The path towards mitigation of anthropogenic greenhouse gas emissions lies in the transition from conventional to sustainable energy resources. The Hydrogen Economy, a cyclic economy based on hydrogen as a fuel, is suggested as a tool in the necessary energy transition. Photocatalysis makes use of sunlight to promote thermodynamically non-favoured reactions such as water splitting, allowing for sustainable hydrogen production. Harvesting thermal energy along with photonic energy is an interesting concept to decrease the activation energy of water splitting (i.e. ΔG = + 237.2 kJ∙mol−1). This work aims to confront this hypothesis in a gas phase photo-thermal reactor designed specifically for this study. The photocatalyst chosen is graphitic carbon nitride (g-C3N4), an organic semiconductor possessing a narrow band gap (i.e. 2.7 eV) as well as a band structure which theoretically permits water splitting. The photocatalytic performance of Pt/g-C3N4 for hydrogen evolution was tuned by altering its synthetic temperature. Electron paramagnetic resonance was used to gain insight on the evolution of the photocatalyst activity with synthesis temperature. Then, gold nanoparticles were deposited on g-C3N4 surface. Localized surface plasmon resonance properties of gold nanoparticles are reported in the literature to be influenced by temperature. Therefore Au/g-C3N4 appeared as a promising candidate for photo-thermal water splitting. X-ray spectroscopy unveiled interesting observations on the gold oxidation state. Moreover, under specific reduction conditions, gold nanoparticles with a wide variety of shapes characterized by sharp edges were formed. Finally, the development of the photo-thermal reactor is presented. The design process and the implementation of this innovative reactor are discussed. The reactor was successfully utilized to probe photoreactions. Then, the highly energy-demanding photocatalytic water splitting was proven not to be activated by temperature in the photo-thermal apparatus.

Exploiting coordination bonding of aromatic carboxylic acids at metal surfaces, this thesis explores new directions in the design and application of self-assembled monolayers (SAMs). The SAMs are investigated using a multi-technique approach comprising of a complementary combination of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. In addition, the X-ray standing wave technique (XSW) was used to characterise the substrates. The process of layer formation and the final structures of the SAMs are found to be strikingly dependent on the combination of molecule and substrate, which is discussed in terms of the intermolecular and molecule-substrate interactions, bonding geometries and symmetry of the organic molecules. This is illustrated by the dramatic difference between molecular adsorption on Ag and Cu for molecules such as biphenyl-3,4',5-tricarboxylic acid and biphenyl-4-acetic acid. In the case of self-assembly on Cu, the molecule-substrate interactions play a decisive role in the resulting SAM structure, whereas on Ag, the intermolecular interactions dominate over the weaker molecule-substrate binding. This exploration of the balance of interactions that lead to the formation of these SAM structures lays the foundation for a systematic design of the structures and properties of aromatic carboxylic acid based monolayers. Finally, different applications and properties of some SAMs were investigated, namely coordination of a Pd(II) complex to a pyridine/pyrazole terminated molecule adsorbed on Ag. Evidence of coordination of Pd(II) to single molecules was provided by STM, XPS and NEXAFS spectroscopy. Additionally, controlled STM tip induced modification of local areas of a 1,3,5-tris(4-carboxyphenyl)benzene SAM on Ag was performed, opening an exciting prospect for nanoscale molecular manipulation.

The aim of this work is diagnostic of plasma chemical deposition thin films based on organometallic precursors. Thin layers have recently become one of the most used methods for surface treatment of materials. They are used as a protective, functional layer, they improve surface properties of materials or increase or reduce the adhesion to various compounds. Plasma polymers are a modern trend in surface treatment technology. Their structure is different from classical polymers. The titanium (IV)isopropoxide was chosen as a monomer example, which is frequently used as a monomer for photocatalytic TiO2 films plasma deposition. These thin films are very promising for the removal of various air and water pollutants and thus they can significantly help in the increase of the environmental quality. Measurements took place on a commercial device Plasmatreater AS 400. The theoretical part describes the background needed for the study and diagnostics of plasma processes and technologies. The optical emission spectroscopy was chosen as a diagnostic method, and thus its principles are outlined in the theoretical part. Infrared spectroscopy and X-ray photoelectron spectroscopy were applied for the diagnostics of prepared thin films and they are also described in the theoretical part. The experimental part contains two sections. The first section is dedicated to the plasma diagnostics by optical emission spectroscopy. Discharge was generated in nitrogen or in the air. Measurements were performed at seven different duty cycles and at two different flow rates for each of the working gases. The molecular bands of nitrogen first negative and second systems, CN violet bands, and atomic lines of oxygen and nozzle elements (Cu, Cr) were identified in the spectra. The titanium lines, and bands of TiO were determined if the precursor was added. Electron temperature was calculated using chromium lines, and electron temperature maps were obtained for continuous mode and pulse mode with duty cycle 70% for nitrogen plasma with 500 sccm precursor flow. Similar discharge maps were also processed using the selected line of titanium (520 nm) TiO band (625 nm) again for the same discharge conditions. Furthermore, the dependences of the same quantities were obtained along the discharge axis as a function of duty cycle in both gases with precursor flow of 1000 sccm. The second part of results brings material analyzes of the deposited samples. The peaks of anatase and rutile have been identified by infrared spectroscopy. Using X-ray photoelectron spectroscopy, we found that our layers contain a significant amount of non-dissociated precursor. Moreover, a large number of radicals, which can interact with atmospheric gases, was determined on the surface. These radicals are removable by annealing or by ion etching. All results obtained during this research can significantly help us to improve the quality of deposited layers and allow us also some prediction of the thin film properties at given plasma conditions. Of course, further experimental as well as theoretical studies should be completed to obtain complete knowledge needed for the wide applications of these layers.

Aim of this student research project was to develop an Aluminium Oxide (Al2O3 ) ALD process from trimethylaluminum (TMA) and Ozone in comparison of two shower head designs. Then studying the detailed characteristics of Al2O3 ALD process using various measurement techniques such as Spectroscopic Ellipsometry (SE), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM). The real-time ALD growth was studied by in-situ SE. In-situ SE is very promising technique that allows the time-continuous as well as time-discrete measurement of the actual growth over an ALD process time. The following ALD process parameters were varied and their inter-dependencies were studied in detail: exposure times of precursor and co-reactant as well as Argon purge times, the deposition temperature, total process pressure, flow dynamics of two different shower head designs. The effect of varying these ALD process parameters was studied by looking upon ALD cycle attributes. Various ALD cycle attributes are: TMA molecule adsorption (Mads ), Ligand removal (Lrem ), growth kinetics (KO3 ) and growth per cycle (GPC).:List of abbreviations and Symbols ........................XII Lists of Figures and Tables ...................................XVIII 1 Introduction .......................................................1 I Theoretical Part ..................................................3 2 Alumina in electronic industry ............................5 3 Atomic Layer Deposition ....................................7 3.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2 Process definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.3 Benefits and limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.4 ALD growth mechanism of Aluminium oxide from TMA/O 3 . . . . . . . . 9 3.5 Growth kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.6 Comparison of TMA/O3 and TMA/H2O – A literature survey . . . . 14 4 Spectroscopic Ellipsometry .....................................................17 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.2 Measuring Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.3 Fitting and models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.4 Advantages and limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5 X-Ray Photoelectron Spectroscopy ..............................................25 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5.2 XPS mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5.3 XPS analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5.4 Advantages and limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 6 Atomic Force Microscopy .............................................................29 II Experimental Part ......................................................................31 7 Methodologies ............................................................................33 7 .1 Experimental setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 7 .2 ALD process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 7 .3 Experiment design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 7 .4 Spectroscopic Ellipsometry . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 7 .4.1 Tool and software . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 7 .4.2 Data acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 7 .4.3 Data evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 7 .4.4 Post processing of data . . . . . . . . . . . . . . . . . . . . . . . . . 41 7 .4.5 Sources of errors in SE . . . . . . . . . . . . . . . . . . . . . . . . . 43 8 Results and discussion ..........................................................47 8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 8.2 Kinetic ALD characteristic curves . . . . . . . . . . . . . . . . . . . . . . . . 48 8.2.1 TMA exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 8.2.2 Argon purging after TMA exposure . . . . . . . . . . . . . . . . . . . 50 8.2.3 Ozone exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 8.2.4 Argon purging after ozone exposure . . . . . . . . . . . . . . . . . . 52 8.3 Impact of process parameters on characteristic ALD growth attributes and film properties . . . . . . . . . .. . . . . . . . . . . . . . . . 53 8.3.1 Total process pressure . . . . . . . . . . . . . . . . . . . . . . . . . . 53 8.3.2 Ozone flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 8.3.3 Deposition temperature . . . . . . . . . . . . . . . . . . . . . . . . . 56 8.4 Reproducibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 9 Conclusions and outlook .......................................................63 References ...............................................................................68 III Appendix .............................................................................77 A Reference temperatures and ozone flow.............................. 79 B Process parameters ..............................................................81

ZnO hat wegen seiner potenziellen Anwendung in elektronischen Geräten und als Katalysator viel Aufmerksamkeit erhalten. Die Struktur und Reaktivität von ZnO-Oberflächen haben eine direkte Bedeutung für die Leistung und Funktionalität dieser Geräte. Daher ist die Definition und das Verständnis der atomistischen Details von ZnO-Oberflächenstrukturen von besonderer Bedeutung. Die atomistischen Details von ZnO-Oberflächen hängen von den Präparationsverfahren ab. Nach der Kristallpräparation ist es notwendig, eine Oberflächencharakterisierung durchzuführen, um eine Verbesserung der Funktionalität und Effizienz von ZnO-basierten opto-elektronischen Bauelementen und Katalysatoren zu erreichen. Die atomistische Wahrnehmung der Reaktion zwischen einem organischen Molekül und ZnO-Oberflächen spielt eine entscheidende Rolle bei der Optimierung der Wasserstoff-on-demand-Lieferung in Brennstoffzellen. Das Verständnis der atomistischen Details von Adsorption, Diffusion und Dissoziation eines organischen Moleküls ebnet den Weg, um die Vorgänge bei der Wasserstofffreisetzung für Brennstoffzellen zu enträtseln. Mit dem Ziel, die Struktur- und Stöchiometriebestimmung mit Hilfe der XPS zu ermöglichen, präsentiere ich in dieser Arbeit die Ergebnisse einer umfassenden theoretischen Studie über die Kernniveauverschiebungen von ZnO-Oberflächenrekonstruktionen. Darüber hinaus biete ich eine gründliche Untersuchung der gemischt-terminierten Oberfläche, indem ich zunächst die Bedingungen untersuche, unter denen sich Methanol-Monolagen auf dieser Kristallfläche bilden können, und dann alle möglichen Wege für deren Reaktion erforsche. Diese Studie liefert ein umfassendes Bild, um die wahrscheinlichsten Reaktionsschritte zu identifizieren, die zur Interpretation der experimentellen Ergebnisse herangezogen werden können. Sie wird zukünftigen theoretischen Studien für ähnliche Reaktionen wie die Dehydrierung und die Kinetik der Monolagenbildung, die hier untersucht wurden, helfen. / Zinc-Oxide (ZnO) has been getting much attention over the past decades because of its potential application in electronic devices and as a catalyst. The structure and reactivity of ZnO surfaces have direct relevance for the performance and functionality of these devices. Therefore, defining and understanding the atomistic details of ZnO surface structures is of particular importance. The atomistic details of ZnO surfaces depend on the preparation procedures. After the crystal preparation, it is necessary to perform a surface characterization, to achieve an improvement in the functionality and efficiency of ZnO-based opto-electronic devices and catalysts. The atomistic perception of the reaction between an organic molecule and ZnO surfaces plays a crucial role in optimizing hydrogen-on-demand delivery in fuel cells, and understanding the atomistic details of adsorption, diffusion, and dissociation of a simple organic molecule paves the way towards unraveling the procedures involved in the hydrogen liberation for fuel cells. In this work, with the aim of enabling structure and stoichiometry determination by using X-ray photoelectron spectroscopy, I present the results of a comprehensive theoretical study on the core-level shifts of ZnO surface reconstructions. Moreover, I provide a thorough investigation of the mixed-terminated (10-10) surface by first examining the conditions under which methanol monolayers can form on this crystal face and by then exploring all possible pathways for its adsorption, diffusion, and initial dehydrogenation. This study provides a comprehensive picture to identify the most probable reaction steps that can be used to interpret experimental findings and will help future theoretical studies for reactions similar to dehydrogenation of organic molecules and monolayer-formation kinetics that were studied here.

The wetting behavior of water on methacrylate copolymer films was studied on anodically oxidized and micro-roughened aluminium surfaces and also on smooth model surfaces. The copolymerization of tert-butyl methacrylate with a methacrylate containing a fluoroorganic side chain led to a considerable decrease of the surface free energy, but not to a superhydrophobic behavior of polymer-coated, micro-roughened aluminium surfaces. However, copolymers containing both hydrophobic and hydrophilic sequences are able to form superhydrophobic films. X-ray photoelectron spectroscopy showed that an enrichment of the interface between the solid phase and the air by fluorine-containing polymer components was the reason for the strong decrease of the surface free energy. The hydrophilic segments of the copolymers improved the ability to wet the highly polar aluminium surface and to form films of higher density.

The deposition of boron oxide (B₂O₃) films on silicon substrates is of significant interest in microelectronics for ultrashallow doping applications. However, thickness control and conformality of such films has been an issue in high aspect ratio 3D structures which have long replaced traditional planar transistor architectures. B₂O₃ films are also unstable in atmosphere, requiring a suitable capping barrier for passivation. The growth of continuous, stoichiometric B₂O₃ and boron nitride (BN) films has been demonstrated in this dissertation using Atomic Layer Deposition (ALD) and enhanced ALD methods for doping and capping applications. Low temperature ALD of B₂O₃ was achieved using BCl₃/H₂O precursors at 300 K. In situ x-ray photoelectron spectroscopy (XPS) was used to assess the purity and stoichiometry of deposited films with a high reported growth rate of ~2.5 Å/cycle. Free-radical assisted ALD of B₂O₃ was also demonstrated using non-corrosive trimethyl borate (TMB) precursor, in conjunction with mixed O₂/O-radical effluent, at 300 K. The influence of O₂/O flux on TMB-saturated Si surface was investigated using in situ XPS, residual gas analysis mass spectrometer (RGA-MS) and ab initio molecular dynamics simulations (AIMD). Both low and high flux regimes were studied in order to understand the trade-off between ligand removal and B₂O₃ growth rate. Optimization of precursor flux was discovered to be imperative in plasma and radical-assisted ALD processes. BN was investigated as a novel capping barrier for B₂O₃ and B-Si-oxide films. A BN capping layer, deposited using BCl₃/NH₃ ALD at 600 K, demonstrated excellent stoichiometry and consistent growth rate (1.4 Å/cycle) on both films. Approximately 13 Å of BN was sufficient to protect ~13 Å of B₂O₃ and ~5 Å of B-Si-oxide from atmospheric moisture and prevent volatile boric acid formation. BN/B₂O₃/Si heterostructures are also stable at high temperatures (>1000 K) commonly used for dopant drive-in and activation. BN shows great promise in preventing upward boron diffusion which causes a loss in the dopant dose concentration in Si. The capping effects of BN were extended to electrochemical battery applications. ALD of BN was achieved on solid Li-garnet electrolytes using halide-free tris(dimethylamino)borane precursor, in conjunction with NH₃ at 723 K. Approximately 3 nm of BN cap successfully inhibited Li₂CO₃ formation, which is detrimental to Li-based electrolytes. BN capped Li-garnets demonstrated ambient stability for at least 2 months of storage in air as determined by XPS. BN also played a crucial role in stabilizing Li anode/electrolyte interface, which drastically reduced interfacial resistance to 18 Ω.cm², improved critical current density and demonstrated excellent capacitance retention of 98% over 100 cycles. This work established that ALD is key to achieving conformal growth of BN as a requirement for Li dendrite suppression, which in turn influences battery life and performance.

This talk was presented in the 14th International Conference on Atomic Layer Deposition (ALD 2014) in Kyoto, Japan on 18th June 2014. Abstract Atomic Layer Deposition (ALD) is emerging as a ubiquitous method for the deposition of conformal and homogeneous ultra-thin films on complex topographies and large substrates in microelectronics. Electrochemical deposition (ECD) is the first choice for the deposition of copper (Cu) into the trenches and vias of the interconnect system for ULSI circuits. The ECD of Cu necessitates an electrically conductive seed layer for filling the interconnect structures. ALD is now considered as a solution for conformal deposition of Cu seed layers on very high aspect ratio (AR) structures also for technology nodes below 20 nm, since physical vapor deposition is not applicable for structures with high AR. Cu seed layer deposition by the reduction of Cu2O, which has been deposited from the Cu(I) β-diketonate [(nBu3P)2Cu(acac)] (1) used as Cu precursor, has been successfully carried out on different substrates like Ta, TaN, SiO2, and Ru [1, 2]. It was found that the subsequent gas-phase reduction of the Cu2O films can be aided by introducing catalytic amounts of a Ru precursor into the Cu precursor, so that metallic copper films could potentially obtained also on non-catalytic substrates [3, 4]. In this work, in situ X-ray photoelectron spectroscopy (XPS) investigation of the surface chemistry during Cu2O ALD from the mixture of 99 mol % of 1 and 1 mol % of [Ru(η5 C5H4SiMe3)(η5-C7H11)] (2) as ruthenium precursor, and the reduction of Cu2O to metallic Cu by formic acid carried out on SiO2 substrate are demonstrated. Oxidation states of the Cu in the film are identified by comparing the Cu Auger parameter (α) [5] with literature data. α calculated after ALD equals 362.2 eV and after reduction equals 363.8 eV, comparable to the Cu2O and metallic Cu in thin-films [6] respectively. In addition, <10 % of Cu(I), Cu(II), and Cu(OH)2 species are identified from the Cu 2p3/2 and Cu L3VV Auger spectrum after reduction. Consequently, the ALD Cu2O is successfully reduced to metallic copper by in-situ thermal reduction using formic acid. [1] T. Waechtler et al., J. Electrochem. Soc., 156 (6), H453 (2009). [2] T. Waechtler et al., Microelectron. Eng., 88, 684 (2011). [3] S. Mueller et al., Conference Proceedings SCD 2011, Semiconductor Conference Dresden, pp. 1-4. [4] T. Waechtler et al., US Patent Application Publication, US 2013/0062768. [5] C. D. Wagner, Faraday Discuss. Chem. Soc., 60, 291 (1975). [6] J. P. Espinós et al., J. Phys. Chem. B, 106, 6921 (2002).

Surface chemistry plays a key role in science and technology because materials interact with their environments through their surfaces. Understanding surface chemistry can help alter/improve the properties of materials. However, surface characterization and modification often require multiple characterization and synthesis techniques. Silicon/silica-based materials are technologically important, so studying their surface properties can enable future advancements. In this dissertation, I explore surface modification and characterization of different types of Si/SiO2 thin films, including silicon wafers, fused silica capillary columns, and oblique angle sputtered Si/SiO2 thin films. In Chapters 2-5, I first present a method to rapidly silanize silica surfaces using a gas-phase synthesis that employs a small aminosilane that passivates/deactivates silicon wafers and the inner surfaces of capillary columns. This deposition takes place in a flow-through, atmospheric pressure, gas-phase reactor. This surface modification results in a significant decrease in the number of free surface silanols, which was confirmed by high-sensitivity low energy ion scattering (HS-LEIS), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). I then show that this silanization inhibits atomic layer deposition (ALD) of zinc oxide (ZnO), which is an important optical thin film material. Finally, I performed in-depth characterization of thin films of oblique angle deposited porous Si/SiO2. These films have been used as the active coatings in solid phase microextraction (SPME) devices. The characterization and analysis in this study were mainly by scanning transmission electron microscopy (STEM) and various computational microstructural characterization techniques, e.g., two-point statistics. The rest of my dissertation focuses on XPS data analysis and interpretation. I first show box plots as a simple graphical tool for determining overfitting in XPS peak fitting. I next present a series of chemometrics/informatics analyses of an XPS image dataset from a patterned silicon surface with different oxide thicknesses. This dataset was probed via an initial, graphical analysis of the data, summary statistics with a focus on pattern recognition entropy (PRE), principal component analysis (PCA), multivariate curve resolution (MCR), and cluster analysis (CA).

Progress in chemomechanical functionalization was made by investigating the binding of molecules and surface coverage on the silicon surface, demonstrating functionalization of silicon with gases by chemomechanical means, analyzing atomic force microscopy probe tip wear in atomic force microscopy (AFM) chemomechanical nanografting, combining chemomechanical functionalization and nanografting to pattern silicon with an atomic force microscope, and extending chemomechanical nanografting to silicon dioxide. Molecular mechanics of alkenes and alkynes bound to Si(001)-2x1 as a model of chemomechanically functionalized surfaces indicated that complete coverage is energetically favorable and becomes more favorable for longer chain species. Scribing a silicon surface in the presence of ethylene and acetylene demonstrated chemomechanical functionalization with gaseous reagents, which simplifies sample cleanup and adds a range of reagents to those possible for chemomechanical functionalization. Thermal desorption spectroscopy was performed on chemomechanically functionalized samples and demonstrated the similarity in binding of molecules to the scribed silicon surface and to the common Si(001)-2x1 and Si(111)-7x7 surfaces. The wearing of atomic force microscope probe tips during chemomechanical functionalization was investigated by correlating change over time and force with widths of created lines to illustrate the detrimental effect of tip wear on mechanically-driven nanopatterning methods. In order to have a starting surface more stable than hydrogen-terminated silicon, silicon reacted with 1-octene was used as a starting surface for AFM chemomechanical functionalization, producing chemomechanical nanografting. Chemomechanical nanografting was then demonstrated on silicon dioxide using silane molecules; the initial passivating layer reduced the tip friction on the surface to allow only partial nanografting of the silane molecules. These studies broadened the scope and understanding of chemomechanical functionalization and nanografting.