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Controlling the texture of a nanostructured thin film is an important issue for numerous applications. Although the texture formation of thin films grown by oblique angle deposition has been investigated for a large number of materials, a general trend is missing so far. Thus, the texture formation must be evaluated on a case-by-case basis. In the present study, Molybdenum thin films consisting of separated tilted columns are fabricated by electron beam evaporation at a highly oblique deposition geometry at room temperature on natively and thermally oxidized Si(100) substrates. The film thickness is varied between 10 nm and 2.5 μm. The film morphology is investigated by scanning electron microscopy. Various transmission electron microscope (TEM) measurements on individual Molybdenum columns reveal a single crystalline structure of those columns. It is discussed why the tilt angle of the Molybdenum columns is not equal to the tilt angle of the crystals´ [110] direction. Reflection high-energy electron diffraction, X-ray diffraction in-plane pole figure measurements and cross-sectional TEM specimen are used to further investigate the crystallinity as well as the texture evolution of the Molybdenum thin films depending on the film thickness. The texture changes with increasing film thickness from arbitrarily oriented crystallites to a biaxially textured thin film with a minor fiber texture contribution. The selection of crystal orientations with increasing film thickness is discussed with view to the evolutionary selection process among the growing columns.

Growing highly crystalline nanowires over large substrate areas remains an ambiguous task nowadays. Herein, a time-efficient and easy-to-handle bottom-up approach is demonstrated that enables the self-assembled growth of biaxially textured Ti thin films composed of single-crystalline nanowires in a single-deposition step. Ti thin films are deposited under highly oblique incidence angles by electron beam evaporation on amorphous substrates. Substrate temperature, angle of the incoming particle flux, and working pressure are varied to optimize the crystallinity in those films. Height-resolved structure information of individual nanowires is provided by a transmission electron microscopy (TEM) nanobeam, high-resolution TEM, and electron diffraction. Ti nanowires are polycrystalline at 77 K, whereas for ���300 K, single-crystalline nanowires are tendentially found. The Ti crystals grow along the thermodynamically favored c-direction, but the nanowires��� tilt angle is determined by shadowing. Biaxially textured Ti thin films require a certain temperature range combined with highly oblique deposition angles, which is proved by X-ray in-plane pole figures. A general correlation between average activation energy for surface self-diffusion and melting point of metals is given to estimate the significant influence of surface self-diffusion on the evolution of obliquely deposited metal thin films.

Nickel based nanostructures are grown by glancing angle deposition (GLAD) on flat and pre-patterned substrates. These fabricated porous thin films were subsequently coated by pulsed electroplating with gold. The morphology and conformity of the gold coating were investigated by scanning electron microscopy and X-ray diffraction. Controlled growth of closed gold layers on the nanostructures could be achieved, while the open-pore structure of the nanosculptured thin films was preserved. Such gold coated nanostructures are a candidate for optical sensing and catalysis applications. The demonstrated method can be applied for numerous material combinations, allowing to provide GLAD thin films with new surface properties.

Metals with a wide range of melting points are deposited by electron beam evaporation under oblique deposition geometry on thermally oxidized Si substrates. During deposition the sample holder is cooled down to 77 K. It is observed that all obliquely deposited metals grow as tilted, high aspect ratio columns and hence with a similar morphology. A comparison of such columns with those deposited at room temperature (300 K) reveals that shadowing dominates the growth process for columns deposited at 77 K, while the impact of surface diffusion is significantly increased at elevated substrate temperatures. Furthermore, it is discussed how the incidence angle of the incoming particle flux and the substrate temperature affect the columnar tilt angles and the porosity of the sculptured thin films. Exemplarily for tilted Al columns deposited at 77 K and at 300 K, in-plane pole figure measurements are carried out. A tendency to form a biaxial texture as well as a change in the crystalline structure depending on the substrate temperature is found for those films.

Physical vapor deposition is a fundamental tool to create thin films for countless applications. Deposition at oblique vapor incidence angles can lead to the growth of thin films with dramatically changed morphological features. Techniques such as oblique angle deposition (OAD) and glancing angle deposition (GLAD) utilize this fact to create self-organized nanostructures on surfaces. The changed columnar microstructure of such thin films significantly influences the film properties. The film density, for instance, influences the refractive index and therefore has impact for optical applications, like filters or antireflection coatings. Understanding the influence of the incidence angle in physical vapor deposition is an important step that allows tailoring the nanostructured surfaces for specific applications not only in optics, but also for catalysis or biosensing usage. To investigate thin film growth at oblique deposition conditions, silicon, germanium, and molybdenum nanostructured thin films were dep...

The well-reproducible, fast and cost-effective nanostructuring is a big challenge for laser methods. The laser nanostructuring of fused silica assisted by chromium nanotriangles was studied using a KrF excimer laser (λ = 248 nm, Δtp = 25 ns, top hat beam profile). Therefore, a fused silica substrate was covered with periodically ordered polystyrene (PS) spheres with a diameter of 1.59 μm. Subsequently, this system was covered with 30 nm chromium by electron beam evaporation. Afterwards the PS spheres were removed and the bare and resultant periodic Cr triangles were irradiated. The laser irradiation with high laser fluences resulted in a removal of the chromium and in localized modifications of the fused silica like a localized ablation of the fused silica. The resultant structures were studied by scanning electron (SEM) and atomic force microscopy (AFM) as well as the surface composition was analysed by energy-dispersive X-ray spectroscopy (EDX). The laser process allows the production of well-defined periodic hole structures into the fused silica surface where the resultant surface structure depends on the laser parameters. The multi-pulse irradiation of the Cr/SiO2 sample with moderate laser fluences (Φ ∼ 650 mJ/cm2) allows the fabrication of periodic pyramidal-like structures (depth Δz = 130 nm).

Self-organized processes are of special interest for the laser-induced nanostructuring of surfaces. In this study we combined two self-organized processes: the microsphere lithography and the molten phase transformation for the nanostructuring of dielectrics. A fused silica substrate was covered with periodically ordered polystyrene (PS) spheres and the system was subsequently covered with 30 nm chromium. Afterwards the PS spheres were removed and the bare and resultant periodic Cr triangles were irradiated in two steps using a KrF excimer laser. First step: A low laser fluence treatment results in a melting and shape transformation of the triangles. Second step: A high laser fluence treatment of the pre-treated surface results in a nanostructuring of the dielectric surface (and removal of the metal). The surface topography was studied by scanning electron microscopy. Furthermore, the different steps were simulated and compared with the experimental results.

Electrochemical metallization memories have received much attention as candidates for next generation non-volatile memory applications, due to their fast switching speed, simple structure, high scalability and low energy consumption. Chalcogenide compounds like Ge–Sb–Te-based materials are extensively studied solid electrolytes for such devices and considered within the most promising candidates. In this work, the influence of different electrode materials on bipolar resistive switching characteristics of amorphous Ge–Sb–Te thin films with close composition to 2:2:5, prepared by pulsed laser deposition, is studied. Detailed investigations by current-voltage measurements, secondary ion mass spectrometry and cross-sectional transmission electron microscopy in conjunction with energy-dispersive x-ray spectroscopy are presented. Depending on the utilized electrode material, analog switching (Cu, Ag, Ti), digital switching (Co, Cr, Ta, Al) or no switching (Pt, Au and Cr-CrO x ) occurs. This work shows that the switching behavior of Ge–Sb–Te strongly depends on the solubility and reactivity of the electrode material.

A biosensor chip is developed for the detection of a protein biomarker of endocrine disrupting compounds, vitellogenin (Vg) in aquatic environment. The sensor chip is fabricated by immobilizing anti-Vg antibody on 4-Aminothiophenol (4-ATP) coated nanosculptured thin fi lms (nSTFs) of silver on Si substrates. The biosensor is based on the SERS of 4-ATP, enhanced by the Ag nSTFs. Before the fabrication of the sensor, the performance of the enhancement is optimized with respect to the porosity of nSTFs. Further, the biosensor is developed on the nSTF with optimized enhancement. The SERS signals are recorded from the sensor chip for varying concentrations of Vg. A control experiment is performed on another similar protein Fetuin to confi rm the specifi city of the sensor. The repeatability and reusability of the sensor, along with its shelf life are also checked. The limit of detection of the sensor is found to be 5 pg mL −1 of Vg in PBS within our experimental window. Apart from high sensitivity, specifi city and reusability, the present sensor provides additional advantages of miniaturization, requirement of very small volumes of the analyte solution (15 µL) and fast response as compared to conventional techniques e.g., ELISA, as its response time is less than 3 minutes.

Advanced Pulsed Laser Deposition (PLD) processes allow the growth of oxide thin film heterostructures on large area substrates up to 4-inch diameter, with flexible and controlled doping, low dislocation density, and abrupt interfaces. These PLD processes are discussed and their capabilities demonstrated using selected results of structural, electrical, and optical characterization of superconducting (YBa2Cu3O7−δ), semiconducting (ZnO-based), and ferroelectric (BaTiO3-based) and dielectric (wide-gap oxide) thin films and multilayers. Regarding the homogeneity on large area of structure and electrical properties, flexibility of doping, and state-of-the-art electronic and optical performance, the comparably simple PLD processes are now advantageous or at least fully competitive to Metal Organic Chemical Vapor Deposition or Molecular Beam Epitaxy. In particular, the high flexibility connected with high film quality makes PLD a more and more widespread growth technique in oxide research.

Nanostructured Ti thin films are fabricated by oblique angle deposition (OAD) in combination with electron beam evaporation in an ultrahigh vacuum chamber at room temperature on thermally and natively oxidized Si(100) substrates. The incidence angle θOAD of the incoming particle flux with respect to the substrate normal is varied between 70° ≤ θOAD ≤ 84°. This highly oblique deposition geometry leads to the formation of highly porous, thin, crystalline films consisting of separated Ti columns that are oriented toward the incoming particle flux. The influence of the incidence angle on the texture, morphology, and columnar tilt angles of these Ti thin films is investigated. It is found that the texture depends on the angle θOAD of the incoming particle flux. High-resolution transmission electron microscopy reveals that highly oblique deposited Ti columns tend to grow with single crystalline morphology. The orientation of the lattice planes in the Ti columns with respect to the substrate normal changes remarkably as the incidence angle is varied. Moreover, the orientation of the lattice planes differs from the growth direction of the columns. The samples are analyzed using x-ray diffraction measurements such as in-plane pole figure measurements and θ-2θ x-ray diffraction patterns, as well as by using transmission electron microscopy and scanning electron microscopy.Nanostructured Ti thin films are fabricated by oblique angle deposition (OAD) in combination with electron beam evaporation in an ultrahigh vacuum chamber at room temperature on thermally and natively oxidized Si(100) substrates. The incidence angle θOAD of the incoming particle flux with respect to the substrate normal is varied between 70° ≤ θOAD ≤ 84°. This highly oblique deposition geometry leads to the formation of highly porous, thin, crystalline films consisting of separated Ti columns that are oriented toward the incoming particle flux. The influence of the incidence angle on the texture, morphology, and columnar tilt angles of these Ti thin films is investigated. It is found that the texture depends on the angle θOAD of the incoming particle flux. High-resolution transmission electron microscopy reveals that highly oblique deposited Ti columns tend to grow with single crystalline morphology. The orientation of the lattice planes in the Ti columns with respect to the substrate normal changes remar...

A nanobiosensor chip, utilizing surface enhanced Raman spectroscopy (SERS) on nanosculptured thin films (nSTFs) of silver, was shown to detect Escherichia coli (E. coli) bacteria down to the concentration level of a single bacterium. The sensor utilizes highly enhanced plasmonic nSTFs of silver on a silicon platform for the enhancement of Raman bands as checked with adsorbed 4-aminothiophenol molecules. T-4 bacteriophages were immobilized on the aforementioned surface of the chip for the specific capture of target E. coli bacteria. To demonstrate that no significant non-specific immobilization of other bacteria occurs, three different, additional bacterial strains, Chromobacterium violaceum, Paracoccus denitrificans and Pseudomonas aeruginosa were used. Furthermore, experiments performed on an additional strain of E. coli to address the specificity and reusability of the sensor showed that the sensor operates for different strains of E. coli and is reusable. Time resolved phase contrast microscopy of the E. coli-T4 bacteriophage chip was performed to study its interaction with bacteria over time. Results showed that the present sensor performs a fast, accurate and stable detection of E. coli with ultra-small concentrations of bacteria down to the level of a single bacterium in 10 μl volume of the sample.

A biosensor has been fabricated by using the SERS of 4-Aminothiophenol (4-ATP) on optimized nano-sculptured thin films (nSTFs) of silver over Si substrates. The limit of detection is as small as 5 pg/ml of vitellogenin