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[en] Mechanisms of PTCDI–C8 adsorption and thin films growth on Si(1 1 0)–(16 × 2) have been studied using a combination of X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory. Oxygen atoms of the PTCDI–C8 molecule interact with the substrate increasing substantially the adsorption energy. Adsorbed molecules do not form long-range ordered structures on the surface but local chain-like arrangements. A good agreement between the calculated isosurfaces of electronic charge density and the scanning tunneling microscopy images of the filled electron states of clean and adsorbate-covered surfaces allows to recognize the PTCDI–C8 molecules adsorbed on Si(1 1 0)–(16 × 2).
[en] This paper describes a university level experiment during which students can observe the surface structure and determine the work function of a clean single tungsten crystal and a crystal covered with barium. The authors used a commercial field emission microscope offered by Leybold Didactic and designed an experiment which can be easily reproduced and performed in a students' laboratory. The use of a digital camera and computer allowed simultaneous observation and imaging of the surface of the body-centred cubic structure of the single tungsten crystal. Some interesting results about the changes in tungsten work function with time and with barium coverage are presented and discussed. The data help to improve knowledge and skills in the calculation of measurement uncertainty
[en] This paper presents Auger electron spectroscopy with a retarding field analyser designed for an advanced physics experiment carried out in 'Physics Laboratory II' at the Institute of Experimental Physics, University of Wroclaw, Poland. The authors discuss the process of setting up the experiment and the results of the measurement of Auger spectra. The advantages and disadvantages of the apparatus are discussed along with its implementation in the teaching process
[en] This paper presents an experiment in which students determine the mass sensitivity of three crystal quartz resonators, designed to be carried out in 'Physics Laboratory II' at the Institute of Experimental Physics, University of Wroclaw. The authors discuss the process of setting up the experiment and the results of the measurements. They clearly show that the set-up is simple, easy to assemble and allows obtaining satisfactory results. The advantages and the disadvantages of the apparatus are discussed along with the implementation into the teaching process. The results support the gathering of knowledge and skills necessary for experimental physicists.
[en] The present paper provides the results of structural studies concerning formation of self-assembled indium deposited nanostructures on the (100) surface of In4Se3 layered semiconductor. We used to study growth orientation of indium-induced nanostructures exploiting small rates and low times of indium deposition by scanning tunneling spectroscopy (STM). We carry out our studies using In4Se3 crystals grown with rather different concentrations of the over-stoichiometric indium in the melt. It has been established that shape of subsequent indium-deposited nanostructures varies from 3D islands, in the case of low-indium-doped crystals, to elongated nanowires, for highly doped ones. Based on a high-resolution STM study, we show that self-assembled quasi-periodical nanowires are oriented along the c -axis of (100) In4Se3 surface. The observed nanostructures have metallic origin as it was acquired by the current imaging tunneling spectroscopy (CITS) studies. We considered that formation of different-shaped indium-deposited nanostructures is powered by concentration of indium nuclei on furrowed (100) In4Se3 surface, which is modulated by the degree of the over-stoichiometric indium during crystal growth subsequently intercalated into the interlayer gap.
[en] Hydrogen etching was carried out on the (0001)-oriented 6H-SiC wafer at various temperatures in the range from 1450 to 1650 deg. C. Surface topography and morphology was characterized by the atomic force microscope (AFM). Optimal conditions have been found, under which all scratches due to the polishing process are efficiently removed and the atomically smooth, clean surface of SiC(0001) is achieved. The most characteristic elements observed on the perfectly etched surface were straight-line steps of equal height and nearly the same width. The AFM imaging revealed also intrinsic defects of the samples. Conditions have been found for maintaining the saturation of etching products on the surface at the level enabling the empty core dislocations to be formed during etching. The observed population of the dislocations ranges between 107 and 108 cm-2. Burgers vectors of the dislocations as evaluated on the basis of Frank's model are equal to 2 or 3 lattice constants
[en] We describe a new technique for random surface texturing of a gallium nitride (GaN) light-emitting diode wafer through a mask-less dry etch process. This involves depositing a sub-monolayer film of silica nanospheres (typical diameter of 200 nm) and then subjecting the coated wafer to a dry etch process with enhanced physical bombardment. The silica spheres acting as nanotargets get sputtered and silica fragments are randomly deposited on the GaN epi-layer. Subsequently, the reactive component of the dry etch plasma etches through the exposed GaN surface. Silica fragments act as nanoparticles, locally masking the underlying GaN. The etch rate is much reduced at these sites and consequently a rough topography develops. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) inspections show that random topographic features at the scale of a few tens of nanometres are formed. Optical measurements using angle-resolved photoluminescence show that GaN light-emitting diode material thus roughened has the capability to extract more light from within the epilayers.
[en] The electrical properties and interface chemistry of Cr/6H-SiC(0 0 0 1) contacts have been studied by current-sensing atomic force microscopy (CS-AFM) and X-ray photoelectron spectroscopy (XPS). Cr layers were vapor deposited under ultrahigh vacuum onto both ex situ etched in H2 and in situ Ar+ ion-bombarded samples. The Cr/SiC contacts are electrically non-uniform. Both the measured I-V characteristics and the modeling calculations enabled to estimate changes of the Schottky barrier height caused by Ar+ bombardment. Formation of ohmic nano-contacts on Ar+-bombarded surfaces was observed.
[en] Highlights: • Thin film coatings were prepared by magnetron sputtering in pure oxygen plasma. • Increase of the neodymium concentration caused amorphisation of prepared coatings. • Doping TiO2 with Nd decreased the refractive index and extinction coefficient. • Neodymium addition in the amount of 4, 7 and 10 at.% caused hardening of the coating. • The highest hardness was obtained for (Nd0.07Ti0.93)Ox thin films. - Abstract: TiO2 and (NdyTi1−y)Ox thin films were deposited by reactive magnetron sputtering process from mosaic Ti–Nd targets and characterised by X-ray diffraction (XRD), Raman optical spectroscopy and nanoindentation technique. XRD measurements revealed that as-prepared titanium dioxide and TiO2 thin films with 4 and 7 at.% of Nd had nanocrystalline rutile structure, while coatings with larger amount of Nd were amorphous. Raman spectroscopy investigations showed that the increase of the neodymium concentration caused amorphisation of the coatings and hindered their crystal growth. All as-prepared coatings were transparent in the visible wavelength range with a transmittance of approximately 80%. The refractive index and extinction coefficient of the thin films gradually decreased with the increase of the neodymium concentration. Micro-mechanical properties, i.e. hardness and elastic modulus, were determined using traditional load-controlled nanoindentation testing and continuous stiffness measurements. The highest hardness and elastic modulus values were obtained for thin films with 7 at.% of Nd and were approximately 14.8 GPa and 166.3 GPa, respectively.