Raman spectroscopy of laser induced material alterations

128 Pages·2010·4.96 MB·English

by  Michael Bauer

Raman spectroscopy of laser induced
material alterations
Dissertation
der Fakult¨at fu¨r Geowissenschaften
der Ludwig-Maximilians-Universit¨at
Mu¨nchen
vorgelegt von
Michael Bauer
Mu¨nchen, den 03. M¨arz 2010

Erstgutachter: Prof. Dr. Robert W. Stark
Zweitgutachter: Prof. Dr. Wolfgang M. Heckl
Disputation: 06. Juli 2010

Contents
Table of Contents i
List of Figures iii
List of Abbreviations v
Kurzfassung 1
Abstract 2
1 Introduction 3
2 Raman spectroscopy 5
2.1 Interaction of light with matter . . . . . . . . . . . . . . . . . . . . . 5
2.2 The Raman effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 Selection rules and Raman line determination . . . . . . . . . . . . . 9
2.4 Influence of stress and temperature on Raman spectra . . . . . . . . . 10
3 Methods 17
3.1 The confocal Raman microscope set up . . . . . . . . . . . . . . . . . 17
3.1.1 Pinhole influence and light suppression . . . . . . . . . . . . . 18
3.1.2 Gaussian laser focusing and beam parameters . . . . . . . . . 19
3.2 Local heating due to the focused laser beam . . . . . . . . . . . . . . 21
3.3 Image generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4 Spectroscopic characterisation 23
4.1 Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.1.1 Phonon dispersion curve and band structure . . . . . . . . . . 23
4.1.2 Raman scattering in silicon . . . . . . . . . . . . . . . . . . . 25
4.1.3 Local heating . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.1.4 Experimental results . . . . . . . . . . . . . . . . . . . . . . . 27
4.2 Silicon carbide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
i
ii Table of Contents
4.2.1 Crystal structure and polytypes . . . . . . . . . . . . . . . . . 28
4.2.2 Phonon structure and mode folding . . . . . . . . . . . . . . . 29
4.2.3 Raman line shift . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.2.4 Local heating . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.2.5 Experimental results . . . . . . . . . . . . . . . . . . . . . . . 33
4.3 Alteration of calcium fluoride caused by UV-light . . . . . . . . . . . 34
4.3.1 Material properties of calcium fluoride . . . . . . . . . . . . . 36
4.3.2 Identification of kerogeneous carbon . . . . . . . . . . . . . . . 37
4.3.3 Experimental results . . . . . . . . . . . . . . . . . . . . . . . 38
4.4 Titanomagnetites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5 Summary 43
6 References 45
7 Publications 55
7.1 Visualizing stress in silicon microcantilevers using scanning confocal
Raman spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
7.2 Temperature depending Raman line-shift of silicon carbide . . . . . . 61
7.3 Nanoscale residual stress-field mapping around nanoindents in SiC by
IR s-SNOM and confocal Raman microscopy . . . . . . . . . . . . . . 71
7.4 Exterior surface damage of calcium fluoride out coupling mirrors for
DUV lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
7.5 Onset of the optical damage in CaF optics caused by deep-UV lasers 95
2
Appendix I
Acknowledgements XV
Curriculum Vitae XVI
Publication list XVII
List of Figures
2.1 Typical configuration of IR and Raman spectroscopy . . . . . . . . . 6
2.2 Jablonksi energy diagram of the scattering processes . . . . . . . . . . 7
3.1 Schematic of the confocal setup . . . . . . . . . . . . . . . . . . . . . 17
3.2 Lateral resolution of a scattering point as a function of detector size . 18
3.3 Illustrated Gaussian beam of a focused laser beam . . . . . . . . . . . 20
3.4 Filter region for sum filtering and Lorentz fits . . . . . . . . . . . . . 22
4.1 Electronic band structure and phonon dispersion curves of silicon . . 24
4.2 Refraction and extinction index of silicon with penetration depth and
adsorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.3 Variation of peak centre and peak width due to local heating . . . . . 26
4.4 Measurements of a silicon AFM cantilever . . . . . . . . . . . . . . . 27
4.5 Side view ABC layer stacking and of silicon carbide . . . . . . . . . . 29
4.6 Phonon dispersion curve of silicon carbide . . . . . . . . . . . . . . . 30
4.7 Mode folding of silicon carbide . . . . . . . . . . . . . . . . . . . . . . 30
4.8 Raman spectra of silicon carbide . . . . . . . . . . . . . . . . . . . . . 31
4.9 Temperature-induced peak shift and increasing peak width of silicon
and silicon carbide . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.10 Temperature-dependent shifting of peak centres and stress fields
around a nanoindentation in SiC . . . . . . . . . . . . . . . . . . . . 33
4.11 Layer materials used for ultraviolet optical components . . . . . . . . 35
4.12 First- and second-order Raman spectra of kerogen carbon . . . . . . . 37
4.13 Damage structure due to UV photon irradiation . . . . . . . . . . . . 39
4.14 Raman spectra of synthetic magnetite and titanomagnetite . . . . . . 40
4.15 Titanium concentration against laser power for beginning material
alteration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.16 Stripes of different titanomagnetites in a geologic sample . . . . . . . 42
iii
iv List of Figures
List of Abbreviations
AFM atomic force microscope
ArF argon fluoride
CaF calcium fluoride
2
CaCO calcium carbonate
3
CCD charge coupled device
DUV deep ultraviolet
FLA folded longitudinal acoustic phonon
FLO folded longitudinal optical phonon
FTA folded transversal acoustic phonon
FTO folded transversal optical phonon
FWHM full width at half maximum
HR high reflective (mirror)
IR infrared
KrF krypton fluoride
LA longitudinal acoustic phonon
LO longitudinal optical phonon
LOPC LO-phonon plasmon coupled
MEMS micro(electro) mechanical systems
MgF magnesium fluoride
2
NA numerical aperture
Nd:YAG neodymium doped yttrium aluminium garnet
OC out coupling (mirror)
PDP phonon deformation potential
PSF point spread function
Si silicon
SiC silicon carbide
SHG second harmonic generation
s-SNOM scattering scanning nearfield optical microscope
TA transversal acoustic phonon
TEM transverse electro magnetic (laser);
or transmission electron microscope
TO transversal optical phonon
UV ultraviolet
VUV vacuum ultraviolet
v
vi List of Abbreviations