We present structural, optical and electrical investigations of layered WS2 films prepared on tungsten. A two-step technique has been used to synthesize layered WS2 films using sulfurization of W films sputtered with thinner (1 and 2 nm) and thicker (14 and 28 nm) thicknesses at 800 degrees C. XRD analysis revealed that the examined films are polycrystalline with texture and have a 2H-WS2 hexagonal microstructure. Using Raman spectroscopy with the 532 nm laser excitation, the presence of E-2g(1), and A(1g) vibration modes was observed and the layered nature of WS2 was confirmed. FE SEM observations showed two different surface morphologies. The samples grown on thinner W films were not compact over the surface and agglomeration of nanosize grains in combination of triangles and flakes was visible. In another group the surface was lamellar and contained plenty of nanorods embedded vertically and/or inclined at different angles to the surface. Layered WS2 films exhibited a direct band gap in the range of 2.1-2.5 eV and they were n-type semiconductors with the sheet resistance in the order of several M Omega at room temperature.

We present the basic growth knowledge and the building mechanism on layered WS2 thin films prepared on sapphire substrates by sulfurization at 800 degrees C of sputtered precursor W with 14 and 28 nm thicknesses. The recorded XRD patterns from both types of samples indicate that a 2H-WS2 hexagonal microstructure with the grain size of about 9 nm was created. However, the intensities of the (100) and (110) peaks were very weak in comparison with that of the (002) peak. From SEM observations it was identified that the WS2 layer is not compact in its depth and many flakes in combination with nanorods and nanowires are visible and in addition they are embedded into the basal material in both investigated samples. We assume that the quantification of nanorods parameters together with detailed XRD evaluation are effective methods to get more information on non-closed layered WS2 films.

An approach for the reconstruction of the composition profiles of heterostructures with chemically modified interfaces is presented. It is based on the comprehensive simulation of the heterostructure growth stages and the compositional changes occurring at the depth profiling stage during sputtering by secondary ion mass spectrometry. Combining simulation of the growth and the concentration measurement process allows the calculation of the real concentration depth profiles of the heterostructure components. Within the framework of the proposed approach, the composition of the SiC:Ge/Ge/Si:Ge/Si heterostructure is analyzed and the real depth profiles were calculated.

Our activities were focused on the preparation of WS2 films on sapphire substrates by sulfurization of different thick sputtered W films. The influence of very thin W films in the range from 4 nm to 12 nm on the structural, morphological and optical properties of WS2 was investigated. XRD measurements revealed a polycrystalline nature with hexagonal symmetry and randomly connected nanocrystals with grain size about 6 nm for all WS2 films. Using Raman spectroscopy with a 532 nm laser excitation, the presence of characteristic E-2g(1) and A(1g) vibration modes was recorded and the multilayered nature of the prepared WS2 films was confirmed. FESEM observations revealed randomly oriented lamellar and flake-shaped microstructures with the basal plane of the WS2 crystallites. Thinner WS2 films (20 and 24 nm) showed highly dense horizontally aligned flakes. On the other hand, thicker WS2 films (33 and 42 nm) indicated a granular surface and the WS2 crystallites grew perpendicularly to the substrate surface. All examined WS2 films were transparent from 30 to 78% in the spectral range of 500 to 900 nm and showed a direct bandgap of 2.3 eV.

Laser embossing allows the micron and submicron patterning of metal substrates that is of great interest in a wide range of applications. This replication process enables low-cost patterning of metallic materials by non-thermal, high-speed forming which is driven by laser-induced shock waves. In this study the surface topography characteristics as well as the material structure at laser embossing of sub-micrometre gratings into solid copper is presented. The topography of the laser-embossed copper pattern is analysed with atomic force microscopy (AFM) in comparison to the master surface. The height of the embossed structures and the replicated pattern fidelity increases up to a laser fluence of F similar to 10 J/cm(2). For higher laser fluences the height of the embossed structures saturates at 75% of the master pattern height and the shape is adequate to the master. Structural modifications in the copper mono crystals after the laser embossing process were investigated with transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). Almost no modifications were detected. The residual stress after laser embossing of 32 MPa (F = 30 J/cm(2)) has only a limited influence on the surface pattern formation. (C) 2014 The Authors. Published by Elsevier B.V.

Anion–cation radical formation in solid films of M3EH-PPV blended with C60-PCBM, C120-O-PCBM and C60-MDHE, C120-O-MDHE under diode laser (532nm) and Xe-lamp light excitation studied by means of X,W-band at temperatures 30–80K is reported. Subsequent high frequency W-band ESR data demonstrate the reproducible, but variable effect of appreciable dispersion (D) contribution in the ESR spectral line for the di-fullerene anion radicals. It is suggested that the increase of the D part relative to the absorption (A) in the summarized ESR absorption line in blends with difullerenes is caused by the higher value of difullerene medium conductivity. The obtained data are quantitatively discussed by the D/A∼F(d/δ) functional dependence in approach of plane film geometry, where d is the film thickness and δ is the skin-depth. The influence of ν-dependent δ at D/A value has been checked using X-band LESR.

Commercial titanium was treated in ambient atmosphere using pulsed Nd:YAG (λ=1064nm) laser irradiation. Repeated laser treatments induce a removal of surface contaminants as well as the formation of a nanostructured top layer exhibiting a large effective surface and nanometer roughness. The laser induced oxidation leads to the presence of a surface layer with strongly improved, hydrothermally stable adhesion when joined to a one-component, hot-curing epoxy-based adhesive. Changes in the material properties have been characterized with respect to the topography, the chemical composition and the crystal structure using SEM, cross-beam FIB, XPS and XRD analyses in order to correlate the adhesion behavior with the structural and chemical characteristics of the surface.

We present the realization of high electron mobility transistors (HEMTs) based on AlGaN/GaN heterostructures, which were grown on silicon substrates using an ultrathin SiC transition layer. The growth of AlGaN/GaN heterostructures on 3C-SiC(111)/Si(111) was performed using metalorganic chemical vapour deposition (MOCVD). The 3C-SiC(111) transition layer was realized by low pressure CVD and prevented Ga-induced meltback etching and Si-outdiffusion in the subsequent MOCVD growth. The two-dimensional electron gas (2DEG) formed at the AlGaN/GaN interface showed an electron sheet density of 1.5×1013cm−3 and a mobility of 870cm2/Vs. The HEMTs DC and RF characteristics were analysed and showed a peak cut-off frequency as high as 29GHz for a 250nm gate length.

Thin films and coatings have developed as a prerequisite for many technical applications. In this paper, some applications for electrical, electronic, biomedical and optical applications are presented. In this contribution, examples for coatings for conductive and transparent films in photovoltaics, films for biomedical electrodes, for semiconductor contacts and for high-temperature contacts are presented and discussed. The films are prepared by magnetron-sputtering and pulsed laser deposition. The influence of the processing parameters on the functional properties of the films is presented.

In this paper we present a two-step micro continuous flow-through method for synthesizing colloidal dispersions of noble metal core/shell and multishell nanoparticles in aqueous solutions in the presence of cetyltrimethylammonium bromide (CTAB). The synthesis is based on the reduction of the metal salts HAuCl4 and AgNO3 at the surface of seed particles by ascorbic acid. In the micro fluidic system, constant residence times and an effective mixing were achieved by applying the segmented flow principle. The colloidal solutions were analyzed by differential centrifugal sedimentation, UV–vis spectrophotometry, and scanning electron microscopy. The size distribution of the Au/Ag core/shell and multishell nanoparticles synthesized by the micro flow-through technique was very narrow. In case of Au/Ag core/shell nanoparticles, an average diameter of 20nm with a distribution half width of 3.8nm, and for Au/Ag/Au multishell nanoparticles an average diameter of 46nm with a distribution half width of 7.4nm were obtained. The optical spectra of the particle solutions exhibited drastic changes with the deposition of each additional metal shell. Due to the intense changes in their optical properties, the prepared particles are of interest for future sensing applications as well as for labelling in bioanalytics or as nonlinear optical devices. Furthermore, it is shown that micro reactors are well suited to control the synthesis of complexly structured Au/Ag multishell nanoparticles with a high homogeneity and an extremely narrow size distribution. Especially by applying a micro segmented flow, an improvement of the product quality is achieved because of a high internal segment mixing efficiency and a suppression of residence time distribution.

We report on the growth of silicon nanowires on photostructurable glass by low-pressure chemical vapour deposition. Thereby, no additional catalyst was needed to stimulate the growth process. Instead, a self-organized crystallization process leads to the formation of metallic clusters and seed crystals within the glass, which are supposed to initialize the nanowire growth. The nanowires were contacted by direct deposition of Pt using a focussed ion beam system and characterized electrically.

Knowledge of tip geometry is necessary for reproducible atomic force microscope (AFM) measurements. This is particularly important for measurements in contact mode, in which a certain wear of the tip will always occur. For small or flat structures or for structures of larger dimensions, knowledge of the tip radius and the entire tip geometry is important. Additionally, the tilt of the tip in relation to the sample is of importance. Normally, very complicated lithographically manufactured structures for tip characterization are used. In contrast, the structures shown in this work are very simple. For measuring the tip geometry very thin foils patterned by focused ion beam (FIB) were used. In this work we demonstrate the possibility of determining the AFM tip geometry and the tilt based on several different large structures. A proven algorithm was developed for the reconstruction of the tips. The shape of FIB-structured foils was determined by electron microscopy prior to AFM measurements. This new method for determining tip shape is also presented as it compares to other current methods. In this case a discussion on the stability and advantages of the new method is presented.

In 2 O 3 nanoparticles were synthesized at low substrate temperatures by the metal organic chemical vapor deposition technique. Nanoparticles with a mean diameter from 3 to 33 nm can be obtained by varying the growth temperature. Photoreduction and oxidation studies were carried out for particle-containing layers exhibiting a resistance change of more than five orders of magnitude after ultraviolet irradiation and oxidation by ozone. A grain boundary model was proposed to understand the photoreduction and oxidation mechanism for the nanoparticle layers. It was suggested that by photoreduction the nanoparticles are reactivated throughout the layer. The Schottky barrier between the nanoparticles decreases inducing a reduction of the space-charge-limited region. After oxidation, a completely depleted space-charge region covering the whole volume of In2O3 nanoparticles is formed. Furthermore, the bulk diffusion process dominates the response of thick layers during the oxidation process. By decreasing the layer thickness down to 10 nm, surface effects dominate, resulting in an ultrafast response to changes in ozone concentration. The typical response time of very thin In2O3 nanoparticle layers was determined to be less than 1 s.

In this work, we propose a method to estimate basic parameters like the rms roughness and the mean grain size of nanocrystalline thin films on rough substrates. The method is based on the analysis of the power spectral density (PSD) of the surface profile, which allows distinguishing between the two participating components from surface and film. The effectiveness will be demonstrated for thin NiOx layers for gas sensing on Al2O3 ceramic substrates, and for protective WC coatings on steel.

Nanocrystalline NiO thin films were deposited by dc reactive magnetron sputtering in a mixture of oxygen and argon and subsequently coated by Au on a NiO film surface. Very thin Au overlayers with a thickness of about 1 and 7 nm have been prepared by magnetron sputtering. Then, the surface modified NiO films have been analysed by TEM, EDX and SEM. NiO thin films showed a polycrystalline structure with the size of nanocrystals ranging from a few nanometers to 10 nm. Electrical responses of NiO-based structure towards hydrogen have been measured.

In atomic force microscopy (AFM), knowledge of the probe (tip) geometry is a critical factor for obtaining reproducible images. This is particularly important for measurements in the contact mode, in which a certain amount of wear of the probe always occurs affecting the image quality of small, flat and/or larger surface structures. In addition to probe geometry, the slope of the probe with respect to the sample is of importance. In this work, probe geometry is determined by the use of structured foils obtained using focused ion beam (FIB). In this manner, we demonstrate the possibility of determining the AFM probe geometry and the slope on the basis of differently-sized structures. An established algorithm was implemented for the reconstruction of the probes. The shape of FIB structured foils was determined separately by scanning electron microscopy (SEM).