Thin film growth

We have studied the exchange anisotropy of ferromagnetic Fe films grown on antiferromagnetic FeF2 single crystals. The behavior of the hysteresis loops of the Fe above and below the Néel temperature TN of FeF2 indicates a 90° rotation of the ferromagnetic easy axis due to the antiferromagnetic ordering. By examining the Fe hysteresis loops together with the FeF2 susceptibility behavior we infer that below TN the ferromagnetic and antiferromagnetic spins are coupled perpendicular to each other. This behavior can be explained by recent micromagnetic calculations on exchange bias systems, or by magnetoelastic effects.

A drastic reduction in temperature dependent cross-plane thermal conductivity κ⊥ occurs in Ge quantum dot superlattices (QDSLs), depending on the vertical correlation between dots. Measurements show at least a twofold decrease of κ⊥ in uncorrelated dot structures as compared to structures with the same Si spacer of 20nm but good vertical dot alignment. The observed impact of disorder on the conductivity provides an alternative route to reduce the thermal conductivity of QDSLs. The results of this work have implications for the development of highly efficient thermoelectric materials and on-chip nanocooling devices.

This investigation aims at studying-by in situ grazing-incidence small-angle x-ray scattering-the process of growth of hexagonal CoSi 2 nanoplatelets endotaxially buried in a Si(001) wafer. The early formation of spherical Co nanoparticles with bimodal size distribution in the deposited silica thin film during a pretreatment at 500 C and their subsequent growth at 700 C were also characterized. Isothermal annealing at 700 C promotes a drastic reduction in the number of the smallest Co nanoparticles and a continuous decrease in their volume fraction in the silica thin film. At the same time, Co atoms diffuse across the SiO 2 /Si(001) interface into the silicon wafer, react with Si, and build up thin hexagonal CoSi 2 nanoplatelets, all of them with their main surfaces parallel to Si{111} crystallographic planes. The observed progressive growths in thickness and lateral size of the hexagonal CoSi 2 nanoplatelets occur at the expense of the dissolution of the small Co nanoparticles that are formed during the pretreatment at 500 C and become unstable at the annealing temperature (700 C). The kinetics of growth of the volume fraction of hexagonal platelets is well described by the classical Avrami equation. V

A series of polyanions and polycations have been synthesized from atactic, syndiotactic, and isotactic forms of poly(methyl methacrylate) and used to construct polyelectrolyte multilayers (PEMs). Polymer tacticity has been found to have a large influence on film growth but only a slight effect on H2/N2 permeation selectivities and no significant influence on CO2/N2 permeation selectivities. The permeances of H2, CO2, and N2 across those PEMs exhibiting the highest H2/N2 selectivities were found to vary by as much as factors of 3, 6, and 5, respectively, depending on the tacticities employed. A simple model that accounts for the strong dependency of film growth on tacticity is presented.

The growth of indium on a vicinal Si(100)-(2×1) surface at room temperature by femtosecond pulsed laser deposition (fsPLD) was investigated by in situ reflection high-energy electron diffraction (RHEED). Recovery of the RHEED intensity was observed between laser pulses and when the growth was terminated. The surface diffusion coefficient of deposited In on initial two-dimensional (2D) In-(2×1) layer was determined. As growth proceeds, three-dimensional In islands grew on the 2D In-(2×1) layer. The RHEED specular profile was analyzed during film growth, while the grown In islands were examined by ex situ atomic force microscopy. The full width at half maximum of the specular peak decreased during the deposition, indicative of well-ordered growth and an increase of the island size. The In islands developed into elongated-polyhedral, circular, and triangular shapes. The elongated and triangular islands were highly oriented, parallel and perpendicular to the surface terrace edges, while...

It is commonly assumed that in uncompensated FM/AF interfaces, the easy axes of antiferromagnetic grains are aligned toward the magnetic field direction applied during the film growth. However, due to several intrinsic and extrinsic factors, these easy axes can be aligned away from the unidirectional axis. In this context, the aim of this work is to study the relationship between the easy axes distribution (EAD) and thickness of both the ferromagnetic (FM) and antiferromagnetic (AF) layers in Co/IrMn bilayer systems. A phenomenological model for the free energy of the system that takes into account a domain wall formation in the AF layer and a Gaussiantype distribution of their easy axes is used. Thus, we simulate and fit the magnetization curves and get several magnetic parameters like rotatable anisotropy field, exchange bias field, coercivity and magnetic anisotropy. Our results show that when the AF thickness is increased, the width of the easy-axis distribution also increases following a power-law relationship. However, no correlation is observed when the FM thickness is varied. Furthermore, considering an easy-axis distribution we observe a significant reduction in coercivity as well as a slight decrease of the exchange bias field.

Experimental technique Donor doped Strontium Titanate is well known for its capability as resistive high temperature oxygen sensor. An interesting application of this sensor would be the analysis of automobile exhaust, as it would allow the optimisation of fuel injection and of catalytic oxidation of toxic exhaust, thus reducing fuel consumption and pollution of the environment. Before this application can be implemeted, preliminary studies aiming at the interaction of SrTiO with reactive gases must demonstrate the stability of the material in this environment. Also, an interpretation of the sensor's signal in such an environment will only be possible with an understanding of the cross-sensitivity of the strontium titanate for other present gases like water or carbon dioxide. We use Metastable Impact Electron Spectroscopy and Ultraviolet Photoelectron Spectroscopy to analyse the valence band structure of SrTiO and its adsorbates. X-ray Photoelectron Spectroscopy is used to check...

Differential entropy, along with fractal dimension, is herein employed to describe and interpret the shape complexity of self-similar organic islands. The islands are imaged with in situ Atomic Force Microscopy, following, step-by-step, the evolution of their shape while deposition proceeds. The fractal dimension shows a linear correlation with the film thickness, whereas the differential entropy presents an exponential plateau. Plotting differential entropy versus fractal dimension, a linear correlation can be found. This analysis enables one to discern the 6T growth on different surfaces, i.e., native SiOx or 6T layer, and suggests a more comprehensive interpretation of the shape evolution. Changes in fractal dimension reflect rougher variations of the island contour, whereas changes in differential entropy correlates with finer contour details. The computation of differential entropy therefore helps to obtain more physical information on the island shape dependence on the substra...

In situ Atomic Force Microscopy (AFM) allowed us to investigate the evolution at the early stages of the growth of organic thin films. An Ultra-High Vacuum AFM, integrated with a Knudsen effusion cell for the sublimation of -sexithiophene (6T), continuously scans the same region during the deposition of sublimed molecules on native silicon oxide as a function of the substrate temperature. Non-Contact AFM images acquired sequentially, provide snapshots of the time evolution of the film morphology that is monitored up to the deposition of five monolayers. At all substrate temperatures, a Stranski-Krastanov growth mode of organic films is observed: the first two monolayers grow layer-by-layer (2D) then films evolve into islands (3D). Despite the apparent similarity, we find an anomalous dynamic scaling characterized by the abrupt change of the growth exponent β vs substrate temperature. This novel transition, induced by the substrate temperature, is ascribed to the morphological transition from ziggurat islands to large terraces. The analysis of the evolution of the rootmean-square roughness (RMS) based on the Distributed Growth Model underlines the role of downhill mass transport for the growth of the first two monolayers, transport that is progressively hindered for the next monolayers.

Organic molecular beam deposition has been used to surpass the chemical approach commonly adopted for coating SiOx surfaces, obtaining a smooth and uniform monomolecular layer of sexithiophene that fully covers the SiOx surface on the centimetre length scale. This result has been achieved by submitting sexithiophene sub-monolayer films grown at different substrate temperatures to a post-deposition annealing process. Through Scanning Probe Microscopy techniques, morphological, tribological and mechanical measurements have highlighted the existence of face-on molecular aggregates on the SiOx surface and their reorganization by means of a post-annealing process. Atomistic molecular dynamics simulations complement experimental observations, shedding light on the microscopic aspects of molecular diffusion and aggregates reorganization. Exploiting the molecular reorganization upon post-annealing, almost perfect 6T monolayers were grown through a sequence of deposition and annealing steps. This preparation technique represents a new route for changing surface properties by using high controlled monomolecular layers.

Drain-source current in organic thin-film transistors has been monitored in situ and in real time during the deposition of pentacene. The current starts to flow when percolation of the first monolayer (ML) occurs and, depending on the deposition rate, saturates at a coverage in the range 2-7 MLs. The number of active layers contributing to the current and the spatial distribution of charge carriers are modulated by the growth mode. The thickness of the accumulation layer, represented by an effective Debye length, scales as the morphological correlation length. These results show that the effective Debye length is not just a material parameter, but depends on the multiscale morphology. Earlier controversial results can be unified within this framework.

Charge transport in organic thin film transistors takes place in the first few molecular layers in contact with the gate dielectric. Here we demonstrate that the charge transport pathways in these devices are extremely sensitive to the orientational defects of the first monolayers, which arise from specific growth conditions. Although these defects partially heal during the growth, they cause depletion of charge carriers in the first monolayer, and drive the current to flow in the monolayers above the first one. Moreover, the residual defects induce lower crystalline order and charge mobility. These results, which are not intuitively explained by electrostatics arguments, have been obtained by combining in situ real time structural and electrical characterization together with ex situ AFM measurements, on thin films of a relevant n-type organic semiconductor, N,N 0-bis(n-octyl)-dicyanoperylene-3,4:9,10-bis dicarboximide grown by sublimation in a quasi-layer-by-layer mode at different substrate temperatures.

Summary: A computer simulation model is proposed to study film growth and surface roughness in aqueous (A) solution of hydrophobic (H) and hydrophilic (P) groups on a simple three dimensional lattice of size $L_x \times L_y \times L_z$ with an adsorbing substrate. Each group is represented by a particle with appropriate characteristics occupying a unit cube (i.e., eight sites). The Metropolis algorithm is used to move each particle stochastically. The aqueous constituents are allowed to evaporate while the concentration of H and P is constant. Reactions proceed from the substrate and bonded particles can hop within a fluctuating bond length. The film thickness ($h$) and its interface width ($W$) are examined for hardcore and interacting particles for a range of temperature ($T$). Simulation data show a rapid increase in $h$ and $W$ followed by its non‐monotonic growth and decay before reaching steady‐state and near equilibrium ($h_{\rm s}, W_{\rm s}$) in asymptotic time step limit. ...

Metal-oxide thin films (ZnO, TiO 2 and other so on) have received considerable interest from scientists due to their remarkable performance in electronics, optics and photonics. In this study we have reported a way of fabricating films applying different conditions in a computerized way where PC has been interfaced with Keithley 2400 Source Measure Unit (SMU) with Lab-view software and controls the electrodeposition mechanism either in a voltage or current controlled way. The potential difference between the electrodes, current flow and resistivity of the electrolyte, duration of deposition of molecule on the substrate and their corresponding features as well as curves (I-V, R-V and IT) become visible in the computer monitor using 'LabVIEW' software. Additionally, we fabricated ZnO films on Fluorine Doped Tin Oxide (FTO, SnO 2 :F) substrate from an electrolyte of metallic-salt [Zn(NO 3) 2 ]. Almost precise potential difference of 0.718V (DC) was provided by Keithley 2400 Source Measure Unit between the working electrode and counter electrode of a zinc nitrate electrolyte [0.5M of Zn(NO 3) 2 solution; 0.0125:1.375 = zinc nitrate : water (molar weight)] resulting in a smooth deposition of metallic oxide on FTO substrate. I-V, R-V and IT curves have been analyzed to prove the already built ZnO formation mechanism. Both the as-deposited and annealed films stance with semi-conductive behavior where a marginal differences in resistivity exist between this two.

In situ Atomic Force Microscopy (AFM) allowed us to investigate the evolution at the early stages of the growth of organic thin films. An Ultra-High Vacuum AFM, integrated with a Knudsen effusion cell for the sublimation of -sexithiophene (6T), continuously scans the same region during the deposition of sublimed molecules on native silicon oxide as a function of the substrate temperature. Non-Contact AFM images acquired sequentially, provide snapshots of the time evolution of the film morphology that is monitored up to the deposition of five monolayers. At all substrate temperatures, a Stranski-Krastanov growth mode of organic films is observed: the first two monolayers grow layer-by-layer (2D) then films evolve into islands (3D). Despite the apparent similarity, we find an anomalous dynamic scaling characterized by the abrupt change of the growth exponent β vs substrate temperature. This novel transition, induced by the substrate temperature, is ascribed to the morphological transition from ziggurat islands to large terraces. The analysis of the evolution of the rootmean-square roughness (RMS) based on the Distributed Growth Model underlines the role of downhill mass transport for the growth of the first two monolayers, transport that is progressively hindered for the next monolayers.

Charge transport in organic thin film transistors takes place in the first few molecular layers in contact with the gate dielectric. Here we demonstrate that the charge transport pathways in these devices are extremely sensitive to the orientational defects of the first monolayers, which arise from specific growth conditions. Although these defects partially heal during the growth, they cause depletion of charge carriers in the first monolayer, and drive the current to flow in the monolayers above the first one. Moreover, the residual defects induce lower crystalline order and charge mobility. These results, which are not intuitively explained by electrostatics arguments, have been obtained by combining in situ real time structural and electrical characterization together with ex situ AFM measurements, on thin films of a relevant n-type organic semiconductor, N,N 0-bis(n-octyl)-dicyanoperylene-3,4:9,10-bis dicarboximide grown by sublimation in a quasi-layer-by-layer mode at different substrate temperatures.

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Electron paramagnetic resonance (EPR) measurements have been made at X-band (f9.5 GHz) and W-band (f95 GHz) of a-C:H films on (1 0 0) silicon substrates; the sample temperature was varied in the range 5-300 K. Two types of film were examined. The first type are amorphous hydrogenated carbon (a-C:H) films grown by plasma enhanced chemical vapour deposition (PECVD) with negative self bias voltages in the approximate range 100-500 V. The second type were initially highly polymeric-like a-C:H films grown on Si placed on the earthed electrode of a PECVD system but were subsequently implanted with either 6=10 cm B or 2=10 cm B ions. At both X-and W-band and throughout the temperature range 5-300 K 15 y2 q 16 y2 q the EPR signal of the carbon unpaired electrons consists of a single symmetric line with gs2.0026"0.0002. As the temperature is lowered, several samples develop a dependence on sample orientation of the external field required for resonance. This anisotropy is explained in terms of the demagnetising fields more usually encountered in ferromagnetic resonance.

The evolution of clean, In-terminated InP(100)-(2ϫ4) surfaces is investigated by synchrotron-radiationexcited photoemission spectroscopy as a function of annealing temperature. As-prepared InP(100)-(2ϫ4) surfaces are found to be free of metallic indium, and the 4d core level shows two clear surface components. A third, indium-cluster-related component appears after annealing above 360Ϯ10°C, due to phosphorous desorption, and is accompanied by a corresponding reduction in intensity in the In-P surface component. Further annealing leads to a decrease in binding energy of the indium-cluster-related peak due to increased metallicity and hence core-hole screening in the clusters. The increasingly metallic nature of the indium clusters is also revealed by the appearance and growth of a Fermi edge in valence-band spectra.

The growth mechanism and adsorbate-induced surface morphology of metal atoms on semiconducting surfaces crucially determines the electronic and physicochemical properties of these metal/semiconductor systems. In this study, we investigate the kinetically controlled growth of indium (In) atoms on the high index stepped Si(553)-7 × 7 surface and the thermal stability of various novel In-induced superstructural phases formed during adsorption/desorption process. Auger electron spectroscopy analysis reveals that In adsorption at room temperature (RT) and at 350 • C, with a controlled incident flux of 0.0016 ML/s, proceeds in the Stranski-Krastanov growth mode where two dimensional (2D)/three dimensional (3D) islands are formed on top of two complete monolayers. At higher substrate temperature up to 450 • C, the growth of In atoms occurs in the form of islands on the bare Si(553) surface, and In coverage is limited to the sub-monolayer regime. During the thermal desorption of the RT grown In/Si(553) system, the In clusters rearrange themselves and an unusual "cluster to layer" transformation occurs on top of the stable monolayer. In situ low energy electron diffraction analysis during adsorption and desorption shows the development of various coverage and temperature dependent In-induced superstructural phases on Si(553) surface, such as: (8 × 2) after annealing at 520 • C with coverage 0.5 ML, (8 × 4) after annealing at 580 • C (∼1 ML coverage) and (553)-7 × 1 + (111)-√ 3 × √ 3-R30 • at 0.3 ML (630 • C). These adsorbate-induced superstructural phases could potentially be utilized as templates for pattern assisted growth of various exotic 1D/2D structures for optoelectronics and photovoltaic applications.

A combination of electron spin resonance and Raman spectroscopy measurements is applied to fully characterise a-C 1Àx N x :H films (x 6 20 at.%), grown by plasma decomposition of C 2 H 2-N 2 mixtures. The observed decrease in the spin density (8:5 Â 10 19-1:6 Â 10 19 cm À3) when the N content increases is consistent with the decrease in the disorder of the sp 2 nanostructure evidenced by resonant Raman spectroscopy (at 488 and 514.5 nm excitations), which shows an increase in the I D =I G ratio and a narrowing of the D-peak.

Cataphoretic deposition of an epoxy primer was carried out on four different substrates: bare steel; phosphated steel; bare zinc-plated steel; and phosphated zinc-plated steel. Film growth was followed by observing the deposition current and local temperature throughout the deposition. The protective properties of the cured films at two different thicknesses formed on different substrates were observed by a.c. impedance measurements following exposure to 3% NaCl solution. It appears that the substrate affects the properties of the first-deposited layers of the coating. Models which explain the different properties of fihns formed on different substrates are given.

Renewable energy sources offer a viable green energy solution to the increasing global energy demands, and the photovoltaics offers a means of tapping into the abundance of the solar energy. Molybdenum (Mo) thin film has been used as a back-contact electrode in high-efficiency solar cells mainly due to its ohmic nature with the absorber material (especially with chalcopyrites and kesterites), low resistivity, adequate reflectance, and porosity to alkali materials. Mo thin films used in solar cells are deposited by direct current (DC) sputtering under argon ion atmosphere. The present work deals with the effects of the sputtering deposition conditions (i.e., working pressure and power) on the electrical properties of Mo thin films deposited on soda-lime glass using DC magnetron sputtering at different working pressures (5-20 mTorr) and deposition powers (100-800 W). Optimized deposition power and sputtering pressure were used to deposit a Mo bilayer thin film intended for solar cells application. X-ray diffractometric studies showed the (110) plane corresponding to the body-centered cubic structure of the Mo material. Calculated values were used to estimate other parameters of the deposited films (e.g., stress, dislocation density), as these properties affect the potential diffusion of sodium (Na) through the soda-lime glass into the absorber layer that is important as the moderate inclusion of Na improves the cell efficiency. The cross-section of the deposited film was analyzed using a field-emission scanning electron microscopy, to confirm the successful deposition of the bilayer. The surface of the films plays a vital role in the Mo interface with the absorber layer. Atomic force microscopy was used to acquire the topographical information from the sputtered bilayer film. The resistivity, as measured using a four-point probe, of the Mo films deposited at different conditions was in the order of 10 −6 Ω m while the resistivity of the bilayer was 0.60 × 10 −6 Ω m.

Molybdenum thin films were sputter deposited under different conditions of DC power and chamber pressure. The structure and topography of the films were investigated using AFM, SEM and XRD techniques. Van der Pauw method and tape test were employed to determine electrical resistivity and interfacial strength to the substrate, respectively. All the films are of sub-micron thickness with maximum growth rate of 78 nm/min and crystallite size in the range of 4 to 21 nm. The films produced at high power and low pressure exhibit compressive residual strains, low electrical resistivity and poor adhesion to the glass substrate, whereas the converse is true for films produced at high pressure.

Using spectroscopic ellipsometry we investigated and analyzed the pseudo-optical constants of Cu2ZnSnSe4 bulk crystals, grown by the Bridgman method, over 0.8–4.5 eV photon energy range. The structures found in the spectra of the complex pseudodielectric functions were associated to E0, E1A, and E1B interband transitions and were analyzed in frame of the Adachi's model. The interband transition parameters such as strength, threshold energy, and broadening were evaluated by using the simulated annealing algorithm. In addition, the pseudo-complex refractive index, extinction coefficient, absorption coefficient, and normal-incidence reflectivity were derived over 0.8–4.5 eV photon energy range.

The growth mode of domains of the hexagonal lattice of strained gadolinium deposited on Mo(112) has been investigated with low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The molybdenum substrate corrugations and the expansive strain within the gadolinium ®lms dominate the growth of the thin Gd ®lms, which is characterized by a preferential domain growth direction of the hexagonal Gd crystal structure, unlike the more uniform, epitaxial growth of`unstrained' gadolinium, grown on W(110).

The adsorption of hydrogen and Cs alone as well as the coadsorption of Cs and hydrogen on W(110) was studied by metastable impact electron spectroscopy (MIES) and supplemented by UPS, AES, and work function measurements. The main conclusions are: (a) ionization of the es(Q) level is not observed for Cs coverages 8,, s 0.4 ML, (b) the formation of a H(lS)-metal bond occurs at a binding energy of E, = 4.7 eV, (c) upon Cs and hydrogen coadsorption an independent layer of hydrogen is formed between the substrate and the Cs adlayer. The charge density of the Cs adlayer is lowered by about 25% upon the formation of the hydrogen intermediate layer.

The initial stages of degradation of high-T, superconductor surfaces by interaction with atmospheric gases have been studied using ultraviolet photoelectron spectroscopy. 02 has little eN'ect, awhile H2O adsorbs dissociatively with an initial sticking coef5cient S0-1, and forms a surface hydroxide. CO2 adsorbs forming a carbonatelike surface species with an initial sticking coeScient

The initial stages of degradation of high-T, superconductor surfaces by interaction with atmospheric gases have been studied using ultraviolet photoelectron spectroscopy. 02 has little eN'ect, awhile H2O adsorbs dissociatively with an initial sticking coef5cient S0-1, and forms a surface hydroxide. CO2 adsorbs forming a carbonatelike surface species with an initial sticking coeScient

Low-energy electron diffraction, scanning tunneling microscopy, and photoelectron spectroscopy results from the submonolayer Smand Yb-induced surface structures are presented. Several similar metal-induced surface reconstructions are found to exist for Yb and Sm on Si(111)for low submonolayer coverages: 3 X 2, 5 X 1, and 7 X 1. At higher submonolayer coverage, Yb induces a 2 X 1 reconstruction while Sm induces a (&3X&3)R30'-like reconstruction. Yb is found to be divalent in all structures, whereas the Sm valence increases with increasing coverage. In the 3X2 structure only divalent Sm is present, in the 5 X 1 and 7X 1 structures a small amount of trivalent Sm appears, and, finally, in the (&3X &3)R 30 structure approximately half of the Sm atoms are trivalent. The surface Fermi-level position in the band gap for the different Sm and Yb reconstructions has been measured. The difference in valence stability between Sm and Yb is suggested to be the cause of the difference in the high-coverage structures found and the differences in pinning level for the two elements observed for the 5 X 1 and 7 X 1 structures.

Highlights:  New organic free Bi2S3 nanoflakes were synthesized using the HMDS-assisted wet chemical method  Gram scale synthesis (2 g) with 98% morphological yield of flakes was demonstrated  Prototype photodetector was fabricated, and its photo-response was analysed  Synthesis, processing and device making were performed in ambient conditions

Motivated by recent experiments on submonolayer organic film growth with anomalous diffusion, a general rate-equation (RE) theory of submonolayer island nucleation and growth was developed (Amar and Semaan, 2016) [23], which takes into account the critical island-size i , island fractal dimension d f , substrate dimension d , and diffusion exponent , and good agreement with simulations was found for the case of irreversible growth corresponding to a critical island-size = 1 with = 2. However, since many experiments correspond to a critical island-size larger than 1, it is of interest to determine if the RE predictions also hold in the case of reversible island nucleation with anomalous diffusion. Here we present the results of simulations of submonolayer growth with = 2 (= 2) which were carried out for both the case of superdiffusion (> 1) and subdiffusion (< 1) as well as for both ramified islands (d f ≃ 2) and point-islands (= ∞). In the case of superdiffusion, corresponding to 'hot ' freshly deposited monomers, excellent agreement is obtained with the predictions of the generalized RE theory for the exponents () and 1 () which describe the dependence of the island and monomer densities at fixed coverage on deposition rate F. In addition, the exponents do not depend on whether or not monomers remain superdiffusive or are thermalized (e.g. undergo regular diffusion) after detaching from a dimer. However, we also find that, as was previously found in the case of irreversible growth, the exponent only approaches its asymptotic value logarithmically with increasing 1/ F. This result has important implications for the interpretation of experiments. Good agreement with the RE theory is also found in the case of subdiffusion for point-islands. However, in the case of ramified islands with subdiffusion and = 2 , the exponents are significantly higher than predicted due to the fact that monomer capture dominates in the nucleation regime. A modified RE theory which takes this into account is presented, and excellent agreement is found with our simulations.

Silver-diamond like carbon (Ag-DLC) nanocomposite films were deposited on glass and silicon substrates by co-deposition of RF-sputtering and RF-PECVD method in acetylene plasma. The effects of deposition time on creation of conductive percolation pathway in Ag-DLC nanocomposite films were investigated. The films were characterized by XRD pattern, AFM images, UV-Vis and FTIR spectra. Pressure of chamber's variation over time was illustrated the rate of carbon and silver deposition changing. The results showed that nanoparticles' size and surface roughness was increased by increasing deposition time. Surface plasmon resonance peak's red shift in optical absorption spectra of samples could be depends on silver nanoparticles' scale up. Based on electrical measurements, electrical percolation threshold was observed only in the film with 35 min deposition time. Pathway was created for electric current by Ag nanoparticles' moving in carbon matrix due to sp3 bonds and silver content in the films. The aging effect was studied for sample #2 in the threshold of percolation, where obtained Ag nanoparticles memorize its previous pathway. This investigation provides a better understanding for electric properties of Ag-DLC nanocomposite based on the percolation theory.

Flower-like morphology of ZnO thin films were successfully electrodeposited via a one-step route only by changing electrodeposition duration and potential at a fixed concentration on n-Si (100) in78.10-4 M Zn (NO3)2, 6H2O and 0.1M KNO3 solution at 70 °C without using any catalyst, additives or seed layer. The as electrodeposited products were characterized by X-ray diffraction, scanning electronic microscopy and photoluminescence. The effects of the electrodeposition potential and duration on the morphology, structure and photoluminescence properties were studied. The results show that the product morphology changes with a change in the applied voltage and electrodeposition duration. Well defined shape of flower like ZnO morphology was generated under the limited conditions of-1.2 V for 60 min, with (002) preferred orientation Strong UV emission is obtained in the case of ZnO flower like morphology electrodeposited at-1.2 V for 60 min. The band gap energy value of ZnO flower-like, determinate from optical reflectance spectra, is 3.37 eV.

We investigated Bi thin film growth on Ge(111) by using low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). In the submonolayer regime, adsorbed Bi atoms form patches of the (2 × 1) structure. However, the structure does not grow to a long-range order. Following the formation of a (1 × 1) monolayer (ML) film, two-dimensional (110)-orientated Bi islands grow. The film orientation changes from (110) to (111) at 6-10 ML. The (110)-oriented Bi film shows a sixdomain LEED pattern with missing spots, associated with a glide-line symmetry. The hexagonal (111) film at 14 ML has a lattice constant 2% smaller than bulk Bi(111).

In this Letter we stress the importance of final-state eAects in photoelectron spectroscopy. In particular, we address the problem of Schottky-barrier formation, as studied via core-level shifts in photoemission. We have calculated the shift of the core-level distribution when a semiconductor surface is covered with a metal, using a wave-vector-dependent image-screening model. We conclude that final-state eftects, which are generally neglected in this context, are in fact quite important. This conclusion is supported by experimental observations reported in the literature.

The structural properties of Cs adsorption and Cs and 0 coadsorption on Mo(100) at room temperature are studied by LEED and AES. With increasing Cs coverage we observe: (i) At 6'=0.3 ML. a fi~fi R45O structure with an overall 4mm symmetry attributed to the reconstruction of the substrate caused by the Cs atoms; two precursor stages are observed for that structure. (ii) A p(2 x 2) structure at 6' = 0.58 ML. (iii) Up to 0.7 ML a rectangular centered mesh resulting from contraction of the p(2 x 2) structure along one [I 101 direction, and for 0.7 < 8 < 1 ML a quasi-hexagonal structure. (iv) At 1 ML a true hexagonal structure, present in two unequally populated domains rotated by 90 o with the [1120] Cs direction parallel to Mo[l IO]; from the spot intensity of the (ih ih } reflections. we conclude that the Mo(100) face is reconstructed with a fi x $2 R45 o mesh and a p2mg space group. For Cs adsorption on a surface with a high density of up and down steps parallel to [loo] no domain selection occurs and the reconstructed substrate domains are limited by the terrace width. For Cs and 0 coadsorption. the numerous structures which occur for the W(lOO)-Cs-0 system are not observed. The presence of steps hinders the formation of the p(4 x 1) structure observed on the flat surface.

2014 Nous avons étudié l'adsorption de Na et de K sur la face (100) du W à la température ambiante par variation du travail de sortie, diffraction d'électrons lents et spectroscopie de perte d'énergie d'électrons résolue angulairement. Pour ces deux alcalins, des diagrammes de diffraction C(2 x 2) sont observés jusqu'à la monocouche. Nous interprétons ces diagrammes à bas taux de couverture par une reconstruction du substrat provoquée par l'alcalin adsorbé. La variation de l'énergie de la perte principale en fonction du taux de couverture présente un minimum marqué (peu accentué) pour Na(K). Au-delà de ce minimum, la perte est due à l'excitation d'oscillations collectives. Ce comportement est comparé à celui observé pour une couche de Cs adsorbée sur le même substrat : les liaisons entre les atomes de Na, K et Cs et la face (100) du W sont de même nature.

The atomic structures of Na and Cs layers adsorbed on the Pt(ll1) face have been studied at 85 K and room temperature by LEED. At room temperature, Na layers are fully disordered while Cs overlayers exhibit ordered structures. At low temperature, (2x2) and (fi X fi)R30° phases are observed at Na coverage below 0.33. At high er coverages, the Na layer is formed by a mosaic of domains with incommensurate hexagonal structures which are either aligned or rotated relative to the substrate. The rotation angle of the rotated domains depends on the interatomic spacing in the layer. For Cs layers at low temperature the (2 x 2) structure is observed but the (& x 6) structure is rotationally disordered. For Cs coverage beyond 0.33, a mosaic of domains with incommensurate structures which are either aligned or angularly disordered is formed at 85 K while at room temperature only the aligned structure is observed. The origin of the incommensurate aligned phases observed for both alkali layers is discussed and may be attributed to the influence of steps during the overlayer growth.

The effect of energetic ion bombardment on the properties of tantalum thin films was investigated. To achieve such energetic ion bombardment during the process the Ta thin films were deposited by deep oscillation magnetron sputtering (DOMS), an ionized physical vapor deposition technique related to high power impulse magnetron sputtering. The peak power was between 49 and 130 kW and the substrate was silicon at room temperature and ground potential. The directionality and the energy of the depositing species was controlled by changing the ionization fraction of the Ta species arriving at the substrate at different peak powers. In this work, the surface morphology (AFM), microstructure (SEM), structure (XRD) and hardness and Young's modulus (nanoindentation) of the films were characterized. The ion energy distributions (IEDs) were measured using an electrostatic quadrupole ion energy and mass spectrometer (HIDEN EQP 300). The IEDs showed that the DOMS process applies a very energetic (up to 120 eV) ion bombardment on the growing tantalum films. Therefore, with such conditions it was possible to deposit pure α-Ta (of 2 µm of thickness) without the use of additional equipment, i.e., without substrate bias or substrate heating. Conditions are therefore significantly different than in previous works, offering a much simpler and cheaper solution to up-scale for industrial operation.

The structure stability under high pressure and thermal expansion behavior of Na 3 OBr and Na 4 OI 2 , two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temperature. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na 3 OBr and Na 4 OI 2 , respectively. The cubic Na 3 OBr structure and tetragonal Na 4 OI 2 with intergrowth K 2 NiF 4 structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na 4 OI 2 exhibits nearly isotropic compressibility. Negative thermal expansion was observed at low temperature range (20-80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined and confirmed by first-principles calculations among various possible polymorphisms qualitatively. The results provide in-depth understanding of the negative thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications.

The aim of this work was to study different strategies for the synthesis of mordenite coatings on thin FeCrAl alloy foils in order to obtain adherent, stable and homogeneous films for their use as catalytic microreactors. For this purpose, the substrate pretreatments and growth conditions of the films by secondary synthesis were investigated. The best results were obtained by applying a brief calcination of the foils at 700 • C that developed a smooth alumina film with hydrophilic properties, followed by immersion in a 0.4 wt.% aqueous solution of the cationic polymer poly-(diallyldimethilammoniumchloride), PDDA. The subsequent seeding with diluted nanocristal suspensions (2 g L) of Na-mordenite allowed the development of zeolite films with the desired properties and the additional benefit of a marked preferential growth on the metallic surface at the expense of a negligible growth within the synthesis solution. Finally, homogenous zeolite films were obtained in micro-corrugated foils, after which Cu and Ce were incorporated as catalytic ingredients and used in a microreactor for the CO oxidation reaction under different conditions.

The purpose of this study was to describe the 3-D nano-scaled surface texture of the Nickel-Carbon (Ni-C) nanocomposite thin films composed of Ni nanoparticles with different average sizes embedded in amorphous hydrogenated carbon using stereometric analysis. The 3-D nanoscaled surface texture was studied by atomic force microscopy (AFM) and stereometric analysis. In a wider context, we also discuss our findings with regard to manufacture of the Nickel-Carbon composite thin films with desired surface characteristics.

The purpose of this study was to investigate the topography of silicon carbide films at two steps of growth. The topography was measured by atomic force microscopy. The data were processed for extraction of information about surface condition and changes in topography during the films growth. Multifractal geometry was used to characterize three-dimensional micro-and nano-size features of the surface. X-ray measurements and Raman spectroscopy were performed for analysis of the films composition. Two steps of morphology evolution during the growth were analyzed by multifractal analysis. The results contribute to the fabrication of silicon carbide large area substrates for micro-and nanoelectronic applications.

The purpose of this study was to investigate the topography of silicon carbide films at two steps of growth. The topography was measured by atomic force microscopy. The data were processed for extraction of information about surface condition and changes in topography during the films growth. Multifractal geometry was used to characterize three-dimensional micro- and nano-size features of the surface. X-ray measurements and Raman spectroscopy were performed for analysis of the films composition. Two steps of morphology evolution during the growth were analyzed by multifractal analysis. The results contribute to the fabrication of silicon carbide large area substrates for micro- and nanoelectronic applications.

High-aspect ratio porous structures with controllable pore diameters and without a stiff substrate can be fabricated using the ion track technique. Atomic layer deposition is an ideal technique for depositing thin films and functional surfaces on complicated 3D structures due to the high conformality of the films. In this work, we studied Al 2 O 3 and TiO 2 films grown by ALD on pristine polyimide (Kapton HN) membranes as well as polyimide membranes etched in sodium hypochlorite (NaOCl) and boric acid (BO 3) solution by means of RBS, PIXE, SEM-EDX and helium ion microcopy (HIM). The focus was on the first ALD growth cycles. The areal density of Al 2 O 3 film in the 400 cycle sample was determined to be 51 ± 3 Â 10 16 at./cm 2 , corresponding to the thickness of 55 ± 3 nm. Furthermore, the growth per cycle was 1.4 Å/cycle. The growth is highly linear from the first cycles. In the case of TiO 2 , the growth per cycle is clearly slower during the first 200 cycles but then it increases significantly. The growth rate based on RBS measurements is 0.24 Å/cycle from 3 to 200 cycles and then 0.6 Å/cycle between 200 and 400 cycles. The final areal density of TiO 2 film after 400 cycles is 148 ± 3 Â 10 15 at./cm 2 which corresponds to the thickness of 17.4 ± 0.4 nm. The modification of the polyimide surface by etching prior to the deposition did not have an effect on the Al 2 O 3 and TiO 2 growth.

Hard coating materials were widely applied on top surface of the molding dies to prolong lifetime and enhance the mechanical properties for glass molding mass production. The glass molding process can be recognized as both a cyclic thermal aging treatment and a high temperature oxidation process to the die materials. Thus, to remove damaged coating resulted from production injury is as important as to deposit it on the molding die. In this study, the Mo-Ru hard films selected as the protective coatings with Cr and Ti twin interlayers were deposited on tungsten carbide substrates. Chemical etching process was performed to remove the hard coating for recycling process. The stripping process was also monitored by the in-situ liquid mode atomic force microscopy. It is clarified that the Mo-Ru hard coating was etched to form some pits through surface defects in the beginning, then Cr interlayer was reacted with etchant to become soluble products. The Mo-Ru coating cracked and ejected due to the relaxation of residual stress and accumulation of etch products. On the other hand, the Ti interlayer was still effective to protect the tungsten carbide substrate from the etchant attack.

The structure stability under high pressure and thermal expansion behavior of Na 3 OBr and Na 4 OI 2 , two prototypes of alkali-metal-rich antiperovskites, were investigated by in situ synchrotron X-ray diffraction techniques under high pressure and low temperature. Both are soft materials with bulk modulus of 58.6 GPa and 52.0 GPa for Na 3 OBr and Na 4 OI 2 , respectively. The cubic Na 3 OBr structure and tetragonal Na 4 OI 2 with intergrowth K 2 NiF 4 structure are stable under high pressure up to 23 GPa. Although being a characteristic layered structure, Na 4 OI 2 exhibits nearly isotropic compressibility. Negative thermal expansion was observed at low temperature range (20-80 K) in both transition-metal-free antiperovskites for the first time. The robust high pressure structure stability was examined and confirmed by first-principles calculations among various possible polymorphisms qualitatively. The results provide in-depth understanding of the negative thermal expansion and robust crystal structure stability of these antiperovskite systems and their potential applications.