Influence Of Growth Temperature Research Articles

Influence of growth temperature on the magnetization dynamics of sputtered CoFeB thin films on various substrates and their microwave device functionality

In the present investigation, sputtering growth of 100 nm thick Co40Fe40B20 (CoFeB) film has been investigated in a low temperature range from room temperature (RT) to 400 ℃ on silicon (Si), silicon dioxide (Si/SiO2), and sapphire (Al2O3) substrates. The film surface morphology, static and dynamic magnetization were measured as a function of growth temperature and substrate. The grown films were further tested as a potential material for microwave device functionality in terms of filter and phase shifter. Surface roughness was lowest for the film grown on Si/SiO2 substrate at 200 ℃ (0.39 nm) measured from atomic force microscopy. Static magnetic properties measured by tracing magnetic hysteresis loop suggest a soft magnetic behaviour with in-plane magnetic anisotropy. Film saturation magnetization increases with the increase in growth temperature up to 200 ℃ and then decreases from 200 ℃ to 400 ℃. This suggest that the sputtering growth from room temperature to 200 ℃ offer a moderate to low interfacial stress resulting in low defects density. Gilbert damping constant (αeff) of the thin film is obtained from the ferromagnetic resonance measurements in a broad band of microwave frequencies. Damping was lowest (5.4×10−3) in the film grown at 200 ℃ on the Si/SiO2 substrate which correlates with the roughness and magnetization data. A low value of αeff is desirable for a material to be used in energy efficient spintronics and magnonic applications. The CoFeB films were also utilized in prototype microwave band-stop filter and phase shifter device applications. The filter has been tested in the frequency range from 6GHz to 25GHz with an applied magnetic bias up to 4.0 kOe. The frequency tunability with respect to the applied magnetic bias measured to be around 3.64 GHz/kOe. The maximum attenuation of −4dB was observed for the film grown on Si/SiO2 substrate at 200 ℃. Whereas, phase shifter fabricated on Si/SiO2/CoFeB film grown at 200 ℃ shows a differential phase shift up to 75°/cm. These results indicates that the CoFeB film deposited at low growth temperature can be a potential material in spintronics and CMOS applications where low temperatures are required for device fabrications.

Investigation of temperature and H2 on GePb/Ge multiple quantum well growth

To reveal the growth behavior of GePb/Ge multiple quantum well (MQW) samples, both the influence of growth temperature and H2/Ar atmosphere are investigated by sputtering epitaxy. As the growth temperature increases from 250 °C to 400 °C, Pb atoms become more active and migrate easily to the surface, forming Pb clusters. As a result, the Pb composition in the GePb/Ge MQW is decreased from 3.5% to 1.8%. When H2 is introduced into the chamber, it is found that the MQW disappears and GePb film with uniform Pb distribution is formed. This is possibly because that the introduction of H2 can retain Pb atoms and the GePb is still grown even if the Pb flux is off. The results show that low temperature and H2 atmosphere are effective methods to further break the low solid solubility limit of Pb in Ge.

Influence of growth temperature on the properties of aluminum nitride thin films prepared by magnetron sputter epitaxy

High quality, uni-polar, epitaxial AlN with minimum oxygen content promises excellent surface acoustic wave and bulk acoustic wave resonator characteristics such as high electromechanical coupling coefficient and power handling capabilities, which is particularly useful for RF filter applications. By systematically varying the growth temperature, the study investigates its impact on the oxygen levels, defect states, and crystallographic texture of the AlN thin films using a combination of atomic force microscopy, X-ray diffraction, time-of-flight secondary ion mass spectrometry, spectroscopic ellipsometry, scanning transmission electron microscopy, as well as room temperature and temperature dependent I–V measurements. The research demonstrates that the films grown at a temperature of 700°C exhibit the most favorable results. These films exhibit the lowest oxygen levels, possess epitaxial growth, and display the highest crystalline quality (XRD AlN 0002 ω−FWHM=1.3°). Additionally, these films demonstrate a significant reduction in sub-bandgap absorption. By comparing the cathode current measured during deposition, we suggest that the presence of an impurity layer formed during idle time between depositions as a possible source of oxygen in the sputter chamber. In addition, the study presents a possible model to explain the mixed polarity observed in AlN and proposes various ways to achieve uni-polar AlN on silicon substrates.

Antimony Selenide Solar Cells Fabricated by Hybrid Reactive Magnetron Sputtering.

The fabrication of Sb2Se3 thin-film solar cells deposited by a pulsed hybrid reactive magnetron sputtering (PHRMS) was proposed and examined for different growth conditions. The influence of growth temperature and Se pulse period were studied in terms of morphology, crystal structure, and composition. The Sb2Se3 growth showed to be dependent on the growth temperature, with a larger crystal size for growth at 270 °C. By controlling the Se pulse period, the crystal structure and crystal size could be modified as a function of the supplied Se amount. The solar cell performance for Sb2Se3 absorbers deposited at various temperatures, Se pulse periods and thicknesses were assessed through current-voltage characteristics. A power conversion efficiency (PCE) of 3.7% was achieved for a Sb2Se3 solar cell with 900 nm thickness, Sb2Se3 deposited at 270 °C and Se pulses with 0.1 s duration and period of 0.5 s. Finally, annealing the complete solar cell at 100 °C led to a further improvement of the Voc, leading to a PCE of 3.8%, slightly higher than the best reported Sb2Se3 solar cell prepared by sputtering without post-selenization.

PLD of α-Ga2O3 on m-plane Al2O3: Growth regime, growth process, and structural properties

Phase-pure α-Ga2O3 thin films with high surface quality and crystallinity have been grown on m-plane sapphire using pulsed laser deposition (PLD). Therefore, the influence of growth temperature, oxygen background pressure, and film thickness on the structural properties is investigated to determine the growth window for phase-pure corundum structured α-Ga2O3. Samples were analyzed using x-ray diffraction (XRD), atomic force microscopy (AFM), and spectroscopic ellipsometry measurements. A distinct growth window in favor of phase-pure (10.0)-oriented α-Ga2O3 for growth temperatures above 480 °C and low oxygen partial pressures p(O2) of 3 × 10−4 mbar is identified. The growth rate increases significantly with increasing oxygen pressure. Furthermore, it shows an Arrhenius-like decrease for lower temperatures, caused by the increasing desorption of volatile Ga2O suboxides. It was found that for thicker layers, the growth of monoclinic β-Ga2O3 is promoted likely facilitated by the c-facets of the α-Ga2O3 grains. This leads to a (010)-oriented island growth corroborated by stripe-like features in AFM scans and a corresponding in-plane orientation confirmed by XRD ϕ-scans. For oxygen partial pressures above 3 × 10−4 mbar and Tg < 540 °C, the formation of mixed (10.0) α-Ga2O3 and spinel-defective (110)-γ-Ga2O3 manifesting as defective inclusions was observed independent of the layer thickness d. A corresponding p(O2) − d − T phase diagram for the growth of Ga2O3 on m-plane sapphire by PLD is provided.

Membrane lipid adaptation of soil Bacteroidetes isolates to temperature and pH.

3-hydroxy fatty acids (3-OH FAs) are characteristic components of the Gram-negative bacterial membrane, recently proposed as promising temperature and pH (paleo) proxies in soil. Nevertheless, to date, the relationships between the 3-OH FA distribution and temperature/pH are only based on empirical studies, with no ground truthing work at the microbial level. This work investigated the influence of growth temperature and pH on the lipid composition of three strains of soil Gram-negative bacteria belonging to the Bacteroidetes phylum. Even though non-hydroxy FAs were more abundant than 3-OH FAs in the investigated strains, our results suggest that 3-OH FAs are involved in the membrane adaptation of these bacteria to temperature. The strains shared a common adaptation mechanism to temperature, with a significant increase in the ratio of anteiso vs. iso or normal 3-OH FAs at lower temperature. In contrast with temperature, no common adaptation mechanism to pH was observed, as the variations in the FA lipid profiles differed from one strain to another. We suggest that models reconstructing environmental changes in soils should include the whole suite of 3-OH FAs present in the membrane of Gram-negative bacteria, as all of them could be influenced by temperature or pH at the microbial level.

Influence of growth temperature and miscut angle of m-plane sapphire substrate on the semi-polar (11–22) AlN film grown by HVPE

The high-quality semi-polar (11-22) AlN thin films were grown on m-plane sapphire substrates by hydride vapor phase epitaxy (HVPE). The surface morphology and crystalline quality of the AlN film were greatly influenced by the growth temperature and the substrate miscut angle. As the temperature increased, the grain size on the surface increased and the grain density decreased. In addition, the higher growth temperature also resulted in smaller values of the full width at half maximum (FWHM) of X-ray rocking curves (XRC) when temperature was more than 1,460 °C. At high temperature of 1,530 °C, the introduction of 1° -off miscut angle to the substrate resulted in smooth surface, low density of stacking faults and low FWHM of XRC. The misfit dislocation density was calculated from the tilt angle of epilayer measured by X-ray reciprocal space mappings along [−1−123] AlN. The misfit dislocation density of the sample grown on 1° -off substrates was 6.7 × 105 cm−2. The improvement of crystal quality is believed to be due to the enhancement of adatom mobility at higher temperatures and also the appropriate miscut variation.

Influence of growth temperature on microstructural and electromagnetic properties of nickel thin films

Nickel thin films were grown on quartz substrates in ultra‐high vacuum at laser fluence of 98 J/cm2 using pulsed laser deposition. Effects of substrate temperature on the electromagnetic properties of the films were investigated. XRD data reveal crystalline growth at substrate temperature (Ts) of 500°C. Roughness of the thin films at Ts of 100°C was noted as 8 nm which was decreased to 3 nm at 500°C. Coercive field and electrical resistivity were decreased from 10 to 5 mT and 0.71 to 0.064 μΩ‐m, respectively, at higher substrate temperature. Magnetoresistance for both modes of configuration and Hall mobility were decreased, while carrier density and Hall coefficient showed opposite behavior with increased substrate temperature.

Inactivation efficacy and mechanisms of atmospheric cold plasma on Alicyclobacillus acidoterrestris: Insight into the influence of growth temperature on survival.

The bactericidal effect of dielectric barrier discharge-atmospheric cold plasma (DBD-ACP, 20, and 30 kV) against Alicyclobacillus acidoterrestris on the saline solution and apple juice was investigated. Results show that DBD-ACP is effective for the inactivation of A. acidoterrestris by causing significant changes in cell membrane permeability and bacterial morphology. The effect of culture temperatures on the resistance of A. acidoterrestris to DBD-ACP was also studied. A. acidoterrestris cells grown at 25°C had the lowest resistance but it was gradually increased as the culture temperature was increased (25–45°C) (p < 0.05). Moreover, results from Fourier transform infrared spectroscopy (FT-IR) and Gas Chromatography-Mass Spectrometer (GC-MS) analysis showed that the increase in the culture temperature can gradually cause the decreased level of cyclohexaneundecanoic acid in the cell membrane of A. acidoterrestris (p < 0.05). In contrast, cyclopentaneundecanoic acid, palmitic acid, and stearic acid showed an increasing trend in which the fluidity of the bacterial cell membrane decreased. This study shows a specific correlation between the resistance of A. acidoterrestris and the fatty acid composition of the cell membrane to DBD-ACP.

Influence of growth temperature on the pinning landscape of YBa2Cu3O7− δ films grown from Ba-deficient solutions

Cuprate coated conductors are promising materials for the development of large-scale applications, having superior performance over other superconductors. Tailoring their vortex pinning landscape through nanostructure engineering is one of the major challenges to fulfill the specific application requirements. In this work, we have studied the influence of the growth temperature on the generation of intrinsic pinning defects in YBa2Cu3O7−δ films grown by chemical solution deposition using low Ba precursor solutions. We have analysed the critical current density as a function of the temperature, applied magnetic field magnitude and orientation, J c(T,H,θ), to elucidate the nature and strength of pinning sites and correlate the microstructure of the films with their superconducting performance. An efficient pinning landscape consisting of stacking faults and associated nanostrain is naturally induced by simply tuning the growth temperature without the need to add artificial pinning sites. Samples grown at an optimized temperature of 750 °C show very high self-field J c values correlated with an overdoped state and improved J c(T,H,θ) performances.

Characterization of low-temperature-grown ZnO nanoparticles: The effect of temperature on growth

The growth temperature of semiconducting nanoparticles is well known to be an essential factor in determining their structure and quality of characteristics. To create high-quality ZnO nanostructures, it is critical to optimize the growth temperature. The sol-gel approach is used to render ZnO NPs at different growth temperatures in this report. The influence of growth temperature on the material properties of ZnO nanoparticles has been extensively investigated. The scanning electron microscopy (SEM) images show needle-like structures when synthesized at low temperatures (35 and 45 °C) that transformed into spherical particles as the temperature of the growing medium increased to 75 °C. X-ray diffraction (XRD) analysis displays an increase in crystallinity with annealing temperatures. The average crystallite sizes of ZnO nanoparticles rose with increasing growth temperature and varied from 28 to 34 nm. The XRD peaks positions shift slightly towards lower 2θ angles with the growth temperatures brought about by a change in lattice parameters. The Fourier transform infrared spectroscopy (FTIR) study revealed the presence of a Z–O bond at around 680 cm−1. The intensity of the defect level emission (DLE) band decreased, as the growth temperature exceeded 35 °C. The photoluminescence (PL) study further demonstrated that the prepared nanoparticles had a strong emission peak at 546 nm. PL measurements confirm that with increasing growth temperature, the excitonic peak intensity increases, indicating that the quality of ZnO nanoparticles improves. The estimated bandgap changed from 3.31 to 3.24 eV with the growth temperature.

Influence of growth temperature on dielectric strength of Al2O3 thin films prepared via atomic layer deposition at low temperature

Thin films grown via atomic layer deposition (ALD) suffer from insufficient growth rate and unreliability for temperature-sensitive electronic substrates. This study aimed to examine the growth characteristics and dielectric strength of ALD Al2O3 films grown at low temperatures (≤ 150 °C) for potential application in flexible electronic devices. The growth rate of the Al2O3 films increased from 0.9 to 1.1 Å/cycle with increasing temperature and saturated at growth temperatures ≥ 150 °C, which is the critical temperature at which a complete oxidation reaction occurred. The dielectric strength was also improved with increasing growth temperature, and the films grown at 150 °C showed a high breakdown field strength (~ 8.3 MV/cm), attributable to the decrease in the carbon impurities and oxygen defects, as confirmed by X-ray photoelectron spectroscopy. Even at low growth temperatures (≤ 150 °C), ALD Al2O3 films showed an overall amorphous structure and extremely smooth surfaces regardless of the growth temperature.

Influence of growth temperature on light trapping properties of ZnO:Al nanorods grown on seed layers with crater-like structures

We report the growth and characterization of textured ZnO:Al (AZO) films with excellent optoelectronic properties. The surface morphology depended strongly on growth temperature; in particular, the effect of hydrothermal growth temperature on the optoelectronic properties and light trapping abilities of AZO nanorods grown on the crater-like AZO seed layers was investigated systematically. The AZO nanorods grown at 110°C were relatively dense, indicating that hydrothermal growth temperature can promote the growth of AZO nanorods along the direction perpendicular to the substrates. The difference in the height and orientation of AZO nanorods prepared at 100°C resulted in significant enhancement of light trapping abilities. In addition, the textured AZO films maintained low sheet resistance and high total transmittance.

Temperature Dependence of Ultrathin Mixed-Phase Ga2O3 Films Grown on the α-Al2O3 Substrate via Mist-CVD.

Alpha (α)- and beta (β)-phase gallium oxide (Ga2O3), emerging as ultrawide-band gap semiconductors, have been paid a great deal of attention in optoelectronics and high-performance power semiconductor devices owing to their ultrawide band gap ranging from 4.4 to 5.3 eV. The hot-wall mist chemical vapor deposition (mist-CVD) method has been shown to be effective for the growth of pure α- and β-phase Ga2O3 thin films on the α-Al2O3 substrate. However, challenges to preserve their intrinsic properties at a critical growth temperature for robust applications still remain a concern. Here, we report a convenient route to grow a mixed α- and β-phase Ga2O3 ultrathin film on the α-Al2O3 substrate via mist-CVD using a mixture of the gallium precursor and oxygen gas at growth temperatures, ranging from 470 to 700 °C. The influence of growth temperature on the film characteristics was systematically investigated. The results revealed that the as-grown Ga2O3 film possesses a mixed α- and β-phase with an average value of dislocation density of 1010 cm–2 for all growth temperatures, indicating a high lattice mismatch between the film and the substrate. At 600 °C, the ultrathin and smooth Ga2O3 film exhibited a good surface roughness of 1.84 nm and an excellent optical band gap of 5.2 eV. The results here suggest that the mixed α- and β-phase Ga2O3 ultrathin film can have great potential in developing future high-power electronic devices.

Evaluation of high-performance, self-powered and wavelength-selective InGaN/GaN multiple quantum well UV photodetectors fabricated on sapphire substrate: Analysis of the influence of growth temperature

The impact of growth temperature (GT), in the range from 875° to 825°C, on the morphological, structural, electrical, and optical properties of InGaN/GaN multiple quantum well ultraviolet photodetectors (UV-PDs) is investigated. Lowering of GT is found to increase In composition in the well layers and deteriorates surface and crystalline quality as confirmed via atomic force microscopy, and X-ray diffraction analyses. Under suitable light, all the fabricated devices show outstanding photoresponse properties. The detector fabricated using the epilayer grown at 825 °C (PD-A) exhibits the lower value of open circuit voltage which is related to the incorporation of In composition upon decreasing of GT. Despite the high dark current, PD-A shows the larger short circuit current density under a 1-sun-intensity measurement due to enlarged sub-bandgap photons absorption, resulting in a significant enhancement in energy conversion efficiency. The photocurrent measurements suggest that PD-A has a relatively better performance compared to others (higher GT) because of its higher values of responsivity, detectivity, superior bias, and light power-dependent photo-electric characteristics. In addition, the time-dependent photo-response characteristics reveal that PD-A has a greater capability to monitor fast varying UV signals. Finally, the evaluated results imply that the performance of UV-PDs is intensely influenced by GT.

Optical and surface properties of 3C–SiC thin epitaxial films grown at different temperatures on 4H–SiC substrates

A series of 3C–SiC films were grown on 4H–SiC substrates with different growth conditions using high-temperature chemical vapor deposition (HT-CVD). The influences of growth temperature (Tg) on the morphology, optical and material properties of films were assessed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman scattering spectroscopy (RSS). Significant effects of Tg on the film crystalline quality were observed from analyzing XRD and RSS results. XPS characterized the surface states of Si, C, O elements, and variations with Tg. The 3C–SiC Raman TO mode was found to shift to lower frequency with the increase of Tg in 1530–1580 °C. Temperature dependent Raman studies indicated the anharmonic coupling and variation of phonon lifetimes. The optimized Tg is obtained. • XRD/XPS/Raman: 3C/4H-SiC films. • Quantified defects- depth variation. • Optimized growth temperature. • HT phonon coupling.

The insertion of the ALD diffusion barriers: An approach to improve the quality of the GaN deposited on Kapton by PEALD

The influence of growth temperature (200–300 ℃) on the properties of gallium nitride (GaN) directly deposited on Kapton by plasma-enhanced atomic layer deposition (PEALD) has been systematically investigated. With increasing growth temperatures, the O content and surface roughness of the GaN thin films increase. Besides, the diffusion behavior of GaN in Kapton was found when the growth temperature exceeds 250 ℃. In this study, ultrathin ALD aluminum oxide (Al2O3) and aluminum nitride (AlN) films were proposed to see if they could alleviate and/or even suppress the negative effects of interface diffusion during high-temperature (≥250 ℃) GaN growth. It was found that oxygen impurities were significantly decreased within the as-deposited GaN. Furthermore, we observed a complete suppression of GaN diffusion into the Kapton throughout the entire growth process. Additionally, an introduction of either the Al2O3 or AlN before the GaN deposition could improve the surface morphology of the GaN deposited on Kapton.

The influence of temperature and TMGa flow rate on the quality of p-GaN

This paper studies in detail the influence of growth temperature and the TMGa flow rate on the quality of p-GaN. Through Hall and atomic force microscope tests on six samples of two growth series, we can find that a higher growth temperature and lower TMGa flow rate can enhance the electrical properties and improve the surface morphology of the material, that is, lower resistivity, greater carrier concentration, higher mobility, and lower roughness. These two growth methods share similar processes to improve material properties. The enhancement of gallium atom migration is the reason for the improvement in surface morphology. The reduction in carbon impurities is key to improving electrical device performance through secondary ion mass spectroscopy and room temperature photoluminescence tests. Moreover, the severity of contamination on the sample surface is positively correlated with the roughness of the sample, which further illustrates the importance of better surface quality.

Highly crystalline methylammonium lead iodide films: Phase transition from tetragonal to cubic structure by thermal annealing

Herein, a very simple, solvent free, scalable, and single-step approach to prepare organometal halide perovskite powders via mechanochemical synthesis followed by the deposition of perovskite films by spin coating is reported. This work particularly deals with various parameters that influence the crystallization process and morphology (hyperbranched) of methylammonium lead iodide films. Moreover, the influence of growth temperature on the morphology and the transition from tetragonal to cubic structure are investigated. The mechanosynthesized perovskite provides hyperbranched morphology and crystalline films in a hexagonal shape and serves as a better precursor for the absorber layer in perovskite solar cells.

Growth and Atomically Resolved Polarization Mapping of Ferroelectric Bi2WO6 Thin Films

Aurivillius ferroelectric $Bi_2WO_6$ (BWO) encompasses a broad range of functionalities, including robust fatigue-free ferroelectricity, high photocatalytic activity, and ionic conductivity. Despite these promising characteristics, an in-depth study on the growth of BWO thin films and ferroelectric characterization, especially at the atomic scale, is still lacking. Here, we report pulsed laser deposition (PLD) of BWO thin films on (001) $SrTiO_3$ substrates and characterization of ferroelectricity using the scanning transmission electron microscopy (STEM) and piezoresponse force microscopy (PFM) techniques. We show that the background oxygen gas pressure used during PLD growth mainly determines the phase stability of BWO films, whereas the influence of growth temperature is comparatively minor. Atomically resolved STEM study of a fully strained BWO film revealed collective in-plane polar off-centering displacement of W atoms. We estimated the spontaneous polarization value based on polar displacement mapping to be about 54 $\pm$ 4 ${\mu}C cm^{-2}$, which is in good agreement with the bulk polarization value. Furthermore, we found that pristine film is composed of type-I and type-II domains, with mutually orthogonal polar axes. Complementary PFM measurements further elucidated that the coexisting type-I and type-II domains formed a multidomain state that consisted of 90$\deg$ domain walls (DWs) alongside multiple head-to-head and tail-to-tail 180$\deg$ DWs. Application of an electrical bias led to in-plane 180$\deg$ polarization switching and 90$\deg$ polarization rotation, highlighting a unique aspect of domain switching, which is immune to substrate-induced strain.