Early Stage Of Deposition Research Articles

Non-marine ostracod biostratigraphy of Cretaceous rift lake deposits (Sousa Basin, Brazil): Paleogeographical implications and correlation with Gondwanic basins

The Cretaceous section of the Sousa Basin represents alluvio-fluvio-lacustrine deposits from rift lakes generated in NE Brazil as a consequence of the West Gondwana break-up process, marked by progressive separation of the African and South American plates. The chronostratigraphic age of the sedimentary succession is controversial due to the few biostratigraphic data available, based on palynomorphs, ostracods and ‘conchostracans’ (Spinicaudata), and taxonomic problems of some of the fossils. Non-marine ostracods (microcrustaceans) are useful index fossils and have been used for a regional biozonation of the lacustrine deposits. Due to this factor non-marine ostracods from the core 2-FC-01-PB, which comprises rocks of the Sousa Formation (Rio do Peixe Group), were analysed. The core 2-FC-01-PB assemblage includes index taxa for biozones RT-002 to RT-005 (Alicenula leguminella, Brasacypris ovum, Cypridea ambigua and Reconcavona swaini), indicating a Berriasian to Hauterivian age (Rio da Serra/Aratu local stages). The previous assignment of a Jurassic age to the early stage of deposition of the Rio do Peixe Group is refuted here. We discuss and revise the stratigraphic range and paleogeographical distribution of relevant index ostracods. Our revised non-marine ostracod biostratigraphy facilitates correlations of non-marine strata of the Sousa Basin with those of Brazilian (Recôncavo, Tucano and Sergipe) and African (Gabon and Congo) sedimentary basins of West Gondwana.

Effects of Asian Dust and Phosphorus Input on Abundance and Trophic Structure of Protists in the Southern Yellow Sea

To reveal the effects of Asian dust and phosphorus (P) input on the structure and function of micro-food web in the Yellow Sea, an experiment was conducted onboard the southern Yellow Sea where P was deficient. The response of the abundance and trophic structure of planktonic protists to different concentrations of dust and P were studied. The results showed that the sand-dust deposition presented variable effects on different sizes of protists during incubation periods. At the initial stage of incubation with dust, the amount of all sizes of autotrophic protists, especially 10–20 µm, were improved; on the contrary, the heterotrophic and mixotrophic protists were inhibited. At the late period, the increase of autotrophic protists was restricted, while the 2–5 µm heterotrophic and mixotrophic protists obviously increased. Similarly, adding P demonstrated the obviously positive effect on the 10–20 µm autotrophic protists at the initial period, and then the growth was restricted at the late period. These results were consistent with that of sand-dust deposition. Hence, it could be presumed that the positive effect of sand-dust deposition on autotrophic protists in the southern Yellow Sea was achieved by the release of P from dust. P in the early stage of sand-dust deposition promotes the growth of large-size autotrophic protists, which may accelerate red tides in eutrophic ocean. The stimulation of small-size heterotrophic protists at the late period of sand-dust deposition contributed to the material cycle and food transmission in the ocean. Therefore, the effects of sand-dust deposition on the abundance and trophic structure of different sizes of planktonic protists could change the structure of micro-food web in the southern Yellow Sea and further affected the ecological function of planktonic protists.

Characterization of initial film formation during cathodic electrodeposition of coatings

The purpose of this study was to develop a detailed understanding of the initial stages of coating electrodeposition. Of particular interest were the changes that take place during the induction period before a steep change in the voltage at constant current is observed. Experiments designed to elucidate the role of concentration buildup clearly showed that a local change in concentration was not solely responsible for the observed induction period. This conclusion is further supported by experiments where the induction time at a specified current was observed to vary with the type of substrate used for deposition. Consequently, scanning electron microscopy was used to study the morphology of the initial deposit on different substrate surfaces including bare steel, galvanized steel, and phosphated steel. It was found that the initial film formed preferentially at specific locations on the metal surfaces, such as on defects or scratches, where the local current density was likely to be higher. The initial film also appeared to form around gas bubbles that were present on the substrate surface. Preferential film deposition at areas of high local current density was observed directly in experiments with intentionally scratched surfaces. The additional insight provided by this study will help to improve our ability to model accurately the early stages of E-coat deposition and, eventually, the accuracy of large-scale simulations for process performance prediction and optimization.

Stratigraphic analysis of a sediment pond within the New England Mud Patch: New constraints from high-resolution chirp acoustic reflection data

The New England Mud Patch (NEMP) is an anomaly on the Atlantic coast of North America. This ~13,000 km2 area, located south of Cape Cod between the ~60 m and 160 m isobaths, is a region of active fine-grained deposition on a shelf that is predominantly non-depositional or erosional. Prior studies theorized that NEMP sediments are derived from fines winnowed from Georges Bank, transported westward by coastal currents, and then settled in more quiescent conditions. A chirp seismic reflection (2015) and coring (2016) survey of part of the NEMP was conducted in support of a planned acoustic experiment for the Office of Naval Research. The survey focused on a ~30 km (E-W) by ~8 km (N-S) region between the 70 m and 85 m isobaths, encompassing a sediment “pond” >12 m thick. The dense (250 m) survey lines allow a pseudo-3D stratigraphic interpretation. The sediment pond occupies an embayment eroded into pre-LGM substrate sediments, perhaps by glacial outwash. Marine sands beneath the mud are organized into oblique sand ridge morphology. The sense of obliquity, morphologic asymmetry, and internal dipping reflectors indicate that the sand ridges formed under east-directed transport. However, as evidenced by westward-prograding depocenters and onlap, NEMP deposition occurred under west-directed transport, consistent with modern shelf conditions. The onset of fine-grained deposition was therefore contemporaneous with a significant shift in the hydrologic regime. Muds deposited immediately above the sand ridges include a significant sand component, whose modal grain size is identical to that of the sand ridges. This admixture may indicate that, during the early stages of mud deposition, the tops of the sand ridges remained unburied and exposed to reworking. Episodic, storm-driven transport of sand to the muddy deposits may account for some of the sand component of NEMP sediments.

Opposing Roles of apolipoprotein E in aging and neurodegeneration.

Apolipoprotein E (APOE) effects on brain function remain controversial. Removal of APOE not only impairs cognitive functions but also reduces neuritic amyloid plaques in mouse models of Alzheimer's disease (AD). Can APOE simultaneously protect and impair neural circuits? Here, we dissociated the role of APOE in AD versus aging to determine its effects on neuronal function and synaptic integrity. Using two-photon calcium imaging in awake mice to record visually evoked responses, we found that genetic removal of APOE improved neuronal responses in adult APP/PSEN1 mice (8-10 mo). These animals also exhibited fewer neuritic plaques with less surrounding synapse loss, fewer neuritic dystrophies, and reactive glia. Surprisingly, the lack of APOE in aged mice (18-20 mo), even in the absence of amyloid, disrupted visually evoked responses. These results suggest a dissociation in APOE's role in AD versus aging: APOE may be neurotoxic during early stages of amyloid deposition, although being neuroprotective in latter stages of aging.

Discrete-element model of electrophoretic deposition in systems with small Debye length: effective charge, lubrication force, characteristic scales, and early-stage transport

Electrophoresis was recently proposed as a new method for controlling properties and structure of the interface between cement and steel elements in petroleum and construction industries (Lavrov A et al., 2018). Cement slurries typically contain a wide range of particle sizes (micron to hundred micron), and the particles have small Debye lengths (nanometer). The relative magnitude of different forces acting on particles in such systems was examined. A formulation based on the DLVO theory was used to calculate van der Waals forces and electric repulsion forces between particles. It was shown that the following forces need to be included in a discrete-element model of electrophoretic deposition in this case: viscous drag force, force due to the external electric field, gravity + buoyancy force, lubrication force, van der Waals force, and direct mechanical contact force. The recommended cut-off gaps for van der Waals and lubrication forces are equal to the radius of the larger particle participating in the interaction. An example DEM simulation has revealed that deposition starts with deposing finer particles. Shortly after, larger particles are deposited on the finer substrate. This is due to the larger speed-up time of larger particles. The difference in the speed-up time leads to some size segregation at the early stage of deposition, even though the particle mobility is independent of the particle size. The model enables some insight into the processes that take place during the earlier stages of electrophoretic deposition that are difficult to capture and analyze in laboratory experiments.

Electrochemical aspects of tin electrodeposition on copper in acid solutions

The electrodeposition of tin on copper electrodes was studied in sulphuric acid solutions in the 283–338 K range by employing electrochemical techniques, including electrochemical quartz crystal microbalance, and scanning electron microscopy imaging. The voltammetric profiles show the presence of both, underpotential and overpotential electrodeposition of tin. While the first process (upd) involves surface controlled reactions, the latter (opd) is under mass transport control. SEM imaging shows the formation of nanoparticles under upd conditions and larger ones in the opd potential region. Analysis of chronoamperometric response indicates an instantaneous nucleation and 2D growth coupled to an adsorption process during the early stages of underpotential deposition. Conversely, data obtained in the overpotential deposition range is consistent with the occurrence of a progressive nucleation and 3D growth under diffusion control. Electrochemical impedance experiments are characterised by Nyquist plots that exhibit two capacitive time constants and a single capacitive time constant followed by a Warburg contribution in the upd and opd potential ranges, respectively. Rotating ring-disc voltammograms display current peaks in the corresponding ring profiles associated with the formation of adsorbates on the disc during the underpotential deposition. From rotating disc data the diffusion coefficient of Sn(II) ions at the different temperatures and the corresponding diffusion activation energy were determined. A reaction scheme for the electrochemical behaviour of tin on copper electrodes in the range between the threshold potentials for the copper electrodissolution and the hydrogen evolution reactions is proposed. Mass transport of soluble species, formation of weakly and strongly adsorbed species on copper and the diffusion of tin atoms into the copper lattice are considered.

Topological defects in weak perpendicular magnetic anisotropy NdCo honeycomb lattices

Domain configuration has been studied by magnetic force microscopy and micromagnetic simulations in NdCo honeycomb lattices in comparison with similar patterned structures made of polycrystalline Co. The change in material anisotropy from in-plane to weak perpendicular magnetic anisotropy (wPMA) modifies the basic domain structure and relevant topological defects in the magnetization in each case: from in-plane domains, vortices, antivortices and half vortices in Co lattices to parallel stripe patterns with dislocations in NdCo samples with large enough thickness. A characteristic feature of wPMA materials is the possibility to drive the system from in-plane to stripe pattern configuration playing with sample thickness (during growth) or with magnetic anisotropy (as a function of temperature). It has allowed us to observe complex magnetic textures within the stripe pattern of NdCo samples imprinted from previous magnetic vortex and antivortex states that nucleate within the honeycomb lattice during the early stages of deposition and, then, become frozen by local rotatable anisotropy as sample thickness increases.

Diffusion‐Mediated Growth and Size‐Dependent Nanoparticle Reactivity during Ruthenium Atomic Layer Deposition on Dielectric Substrates

AbstractUnderstanding the growth mechanisms during the early stages of atomic layer deposition (ALD) is of interest for several applications including thin film deposition, catalysis, and area‐selective deposition. The surface dependence and growth mechanism of (ethylbenzyl)(1‐ethyl‐1,4‐cyclohexadienyl)ruthenium and O2 ALD at 325 °C on HfO2, Al2O3, OH, and SiOSi terminated SiO2, and organosilicate glass (OSG) are investigated. The experimental results show that precursor adsorption is strongly affected by the surface termination of the dielectric, and proceeds most rapidly on OH terminated dielectrics, followed by SiOSi and finally SiCH3 terminated dielectrics. The initial stages of growth are characterized by the formation and growth of Ru nanoparticles, which is mediated by the diffusion of Ru species. Mean‐field and kinetic Monte Carlo modeling show that ALD on OSG is best described when accounting for (1) cyclic generation of new nanoparticles at the surface, (2) surface diffusion of both atomic species and nanoparticles, and (3) size‐dependent nanoparticle reactivity. In particular, the models indicate that precursor adsorption initially occurs only on the dielectric substrate, and occurs on the Ru nanoparticles only when these reach a critical size of about 0.85 nm. This phenomenon is attributed to the catalytic decomposition of oxygen requiring a minimum Ru nanoparticle size.

Gene Transfer Induced Hypercholesterolemia in Amyloid Mice.

A risk factor for cardiovascular disease (CVD), mutant PCSK9, was expressed in APP/PS1 mice to study the CVD-Alzheimer's disease inter-relationship. Cholesterol levels were elevated by 5-6-fold from 3 to 13 weeks after PCSK9 gene transfer. We tested whether hypercholesterolemia would increase amyloid-β plaques at a relatively early stage of plaque deposition. Plaque burden was increased in the hippocampus of PCSK9 treated mice though the increase was modest compared to the large elevation in cholesterol. Elevating cholesterol via gene transfer could be valuable in a variety of disease models compared to making crosses with germ-line transgenic mouse models of CVD.

Effects of Polymer Coatings on Electrodeposited Lithium Metal.

The electrodeposition of lithium metal is a key process in next-generation, high energy density storage devices. However, the high reactivity of the lithium metal causes short cycling lifetimes and dendrite growth that can pose a serious safety issue. Recently, a number of approaches have been pursued to stabilize the lithium metal-electrolyte interface, including soft polymeric coatings that have shown the ability to enable high-rate and high-capacity lithium metal cycling, but a clear understanding of how to design and modify these coatings has not yet been established. In this work, we studied the effects of several polymers with systematically varied chemical and mechanical properties as coatings on the lithium metal anode. By examining the early stages of lithium metal deposition, we determine that the morphology of the lithium particles is strongly influenced by the chemistry of the polymer coating. We have identified polymer dielectric constant and surface energy as two key descriptors of the lithium deposit size. Low surface energy polymers were found to promote larger deposits with smaller surface areas. This may be explained by a reduced interaction between the coating and the lithium surface and thus an increase in the interfacial energy. On the other hand, high dielectric constant polymers were found to increase the exchange current and gave larger lithium deposits due to the decreased overpotentials at a fixed current density. We also observed that the thickness of the polymer coating should be optimized for each individual polymer. Furthermore, polymer reactivity was found to strongly influence the Coulombic efficiency. Overall, this work offers new fundamental insights into lithium electrodeposition processes and provides direction for the design of new polymer coatings to better stabilize the lithium metal anode.

Method to reduce the formation of crystallites in ZnO nanorod thin-films grown via ultra-fast microwave heating

This paper discusses the nucleation and growth mechanisms of ZnO nanorod thin-films and larger sized crystallites that form within the solution and on surfaces during an ultra-fast microwave heating growth process. In particular, the work focusses on the elimination of crystallites as this is necessary to improve thin-film uniformity and to prevent electrical short circuits between electrodes in device applications. High microwave power during the early stages of ZnO deposition was found to be a key factor in the formation of unwanted crystallites on substrate surfaces. Once formed, the crystallites, grow at a much faster rate than the nanorods and quickly dominate the thin-film structure. A new two-step microwave heating method was developed that eliminates the onset of crystallite formation, allowing the deposition of large-area nanorod thin-films that are free from crystallites. A dissolution-recrystallization mechanism is proposed to explain why this procedure is successful and we demonstrate the importance of the work in the fabrication of low-cost memristor devices.

From the Very First Stages of Mn Deposition on Ge(001) to Phase Segregation

In this work, we have combined scanning tunneling microscopy with high-resolution transmission electron microscopy (HR-TEM) to investigate the initial stages of Mn deposition on Ge(001) surfaces. The growth temperature was chosen to be (353 ± 5) K, which is typical for the synthesis of Ge1–xMnx thin films. At the early stage of the Mn deposition, two distinct kinds of islands are observed even for Mn coverage much smaller than a monolayer with an average size of 1–2 nm and 4–5 nm, respectively. Small islands were found to nucleate in the hollow between the Ge dimer rows, and they were formed by consuming Ge from two adjacent rows. This indicates that Mn–Ge alloying has been taken place even at the early stage of the Mn deposition. When the Mn coverage increases, coarsening between small islands with newly deposited ad-atoms occurs, giving rise to the formation of monosized islands. Interestingly, these nanostructures have an average size of 4–5 nm and separated by a spacing of 7–8 nm that are similar to the spatial ordering of nanocolumns resulting from spinodal decomposition in (Ge,Mn) thin films. HR-TEM analyses indicate that those nanoislands are epitaxial, defect-free, and perfectly coherent with the Ge substrate. A subsequent anneal will result in the formation of Mn5Ge3 islands.

In-Situ Measurements of Stress during Electrodeposition of Copper Nanofilms: Surface and Grain-Boundary Migration of Atoms and the Effect of Chloride Ions

Electrodeposited metal films are often in a state of stress and this has been the subject of extensive experimental investigation and theoretical analysis1-4. We have been measuring stress development in situ during electrodeposition and correlating the results with in-situ AFM imaging during electrodeposition under similar conditions. In this paper we present results on the early stages of copper deposition from acidic CuSO4 electrolytes with and without chloride as an additive. To examine the effect of growth rate, sequential galvanostatic depositions were carried out (after an initial potentiostatic deposition of a thin layer of copper) over a relatively large range of growth rates (from 0.22 nm s-1 to 6.9 nm s-1) in additive-free electrolyte. At low growth rates, steady state stress was compressive. As growth rate was increased, the stress became less compressive and eventually became tensile. Crossover from compressive to tensile stress occurred at a growth rate of ~1 nm s-1. Both in-situ AFM imaging during deposition and ex-situ SEM imaging were used to characterise the evolution of grain size during the sequence of galvanostatic depositions used in the stress measurements. In general, grain size increased with continued deposition but eventually reached a constant value. Simulations based on Chason’s kinetic model3 gave a good fit of our experimental stress measurements in the region of constant grain size (~970 nm). The parameters from this fit were then used to model the steady state stress as a function growth rate and grain size. The values predicted by the model are plotted against the values from the experimental measurements in Figure 1. It can be seen that there is good agreement between model and experiment. The effect of added chloride in the electrolyte was also investigated. Even at low concentrations (< 1 ppm), the presence of chloride considerably reduced the tensile stress. Chloride-free and chloride-containing electrolytes also showed very different behaviours after interruption of electrodeposition. In chloride-free electrolyte, the tensile steady-state stress observed during deposition changed to compressive stress on interruption of the deposition. However, in chloride-containing electrolyte, the stress became even more tensile on interruption of deposition. Our experimental results on the change from one type of behaviour to the other as the chloride concentration was increased will be described and possible mechanisms will be discussed. References O.E. Kongstein, U. Bertoci and G.R. Stafford, J. Electrochem. Soc. 152, C116 (2005).S. Ahmed, T.T. Ahmed, M. O'Grady, S. Nakahara and D.N. Buckley, J. Applied Physics 103, (2008).E. Chason, Thin Solid Films 526, 1 (2012).E. Chason, A. Engwall, F. Pei, M. Lafouresse, U. Bertocci, G. Stafford, J.A. Murphy, C. Lenihan and D.N. Buckley, J. Electrochem. Soc. 160, D3285 (2013) Figure 1

Mechanism of Initial Film Formation during Cathodic Electrodeposition of Coatings

Electrodeposition of coatings is an effective way to form a protective layer on metal surfaces of complex shape. The uniformity of the deposit is a function of the current distribution, and depends on the induction time (time prior to “initiation” of deposition), the local deposition rate and the resistivity of the film that is formed. In cathodic electrodeposition, hydrogen gas evolves on the deposition surface, leading to an increase in the local pH. The change in pH reduces the solubility of the positively charged resin-containing micelles and causes a coating to form on the surface. The induction time, which is a key factor in the prediction of film thickness, has been attributed to the time that is required to increase the local pH to about 12 [1, 2]. The deposition rate, which is initially low, changes significantly during the induction period and eventually increases to a steady value that is proportional to the charge passed. An increased fundamental understanding is needed to improve our ability to accurately model E-coat systems in order to optimize performance. The purpose of this study is to develop a detailed understanding of the initial stages of deposit growth. Of particular interest are the changes that take place during the induction time. Experiments designed to elucidate the role of pH change clearly show that the local change in pH alone is not responsible for the induction time. This observation was further supported by additional experiments where the induction time at a specified current was observed to vary with the type of substrate used for deposition. Consequently, scanning electron microscopy was used to study the morphology of the initial deposit on different substrate surfaces including bare steel, galvanized steel, and phosphated steel. It was found that the initial film tends to form preferentially on defects and scratches in the metals. This observation was validated by experiments with intentionally scratched surfaces. The initial film also appeared to form around gas bubbles that were present on the substrate surface. The mechanism for preferred deposition at defects and bubbles is currently under investigation. As part of this effort, deposition on “defect free” surfaces has been performed. Microscopic images are used to track deposit formation as a function of time during the initial stages of deposition before formation of a highly resistive film. The rate of deposition increases with time, which may be connected to an increase in the local current density in the deposit free areas. The additional insight provided by this study will provide the basis for an improved model of the early stages of E-coat deposition. This model will then be incorporated into a large-scale simulation tool to enable improved process prediction and optimization. Acknowledgment The authors gratefully acknowledge funding from the Ford Motor Company under their University Research Program (URP). References Miskovic-Stankovic, V.B. and M.D. Maksimovic, The effect of concentration on the cathodic electrodeposition process. Process in Organic Coating, 1988. 16: p. 255-263.Pierce, P.E., The physical chemistry of the cathodic electrodeposition process. Journal of Coatings Technology and Research, 1981. 53: p. 52.

Early stage of CVD graphene synthesis on Ge(001) substrate

In this work we shed light on the early stage of the chemical vapor deposition of graphene on Ge(001) surfaces. By a combined use of μ-Raman and x-ray photoelectron spectroscopies, and scanning tunneling microscopy and spectroscopy, we were able to individuate a carbon precursor phase to graphene nucleation which coexists with small graphene domains. This precursor phase is made of C aggregates with different size, shape and local ordering which are not fully sp2 hybridized. In some atomic size regions these aggregates show a linear arrangement of atoms as well as the first signature of the hexagonal structure of graphene. The carbon precursor phase evolves in graphene domains through an ordering process, associated to a re-arrangement of the Ge surface morphology. This surface structuring represents the embryo stage of the hills-and-valleys faceting featured by the Ge(001) surface for longer deposition times, when the graphene domains coalesce to form a single layer graphene film.

Crystal Growth and Atom Diffusion in (Cu)ZnTe/CdTe via Molecular Dynamics

Molecular dynamics (MD) simulations and experimental evaporation were applied to study the growth of evaporated (Cu)ZnTe on mono- and polycrystalline CdTe. The simulated structures show polytypism and polycrystallinity, including texturing and grain boundaries, diffusion, and other phenomena in excellent qualitative agreement with experimental atomic probe tomography, transmission electron microscope, and secondary ion mass spectrometry. Results show formation of Cu clusters in nonstoichiometric growths even at early stages of deposition. Results also show significantly faster diffusion along defected regions (uncorrelated CdTe grain boundaries) as compared with more highly crystalline areas (high-symmetry grain boundaries and pristine regions). Activation energies and pre-exponential factors of Cu, Zn, and Te diffusion were determined using simulation. The MD model captures crystal growth phenomena with a high degree of fidelity.

Microstructure evolution and indentation cracking behavior of MoN multilayer films

Molybdenum nitride, MoN, multilayer films tailored by MoN single layers with versatile structure features are produced through radio frequency magnetron sputtering technique. The MoN layers were manipulated to exhibit crystalline (C), preferred orientation (P) and amorphous (A) phases with gas inlet and input power control. The MoN multilayer films were successfully prepared using alternatively stacking of single layers to form C/P, C/A, and P/A assemblies, i.e. MCP, MCA, and MPA films respectively. The multilayer coatings were controlled at a total thickness of 1 μm with each building layer of 50 nm. Through microstructure analyses, the columnar crystalline structure in single layer films was suppressed by tailored layers. Intact heterostructural interfaces with building layers at early deposition stages could be observed for crystalline incorporated multilayers, like MCP and MCA assemblies. On the other hand, the continuous columnar crystalline structure could be found in multilayers containing amorphous layers, which tended to be pliant to the crystalline phases and preferred orientation during deposition. The columnar grains grew through several layer interfaces in late deposition stages for multilayers, especially for MPA film. Through Rockwell C indentation test, adhesion and cracking behaviour of the single and multilayer MoN films were evaluated. The structure tailored MoN multilayers showed better adhesion as compared to the single layer films. Adhesive cracking due to preferred orientation was suppressed by the tailoring structure with crystalline layers.

In situ study of electric field controlled ion transport in the Fe/BaTiO3 interface

Electric field controlled ion transport and interface formation of iron thin films on a BaTiO3 substrate have been investigated by in situ nuclear resonance scattering and x-ray reflectometry techniques. At early stage of deposition, an iron-II oxide interface layer was observed. The hyperfine parameters of the interface layer were found insensitive to the evaporated layer thickness. When an electric field was applied during growth, a 10 Å increase of the nonmagnetic/magnetic thickness threshold and an extended magnetic transition region was measured compared to the case where no field was applied. The interface layer was found stable under this threshold when further evaporation occurred, contrary to the magnetic layer where the magnitude and orientation of the hyperfine magnetic field vary continuously. The obtained results of the growth mechanism and of the electric field effect of the Fe/BTO system will allow the design of novel applications by creating custom oxide/metallic nanopatterns using laterally inhomogeneous electric fields during sample preparation.

Crystallization Mechanism and Charge Carrier Transport in MAPLE-Deposited Conjugated Polymer Thin Films.

Although spin casting and chemical surface reactions are the most common methods used for fabricating functional polymer films onto substrates, they are limited with regard to producing films of certain morphological characteristics on different wetting and nonwetting substrates. The matrix-assisted pulsed laser evaporation (MAPLE) technique offers advantages with regard to producing films of different morphologies on different types of substrates. Here, we provide a quantitative characterization, using X-ray diffraction and optical methods, to elucidate the additive growth mechanism of MAPLE-deposited poly(3-hexylthiophene) (P3HT) films on substrates that have undergone different surface treatments, enabling them to possess different wettabilities. We show that MAPLE-deposited films are composed of crystalline phases, wherein the overall P3HT aggregate size and crystallite coherence length increase with deposition time. A complete pole figure constructed from X-ray diffraction measurements reveals that in these MAPLE-deposited films, there exist two distinct crystallite populations: (i) highly oriented crystals that grow from the flat dielectric substrate and (ii) misoriented crystals that preferentially grow on top of the existing polymer layers. The growth of the highly oriented crystals is highly sensitive to the chemistry of the substrate, whereas the effect of substrate chemistry on misoriented crystal growth is weaker. The use of a self-assembled monolayer to treat the substrate greatly enhances the population and crystallite coherence length at the buried interfaces, particularly during the early stage of deposition. The evolution of the in-plane carrier mobilities during the course of deposition is consistent with the development of highly oriented crystals at the buried interface, suggesting that this interface plays a key role toward determining carrier transport in organic thin-film transistors.