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Deposition of epitaxial oxide semiconductor films using physical vapor deposition methods requires a detailed understanding of the role of energetic particles to control and optimize the film properties. In the present study, Ga 2 O 3 thin films are heteroepitaxially grown on Al 2 O 3 (0001) substrates using oxygen ion beam sputter deposition. The influence of the following relevant process parameters on the properties of the thin films is investigated: substrate temperature, oxygen background pressure, energy of primary ions, ion beam current, and sputtering geometry. The kinetic energy distributions of ions in the film-forming flux are measured using an energy-selective mass spectrometer, and the resulting films are characterized regarding crystalline structure, microstructure, surface roughness, mass density, and growth rate. The energetic impact of film-forming particles on the thin film structure is analyzed, and a noticeable decrease in crystalline quality is observed above the average energy of film-forming Ga + ions around 40 eV for the films grown at a substrate temperature of 725 ° C.

Deposition of epitaxial oxide semiconductor films using physical vapor deposition methods requires a detailed understanding of the role of energetic particles to control and optimize the film properties. In the present study, Ga 2 O 3 thin films are heteroepitaxially grown on Al 2 O 3 (0001) substrates using oxygen ion beam sputter deposition. The influence of the following relevant process parameters on the properties of the thin films is investigated: substrate temperature, oxygen background pressure, energy of primary ions, ion beam current, and sputtering geometry. The kinetic energy distributions of ions in the film-forming flux are measured using an energy-selective mass spectrometer, and the resulting films are characterized regarding crystalline structure, microstructure, surface roughness, mass density, and growth rate. The energetic impact of film-forming particles on the thin film structure is analyzed, and a noticeable decrease in crystalline quality is observed above the average energy of film-forming Ga + ions around 40 eV for the films grown at a substrate temperature of 725 ° C. [ABSTRACT FROM AUTHOR]

Gallium oxide thin films were grown by ion beam sputter deposition (IBSD) at room temperature on Si substrates with systematically varied process parameters: primary ion energy, primary ion species (O 2 + and Ar +), sputtering geometry (ion incidence angle α and polar emission angle β), and O 2 background pressure. No substrate heating was applied because the goal of these experiments was to investigate the impact of the energetic film-forming species on thin film properties. The films were characterized with regard to film thickness, growth rate, crystallinity, surface roughness, mass density, elemental composition and its depth profiles, and optical properties. All films were found to be amorphous with a surface roughness of less than 1 nm. The stoichiometry of the films improved with an increase in the energy of film-forming species. The mass density and the optical properties, including the index of refraction, are correlated and show a dependency on the kinetic energy of the film-forming species. The ranges of IBSD parameters, which are most promising for further improvement of the film quality, are discussed.

This work focuses on the generation of ferromagnetism at the surface of anatase TiO2 films by low-energy ion irradiation. Controlled Ar+-ion irradiation resulted in a thin (∼10) nm ferromagnetic surface layer. The intrinsic origin and robustness of the magnetic order has been characterized by x-ray magnetic circular dichroism at room temperature revealing that a Ti band is spin-polarized. These results, together with density functional theory calculations, indicate that Ti vacancy-interstitial pairs are responsible for the magnetic order. Superconducting quantum interference device measurements show the existence of a perpendicular magnetic anisotropy and a low remanent magnetization. Magnetic force microscopy reveals that this low remanence is due to oppositely aligned magnetic domains with magnetization vectors normal to the main surface. The weak domain-wall pinning, the magnetic anisotropy, together with the simplicity of the preparation method, open up interesting possibilities for future applications. As an example, single domain patterns of ∼1μm width and several μm length can be easily prepared.

There is an increasing demand for thin films with tailored properties, which requires the use and control of adequate deposition techniques. Ion beam sputter deposition (IBSD) is a physical vapor deposition (PVD) technique that is capable of fulfilling the technological challenges. In contrast to other PVD techniques, IBSD offers a unique opportunity to tailor the properties of the film-forming particles (sputtered target and scattered primary particles) and, hence, thin film properties. This is related to the fact that the generation and acceleration of the primary particles from the ion beam source, the generation of film-forming particles at the target, and thin film growth on the substrate are spatially separated. Thus, by changing ion beam parameters (ion species and ion energy) and geometrical parameters (ion incidence angle and emission angle), the energy distributions of the film-forming particles are modified. Even though in use for several decades, IBSD was not investigated systematically until lately. Utilizing the full potential of IBSD requires a comprehensive understanding of the physical processes. This tutorial describes the systematics of IBSD: The correlation between process parameters, properties of the film-forming particles, and thin film properties. The most important process parameters are the scattering geometry and the primary particle species. Depending on the material, different film properties can be influenced. Examples are adhesion, structural properties, composition, surface roughness, mass density, optical properties, stress, and electrical resistivity. In addition to the experimental results, fundamental physical aspects, experimental setups, and techniques for thin film deposition and particle characterization are described. [ABSTRACT FROM AUTHOR]

The energy distributions of secondary ions for the ion beam sputtering of a Ga 2 O 3 target using O 2 + and Ar + ions are measured in dependence on various process parameters using energy-selective mass spectrometry. The process parameters include sputtering geometry (ion incidence angle α , polar emission angle β , scattering angle γ), the energy of incident ions E ion , and the background pressure of O 2. The main secondary ion species are identified to be Ga + , O + , O 2 + , and, when argon is used as a process gas, Ar +. The changes in the sputtering geometry and the primary ion energy have the most impact on the energy distributions of secondary Ga + and O + ions, giving control over the high-energy tail, which is attributed to anisotropy effects in sputtering. The formation of O 2 + ions is attributed to collisions with background gas molecules, as their energy distributions are not influenced by the sputtering geometry or the primary ion energy. The increase of the O 2 pressure leads to a minor decrease of the energy of Ga + ions due to collisions with the background gas particles. The use of primary Ar + ions with O 2 background pressure does not show any specific effect on energy distributions of Ga + , O + , and O 2 + ions except for the case without additional O 2 background. In the latter case, much fewer O + and O 2 + ions are produced indicative of oxygen depletion of the surface due to preferential sputtering of oxygen. At all considered O 2 pressures, the energy distributions of Ar + ions have a high-energy peak, attributed to direct scattering events. The trends in experimental data show qualitative agreement to simulations using the Monte Carlo code SDTrimSP. [ABSTRACT FROM AUTHOR]

The ion beam sputtering of a metallic Ti and a ceramic TiO2 target by bombardment with oxygen ions was investigated systematically. Emphasis was put on the properties of the secondary particles emitted from the target, namely, the angular distribution of the sputtered Ti and the energy distribution of the secondary ions. Ion energies of 0.5, 1.0, and 1.5 keV and incidence angles of 0°, 30°, and 60° were used. The angular distribution of the flux of sputtered Ti particles was determined by measuring the thickness of TiO2 films that were deposited under emission angles in the range between -40° and +80°. An empirical formula was used to describe the angular distribution as a superposition of an isotropic and an anisotropic cosinelike function. Increasing the ion energy or decreasing the ion incidence angle leads to a more isotropic emission of the sputtered Ti particles. The mass and energy distribution of the secondary ions were measured using an energy-selective mass spectrometer. The most prevalent ion species are O+, O2+, Ti+, and TiO+. Ion energy and sputtering geometry, i.e., the combination of an ion incidence angle and an emission angle, were found to have a strong influence on the energy distribution of the secondary ions. [ABSTRACT FROM AUTHOR]

Summary: Ion Beam Sputter Deposition – Fundamentals and Application for Tailoring Thin Film Properties Ion beam sputter deposition (IBSD) is a PVD technique, which, in comparison to other PVD techniques, is known to produce thin films with desirable properties, for instance, with improved adhesion, dense film structure, less defects, higher purity, less particle contamination, and better controlled composition. Recent systematic and comprehensive investigations of the fundamentals of the whole IBSD process revealed previously unemployed opportunities for tailoring thin film properties over a wide range. The main process parameters were identified to be the scattering geometry and the ion species, or, to be more precise, the mass of the primary ion relative to the mass of the target particle. By choosing these parameters appropriately, structural, optical or electrical properties, to name but a few, can be adjusted according to the technological requirements. The present contribution aims on illustrating these opportunities by presenting the main fundamentals and selected examples. [ABSTRACT FROM AUTHOR]

Ion beam sputter deposition (IBSD) is an established physical vapour deposition technique that offers the opportunity to tailor the properties of film-forming particles and, consequently, film properties. This is because of two reasons: (i) ion generation and acceleration (ion source), sputtering (target) and film deposition (substrate) are locally separated. (ii) The angular and energy distribution of sputtered target atoms and scattered primary particles depend on ion incidence angle, ion energy, and ion species. Ion beam sputtering of a Si target in a reactive oxygen atmosphere was used to grow SiO2 films on silicon substrates. The sputtering geometry, ion energy and ion species were varied systematically and their inuence on film properties was investigated. The SiO2 films are amorphous. The growth rate increases with increasing ion energy and ion incidence angle. Thickness, index of refraction, stoichiometry, mass density and surface roughness show a strong correlation with the sputtering geometry. A considerable amount of primary inert gas particles is found in the deposited films. The primary ion species also has an impact on the film properties, whereas the inuence of the ion energy is rather small. [ABSTRACT FROM AUTHOR]