the research programme of the ”Stichtingvoor Fundamenteel Onderzoek der Materie (FOM)”, which is financially supported bythe ”Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)”.

Rijksuniversiteit Groningen

Induced Excitations In Some MetalOxides.

Proefschrift

ter verkrijging van het doctoraat in deWiskunde en Natuurwetenschappenaan de Rijksuniversiteit Groningen

op gezag van deRector Magnificus, dr. F. Zwarts,in het openbaar te verdedigen op

vrijdag 21 november 2008om 13.15 uur

door

Silviu Sirbu

geboren op 22 januari 1978te Craiova, Roemenie

Promotor: Prof. Dr. Ir. P. H. M. van Loosdrecht

Beoordelingscommissie: Prof. Dr. T. T. M. PalstraProf. Dr. M. BonnProf. Dr. J. Demsar

5

6

Contents

1 Introduction 9

2 Nonlinear transport in β−Na0.33V2O5 132.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.2 The structure and thermodynamical properties . . . . . . . . . . . . . . 142.3 Description of the experiment . . . . . . . . . . . . . . . . . . . . . . 182.4 Temperature dependent transport . . . . . . . . . . . . . . . . . . . . . 192.5 Field dependent transport . . . . . . . . . . . . . . . . . . . . . . . . . 222.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3 Terahertz Time-Domain Spectroscopy 373.1 Principles of Terahertz Time-Domain Spectroscopy . . . . . . . . . . . 37

3.1.1 Maxwell’s equations. Wave equation and its solution in the farfield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.1.2 Linear and nonlinear contributions to polarization . . . . . . . . 393.1.3 Optical rectification and second harmonic generation . . . . . . 413.1.4 Linear electrooptic effect and phase retardation . . . . . . . . . 42

3.2 Design and characterization of the Terahertz Time-Domain Spectrometer 453.2.1 Generation of picosecond Terahertz pulses . . . . . . . . . . . 453.2.2 Detection of Terahertz pulses . . . . . . . . . . . . . . . . . . . 49

3.3 Transmission Time-Domain Terahertz Spectrometer . . . . . . . . . . . 513.3.1 Propagation of an electromagnetic wave packet through the medium.

Terahertz spectral analysis. . . . . . . . . . . . . . . . . . . . . 603.4 Time-Resolved Optical-Pump Terahertz-Probe Spectroscopy . . . . . . 66References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

7

8 Contents

4 Induced terahertz response in Cu2O 794.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

4.1.1 Optical properties in semiconductors . . . . . . . . . . . . . . . 794.1.2 Properties of Cu2O . . . . . . . . . . . . . . . . . . . . . . . . 81

4.2 Optical-pump Terahertz-probe Time-Domain Spectroscopy . . . . . . . 874.2.1 Temperature dependence . . . . . . . . . . . . . . . . . . . . . 934.2.2 Power dependence . . . . . . . . . . . . . . . . . . . . . . . . 93

4.3 Theoretical considerations . . . . . . . . . . . . . . . . . . . . . . . . 974.3.1 Drude + Lorentz mathematical description . . . . . . . . . . . 974.3.2 Drude+Lorentz fit parameters. Time and power dependence . . 994.3.3 Drude + Droplet mathematical description . . . . . . . . . . . 1044.3.4 Drude+Droplet fit parameters. Time and power dependence . . 107

4.4 Summary and preliminary discussions . . . . . . . . . . . . . . . . . . 112References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

5 Terahertz response of EuO thin film 1195.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1195.2 Structure and growth . . . . . . . . . . . . . . . . . . . . . . . . . . . 1195.3 Optical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1205.4 Transport properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1225.5 Photodoping and field doping . . . . . . . . . . . . . . . . . . . . . . . 1245.6 Motivation and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 1265.7 EuO terahertz response . . . . . . . . . . . . . . . . . . . . . . . . . . 127

5.7.1 Terahertz Time-Domain Spectroscopy . . . . . . . . . . . . . . 1275.7.2 Optical-Pump Terahertz-Probe Spectroscopy . . . . . . . . . . 1315.7.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138