Ken Ritley

Ken Ritley
Bern University of Applied Sciences | BFH · Department of Engineering and Information Technology

PhD

About

41
Publications
788
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722
Citations
Citations since 2017
0 Research Items
136 Citations
2017201820192020202120222023051015202530
2017201820192020202120222023051015202530
2017201820192020202120222023051015202530
2017201820192020202120222023051015202530

Publications

Publications (41)
Article
The scaling exponents alpha, beta, and 1/z in thin films of the organic molecule diindenoperylene deposited on SiO2 under UHV conditions are determined. Atomic-force microscopy, x-ray reflectivity, and diffuse x-ray scattering were employed. The surface width displays power law scaling over more than 2 orders of magnitude in film thickness. We obta...
Article
The planar organic molecule 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) deposited on Ag(111) has been used as a model system for organic molecular-beam epitaxy (OMBE). The crystal structure and morphology of thin films in the range of 50-200 Å have been examined in detail as a function of the growth parameters by x-ray diffraction and nonc...
Article
A process is described whereby highly ordered arrays of epitaxial thin-film nano- and mesostripes can be grown using molecular beam epitaxy (MBE) techniques on M-plane sapphire α-Al2O3 (100) substrates. The planar sapphire substrate surface is unstable, and spontaneously forms primarily (101) and (102) nanofacets upon annealing at a high temperatur...
Article
A process is described whereby highly ordered arrays of epitaxial thin-film nano- and mesostripes can be grown using molecular beam epitaxy (MBE) techniques on M-plane sapphire alpha-Al2O3 (10 (1) over bar0) substrates. The planar sapphire substrate surface is unstable, and spontaneously forms primarily ((1) over bar 101) and (1 (1) over bar 02) na...
Article
The analysis of X-ray standing wave (XSW) data for the determination of structural parameters of adsorbates (coherent position, PCh, and coherent fraction, FCh) is usually done in the dipole approximation. Using carbon and oxygen containing molecular adsorbates on Ag(111), we show how the non-dipolar contributions can be quantified and that they ca...
Article
The ability to analyze the topography of two-dimensional images is essential for many applications in the physical, chemical, and biological sciences. We describe a computer program to graphically display and perform numerical operations on large two-dimensional arrays of double-precision numbers. It contains an intuitive graphical user interface,...
Article
The structure and epitaxy of thin films of PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride, C24H8O6) grown at 180°C on Ag(111) have been studied in situ using grazing-incidence X-ray diffraction. An extensive map of Bragg reflections has been recorded. A pronounced peak splitting is found, which provides evidence for the coexistence of α and β-...
Article
A portable UHV molecular beam deposition system has been developed for synthesis, in situ, and real-time x-ray diffraction measurements of organic thin films, multilayers, and superlattices. The system has been optimized for small size, while still incorporating full features necessary to achieve thin film growth under molecular beam epitaxy (MBE)...
Article
The structure and epitaxy of thin films of PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride, C24H8O6) grown at 180 degreesC on Ag(1 1 1) have been studied in situ using grazing-incidence X-ray diffraction. An extensive map of Bragg reflections has been recorded. A pronounced peak splitting is found, which provides evidence for the coexistence of...
Article
Thin films of ZrO 2 were deposited from aqueous solution on Si(100) substrates precovered by functionalized alkyltrichlorosilane self-assembled monolayers (SAMs). The interface structure, thermal stability, and densification of these films in the temperature range from room temperature to 750 °C in vacuum were measured using in situ x-ray reflectiv...
Article
Thin films of ZrO2 were deposited from aqueous solution on Si(100) substrates precovered by alkyltrichlorosilane self-assembled monolayers. The interface structure, thermal stability and densification of these films in the temperature range from room temperature to 750 degree(s)C in vacuum were measured using in situ x-ray reflectivity. The growth...
Article
A MBE growth protocol has been developed to grow thin films and superlattices of rare earths with the HCP (1 1¯ 0 0) b-axis normal to the growth plane. To explore the role of strain, clamping and symmetry-breaking in modifying the magnetic ordering temperatures, ultrathin films of strained Dy have been prepared between YxLu(1-x) alloy buffer layers...
Article
The rare earth metals have the largest known magnetostrictions, so that their magnetic properties and structural properties are strongly coupled. This coupling is ideally suited for investigation with thin films, in which single crystal films of high quality can be prepared on substrates which cause their lattice parameters to differ from bulk valu...
Article
This paper gives un update on stability and protection of CICCs, with the main focus on simple analytical formulae to be used for cable design purposes. The status of the present understanding is reviewed, collecting the main results as far as possible into a consistent notation. Various additional aspects of present interest are briefly discussed,...
Article
Accurately modeling the behavior of a beam of positrons incident upon a solid is of crucial importance for depth-profiling and data analysis in slow positron experiments. We describe a suite of Fortran programs to perform a Monte Carlo calculation of positron implantation in amorphous metals and small bandgap semiconductors. This provides statistic...
Article
A process is described whereby hcp rare-earth metals can be grown heteroepitaxially as high-quality single-crystal films with the b axis normal to the growth plane. The growth employs molecular beam epitaxy, starting from available sapphire substrates. The results of characterization by several techniques are described. © 1998 American Institute of...
Article
The magnetic properties of MBE-grown Dy/Y superlattices (SLs) have been studied by neutron diffraction. The SL growth direction is at an angle of approximately 35° to the c-axis instead of being along one of the principal axis directions. The results confirm the coexistence of helical antiferromagnetic order and ferromagnetic order up to the Néel t...
Article
SPRITE (Simulation of Particle Reemission, Implantation and Transmission--Extensible) is a Fortran computer program designed to model the transport of a stream of energetic particles as they scatter through a solid or multilayer. SPRITE is intended to be a user-friendly and easily-extensible engine for performing basic transport calculations, and S...
Article
Neutron diffraction studies on Dy/Y superlattices grown with the c axis at an angle of approximately 35° to the film plane reveal a coexistence of helical antiferromagnetic order and ferromagnetic order. The coexistence of magnetic phases has been determined to arise from the development during growth of surface facets of the Y buffer layer, which...
Article
Dy/Y superlattices have been grown by molecular beam epitaxy with the film normal between [1bar 103] and [1bar 102]. During the growth of the rare earth material strong facets develop having smooth (1bar 102) surfaces on one facet side and smooth (0001) terraces on the other side. Depending on the step density, the (0001) terraces form different su...
Article
Epitaxial Dy/Y rare earth superlattices were prepared by molecular beam epitaxy on Ta(211) and Nb(211) buffer layers on α-Al2O3 (100) and characterized via in situ reflection high-energy electron diffraction (RHEED), in situ scanning tunneling microscopy (STM) and ex situ X-ray and neutron diffraction. The Y buffer and the Dy/Y superlattice are fou...
Article
Epitaxial (11¯02) Dy/Y rare earth superlattices and a thick (11¯02) Dy film, grown on sapphire with Y/Ta buffer layers, have been prepared by molecular beam epitaxy. Neutron diffraction and SQUID magnetization measurements on a single 200 nm thick (11¯02) Dy layer showed nearly bulk behavior. However, for the (11¯02) Dy/Y superlattices we found dif...
Conference Paper
Epitaxial <(1(1)over bar 02)> Dy/Y rare earth superlattices and a thick <(1(1)over bar 02)> Dy film, grown on sapphire with Y/Ta buffer layers, have been prepared by molecular beam epitaxy. Neutron diffraction and SQUID magnetization measurements on a single 200 nm thick <(1(1)over bar 02)> Dy layer showed nearly bulk behavior. However, for the <(1...
Article
Diffraction of neutron standing waves in thin films has been demonstrated for the first time with experiments on an epitaxial Y/Gd/Y/Nb/Al2O3 sample. Resonance enhancement in the diffraction intensity has been observed. The new diffraction scheme for neutrons and X-rays provides an oscillatory spatial concentration in thin films, in contrast to the...
Article
Epitaxial [Dymid Y] rare earth superlattices and a thick Dy film have been grown along the (1bar 102) direction on sapphire substrates by molecular beam epitaxy. This direction is approximately 42^circ away from the c-axis propagation direction for the helimagnetic structure of Dy. Neutron diffraction and SQUID magnetization measurements on the 200...
Article
Diffraction of neutron standing waves in thin films has been demonstrated with experiments on an epitaxially grown Y/Gd/Y/Nb/Al2O3 sample. Resonance enhancement in the diffraction intensity has been observed. The diffraction intensity distribution has been well explained within the distorted-wave Born approximation. The effect of surface miscut and...
Article
Thin film reactions between 100 nm of Ni and 400 nm of Ge deposited on thermally oxidized Si wafers have been studied as a function of annealing conditions, using X-ray diffraction (XRD), cross-sectional transmission electron microscopy, four-point kelvin resistance measurements and X-ray photoelectron spectroscopy (XPS); these last two techniques...
Conference Paper
Existing Monte‐Carlo models are capable of simulating the behavior of positrons incident at keV energies, then following the energy loss process to arbitrary final kinetic energies of from 20 eV to 100 eV. In the present work we describe a Monte‐Carlo simulation of the final stages of positron thermalization in Al, from 25 eV to thermal energies, v...
Article
A detailed knowledge of low‐energy positron implantation is of considerable importance for depth profiling and data analysis in slow positron experiments. Existing Monte Carlo models are capable of simulating the behavior of positrons incident at keV energies, then following the energy‐loss process to final kinetic energies of from 20 to 100 eV. A...
Article
Full-text available
We compare electrical resistance noise in commensurate and incommensurate phases of the spin-density wave (SDW) in Cr and dilute CrMn alloys. The commensurate phase gives much less polarization fluctuation noise than the incommensurate phase. The incommensurability of the SDW and the lattice in Cr may affect the SDW dynamics through the existence o...
Article
Full-text available
High-resolution X-ray scattering studies of niobium [10] films grown by molecular beam epitaxy on sapphire [1120] substrates have revealed novel structural features. In transverse scans of the out-of-plane Nb (110) Bragg peak we find two components, the sharper of which implies mosaicities an order of magnitude better than bulk single crystal Nb. T...
Article
We have investigated the elastic effects of hydrogen loading on thin films of niobium. It has been shown recently [1] that epitaxial Nb films grown with MBE on sapphire substrates exhibit a one-dimensional expansion, perpendicular to the film surface, on loading with hydrogen, up to a critical hydrogen concentration. This can be understood as an ep...
Article
The energy loss, stopping profiles and backscattered fraction and energy distribution of positrons and electrons with incident energies up to 10 keV incident upon amorphous elemental metals are stochastically modeled within a Monte-Carlo framework. Elastic Coulomb scattering is considered using the partial wave approximation for low incident energi...
Article
This paper reports on a search for anomalous heat generation and tritium production associated with cold fusion in electrolytically deuterided palladium which was carried out for < 180 days. Ten cathodes were mounted in electrolytic cells with LiOD and LiOH electrolytes and galvanostatically charged at current densities between 15 and 348 mA/cm²....
Article
Knowledge of the basic electrochemical behavior found in typical cold fusion experiments is important to understanding and preventing experimental errors. For a Pd/LiOH(D)/Pt electrochemical cell, the applied cell voltage/current relationship (the effective cell resistance) does not obey Ohm's law directly, but instead exhibits a complicated respon...
Article
The results of a series of two experiments to observe cold fusion in electrolytically deuterated Pd are reported. The experiments were sensitive to excess heat, sudden temperature fluctuations, neutron and tritium production. No evidence was found to substantiate recent claims regarding this phenomena. 7 refs., 7 figs., 2 tabs.
Article
Full-text available
Thin films and multilayers of organic molecules are receiving considerable attention due to their exciting optical, optoelectronic, and electronic properties and their potential tunability. Several applications like organic light-emitting devices, solar cells, sensors, transistors, etc. have already been demonstrated [1]. However, compared to inorg...

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