The present work represents a systematical study of the growth of columnar, metallic thin films deposited under highly oblique vapor incidence on planar substrates. Oblique angle deposition is a physical vapor deposition technique that is based on the self-shadowing effect. This enables the fabrication of highly porous thin films that are composed of three-dimensionally separated, micro-, and nano-sized columns.
For this study, metals that cover a wide range of melting points and crystal structures have been chosen, and the observed growth characteristics are compared with each other to gain information about the growth of obliquely deposited metallic thin films in general. Among the various parameters that have an influence on the growth of columnar thin films, in the focus of this work are the angle of the incoming particle flux, substrate rotation frequency, and substrate temperature as well as the influence of the residual gas atmosphere.
The first part deals with a morphological analysis of the columnar, metallic thin films by scanning electron microscopy (SEM). The columnar shape, the columnar tilt angle, and the thin film porosity are investigated depending on the incidence flux direction as well as substrate temperature and rotation. It is examined how a reduction of the substrate temperature down to 77 K - realized by a liquid nitrogen cooled sample holder - influences the growth of the columnar thin films. Further, it is analyzed how substrate rotation influences the local deposition geometry and accordingly the growth behavior of tilted columns, spirals, screws, and upright columns. Based on geometrical considerations, a theoretical model is proposed and compared with the made observations.
The second part focusses on the high-resolution local structure analysis of individual columns via (scanning) transmission electron microscopy (TEM). On the one hand, the columnar structure is analyzed depending on the substrate temperature and substrate rotation via high resolution TEM. On the other hand, the crystallinity of individual columns is studied along the entire column by nanobeam electron diffraction. This technique is also applied to gain information about the orientation of the crystallites at the substrates surface and to investigate the selection processes of crystalline orientations during the growth. Moreover, the presented studies reveal under which conditions single crystalline columns are forming.
In the final part, the texture of the columnar, metallic thin films is analyzed depending on the film thickness, the angle of the incoming particle flux as well as on the substrate temperature. X-ray diffraction (XRD) measurements, such as pole figures, are applied to determine the orientation of the lattice planes in the columns depending on the incident flux direction and on the substrate temperature. The observations are backed by reflection high-energy electron diffraction (RHEED) investigations. A model is developed that enables to explain why the tilt of the lattice directions in the columns is not equal to the tilt angle of the columns. A further theoretical model is introduced that enables to roughly estimate the tilt angle of the lattice direction that ensures the fastest vertical columnar growth.:1 MOTIVATION 7
2 BASICS OF OBLIQUE ANGLE DEPOSITION 9
2.1 Thin film growth by oblique deposition 9
2.1.1 Physical vapor deposition 9
2.1.2 Nucleation 10
2.1.3 Shadowing 11
2.1.4 Structure of individual columns 12
2.2 Sculpturing thin films on the nanometer scale 13
2.2.1 Angle of the incoming particle flux 13
2.2.2 Substrate rotation 16
2.2.3 Substrate temperature 17
2.3 Application areas for metallic nanostructured thin films 20
3 EXPERIMENTAL DETAILS 23
3.1 Sample fabrication 23
3.1.1 General deposition system setup and evaporation process 23
3.1.2 Crucibles, substrates, and sample holders 25
3.1.3 Controlling substrate movement and temperature 26
3.1.4 Controlling film thickness and deposition rate 29
3.2 Sample characterization 30
3.2.1 Scanning electron microscope (SEM) 30
3.2.2 Transmission electron microscopy (TEM) 31
3.2.3 X-Ray Diffraction (XRD) and In-Plane Pole Figure measurements (IPPF) 33
3.2.4 Reflection high-energy electron diffraction (RHEED) 36
3.2.5 Raman scattering spectroscopy 36
4 MORPHOLOGICAL ANALYSIS OF COLUMNAR THIN FILMS 39
4.1 Oblique angle deposition 40
4.1.1 Deposition at room temperature 40
4.1.2 Deposition at different temperatures 43
4.2 Glancing angle deposition 61
4.2.1 Continuous substrate rotation 61
4.2.2 Discrete substrate rotation 66
4.3 Summary of results 69
5 STRUCTURAL ANALYSIS OF INDIVIDUAL COLUMNS 71
5.1 Oblique angle deposition 71
5.1.1 Tilted columns grown at room temperature 71
5.1.2 Tilted columns grown at different substrate temperatures 78
5.2 Glancing angle deposition 82
5.2.1 Vertical columns grown by continuous substrate rotation 82
5.2.2 Zigzag columns grown by discrete substrate rotation 85
5.3 Discussion 87
5.4 Summary of results 89
6 TEXTURE ANALYSIS OF COLUMNAR THIN FILMS 91
6.1 Influence of the film thickness 91
6.2 Influence of the incoming flux direction 99
6.3 Influence of the substrate temperature 110
6.4 Summary of results 116
7 SUMMARY AND CONCLUSIONS 119
8 LIST OF LITERATURE 123
9 LIST OF ABBREVIATIONS 134
10 LIST OF VARIABLES AND CONSTANTS 136
11 ACKNOWLEDGEMENTS 139
PUBLICATION LIST 140
SELBSTSTÄNDIGKEITSERKLÄRUNG 143
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:33615 |
| Date | 22 March 2019 |
| Creators | Liedtke-Grüner, Susann |
| Contributors | Universität Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/acceptedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
Page generated in 0.0027 seconds