Intrinsic charge transport properties of an organic single crystal determined using a multiterminal thin-film transistor

We present an experimental approach to determine the intrinsic field-effect mobility in an organic single crystal as a function of the in-plane crystal-axis direction. Using a multiterminal geometry the experiment also excludes the effects of the contact resistances on the transport properties. We have applied the method to quaterthiophene thin films. At gate voltages above the threshold voltage, the channel conductance varies linearly with the applied gate voltage. The resulting charge carrier mobility is 1.2×10−3 cm2/V s. This value is constant over a period of weeks of continuous operation and does not vary from sample to sample, in contrast to the typically observed lower mobilities of polycrystalline quaterthiophene thin-film transistor devices. These results emphasize the need for well-characterized model systems to study the intrinsic transport properties of organic materials

Surfactant effect in heteroepitaxial growth. The Pb - Co/Cu(111) case

A MonteCarlo simulations study has been performed in order to study the effect of Pb as surfactant on the initial growth stage of Co/Cu(111). The main characteristics of Co growing over Cu(111) face, i.e. the decorated double layer steps, the multiple layer islands and the pools of vacancies, disappear with the pre-evaporation of a Pb monolayer. Through MC simulations, a full picture of these complex processes is obtained. Co quickly diffuses through the Pb monolayer exchanging place with Cu atoms at the substrate. The exchange process diffusion inhibits the formation of pure Co islands, reducing the surface stress and then the formation of multilayer islands and the pools of vacancies. On the other hand, the random exchange also suppress the nucleation preferential sites generated by Co atoms at Cu steps, responsible of the step decoration.Comment: 4 pages, latex, 2 figures embedded in the tex

Anisotropy of Growth of the Close-Packed Surfaces of Silver

The growth morphology of clean silver exhibits a profound anisotropy: The growing surface of Ag(111) is typically very rough while that of Ag(100) is smooth and flat. This serious and important difference is unexpected, not understood, and hitherto not observed for any other metal. Using density functional theory calculations of self-diffusion on flat and stepped Ag(100) we find, for example, that at flat regions a hopping mechanism is favored, while across step edges diffusion proceeds by an exchange process. The calculated microscopic parameters explain the experimentally reported growth properties.Comment: RevTeX, 4 pages, 3 figures in uufiles form, to appear in Phys. Rev. Let

Monolayer resolution in medium-energy ion-scattering experiments on the NiSi2(111) surface

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Shared decision-making with people with intellectual disabilities in the last phase of life : a scoping review

Shared decision-making (SDM) is the process in which healthcare professionals and patients jointly discuss and decide which care and treatment policy is to be followed. The importance of SDM is increasingly being recognised across health settings, including palliative care. Little is known about SDM with people with intellectual disabilities (IDs) in the last phase of life. This review aimed to explore to which extent and in which way people with ID in the last phase of life are involved in decision-making about their care and treatment. In this scoping review, we systematically searched in the Embase, Medline and PsycINFO databases for empirical studies on decision-making with people with ID in the last phase of life. Of a total of 281 identified titles and abstracts, 10 studies fulfilled the inclusion criteria. All focused on medical end-of-life decisions, such as foregoing life-sustaining treatment, do-not-attempt-resuscitation orders or palliative sedation. All studies emphasise the relevance of involving people with ID themselves, or at least their relatives, in making decisions at the end of life. Still, only two papers described processes of decision-making in which persons with ID actively participated. Furthermore, in only one paper, best practices and guidelines for decision-making in palliative care for people with ID were defined. Although the importance of involving people with ID in the decision-making process is emphasised, best practices or guidelines about what this should look like are lacking. We recommend developing aids that specifically support SDM with people with ID in the last phase of life

Single crystallites in "planar polycrystalline" oligothiophene films:Determination of orientation and thickness by polarization microscopy

Thin films of evaporated oligothiophenes (alpha-nT, n = 4-8) show a "planar polycrystalline" structure: each of the individual crystallites has a random azimuthal orientation, the (a, b) face of its unit cell is aligned with the surface plane, We introduce a technique to determine the orientation and thickness of such aligned thiophene crystals by optical polarization microscopy. Due to the optical birefringence of the crystal, It appears with different colors in the microscope dependent on its orientation and thickness. To support the method proposed, we solve Maxwell's equations and obtain quantitative agreement with the observed colors. The organic crystal shows biaxial anisotropy. For unsubstituted quaterthiophene, alpha-4T, we find effective refractive indices n(b) = 1.84 +/- 0.1 and n(a) = 1.61 +/- 0.1 for waves under normal incidence. Our conclusions are fully confirmed by atomic force microscopy with molecular resolution. Our analyses result in a simple recipe to obtain the directions of the rr and b crystal axes from the optical experiment. (C) 1998 American Institute of Physics. [S0021-8979(98)02007-6]

Shared decision making with frail people with intellectual disabilities in the palliative phase:A process evaluation of the use of the In-Dialogue conversation aid in practice

Background: This study reports the process evaluation of the In-Dialogue conversation aid to facilitate shared decision-making with people with intellectual disabilities in the palliative phase. Methods: Training for In-Dialogue was evaluated by 53 support staff members through questionnaires. The use of In-Dialogue in four residential care facilities for frail people with mild to severe intellectual disabilities was evaluated with semi-structured interviews with five relatives, nine support staff and three people with intellectual disabilities. Results: Most participants considered the training helpful to apply shared decision-making. Sixty-three people with intellectual disabilities participated in In-Dialogue conversations. Almost all interviewees stated that these conversations provided additional insight into people's concerns and preferences. Involvement of people with profound intellectual disabilities and their relatives appeared to be challenging.Conclusion: Conversations about illness and the end of life appeared to be feasible with the In-Dialogue conversation aid and provided insight into people's experiences and preferences.</p

Island nucleation in the presence of step edge barriers: Theory and applications

We develop a theory of nucleation on top of two-dimensional islands bordered by steps with an additional energy barrier $\Delta E_S$ for descending atoms. The theory is based on the concept of the residence time of an adatom on the island,and yields an expression for the nucleation rate which becomes exact in the limit of strong step edge barriers. This expression differs qualitatively and quantitatively from that obtained using the conventional rate equation approach to nucleation [J. Tersoff et al., Phys. Rev. Lett.72, 266 (1994)]. We argue that rate equation theory fails because nucleation is dominated by the rare instances when two atoms are present on the island simultaneously. The theory is applied to two distinct problems: The onset of second layer nucleation in submonolayer growth, and the distribution of the sizes of top terraces of multilayer mounds under conditions of strong step edge barriers. Application to homoepitaxial growth on Pt(111) yields the estimate $\Delta E_S \geq 0.33$ eV for the additional energy barrier at CO-decorated steps.Comment: 13 pages, 3 figure

Surface Kinetics and Generation of Different Terms in a Conservative Growth Equation

A method based on the kinetics of adatoms on a growing surface under epitaxial growth at low temperature in (1+1) dimensions is proposed to obtain a closed form of local growth equation. It can be generalized to any growth problem as long as diffusion of adatoms govern the surface morphology. The method can be easily extended to higher dimensions. The kinetic processes contributing to various terms in the growth equation (GE) are identified from the analysis of in-plane and downward hops. In particular, processes corresponding to the (h -> -h) symmetry breaking term and curvature dependent term are discussed. Consequence of these terms on the stable and unstable transition in (1+1) dimensions is analyzed. In (2+1) dimensions it is shown that an additional (h -> -h) symmetry breaking term is generated due to the in-plane curvature associated with the mound like structures. This term is independent of any diffusion barrier differences between in-plane and out of-plane migration. It is argued that terms generated in the presence of downward hops are the relevant terms in a GE. Growth equation in the closed form is obtained for various growth models introduced to capture most of the processes in experimental Molecular Beam Epitaxial growth. Effect of dissociation is also considered and is seen to have stabilizing effect on the growth. It is shown that for uphill current the GE approach fails to describe the growth since a given GE is not valid over the entire substrate.Comment: 14 pages, 7 figure

Formation of epitaxial β-FeSi2 films on Si(001) as studied by medium-energy ion scattering

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