<p>The work presented in this thesis concernes two sorts of nanostructures: energetic-ion-impact-induced surface tracks and gas-deposited WO₃ nanoparticles. Our aims to characterise these nanostuctures and understand the physical principles behind their formation are of general interests for basic science as well as of the field of nanotechnology.</p><p>AFM studies of irradiated organic surfaces showed that individual ion impacts generate craters, most often accompanied by raised plastically deformed regions. Crater sizes were measured as a function of ion stopping power and incidence angle on various surfaces. Observed crater volumes were converted into estimates of total sputtering yields, which in turn were correlated with data from collector experiments. The observations were compared to predictions of theoretical sputtering models. The observed plastic deformations above grazing-incidence-ion penetration paths agree with predictions of the pressure pulse model. However, closer to the ion track, evaporative sputtering can occur.</p><p>AFM images of gas-deposited WO₃ nanoparticle-films indicated the formation of agglomerates. The size distribution of the agglomerates was measured to be log-normal, <i>i.e.</i> similar to the size distribution of the gas-phase nanoparticles forming the deposit. By simulations we could relatively well reproduce this observation. The agglomerates exhibited high thermal stability below 250°C when considering their size, implying that these porous films can be useful in applications involving elevated temperatures in the 250°C range. The appearance of the nanoparticles in the tapping-mode AFM images was sensitive to the free amplitude of the oscillating tip. We could show by model calculations that the high adhesion between the tip and the sample could account for some of these observations.</p>

<p>The fascinating optical properties of metallic nanostructures, dominated by collective oscillations of free electrons known as plasmons, open new opportunities for the development of devices fabrication based on noble metal nanoparticle composite materials. This thesis demonstrates a low-cost and versatile technique to produce stimuli-responsive ultrafast plasmonic nanostructures with reversible tunable optical properties. Albeit challenging, further control using thermal external stimuli to tune the local environment of gold nanoparticles embedded in VO2 host matrix would be ideal for the design of responsive functional nanocomposites. We prepared Au-VO2 nanocomposite thin films by the inverted cylindrical reactive magnetron sputtering (ICMS) known as hollow cathode magnetron sputtering for the first time and report the reversible tuning of surface plasmon resonance of Au nanoparticles by only adjusting the external temperature stimuli. The structural, morphological, interfacial analysis and optical properties of the optimized nanostructures have been studied. ICMS has been attracting much attention for its enclosed geometry and its ability to deposit on large area, uniform coating of smart nanocomposites at high deposition rate. Before achieving the aforementioned goals, a systematic study and optimization process of VO2 host matrix has been done by studying the influence of deposition parameters on the structural, morphological and optical switching properties of VO2 thin films. A reversible thermal tunability of the optical/dielectric constants of VO2 thin films by spectroscopic ellipsometry has been intensively also studied in order to bring more insights about the shift of the plasmon of gold nanoparticles imbedded in VO2 host matrix.</p>

The work presented in this thesis concernes two sorts of nanostructures: energetic-ion-impact-induced surface tracks and gas-deposited WO3 nanoparticles. Our aims to characterise these nanostuctures and understand the physical principles behind their formation are of general interests for basic science as well as of the field of nanotechnology. AFM studies of irradiated organic surfaces showed that individual ion impacts generate craters, most often accompanied by raised plastically deformed regions. Crater sizes were measured as a function of ion stopping power and incidence angle on various surfaces. Observed crater volumes were converted into estimates of total sputtering yields, which in turn were correlated with data from collector experiments. The observations were compared to predictions of theoretical sputtering models. The observed plastic deformations above grazing-incidence-ion penetration paths agree with predictions of the pressure pulse model. However, closer to the ion track, evaporative sputtering can occur. AFM images of gas-deposited WO3 nanoparticle-films indicated the formation of agglomerates. The size distribution of the agglomerates was measured to be log-normal, i.e. similar to the size distribution of the gas-phase nanoparticles forming the deposit. By simulations we could relatively well reproduce this observation. The agglomerates exhibited high thermal stability below 250°C when considering their size, implying that these porous films can be useful in applications involving elevated temperatures in the 250°C range. The appearance of the nanoparticles in the tapping-mode AFM images was sensitive to the free amplitude of the oscillating tip. We could show by model calculations that the high adhesion between the tip and the sample could account for some of these observations.

The explosive development of the telecom industry and in particular wireless and mobile communications in recent years has lead to a rapid development of new component and fabrication technologies to continually satisfy the mutually exclusive requirements for better performance and miniaturization on the one hand and low cost on the other. A fundamental element in radio communications is time and frequency control, which in turn is achieved by high performance electro-acoustic components made on piezoelectric single crystalline substrates. The latter, however, reach their practical limits in terms of performance and cost as the frequency of operation reaches the microwave range. Thus, the thin film electro-acoustic technology, which uses thin piezoelectric films instead, has been recently developed to alleviate these deficiencies. This thesis explores and addresses a number of issues related to thin film synthesis on the one hand as well as component design and fabrication on other. Specifically, the growth of highly c-axis textured AlN thin films has been studied and optimized for achieving high device performance. Perhaps, one of the biggest achievements of the work is the development of a unique process for the deposition of AlN films with a mean c-axis tilt, which is of vital importance for the fabrication of resonators operating in contact with liquids, i.e. biochemical sensors. This opens the way for the development of a whole range of sensors and bio-analytical tools. Further, high frequency Lamb wave resonators have been designed, fabricated and evaluated. Performance enhancement of FBAR devices is also addressed, e.g. spurious mode suppression, temperature compensation, etc. It has been demonstrated, that even without temperature compensation, shear mode resonators operating in a liquid still exhibit an excellent performance in terms of Q (200) and coupling (~1.8%) at 1.2 GHz, resulting in a mass resolution better than 2 ng cm-2 in water, which excels that of today’s quartz sensors.

Quasicrystals is a new kind of material that have several interesting aspects to it. The unusual atomic structure entails many anomalous and unique physical properties, for example, high hardness, and extremely low electrical and thermal conductivity. In thin films quasicrystals would enable new functional materials with a combination of attractive properties.In this work, AlCuFe and Nanoflex steel, materials that are known to form quasicrystals in bulk, have been deposited as thin films on Si and Al2O3 substrates using DC magnetron sputtering. These thin films were heat treated, and the formation and growth of different phases, among other approximant and quasicrystalline phases, were studied using mainly in-situ X-ray diffraction.During the project several problems with the formation of quasicrystals were encountered, and it is proposed how to overcome these problems, or even how to make use of them. Finally, the quasicrystalline phase was realized, although it was not completely pure. In the end some suggestions for future work is presented.

No description available.

This report describes the growth and characterization of thin amorphous samarium-cobalt alloy films. The samarium-cobalt alloy was grown by DC magnetron sputtering in the presence of an external magnetic field parallel to the thin film. The external magnetic field induces a uniaxial in-plane magnetic anisotropy in the samarium-cobalt alloy. The thin films were characterized with x-ray scattering, and the magnetic anisotropy was characterized with the magneto optic Kerr effect. The measurements showed a uniaxial in-plane magnetic anisotropy in the samarium-cobalt alloy films. It is not clear how amorphous the samples really are, but there are indications of crystalline and amorphous areas in the alloys.

The focus of the presented research is to examine the fundamental physics and chemistry of low-energy electron-stimulated reactions on adsorbate covered single crystal surfaces. Specifically, condensed SiCl₄ on the Si(111) surface and condensed H₂O on the TiO₂ (110) surface have been studied. By varying adsorbate film thicknesses, the coupling strength of the target molecule to the substrate and surrounding media dictates the progression of the electron induced reactions. To investigate the electron interactions with SiCl₄ on the Si(111) surface, desorbing cations and neutrals were detected via time of flight mass spectrometry (ToF-MS) where neutral chlorine atoms were ionized using a resonance enhanced multi-photon ionization (REMPI) technique. Structure in the cation and neutral yields were assigned to molecular excitations. At an incident electron energy of 10 eV, a resonance structure in the neutral yields was attributed to a negative ion resonance and observed in thick and thin films of SiCl₄. With monoenergetic electrons, specific surface reactions can be controlled which have implications for film growth, surface patterning and masking, and etching. For the H₂O/TiO₂ (110) system, the water interactions with the TiO₂ surface are revealed through the strong electron induced reaction dependencies on the water coverage. Understanding the nonthermal reaction landscape of H₂O on the TiO₂ (110) surface is crucial for developing the system as a catalytic source of hydrogen. The electron-stimulated oxidation of the TiO₂ (110) surface and electron induced sputtering of H ₂O was investigated. Irradiation of water films ([coverage]< 3 ML) oxidized the TiO₂ (110) surface similarly as surface oxidation via O₂ deposition. Each H₂O molecule in the first monolayer seems to be a target for the incoming electron initiating the oxidation. However, water coverages greater than a monolayer limited the oxidation process. The electron-stimulated desorption and sputtering yields of water from the TiO₂ (110) surface were measured as a function of water coverage. Surprisingly, the amount of water sputtered from the surface is nonlinearly dependent on water coverage.

DC and RF magnetron co-sputtering techniques are one of the most suitable techniques in fabrication of thin films with different compositions. In this work, Al2O3 and Si/Al2O3 thin films were fabricated by using magnetron co-sputtering technique. For Al2O3 films, the stoichiometric, optical and crystallographic analyses were performed. For Si contained Al2O3 films, the formation conditions of Si nanocrystals were investigated. To do so, these thin films were sputtered on Si (100) substrates. Post annealing was done in order to clarify the evolution of Al2O3 matrix and Si nanocrystals at different temperatures. Crystallographic properties and size of the nanocrystals were investigated by X-ray diffraction (XRD) method. The variation of the atomic concentrations and bond formations were investigated with X-ray photoelectron spectroscopy (XPS). The luminescent behaviors of Si nanocrystals and Al2O3 matrix were investigated with photoluminescence (PL) spectroscopy. Finally, the characteristic emissions from the matrix and the nanocrystals were separately identified.

In this study, flash memory cells with high-k dielectric HfO2 as tunnel oxide and group IV (Si, Ge) nanocrystals were fabricated and tested. The device structure was grown by magnetron sputtering deposition method and analyzed by various diagnostic techniques such as X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. The use of HfO2 tunnel oxide dielectric with high permittivity constant was one of the main purposes of this study. The ultimate aim was to investigate the use of Si and Ge nanocrystals together with HfO2 tunnel oxide in the memory elements. Interface structure of the fabricated devices was studied by XPS spectroscopy. A depth profile analysis was performed with XPS. Nanocrystal formations were verified using Raman spectroscopy technique. The final part of the study includes electrical characterization of memory devices fabricated using Si and Ge floating gate. C-V (Capacitance Voltage) and G-V (Conductance-Voltage) measurements and charge storage behaviour based on C-V measurements were performed. For comparison, structure of Si and Ge layers either in thin film or in the nanocrystal form were studied. A comparison of the C-V characteristics of these two structures revealed that the memory device with thin films do not confine charge carriers under the gate electrode as should be expected for a continuous film. On the other hand, the device with nanocrystals exhibited better memory behavior as a result of better confinement in the isolated nanocrystals. Trace amount of oxygen was found to be enough to oxidize Ge nanocrystals as confirmed by the Raman measurements. The charge storage capability is weakened in these samples as a result of Ge oxidation. In general, this work has demonstrated that high-k dielectric HfO2 and group IV nanocrystals can be used in the new generation MOS based memory elements. The operation of the memory elements are highly dependent on the material and device structures, which are determined by the process conditions.