Annealing Of Amorphous Films Research Articles

Crystallization features and physical properties of the thin-film heterostructure of lead zirconate titanate – lead oxide

Various diagnostic techniques aimed at studying the structure and physical properties (synchronous thermal analysis, atomic force microscopy operating in the current measurement mode, electron-probe X-ray spectral microanalysis, dynamic method for determining the pyroelectric response) were used to study the crystallization features and physical properties of the thin-film heterostructure PZT – PbO1+x formed by a two-stage technique of RF magnetron sputtering of a ceramic target. During the first stage, amorphous films were deposited on a “cold” platinized silicon substrate, while the second stage involved high-temperature annealing in air. It was shown that annealing of amorphous films and crystallization of the intermediate pyrochlore phase are accompanied by additional oxidation of the structure resulting in the formation of lead orthoplumbate and lead dioxide and additional oxidation of organic inclusions. The presence of a liquid phase of lead oxide contributes to the formation of the pyrochlore phase. It was found that lead oxide layers have significantly higher through conductivity than perovskite blocks. It was assumed that the increased conductivity of lead oxide layers is associated with lead dioxide, which has high conductive properties. Self-polarized thin films were detected to have an abnormal electrical response to the strobing thermal exposure, including the typical pyroelectric response, local photoconductivity shunted by layers of the perovskite phase, and through photoconductivity. The presence of photoconductivity is also associated with the conductive properties of lead dioxide

Morphology of Vapor-Deposited Acetonitrile Films

Crystalline acetonitrile has two polymorphs, a high-temperature (HT) phase that is stable between 217 K and its melting point at 229 K and a low-temperature (LT) phase that is stable below 217 K. Solid acetonitrile films can be prepared by vapor deposition in an ultrahigh vacuum chamber. To prevent sublimation of the film, temperatures are often kept below 150 K. While the LT phase is thermodynamically favored at these low temperatures, such preparation usually results in the formation of the metastable HT polymorph. In this work we use reflection adsorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) experiments to investigate the effects of the deposition temperature and underlying substrate on the morphology of acetonitrile films prepared with molecular beam deposition. We obtained the elusive LT phase when dosing at 120 K on a graphene substrate and on a crystalline decane layer. Dosing acetonitrile on other surfaces produced the HT phase, as did annealing of amorphous films. We used TPD experiments to determine the Gibbs energy difference between the HT and the LT phases. Our ΔG values agree with extrapolation of equilibrium calorimetry data. We also observed that acetonitrile films were amorphous when dosed at temperatures ≤ 60 K and porous for temperatures ≤ 50 K.

Emergence of Rapid Oxygen Surface Exchange Kinetics during in Situ Crystallization of Mixed Conducting Thin Film Oxides.

The oxygen surface exchange kinetics of mixed ionic and electronic conducting oxides (MIECs) play a critical role in the efficiency of intermediate-to-high-temperature electrochemical devices. Although there is increasing interest in low-temperature preparation of MIEC thin films, the impact of the resultant varied degrees of crystallinity on the surface exchange kinetics has not been widely investigated. Here, we probe the effect of crystallization on oxygen surface exchange kinetics in situ, by applying an optical transmission relaxation (OTR) approach during annealing of amorphous films. OTR enables contact-free, in situ, and continuous quantification of the oxygen surface exchange coefficient ( kchem); we previously applied it to Pr xCe1- xO2-δ and SrTi1- xFe xO3-δ thin films. In this work, the OTR approach was successfully extended to other mixed conducting thin film compositions for the first time (i.e., perovskite SrTi0.65Co0.35O3-δ and Ruddlesden-Popper Sr2Ti0.65Fe0.35O4±δ), as well as to Pr0.1Ce0.9O2-δ, enabling quantification of the kchem of their native surfaces and comparison of the behavior of films with different final crystal structures. All thin films were prepared by pulsed laser deposition at 25 or 700-800 °C and subject to subsequent thermal treatments with simultaneous OTR monitoring of kchem. The surface roughness, grain size, and crystallinity were evaluated by scanning probe microscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Fluorite Pr0.1Ce0.9O2-δ films grown at 25 °C did not exhibit an increase in kchem after annealing, as they were already crystalline as grown at 25 °C. For all other compositions, OTR enabled in situ observation of both the crystallization process and the emergence of rapid surface exchange kinetics immediately upon crystallization. Perovskite SrTi0.65Co0.35O3-δ and Ruddlesden-Popper Sr2Ti0.65Fe0.35O4±δ thin films grown at 25 °C exhibited at least 1-2 orders of magnitude enhanced kchem after annealing compared with highly crystalline thin films grown at 800 °C, indicating the benefits of in situ crystallization.

Microstructure and Optical Properties during Annealing of DC Magnetron Sputtered LaB<sub>6</sub>/ITO Films on SiO<sub>2</sub> Substrates

Considering that nanosized LaB6 has unique optical properties and ITO has been widely applied for low-emission window glass, LaB6/ITO composite films were designed and prepared on SiO2 glass substrates by DC magnetron sputtering method in this paper. AFM and HRTEM methods were used for microstructure evolution analysis, and their IR and UV spectra were measured. Results proved that dense LaB6/ITO films with amorphous structure were deposited on the substrate with strong interface bonding. Crystallizing occurred during annealing of amorphous films, and the nanosized grains formed. Compared with the as-deposited films, the annealed films showed improved optical properties. Generally, the glass with the annealed film was available with more than 80% visible light transmittance, and good reflectance on UV light range.

Preparation of Polycrystalline CdTe Films by Annealing of Amorphous Films Electrodeposited from Ammoniacal Alkaline Baths

AbstractA new route to prepare polycrystalline CdTe films using electrodeposition of amorphous Cd-Te films and subsequent annealing was investigated. Amorphous Cd-Te films with Te-rich compositions could be electrodeposited from ammoniacal alkaline aqueous solutions. The deposition rate of the amorphous film was much higher than that of crystalline CdTe. Annealing of the Te-rich amorphous Cd-Te film at 400 °C in air yielded a crystallized CdTe film with a nearly stoichiometric composition. Thermodynamic calculations of the vapor pressures of Cd and Te species suggested that the decrease in the Te content of the annealed film was due to the vaporization of Te in the forms of oxides. Although an isothermal annealing generated a number of large holes in the film, an annealing with a slow temperature ramp resulted in a crystalline CdTe film without the large holes.

Electrical conductivity of M-Ge (M = Al, Sc, Y) films

The microstructure and electrical conductivity of microcrystalline and granular M-Ge (M = Al, Sc, Y) films are studied. The results demonstrate that annealing of amorphous films gives rise to microstructural changes and influences the temperature ranges of different conduction mechanisms. The electrical properties of microcrystalline and granular films are compared.

Effect of crystallization of amorphous vanadium dioxide films on the parameters of a semiconductor-metal phase transition

The hysteresis loops of reflectivity and capacitance of amorphous and polycrystalline vanadium dioxide films in the range of a semiconductor-metal phase transition were studied. The morphology of these films was studied by an atomic-force microscope. It is established that the small number (2–3) of temperature cycles suppress the phase transition due to possible diffusion of oxygen from VO2 clusters into adjacent clusters consisting of the lowest oxides of the Magnelli series. It is shown that the annealing of an amorphous film of vanadium dioxide in oxygen leads to an additional oxidation of low oxides and the formation of VO2, the formation of a polycrystalline film, and the recovery of the phase transition. The above results and the data obtained by atomic-force microscopy are indicative of the high optical quality of the polycrystalline vanadium dioxide films produced by the annealing of amorphous VO2 films. The results also show that these films can be used in interferometers and optical limiters.

Effects of deposition and annealing conditions on the structure and electrical properties of LPCVD silicon thin films

Deposition temperature and annealing conditions have pronounced effects on the structure and electrical properties of LPCVD silicon thin films. Films grown at 580°C are amorphous whereas those grown at 620°C are microcrystalline. All thin films are subjected to phosphorous diffusion followed by different annealing treatments. Annealing of amorphous films at 1000°C results in large grains with no favoured orientation and with a relatively high mobility value. Annealing treatment at 1000°C of the microcrystalline sample results in moderate grain growth with a relatively low mobility which presumably is due to some favoured grain orientation.

Effect of heat treatment on the magnetic compensation state of amorphous Gd–Co and layered Gd/Co films

Abstract The influence of heat treatment on the magnetic properties of amorphous Gd 22 Co 78 and multilayered {Gd(75 A)/Cu(L Cu )/Co(30 A)/Cu(L Cu )} 20 films close to the magnetic compensation state has been investigated. It is found that annealing of amorphous films at temperatures up to 250°C results in the disappearance of perpendicular anisotropy and magnetic compensation. The heat treatment of the multilayered films leads to an increase of the compensation temperature, which is less pronounced in the samples with Cu layers. These changes are attributed to initial stages of phase transformations in amorphous films and to interlayer diffusion in the multilayered films.

Effect of interphase boundaries on resistivity and thermopower of nanocrystalline Re-Si thin film composites

The phase formation, electrical resistivity, and thermoelectric power of the thin film Re-Si composites have been investigated at different stages of the transformation from the amorphous to nanocrystalline state. The nanocrystallization was achieved by the annealing of amorphous films with the initial composition ${\mathrm{Re}}_{0.34}{\mathrm{Si}}_{0.66},$ which is equal to the composition of the crystalline ${\mathrm{ReSi}}_{2}$ semiconductor. The composite films include only two phases: the amorphous phase and the nanocrystalline ${\mathrm{ReSi}}_{2}$ with the mean grain size of about 10 nm; however, a large volume fraction of the composite films is occupied by interfaces and intergrain regions. The transport properties of this semiconductor-semiconductor system show nonmonotonic dependence on the volume fraction of the nanocrystalline phase. The role of the interfaces in this peculiar behavior is discussed.

Magnetic resonance of sputtered Bi2DyFe5O12 films

Magnetic resonance measurements have been performed on amorphous and crystalline Bi2DyFe5O12 films. It is found that the amorphous films containing Fe3+ ions show no magnetic resonance at 71 and 300 K. The crystalline films obtained by annealing of amorphous films above the crystallization temperature exhibit a normal ferromagnetic resonance spectrum. As the annealing temperature increases, the effective magnetization and anisotropy constant increase, the ferromagnetic resonance linewidth decreases, and the g-factor shows a small change.

Optical thin films produced by nonvacuum techniques

A number of nonvacuum techniques applicable in optical thin-film technology are described in some detail. The following are presented: ideal thin optical layers; monocrystalline coatings grown by liquid phase epitaxy; atomic-monolayer growth; chemical aerosol decomposition; spinning and dipping; galvanocoating or electrochemical processing; chemical etching; metal annealing and (laser) annealing of amorphous films.

Preparation and properties of CdSb thin films

CdSb films with various composition were prepared by the two-source vacuum deposition method. Crystallization of the films was investigated for the various evaporating conditions, and electrical properties such as conductivity, Hall mobility and Seebeck coefficient were measured using as-deposited and annealed films with various Cd contents. The films with 10–25% Cd content (weight %) were amorphous of a low conductivity and large Seebeck coefficient. Crystalline state of CdSb appeared at the Cd content of above 30%. Annealing of amorphous films had a remarkable effect on those properties, while crystalline films had little effect.