Deposition of Langmuir-Blodgett layers

The behavior of a liquid being pulled out along a vertical plate is discussed, assuming that, in equilibrium, the liquid has a finite contact angle _e . Using a simplified form of the Huh-Scriven analysis for viscous friction, we show that a steady state solution (with a dynamic contact angle< _e ) exists provided that the velocity of pull-outU is below a certain thresholdU _m(_e). These considerations can be transposed (with a modification in numerical coefficients) to the case where the liquid is covered with a surfactant monolayer, to be transferred towards the solid in theY mode. SinceU _m is predicted in terms of interfacial tensions, this may provide a general scheme of interpretation for reactive deposition.     

Deposition of amorphous chromium layers

Deposition of amorphous chromium-carbon layers is possible from a trivalent chromium electrolyte containing 0.6?mol/l formic acid. The formation of chromium/formic acid complexes inhibits the aging of the electrolyte and the oligomerization. Deposition of a 15–20?μm thick chromium film is possible with DC condition. Thicker films can be deposited with pulse plating using reversed pulse sequences and pulse lengths in the millisecond region. The optimized conditions concerning pulse current densities and pulse times were determined and the composition and morphology of the films investigated.     

Segregation of organic impurities in thin electroplated Cu metallizations

This article presents investigations regarding the incorporation of organic impurities in thin electroplated Cu metallizations. RF-GD-OES (radio frequency glow discharge optical emission spectrometry) was used for detection of C and H as indicators for incorporated hydrocarbon molecules. The presented results indicate a fragmentation of incorporated hydrocarbons and their constrict segregation near the Cu surface. The bilateral relationship between incorporated organic impurities and intrinsic stress behavior is associated with the Gorky effect.     

Determination of carbon in electroplated gold layers by deuteron activation analysis

Carbon is determined in gold layers electroplated on brass, by deuteron activatin analysis using the¹²C/d, n/¹³N reaction. The results range from 2 to 1300 g.g^–1 and the relative standard deviation from 0.9 to 13%. It is quantitatively shown that the hardness of the gold increases with the carbon concentration and that the carbon concentration decreases with increasing plating temperature and increases to a certain limit with the plating current density.     

Preparation of thin films of platinum group metals by pulsed MOCVD. II. Deposition of Ru layers

In situ high-temperature mass spectrometry is used to analyze the thermal decomposition of Ru(acac)₃ and Ru(nbd)(allyl)₂ vapor and possible schemes of thermal transformations on the heated surface. By pulsed MOCVD with in situ mass spectrometric control of deposition processes ultrathin Ru layers with a thickness of several nanometers are obtained. The role of the reaction medium, precursor nature, and deposition temperature in the formation of a nanocrystalline structure of the films is revealed. Ruthenium films with a compact continuous structure are formed from Ru(acac)₃ and hydrogen at a deposition temperature of 340°C and below; an increase in the temperature results in the growth of nanogranular Ru layers. Regardless of deposition conditions, from Ru(nbd)(allyl)₂ granular nanocrystalline Ru layers are formed     

Preparation of thin films of platinum group metals by pulsed MOCVD. I. Deposition of Ir layers

Pulsed MOCVD with the in situ mass spectrometric control of the deposition process is employed to obtain ultrathin Ir layers with a thickness from units to tens of nanometers. The role of the reaction medium, precursor nature, and deposition temperature in the formation of the nanocrystalline structure of films is revealed. The deposition of Ir from Ir(acac)₃ in the oxygen atmosphere results in the formation of dense homogeneous structures, while in vacuum or in the hydrogen atmosphere, nanosized granular Ir layers are deposited. When Ir(CO)₂(acac) is used, Ir films with a granular structure are obtained regardless of the reaction medium.     

Sulfur incorporation in electroplated Cu(Ag) thin films

Cu(Ag) films are a promising interconnect material due to their low electrical resistivity and due to an expected increase of the electromigration resistance by alloying effects compared to pure copper films. Besides the alloying element also impurities are incorporated into the film during the electrochemical deposition process, which can retard or enhance electromigration damage. An impurity element of special interest is sulfur, which could probably improve the interconnect reliability besides the alloying element silver. In this paper, the incorporation, the distribution and the chemical state of sulfur in Cu(Ag) films is discussed in dependence on the thermal history. The investigations were mainly carried out by XPS and GD-OES measurements.     

Deposition of complex multielemental thin films

Modern condensed-matter physics is increasingly concerned with the design, synthesis, analysis, and exploitation of chemically complex materials and structures. Complex metal oxides and strongly correlated electron systems such as YBa₂Cu₃O_7−x and La_1−xSr_xMnO₃ are paradigmatic examples. Their production in the form of high-quality thin films is of both technological and fundamental importance and has stimulated a concerted effort in the last two decades to find and optimize efficient techniques to this end. This review discusses the physics behind and the requirements for synthesizing high-quality films of such materials and examines fundamental aspects of the growth processes associated with magnetron sputtering and pulsed laser deposition, the two techniques which presently offer the best solutions in this burgeoning field.     

Oscillations in thin nematic layers

In the present paper a thin nematic liquid crystal layer between two identical boundary surfaces (solid walls or free surfaces in the case of a freely suspended film) is considered. In a mean field approximation it is shown that the interference between the boundary surface-induced smectic density waves results in oscillations of the free energy of the nematic layer and disjoining pressure acting on the boundary surfaces. Theoretical dependence of disjoining pressure on the nematic layer thickness is in qualitative agreement with experiment. Also we have considered a thin film of polar nematic in which in addition to an ordinary monolayer smectic A phase (S_A1) with the layer thickness d equal to the molecular length l the partial bilayer smectic A phase (S_Ad) occurs. It is shown that the variation of the distance between the boundary surfaces can result in the oscillatory S_A1-A_Ad phase transitions in this nematic film     

Structure of water in thin layers

This paper considers the physical behavior of the boundary layers of water near the hydrophilic and hydrophobic surfaces. The overlapping of these layers leads to the generation of structural forces of repulsion, in the first case, and those of attraction, in the second. Inclusion of structural forces in the DLVO theory and the theory of heterocoagulation allows one to explain the results of measurements of contact angles for water solutions at different concentrations, pH values, and temperatures. The maximum influence of structural effects on colloid stability, wetting phenomena, and liquid flow in thin pores is to be expected in two extreme cases—that of a highly lyophobic system and that of a highly lyophilic one.     

Computer simulations of thin polymer layers

Molecular dynamics calculations are used to explore the structure of dense monolayers of long-chain molecules supported on a planar surface. As a model we consider ensembles of flexible chains consisting of N segments (N=32, 64 and 128) in a box with lateral (x, y) periodicity conditions. The effect of surface coverage on the conformational properties of chains is studied. At high coverages, the results of the simulations show that each chain is strongly stretched along the normal to the surface and the mean layer thickness is linear in N. The segment density distribution along the normal is found to be an universal function A^2/3 f (zA^1/3 N), where A is the surface area per chain. The high-coverage distribution has a well defined broad plateau, in agreement with the so-called blob model. In contrast to the predictions of this model, however, we observe that the chains are strongly stretched at all space scales. Differences between the results of simulations and those predicted by the mean-field theory are also discussed.     

Deposition and characterization of thin boron-carbide coatings

Summary Thin boron-carbide films were deposited using a PACVD process on Si substrates at room temperature. Various mixtures of B₂H₆/He and CH₄, as well as the less hazardous B(CH₃)₃, have been used as process gases. The composition of the deposited films has been correlated with the B₂H₆/He/CH₄ mixture used. When using B(CH₃)₃, the coatings were found to be slightly boron enriched compared to the gas phase stoichiometry. In both cases oxygen contaminants were additionally found (up to 5 at %) in the films. Most of the oxygen was incorporated from the residual gas at the beginning of the deposition. The coatings were hard and showed good adherence to the substrate; no film peel-off was observed after exposure to air. The films have been characterized, in-situ, by electron spectroscopy (XPS, UPS, AES), and by other methods (AES depth profiling, SEM, -step).     

Spreading of trisiloxanes over thin aqueous layers

Surfactants are widely spread in nature and are increasingly used in industry as wetting, cleaning and disinfecting agents. Recently, there are newly discovered trisiloxanes and other silicone based surfactants which show very unusual spreading behaviour. Although a number of experimental and theoretical investigations have been carried out, the underlying spreading mechanism remains unclear. Experiments using trisiloxanes and comparison with 3 different poly(ethylene glycol) monododecyl ethers (C₁₂E₄, C₁₂E₅, and C₁₂E₆) surfactants were performed to understand the influence of Marangoni force as the driving force for the spreading. We then compared our experimental results to available theoretical predictions in the literature. The obtained experimental data showed the opposite trend as compared with the theoretical predictions developed for regular surfactants. The latter is assumed to be a special feature of “superspreaders”. The article is published in the original.     

Deposition and investigation of lanthanum-cerium hexaboride thin films

Thin films of lanthanum-cerium hexaboride, the promising thermoelectric material for low-temperature applications, are deposited on various substrates by the electron-beam evaporation, pulsed laser deposition and magnetron sputtering. The influence of the deposition conditions on the films X-ray characteristics, composition, microstructure and physical properties, such as the resistivity and Seebeck coefficient, is studied. The preferred (100) orientation of all films is obtained from XRD traces. In the range of 780-800 °C deposition temperature the highest intensity of diffractions peaks and the highest degree of the preferred orientation are observed. The temperature dependence of the resistivity and the Seebeck coefficient of films are investigated in the temperature range of 4-300 K. The features appropriate to Kondo effect in the dependences ρ(T) and S(T) are detected at temperatures below 20 K. Interplay between the value of the Seebeck coefficient, metallic parameters and Kondo scattering of investigated films is discussed.     

Molecular structure of thin layers of pentameric polyorganocyclosiloxane

Birefringence in thin layers of a star-shaped pentameric polyorganocyclosiloxane has been studied by the oblique polarized beam method. The coefficient of birefringence is measured in relation to temperature and thickness of the surface layer. On the basis of these data, the melting temperature of the compound concerned is determined and the orientational-order parameter is estimated as ?0.27. The anisotropy of polarizabilities of pentameric polyorganocyclosiloxane molecules is theoretically estimated. A model of supramolecular structures that treats the formation of domains as stacks of pentameric polyorganocyclosiloxane molecules is advanced.