Pattern formation and evolution on Pt(111) by grazing incident ion bombardment [Elektronische Ressource] = Musterbildung und Entwicklung durch streifenden Ionenbeschuss auf Pt(111) / vorgelegt von Henri Hansen

Sujets

• Physik

Informations

• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2005
• Nombre de lectures: 12
• Langue: English
• Poids de l'ouvrage: 39 Mo

Extrait

Pattern formation and evolution on
Pt(111) by grazing incident ion
bombardment
(Musterbildung und Entwicklung durch streifenden
Ionenbeschuss auf Pt(111))
Von der Fakultat¨ fur¨ Mathematik, Informatik und
Naturwissenschaften der Rheinisch Westf¨alischen Tech-
nischen Hochschule Aachen zur Erlangung des akademi-
schen Grades eines Doktors der Naturwissenschaften
genehmigte Dissertation
vorgelegt von
Diplom-Physiker Henri Hansen
aus Luxemburg
Berichter: Universit¨ atsprofessor Dr. Thomas Michely
Universit¨ atsprofessor Dr. Bene Poelsema
Tag der mundlic¨ hen Prufung:¨ 10. Juni 2005
Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfug¨ bar.Contents
1 Introduction 3
2 Theoretical foundations 7
2.1 Interactionbetweenionsandsolids............... 7
2.1.1 Normalincidenceionimpacts..... 9
2.1.2 Off-normalincidenceionimpacts............ 10
2.2 MD-simulationsandgeometricalmodel.... 16
2.2.1 MD-simulations...................... 16
2.2.2 Geometricalmodel 19
2.2.3 Damagepatern........... 20
2.3 Diffusionproceses............... 2
2.3.1 Diffusionontheterace ................. 23
2.3.2 Diffusionrelatedtothestepedges... 25
2.3.3 Ehrlich-Schwoebelbarier ................ 27
2.3.4 Diffusionofvacancies.......... 28
2.4 Bradley-Harper,acontinuumtheory .............. 30
2.4.1 PresentationoftheBradley-Harpertheory....... 30
2.4.2 ExtensionstotheBradley-Harpertheory........ 4
3 Review of previous work 53
3.1 Continuumapproach....................... 54
3.1.1 Crystalline materials .......... 54
iiiContents
3.1.2 Polycrystalline materials ................. 62
3.1.3 Amorphousmaterials........ 63
3.2 Atomisticapproach............. 65
3.3 Summary .................. 67
3.3.1 Evolutionofthewavelength.... 67
3.3.2 Evolutionoftheroghnes ..... 68
4 Experimental 69
4.1 UHV-system............................ 69
4.2 Systemmodifications. 71
4.3 Ioncurrentmeasurement.......... 74
4.4 Ionbeamalignmentandcharacterization............ 75
4.5 Samplepreparation............. 79
4.6 Experimentalprocedure.......... 80
5 Morphology-dependent sputtering yield 83
5.1 Fluence-dependentsputeringyield............... 84
5.2 Temperature-dependentsputeringyield. 87
5.3 Physical model for grazing incidence ion bombardment . . . . 89
5.3.1 Boundary conditions and area of validity ........ 89
rd5.3.2 Extension of the geometrical model to 3 dimensions . 90
5.3.3 Generalsolution...................... 91
5.3.4 Transitionfromsmaltolargeislands.......... 93
5.4 Separationofbothsputeringyields.... 94
5.4.1 Applicationofthemodeltotheexperiment ...... 94
5.4.2 Errordiscussion...................... 98
5.5 Formationofchainsofislands.......10
5.5.1 Bypinchingoffsmalvacancyislands..........10
5.5.2 By chanelling .......................101
iv5.6 Singleionimpacts.........................103
6 Development of periodicity 107
6.1 Fromsingleionimpactstovacancygrooves...........107
6.1.1 Formation of vacancy grooves at T 450K......108
6.1.2 Formation of elongated structures atT>450K....10
6.2 Formationofaperiodicripplepatern .............13
6.2.1 Mechanism at T 450K .......114
6.2.2 Mechanism atT>450K.................15
6.3 Necesityofadatomdiffusion .........19
6.4 FailureoftheBradley-Harpertheory..............121
7 Temperature dependence 129
7.1 Evolutionofthewavelength...................129
7.2 Evolutionoftheroughnes...........13
7.3 Defectanalysis ...............135
7.4 Facetanalysis.......143
7.5 Annealingofripplestohighertemperatures ..........147
8 Fluence dependence 155
8.1 Evolutionoftheroughnes....................15
8.2 Evolutionofthewavelength..........159
8.3 Qualityofthepattern ...........160
8.4 Defectanalysis .................163
8.5 Coarseningbyrippleerasure...................165
9 Angle and energy dependence 169
9.1 Angledependence.........................169
9.2 Energy-dependence....172
10 Summary and Outlook 177
vContents
10.1Summary .............................17
10.2Outlook........180
A Measurement of the reflected ion current 181
B Repoling piezo ceramics 185
C Expressions for the coefficients of equation 2.37 187
D Publications 191
Bibliography 193
Acknowledgements 203
Lebenslauf 205
viList of Figures
2.1 Schematicsofascateringproces................ 8
2.2 Differentkindsofdefects............ 10
2.3 Definition of ϑ and ϑ ........... 1out
2.4 Angle-dependent sputtering yield Y ...... 12
2.5 Locationofthethermalspike.................. 12
...... 132.6 Maximum transverse energy Ei⊥,max
2.7 Normalandgrazingincidentions................ 14
2.8 Shadow cone formation during an atom-atom collision..... 14
2.9 Trajectoriesofscateredatom.................. 15
2.10 Trajectories of a channelling atom....... 15
2.11 MD-simulations: Sputtering yield Y (ϑ)............. 17
2.12 MD-simulations: yield Y (x/∆x) . 18
2.13Geometricmodel......................... 19
2.14MD-simulations:Damagepaternsofsingleionimpacts.... 21
2.15Balmodel:Adatomdiffusion.................. 24
2.16Balmodel:Stepedgediffusion........ 25
2.17Balmodel:Stepedgediffusion......... 26
2.18Ballmodel:Stepedgedetachment....... 26
2.19Balmodel:Cornerflipping ................... 27
2.20Balmodel:Ehrlich-Schwoebelbarier..... 27
2.21Balmodel:Ehrlich-Schwoebelbarier.............. 28
viiList of Figures
2.2Balmodel:Vacancydiffusion.................. 29
2.23Balmodel:Vacancyannealing ...... 29
2.24 Experimental results of M. Navez et al. .. 31
2.25Schamaticsofasingleionimpact................ 31
2.26Coordinatesystem............. 3
2.27 Angle-dependence of the sputtering yield for a planar surface . 36
2.28Ionimpactsonaconcaveandconvexsurface.......... 37
2.29Ripplerotation.......................... 43
2.30 Ripple formation at steep and grazing angles of incidence ϑ.. 43
2.31 Temporal roughness evolution on Ge(001) ........... 46
2.32Adatomcurrentonavicinalsurface............... 52
3.1 Temperature-dependent evolution of facets on Ag(110) . . . . 55
3.2 Temperature-dependent morphology of Ag(110) ........ 56
3.3 Morphology of Ag(110) before and after annealing at T = 300 K 57
3.4 Flux-dependent morphology on Ag(110) ............ 58
3.5 Temperature-dependence of the surface roughness σ on Ag(001) 59
3.6 Temporal evolution of the wavelength on Cu(110) ....... 59
3.7 Azimuthal ripple orientation on Cu(110) ............ 60
3.8 Azimuthal ripple orientation on Cu(001). 61
3.9 Ion bombardment of a polycrystalline Pt sample ........ 62
3.10 Temperature-dependence of the wavelength on SiO ...... 642
3.11 Temperature-dependence of the roughness on Ge(001)..... 65
3.12 Temperature-dependence of the wavelength on Cu(001) . . . . 66
4.1 UHV-chamber – side view .................... 70
4.2 UHV-chamber – cross section ....... 71
4.3 Schematicsofthesamplerotation..... 72
4.4 Incomingandreflectedionbeam................. 76
viii4.5 Calibrationoftheseting-screw................. 7
4.6 STM-topograph:Iradiationofasteppedsurface ....... 78
5.1 Normalandgrazingincidentions................ 83
5.2 STM-topographs: Fluence-dependent morphology T = 720 K . 85
5.3 Fluence-dependenceoftheremovedmaterialΘ......... 86
5.4 STM-topographs: Temperature-dependent morphology F =
0.5MLE..................... 87
5.5 Temperature-dependenceoftheremovedmaterialΘ...... 8
step5.6 Definition of a of a hexagonal vacancy island ........ 91
step5.7 Overestimation of a forsmalandlargeislands....... 93
5.8 Fluence-dependenceoftheremovedmaterialΘ......... 95
5.9 Temperature-dependenceoftheremovedmaterialΘ...... 97
5.10Fluence-andtemperature-dependenteror........... 98
step terr5.11 Correlation of Y and Y ......... 9
5.12 STM-topographs: Formation of chains of vacancy islands . . . 100
5.13Formationofchainsofislandsbysnap-in............101
5.14 STM-topograph: Damage close do an ascending step edge . . 102
5.15Formationofchainsofislandsbychanneling..........103
5.16STM-topographs:Singleionimpacts.....104
6.1 STM-topographs: Pattern development T =450K ......109
6.2 Creation of elongated islands at T 450K...........110
6.3 STM.topographs: Pattern development T=50K.......11
6.4 Creation of elongated islands atT>450K...........12
6.5 Histogram of l at T=50K.........13

6.6 Interactionofvacancygrooves.........114
6.7 Formation of additional vacancy grooves atT>450K....16
6.8 Effectofthevacanciesgeneratedatthetopmostterace....17
6.9 Effectoftheadatomsgeneratedatthetopmostterace....18
ixList of Figures
6.10 Effect of the vacancies generated at the bottom terrace . . . . 118
6.1Effectoftheadatomsgeneratedatthebotomterace.....19
6.12 STM-topographs: Morphology at T = 100 K and 350 K . . . . 120
6.13ComparisonoftheexperimentalandBHwavelength......125
7.1 STM-topographs: Temperature-dependent morphology . . . . 130
7.2 Temperature-dependent wavelength λ ..............131
7.3 STM-topographs: Temperature-dependent morphology . . . . 132
7.4 Temperature-dependent RMS-roughness σ ...........134
7.5 STM-topograph: Morphology overview at T =450K.....136
7.6 Rulestoclassifythedefects...................138
7.7 STM-topographs: Rescaled temperature-dependent morphology 139
7.8 Temperature-dependence of the rescale