Standard Thermal Annealing Research Articles

Hiking down the Free Energy Landscape Using Sequential Solvent and Thermal Processing for Versatile Ordering of Block Copolymer Films.

The kinetics and morphology of the ordering of block copolymer (BCP) films are highly dependent on the processing pathway, as the enthalpic and entropic forces driving the ordering processes can be quite different depending on process history. We may gain some understanding and control of this variability of BCP morphology with processing history through a consideration of the free energy landscape of the BCP material and a consideration of how the processing procedure moves the system through this energy landscape in a way that avoids having the system becoming trapped into well-defined metastable minima having a higher free energy than the target low free energy ordered structure. It is well known that standard thermal annealing (TA) of BCPs leads to structures corresponding to a well-defined stable free energy minimum; however, the BCP must be annealed for a very long time before the target low free energy structures can be achieved. Herein, we show that the same target low-energy structure can be achieved relatively quickly by subjecting as-cast films to an initial solvent annealing [direct immersion annealing (DIA) or solvent vapor annealing (SVA)] procedure, followed by a short period of TA. This process relies on lowering the activation energy barrier by reducing the glass-transition temperature through DIA (or SVA), followed by a multi-interface chain rearrangement through sequential TA. This energy landscape approach to ordering should be applicable to the process design for ordering many other complex materials.

The Effect of Annealing Technique on ZnO Film Properties

ZnO films deposited on glass substrates by ultrasonically chemical spray pyrolysis technique have been investigated to establish the effect of the annealing technique on film properties. For this purpose, films have been exposed to standard thermal annealing and microwave annealing in an air atmosphere. It has been determined that the structural, morphological, compositional, and optical properties of the ZnO films correlate with each other. X-ray diffraction analyses have been revealed the highest crystallization level and changing preferred orientations for microwave annealed films. It has been identified that the optical band gap values of the films decreased from 3.27 eV to 3.23 eV and 3.21 eV after the standard and microwave thermal annealing, respectively. Scanning electron microscope images have been revealed homogeneous morphology at plan-view images of all films. Also, it has been determined that the root-like morphology from the higher magnification scanning electron microscopy images. Thicknesses of the films have been also determined from cross-sectional scanning electron microscope images as 1.04m, 0.92m, and 0.92m for ZnO, standard thermal annealed and microwave annealed ZnO films, respectively. Also, the O/Zn ratio revealed improved stoichiometry for annealed films according to as-deposited film for investigated regions. The dependence of photoluminescence intensity on annealing technique has also been investigated in the current study.

Direct laser interference patterning of nonvolatile magnetic nanostructures in Fe60Al40 alloy via disorder-induced ferromagnetism

Current magnetic memories are based on writing and reading out the domains with opposite orientation of the magnetization vector. Alternatively, information can be encoded in regions with a different value of the saturation magnetization. The latter approach can be realized in principle with chemical order-disorder transitions in intermetallic alloys. Here, we study such transformations in a thin-film (35 nm) Fe60Al40 alloy and demonstrate the formation of periodic magnetic nanostructures (PMNS) on its surface by direct laser interference patterning (DLIP). These PMNS are nonvolatile and detectable by magnetic force microscopy (MFM) at room temperature after DLIP with a single nanosecond pulse. We provide different arguments that the PMNS we observe originate from increasing magnetization in maxima of the interference pattern because of chemical disordering in the atomic lattice of the alloy at temperatures T higher than the critical temperature Tc for the order (B2)-disorder (A2) transition. Theoretically, our simulations of the temporal evolution of a partially ordered state at T>Tc reveal that the disordering rate is significant even below the melting threshold. Experimentally, we find that the PMNS are erasable with standard thermal annealing at T<Tc.

Highly phase-pure spray-pyrolysed Cu2SnS3 thin films prepared by hybrid thermal treatment for photovoltaic applications

The structure and physical properties of thin films of ternary photovoltaic absorber Cu2SnS3 on soda-lime glass substrate deposited by cost effective spray pyrolysis following a hybrid thermal annealing (HTA) have been investigated. The advantage of HTA-sulfurization over standard thermal annealing (STA) and rapid thermal annealing (RTA) is established for Cu2SnS3 (CTS). The X-Ray diffraction (XRD) and Raman spectroscopy reveals highly phase pure Cu2SnS3 is produced through effective relaxation of compressive stress and increased crystallinity by the HTA-sulfurization step. Additionally, scanning electron microscopy (FE-SEM) and energy dispersive x-ray spectroscopy (EDX) reveals that the evolution of secondary phases, CuxSy (x, y: 116, 64; 2, 1; 1.8, 1; 51, 27; 6, 6 etc) could be effectively prevented by the HTA process over the STA and RTA. The optimized HTA-CTS thin films obtained are of p-type conductivity with the carrier concentration, resistivity and mobility of 5.5 × 1020 cm−3, 9.8 × 10−3Ω-cm and 1.15 cm2V−1s−1, respectively. The optical band gap of about 1.65 eV with large absorption coefficient of 105 cm−1 demonstrates it as an ideal candidate for thin film solar cells. A solar cell configuration of glass/F:SnO2/CTS/CdS/ZnO:Al/Al shows an open circuit voltage of 225 mV.

Low-temperature volume radiation annealing of cold-worked bands of Al-Li-Cu-Mg alloy by 20-40 keV Ar+ ion

The processes of radiation-dynamic nature (in contrast to the thermally-activated processes) in the course of short-term irradiation of 1 mm thick bands of cold-worked aluminum alloy 1441 (of system Al-Li-Cu-Mg) with Ar+ 20-40 keV were studied. An effect of in-the-bulk (throughout the whole of metal bands thickness) low-temperature radiation annealing of the named alloy, multiply accelerated as compared with common thermal annealing processes was registered (with projected ranges of ions of considered energies definitely not exceeding 0.1 μm). The processes of recrystallization and intermetallic structure changes (occurring within a few seconds of Ar+ irradiation) have the common features as well as the differences in comparison with the results of two hour standard thermal annealing.

Conditions for formation of germanium quantum dots in amorphous matrices by MeV ions: Comparison with standard thermal annealing

We investigate how MeV ions with different ion-beam parameters (ion type, electronic stopping power, and velocity) influence the formation, arrangement, and ordering quality in three types of ($\mathrm{Ge}+{\mathrm{SiO}}_{2})/{\mathrm{SiO}}_{2}$ multilayer films. The multilayers differ in total thickness, Ge-rich layer thickness, and Ge content. The results show that the most important parameter for structural manipulation with MeV ions is the electronic stopping power ${S}_{e}$. Ion velocity is found to be another crucial parameter, while at the same time it can be seen that the multilayer type does not play an important role. The temperature increase within the ion tracks is estimated using the thermal spike model and cluster separation distribution. The structural changes produced by ion beams and estimated temperatures are compared to those obtained by standard thermal annealing. It is concluded that the estimated temperatures within the ion tracks are in excellent agreement with the annealing temperatures and with the structural changes observed in the irradiated multilayers. Furthermore, a characteristic parameter of the temperature profile that presents the model-predicted temperature increase is determined for which the structural changes caused by ion beams are comparable to those achieved by standard annealing.

Synthesis and laser annealing of embedded CdSe-nanoparticles in SiO2 by pulsed excimer laser radiation

CdSe-semiconductor nanocrystals embedded in SiO2 on silicon have been synthesized by ion implantation of Cd+ and Se+ followed by pulsed excimer laser annealing at room temperature. Transmission electron microscopy and x-ray diffraction-analysis results suggest that wurzite-type embedded CdSe nanocrystals have been formed. Since laser annealing can be applied locally this opens a route towards spatially selective annealing. In a second type of experiment pulsed laser annealing was performed on embedded CdSe nanoparticles synthesized by standard thermal annealing resulting in oriented ellipsoidal deformation and morphological changes of the larger precipitates. Computer simulation results suggest a size-selective temperature increase of the CdSe nanocrystals as the underlying mechanism.

Effect of Annealing Method to Crystalize on Sr0.9Bi2.3Ta2O9+α Thin Film Properties Formed from Alkoxide Solution

Sr0.9Bi2.3Ta2O9+α (SBT) thin films were formed from a mixed alkoxide solution and were heat-treated by various annealing methods. The SBT thin film heat-treated with the standard temperature rising at a rate of 10°C/min (standard thermal annealing: STA) showed higher squareness (effective remanent polarization/effective saturation polarization) and effective remanent polarization values than those of the film heat-treated with a rapid temperature rise at a rate of 125°C/s (rapid thermal annealing: RTA). This difference was large in the region of low applied voltage. The low values of the SBT film with RTA treatment were caused by lower crystal continuity in the direction of film thickness than that of the SBT film with STA treatment. The SBT film with RTA treatment showed a higher leakage current density for the entire applied voltage region than that of the film with STA treatment. The higher leakage current density was caused by fine nonstoichiometric (Bi-rich) particles which exist at grain boundaries of large grains. Therefore, it was concluded that the high squareness ratio and low leakage current density are obtained in SBT film which has only one grain in the film thickness direction and does not have nonstoichiometry fine particles around grain boundaries.

Control of EL2 concentration and dislocation density in liquid encapsulated Czochralski-grown GaAs using laser processing

The authors report the first study of laser processing of GaAs under stoichiometry control. A series of experiments was performed to investigate the influence of laser processing on the electronic and structural properties of liquid encapsulated Czochralski-grown GaAs. A thermal treatment was used to convert samples from semi-insulating to conducting behaviour by severely reducing the EL2 concentration in the material. These samples were subjected to both laser processing and standard thermal annealing under stoichiometry control. Laser-assisted processing resulted in much stronger EL2 recovery rates than for standard thermal annealing and the tendency was more pronounced for arsenic-rich stoichiometry than with gallium-rich stoichiometry. Indeed, selected laser processing conditions were found to yield significantly higher sample resistivities than those of the starting material. Etch pit densities were studied as a function of the laser processing conditions and were found to be a minimum for near-stoichiometric conditions. A simple defect model is proposed and used to explain these experimental results.