Thermochromic vanadium dioxide based materials undergo a metal-to-semiconductor transition. This ability can reduce the energy consumption in buildings with windows or glass facades, especially for passive cooling in warmer climates. In dependence on the temperature, the transmittance of the material for infrared light changes reversibly, regulating the amount of the solar heat transmitted into buildings.
Although thermochromic vanadium dioxide based coatings have been extensively studied at laboratory scale, there are still fundamental challenges for industrial manufacturing. The present work aims to explore the prospects of the deposition of a tungsten-doped vanadium dioxide based coating onto ultra-thin glass in an upscaled roll-to-roll process. An existing laboratory scale layer stack design enabled the achievement of high performance using unipolar pulsed and high power impulse magnetron sputtering. For this purpose, a new oxygen control system was developed. Furthermore, the optical and structural properties of the deposited coatings were characterized, as well as the doping content, and further the potential for energy savings. A newly designed optical model allowed calculation of the dispersion relation of the layers and their electrical properties.:1 Introduction 1
2 Topic of the thesis 4
3 State of the art 6
3.1 Thermochromism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2 Vanadium dioxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2.1 Crystalline Structure . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2.2 Phase transition – Band structure . . . . . . . . . . . . . . . . . . 12
3.2.3 Literature review of thermochromic VO2 coatings . . . . . . . . . 13
3.2.4 Limitations of VO2 in smart window applications . . . . . . . . . 14
3.2.5 Using multifunctional layers . . . . . . . . . . . . . . . . . . . . . 15
3.2.6 Reducing the transition temperature . . . . . . . . . . . . . . . . 15
3.3 Magnetron sputtering of thermochromic coatings . . . . . . . . . . . . . 17
3.3.1 Sputtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.3.2 Magnetron sputtering . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.3.3 Reactive magnetron sputtering . . . . . . . . . . . . . . . . . . . 22
3.3.4 Sputtering using multi-component targets . . . . . . . . . . . . . 24
3.3.5 Pulsed magnetron sputtering . . . . . . . . . . . . . . . . . . . . . 26
3.3.6 High-power impulse magnetron sputtering . . . . . . . . . . . . . 27
3.4 Layer growth and ion assistance . . . . . . . . . . . . . . . . . . . . . . . 30
3.5 Thin film optics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.5.1 Interaction of light with surfaces . . . . . . . . . . . . . . . . . . . 34
3.5.2 Models for thin film optics . . . . . . . . . . . . . . . . . . . . . . 36
4 Methodology 39
4.1 Deposition process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.1.1 Roll-to-roll process . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.1.2 FOSA labX 330 Glass . . . . . . . . . . . . . . . . . . . . . . . . 39
4.1.3 Rotatable magnetrons . . . . . . . . . . . . . . . . . . . . . . . . 41
4.1.4 Materials used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.1.5 Oxygen flow controls . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.1.6 Challenges of the roll-to-roll deposition process on UTG . . . . . 46
4.2 Deposition of ZrO2 multifunctional layer . . . . . . . . . . . . . . . . . . 47
4.3 Deposition of ZrO2/V1-xWxO2/ZrO2 with HiPIMS . . . . . . . . . . . . . 48
4.3.1 The investigation of the effect of oxygen partial pressure . . . . . 48
4.3.2 Deposition of thermochromic layers with optical emission spec-
troscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.4 Deposition of ZrO2/V1-xWxO2/ZrO2 with unipolar pulsed magnetron
sputtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.5 Coating characterisation . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.5.1 UV-Vis-NIR spectrophotometry . . . . . . . . . . . . . . . . . . . 51
4.5.2 Determination of the film properties with optical modelling . . . . 52
4.5.3 Scanning electron microscopy . . . . . . . . . . . . . . . . . . . . 55
4.6 Determination of the film thickness . . . . . . . . . . . . . . . . . . . . . 55
4.6.1 Resistivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.6.2 X-ray diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.6.3 Atomic force microscopy . . . . . . . . . . . . . . . . . . . . . . . 58
4.6.4 Rutherford backscattering . . . . . . . . . . . . . . . . . . . . . . 59
5 Results and discussion 61
5.1 Bottom and top ZrO2 layers for thermochromic V1-xWxO2 coating . . . . 61
5.2 Process design for the deposition of thermochromic V1-xWxO2 coating
with HiPIMS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
5.2.1 The effect of oxygen partial pressure . . . . . . . . . . . . . . . . 70
5.2.2 Deposition of the layer system with optical emission spectroscopy 72
5.2.3 Determination of the W content in the thermochromic films . . . 80
5.2.4 Resistivity measurements and structure assumption . . . . . . . . 86
5.2.5 Dependence of the doping concentration in the target on the film
thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
5.2.6 Influence of the deposition temperature on the thermochromic
properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
5.2.7 Influence of the film thickness on the thermochromic properties . 90
5.3 Thermochromic V1-xWxO2 coating deposited with uPMS . . . . . . . . . 93
5.4 Comparison of HiPIMS (two-layer vs three-layer systems) and uPMS for
V1-xWxO2 coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
6 Summary and outlook 101
6.1 Research goal and achievements . . . . . . . . . . . . . . . . . . . . . . . 101
6.2 Layer deposition and results overview . . . . . . . . . . . . . . . . . . . . 102
6.3 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
7 Appendix 105
8 Abbreviations 108
9 Formula symbols 109
Literature 118
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:90395 |
| Date | 14 March 2024 |
| Creators | Szelwicka, Jolanta |
| Contributors | Hauff, Elizabeth von, Kubart, Tomáš, Technische Universität Dresden, Fraunhofer-Institut für Organische Elektronik, Elektronenstrahl- und Plasmatechnik FEP |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | info:eu-repo/grantAgreement/Europäische Kommission/Horizon2020/869929//LIGHTWEIGHT SWITCHABLE SMART SOLUTIONS FOR ENERGY SAVING LARGE WINDOWS AND GLASS FACADES/Switch2Save |
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