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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.

Pulsed filtered cathodic arc deposition involves formation of energetic multiply charged metal ions, which help to form dense, adherent, and macroparticle-free thin films. Ions possess not only significant kinetic energy, but also potential energy primarily due to their charge, which for cathodic arc plasmas is usually greater than one. While the effects of kinetic ion energy on the growing film are well investigated, the effects of the ions’ potential energy are less known. In the present work, we make a step toward decoupling the contributions of kinetic and potential energies of ions on thin film formation. The potential energy is changed by enhancing the ion charge states via using an external magnetic field at the plasma source. The kinetic energy is adjusted by biasing the arc source (“plasma bias”), which allows us to approximately compensate the differences in kinetic energy, while the substrate and ion energy detector remain at ground. However, application of an external magnetic field also leads to an enhancement of the ion flux and hence the desired complete decoupling of the potential and kinetic energy effects will require further steps. Charge-state-resolved energy distribution functions of ions are measured at the substrate position for different arc source configurations, and thin films are deposited using exactly those configurations. Detailed characterization of the deposited thin films is performed to reveal the correlations of changes in structure with kinetic and potential energies of multiply charged ions. It is observed that the cathode composition (Al:V ratio) strongly affects the formation of the thermodynamically stable wurtzite or the metastable cubic phase. The external magnetic field applied at the arc source is found to greatly alter the plasma and, therefore, to be the primary, easily accessible “tuning knob” to enhance film crystallinity. The effect of “atomic scale heating” provided by the ions’ kinetic and potential energies on the film crystallinity is investigated, and the possibility to deposit crystalline (V,Al)N films without substrate heating is demonstrated. This study shows an approach toward distinguishing the contributions stemming from kinetic and potential energies of ions on the film growth, however, further research is needed to assess and distinguish the additional effect of ion flux intensity (current).

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]

The fabrication of plasmonic 3D microstructures is still a challenge. In this study, the fabrication of gold‐nanoparticle (Au‐NP)‐filled acrylate‐based micron‐scale cuboids forming plasmonic 3D particles is investigated. UV curable acrylate is mixed with HAuCl4 and spin‐coated onto a fused silica wafer. UV light and heat treatment of the layer result in polymerization of the acrylate and formation of Au‐NPs with a plasmonic resonance ranging from 535 to 550 nm. The plasmonic resonance wavelength decreases slightly with increasing UV dose. The resonance wavelength can be shifted by a subsequent annealing process. The decreasing resonance wavelength with increasing annealing temperature is discussed as a result of the increasing Au‐NPs. The size and the distribution of the resulting gold particles in the acrylate matrix is investigated by transmission electron microscopy. The Au‐NPs‐filled acrylate layer is laser structured using a UV‐femtosecond laser, which allows the fabrication of adjustable micro‐cuboids with edge lengths down to 15 μm. The laser‐cut micro‐cuboids are transferred into isopropanol and the plasmonic properties of the structures in the liquid are successfully demonstrated. The presented concept allows easy and large‐scale fabrication of plasmonic microstructures with independently adjustable plasmonic properties and microstructural size and shape. [ABSTRACT FROM AUTHOR]

Phase transformations between amorphous and crystalline states induced by irradiation of pulsed laser deposition grown GeTe thin films with nanosecond laser pulses at 248 nm and pulse duration of 20 ns are studied. Structural and optical properties of the Ge-Te phase-change films were studied by X-ray diffraction and optical reflectivity measurements as a function of the number of laser pulses between 0 and 30 pulses and of the laser fluence up to 195 mJ/cm2. A reversible phase transition by using pulse numbers ⩾5 at a fluence above the threshold fluence between 11 and 14 mJ/cm2 for crystallization and single pulses at a fluence between 162 and 182 mJ/cm2 for amorphization could be proved. For laser fluences from 36 up to 130 mJ/cm2, a high optical contrast of 14.7% between the amorphous and crystalline state is measured. A simple model is used that allows the discussion on the distribution of temperature in dependency on the laser fluence. [ABSTRACT FROM AUTHOR]

In cubic (c‐)GaN Ge has emerged as a promising alternative to Si for n‐type doping, offering the advantage of slightly improved electrical properties. Herein, a study on Ge doping of the ternary alloy c‐AlxGa1−xN is presented. Ge‐doped c‐AlxGa1−xN layers are grown by plasma‐assisted molecular beam epitaxy. In two sample series, both the Al mole fraction x and the doping level are varied. The incorporation of Ge is verified by time‐of‐flight secondary ion mass spectrometry. Ge incorporation and donor concentrations rise exponentially with increasing Ge cell temperature. A maximum donor concentration of 1.4 × 1020 cm−3 is achieved. While the incorporation of Ge is almost independent of x, incorporation of O, which acts as an unintentional donor, increases for higher x. Dislocation densities start increasing when doping levels of around 3 × 1019 cm−3 are exceeded. Also photoluminescence intensities begin to drop at these high doping levels. Optical emission of layers with x > 0.25 is found to originate from a defect level 0.9 eV below the indirect bandgap, which is not related to Ge. In the investigated range 0 ≤ x ≤ 0.6, Ge is a suitable donor in c‐AlxGa1−xN up to the low 1019 cm−3 range. [ABSTRACT FROM AUTHOR]