Crystallization Behavior Of Films Research Articles

The effects of solvent polarity on the crystallization behavior of thin π-conjugated polymer film in solvent mixtures investigated by grazing incident X-ray diffraction

The crystal structure of thin π-conjugated polymer films is critical to their performance. Here, we utilized regio-regular poly (3-hexylthiophene-2,5-diyl) (P3HT) films as a model system with grazing incident X-ray diffraction (GIXD) characterization. We systematically studied the effects of solvent polarity on the control of the crystal structure of thin π-conjugated polymer films in mixed solvent immersion. The polarity of poor solvents plays an important role in the crystallization behavior of the films, and the polarity of good solvents slightly influences the crystallization behavior of the thin P3HT films. Non-polar poor solvents increase the crystallinity of thin π-conjugated P3HT films by producing new crystalline nuclei in the thin polymer films; however, polar poor solvents can improve crystallinity via crystal growth. The results of this work offer a better understanding of the crystallization behavior of thin π-conjugated polymer films induced by liquid mixtures. The results offer important insight into solvent immersion control technologies.

Study on the Crystallization Behavior of Ge2Sb2Te5 and Silicon Doped Ge2Sb2Te5 Films

Ge2Sb2Te5 thin films and Si doped Ge2Sb2Te5 thin films were deposited by electron beam evaporation method. The crystallization behaviors of the films were investigated by using the in situ resistance measurement. Through in situ resistance measurement, the increases of amorphous stability, crystallization rate and crystalline resistivity after Si doping were observed. The promoted nucleation process and the retardation of crystal growth were found in Si doped samples through the calculation of JMAK equation.

Growth Kinetics and Crystallization Behavior of TiO2 Films Prepared by Plasma Enhanced Atomic Layer Deposition

Atomic layer deposition (ALD) of films from tetrakis(dimethylamido) titanium (TDMAT) or titanium tetraisopropoxide (TTIP) precursors was investigated. The growth kinetics, chemical composition, and crystallization behavior of the films were compared for combinations of the two precursors with three different sources of oxygen [thermal ALD using and plasma-enhanced ALD (PEALD) using or plasma]. For TDMAT, the growth rate per cycle (GPC) decreased with increasing temperature; while for TTIP with either water plasma or plasma, a relatively constant growth rate per cycle was observed as a function of substrate temperature. It was found that the crystallization temperature of the films depends both on film thickness and on the deposition conditions. A correlation was observed between the crystallization temperature and the C impurity concentration in the film. The films grown using a plasma exhibit the lowest crystallization temperature and have no detectable C impurities. In situ X-ray diffraction measurements were used to test the diffusion barrier properties of the layers and proved that all films grown using either or plasma are dense and continuous.

Structural and optical properties of pulsed laser deposited SrBi 2Nb 2O 9 thin films

SrBi 2Nb 2O 9 (SBN) thin films were prepared on fused quartz substrates at room temperature by pulsed laser deposition. The influence of deposition parameters such as target-to-substrate distance, oxygen pressure and annealing temperature on film crystallization behavior was investigated by X-ray diffraction. Results indicated that the films grown at the optimum processing conditions have polycrystalline structure with a single layered perovskite phase. The optical transmittance of the films prepared at various oxygen pressures was measured in the wavelength range 200–900 nm using UV–vis spectrophotometer. The results showed that there is a red shift in the optical absorption edge with a rise in the oxygen pressure. Refractive index as a function of wavelength and optical band gap of the films were determined from the optical transmittance spectra. The results indicated that the refractive index increases with increasing oxygen pressure at the same incident light wavelength, while the band gap reduces from 4.13 to 3.88 eV. It may be attributed to an increase in packing density and grain size, and decrease in oxygen defects.

Crystallization behavior of Ge-doped eutectic Sb70Te30 films in optical disks.

We report laser-induced crystallization behavior of binary Sb-Te and ternary Ge-doped eutectic Sb70Te30 thin film samples in a typical quadrilayer stack as used in phase-change optical disk data storage. Several experiments have been conducted on a two-laser static tester in which one laser operating in pulse mode writes crystalline marks on amorphous film or amorphous marks on crystalline film, while the second laser operating at low-power cw mode simultaneously monitors the progress of the crystalline or amorphous mark formation in real time in terms of the reflectivity variation. The results of this study show that the crystallization kinetics of this class of film is strongly growth dominant, which is significantly different from the crystallization kinetics of stochiometric Ge-Sb-Te compositions. In Sb-Te and Ge-doped eutectic Sb70Te30 thin-film samples, the crystallization behavior of the two forms of amorphous states, namely, as-deposited amorphous state and melt-quenched amorphous state, remains approximately same. We have also presented experiments showing the effect of the variation of the Sb/Te ratio and Ge doping on the crystallization behavior of these films.

Unique Features of the Crystallization Kinetics of FeCrBSi Thin Films Obtained by Laser Ablation Deposition

AbstractPulsed laser deposition was used to obtain a metallic glass in thin film form using a Fe77Cr2B16Si5 amorphous ribbon as a target. The as-deposited films were annealed under the same conditions as the parent ribbon samples in order to compare their crystallization behaviors. Transmission Mössbauer measurements were performed to determine the crystallization products formed due to annealing of the Fe77Cr2B16Si5 ribbon. Conversion electron Mössbauer spectroscopy was used to obtain structural and magnetic information from the thin films as well as from the surface layers of the ribbons. Our Mössbauer study showed that crystallization behavior of the FeCrBSi thin films differs from both the surface and bulk crystallization of the ribbon. Crystallization occurs at lower annealing temperature for the thin film than for the bulk ribbon. Annealed films also contain iron oxides which are not observed in the crystallized ribbons. A formation of a very thin, protective oxide film at the surface of the ribbon is taken into account to explain the differences in the crystallization behavior of the films and ribbons.

Residual Stress, Adhesion and Crystallization of Ion-Sputtered and Ibed Processed NiTi Films

AbstractWhen conventional sputtering is used to deposit nickel-titanium thin films at temperatures below ∼623 - 723 Kelvins, the resultant structures are amorphous and the films must be annealed to form the requisite B2 parent ordering. This invites complications related to interface diffusion and chemical reaction with components of the substrate. For the present work, thin films of near-equiatomic NiTi were prepared on potassium chloride, (100) single-crystal silicon, and Si3N4 passivated silicon substrates by ion sputtering and by ion beam enhanced deposition (IBED). We have investigated residual stress levels produced by these processes, evaluated substrate adhesion levels, and explored the crystallization behavior of NiTi films grown under conditions of concurrent low-energy inert gas ion bombardment. Residual stresses of ionsputtered and IBED films were measured using profilometric techniques. Film crystallization behavior was studied by transmission electron microscopy of as-deposited films. Films produced by unassisted ion sputtering showed compressive residual stresses in the as-deposited amorphous state, which became highly tensile after annealing, leading to spontaneous cracking and delamination. Preliminary results from IBED experiments showed a reduction in the asdeposited stress, and improved adhesion. Under certain conditions, ion enhancement of the deposition process promoted film crystallization during deposition at moderate substrate temperature, producing a dispersion of extremely fine particles, indexed as Ni3Ti.

Thermodynamics of the stability of amorphous alloys of two transition metals

A scheme, recently proposed by Miedema and Niessen (MN), by which the concentration range is predicted in which amorphous binary transition metal alloys have high crystallization temperatures, has been tested for several alloy systems. The predictions are based on calculated values of the enthalpies of the amorphous phase and the f.c.c., h.c.p. and b.c.c. solid solutions. Thin films of W-Os, W-Ir, Ta-Re, Ta-Os, Ta-Ir, V-Pd, Nb-Pd and Ta-Pd were deposited at room temperature. The crystallization behaviour of films that were amorphous as deposited was investigated. For the 5d-5d systems, crystallization temperatures from 750 °C to 950 °C were observed. Using transmission electron microscopy and X-ray diffraction, some complex metastable phases were found as crystallization products. In agreement with the MN scheme plots of the crystallization temperature vs. average valence z̄ generally exhibit a maximum around - z = 6.7. However, the range of alloy compositions over which amorphous alloys are formed disagrees, in most cases, with the predicted one. We propose improvements for the calculation of the enthalpy curves.