Temperature-dependent Growth Research Articles

COOLAIR and PRC2 function in parallel to silence FLC during vernalization

Noncoding transcription induces chromatin changes that can mediate environmental responsiveness, but the causes and consequences of these mechanisms are still unclear. Here, we investigate how antisense transcription (termed COOLAIR) interfaces with Polycomb Repressive Complex 2 (PRC2) silencing during winter-induced epigenetic regulation of Arabidopsis FLOWERING LOCUS C (FLC). We use genetic and chromatin analyses on lines ineffective or hyperactive for the antisense pathway in combination with computational modeling to define the mechanisms underlying FLC repression. Our results show that FLC is silenced through pathways that function with different dynamics: a COOLAIR transcription-mediated pathway capable of fast response and in parallel a slow PRC2 switching mechanism that maintains each allele in an epigenetically silenced state. Components of both the COOLAIR and PRC2 pathways are regulated by a common transcriptional regulator (NTL8), which accumulates by reduced dilution due to slow growth at low temperature. The parallel activities of the regulatory steps, and their control by temperature-dependent growth dynamics, create a flexible system for registering widely fluctuating natural temperature conditions that change year on year, and yet ensure robust epigenetic silencing of FLC.

Mapping current and future habitat suitability of Azolla spp., a biofertilizer for small-scale rice farming in Africa.

How do we feed the expanding human population without excessive resource depletion or environmental degradation? Recycling and recapturing nutrients could alleviate these challenges, especially if these strategies are robust to climate change. Co-cultivating rice with Azolla spp. in Asia has demonstrated high yields with reduced fertilizer inputs because Azolla fixes atmospheric nitrogen, limits nitrogen volatilization, recaptures and releases other nutrients, and suppresses weeds. While Azolla is distributed in Africa, this approach has not been widely implemented in African rice-farming. Characterizing the suitability of Azolla is critical in evaluating the potential for Azolla-rice in Africa. To do so, we synthesized 189 field and greenhouse studies from around the world that quantified temperature-dependent growth of A. pinnata and A. filiculoides and developed present and future climate suitability maps at the continental scale using mean temperatures under two Representative Concentration Pathways. Currently, most of Africa is suitable for Azolla with slight differences in regional suitability for each species. We project little change in the continent-wide suitability for both species, but anticipate a regional decline, particularly for A. filiculoides in the Sahel. Collaborating with farmers to validate these projections, evaluate the costs and benefits of Azolla-rice, and facilitate adoption of viable strategies can facilitate equitable food systems that also empower African farmers.

Heat wave-induced microbial thermal trait adaptation and its reversal in the Subarctic.

Climate change predictions suggest that arctic and subarctic ecosystems will be particularly affected by rising temperatures and extreme weather events, including severe heat waves. Temperature is one of the most important environmental factors controlling and regulating microbial decomposition in soils; therefore, it is critical to understand its impact on soil microorganisms and their feedback to climate warming. We conducted a warming experiment in a subarctic birch forest in North Sweden to test the effects of summer heat waves on the thermal trait distributions that define the temperature dependences for microbial growth and respiration. We also determined the microbial temperature dependences 10 and 12 months after the heat wave simulation had ended to investigate the persistence of the thermal trait shifts. As a result of warming, the bacterial growth temperature dependence shifted to become warm-adapted, with a similar trend for fungal growth. For respiration, there was no shift in the temperature dependence. The shifts in thermal traits were not accompanied by changes in α- or β-diversity of the microbial community. Warming increased the fungal-to-bacterial growth ratio by 33% and decreased the microbial carbon use efficiency by 35%, and both these effects were caused by the reduction in moisture the warming treatments caused, while there was no evidence that substrate depletion had altered microbial processes. The warm-shifted bacterial thermal traits were partially restored within one winter but only fully recovered to match ambient conditions after 1 year. To conclude, a summer heat wave in the Subarctic resulted in (i) shifts in microbial thermal trait distributions; (ii) lower microbial process rates caused by decreased moisture, not substrate depletion; and (iii) no detectable link between the microbial thermal trait shifts and community composition changes.

Microbiome and photoperiod interactively determine thermal sensitivity of polar and temperate diatoms.

The effect of temperature on ectothermic organisms in the context of climate change has long been considered in isolation (i.e. as a single driver). This is challenged by observations demonstrating that temperature-dependent growth is correlated to further factors. However, little is known how the chronobiological history of an organism reflected in its adaptation to re-occurring cyclic patterns in its environment (e.g. annual range of photoperiods in its habitat) and biotic interactions with its microbiome, contribute to shaping its realized niche. To address this, we conducted a full-factorial microcosm multi-stressor experiment with the marine diatoms Thalassiosira gravida (polar) and Thalassiosira rotula (temperate) across multiple levels of temperature (4°C; 9°C; 13.5°C) and photoperiod (4 h; 16 h; 24 h), both in the presence or absence of their microbiomes. While temperature-dependent growth of the temperate diatom was constrained by short and long photoperiods, the polar diatom coped with a 24 h photoperiod up to its thermal optimum (9°C). The algal microbiomes particularly supported host growth at the margins of their respective fundamental niches except for the combination of the warmest temperature tested at 24 h photoperiod. Overall, this study demonstrates that temperature tolerances may have evolved interactively and that the mutualistic effect of the microbiome can only be determined once the multifactorial abiotic niche is defined.

A potential growth thermal index for estimating juvenile Atlantic salmon (Salmo salar) size-at-age across geographical scales.

We present a potential growth thermal index (PGTI) and assess its correlation with juvenile Atlantic salmon Salmo salar fork length data collected near the end of the growth season in a range of latitudinal locations and geographic scales (watershed, regional, continental) across the American north-east. The PGTI is based on two components: a water temperature-dependent growth curve and a water temperature time series continuously describing the thermal environment preceding fish sampling. Testing various shapes and characteristics of the temperature-growth curve against fish length data revealed strong positive correlations for all combinations. PGTI warming, calculated only from the beginning of the growth season until maximum summer temperature is reached, consistently performed well in explaining fish size-at-age across the latitudinal gradient and the three geographic scales that were considered. Varying thermal contrasts created by repeat subsampling of the dataset showed that fish length is better explained by the level of thermal contrast within the dataset than the geographical scale of analysis. A simple generalized linear model using a log link function with PGTI warming, fish density and water discharge as predictors explained 87% of the variance of size-at-age of 0+ and 1+ juvenile Atlantic salmon.

Selection of lactic acid bacteria for biopreservation of salmon products applying processing-dependent growth kinetic parameters and antimicrobial mechanisms

Biopreservation using lactic acid bacteria (LAB) is a promising technology to prevent the growth of pathogenic microorganisms in fresh and mildly processed food. The main aim of this study was to select LAB, originally isolated from ready-to-eat (RTE) seafood, for biopreservation of fresh salmon and processed salmon products. Ten LAB strains (five Carnobacterium and five Leuconostoc) were selected based on previously demonstrated bioprotective properties to investigate their antimicrobial mechanisms and temperature-dependent growth kinetics in a sterile salmon juice model system. Furthermore, five strains (three Carnobacterium and two Leuconostoc) were selected to test process-dependent growth kinetic parameters relevant to the secondary processing of salmon. Two strains (Carnobacterium maltaromaticum 35 and C. divergens 468) showed bacteriocin-like activity against Listeria innocua, while inhibitory effect of cell-free supernatants (CFS) was not observed against Escherichia coli. All selected strains were able to grow in sterile salmon juice at tested temperatures (4, 8, 12 and 16 °C), with specific growth rates (μ) ranging from 0.01 to 0.04/h at 4 °C and reaching a maximum population density of 8.4–9 log CFU/ml. All five strains tested for process-dependent growth kinetic parameters were able to grow in the range of 0.5–5% NaCl and 0.13–0.26% purified condensed smoke (VTABB and JJT01), with inter- and intraspecies variation in growth kinetics. According to the temperature-dependent growth kinetics and antimicrobial assay results, two strains, Leuconostoc mesenteroides 68 (Le.m.68) and C. divergens 468 (C d.468), were selected for in situ test to validate their ability to grow in vacuum-packed fresh salmon at 4 °C. Both strains were able to grow at maximum growth rates of 0.29 ± 0.04/d for Le. m.68 and 0.39 ± 0.06/d for C.d.468, and their final concentrations were 7.91 ± 0.31 and 8.02 ± 0.25 log CFU/g, respectively. This study shows that LAB, originally isolated from RTE seafood, have promising potential as bioprotective strains in fresh and processed salmon products.

Toward Quantum Chemical Free Energy Simulations of Platinum Nanoparticles on Titania Support.

Platinum nanoparticles (Pt-NPs) supported on titania surfaces are costly but indispensable heterogeneous catalysts because of their highly effective and selective catalytic properties. Therefore, it is vital to understand their physicochemical processes during catalysis to optimize their use and to further develop better catalysts. However, simulating these dynamic processes is challenging due to the need for a reliable quantum chemical method to describe chemical bond breaking and bond formation during the processes but, at the same time, fast enough to sample a large number of configurations required to compute the corresponding free energy surfaces. Density functional theory (DFT) is often used to explore Pt-NPs; nonetheless, it is usually limited to some minimum-energy reaction pathways on static potential energy surfaces because of its high computational cost. We report here a combination of the density functional tight binding (DFTB) method as a fast but reliable approximation to DFT, the steered molecular dynamics (SMD) technique, and the Jarzynski equality to construct free energy surfaces of the temperature-dependent diffusion and growth of platinum particles on a titania surface. In particular, we present the parametrization for Pt-X (X = Pt, Ti, or O) interactions in the framework of the second-order DFTB method, using a previous parametrization for titania as a basis. The optimized parameter set was used to simulate the surface diffusion of a single platinum atom (Pt1) and the growth of Pt6 from Pt5 and Pt1 on the rutile (110) surface at three different temperatures (T = 400, 600, 800 K). The free energy profile was constructed by using over a hundred SMD trajectories for each process. We found that increasing the temperature has a minimal effect on the formation free energy; nevertheless, it significantly reduces the free energy barrier of Pt atom migration on the TiO2 surface and the transition state (TS) of its deposition. In a concluding remark, the methodology opens the pathway to quantum chemical free energy simulations of Pt-NPs' temperature-dependent growth and other transformation processes on the titania support.

Thermal dependence of Daphnia life history reveals asymmetries between key vital rates

Temperature variation affects virtually every aspect of ectotherms' ecological performance, such as their foraging rate, reproduction, and survival. Although these changes influence what happens at higher levels of organizations, such as populations and communities, qualitative changes in dynamics usually require some degree of asymmetry between key vital rates, i.e. that different vital rates, such as growth, development, fecundity and mortality rates, respond differently to temperature. In order to identify possible asymmetries among vital rates and/or life stages, we characterized the thermal response of individuals a clone of Daphnia sinensis, drawn from a high-mountain environment in Taiwan, and examined the temperature dependence of growth, maturation, reproduction, and mortality rates, as well as fitness measures (r and R0) at eight temperatures. Daphnia sinensis was able to maintain reproductive success over a broad range of temperatures, much wider than the one experienced in its environment. However, negative effects of temperature were perceptible at temperatures much lower than the highest one at which they can achieve reproductive success. Adult mortality greatly increased for temperatures above 23 °C, and other vital rates started to decelerate, resulting in a large drop in lifetime reproductive success. This finding implies that D. sinensis may be able to persist over a wide range of temperatures, but also that it may become more sensitive to the detrimental effect of species interactions at increased temperatures. Different vital rates responded relatively similarly at low temperatures, but the degree of asymmetry among these rates was much more pronounced at higher temperatures. In particular, rates associated with adult performance decelerated more strongly than juveniles’ rates. These findings indicate that elevated temperatures affect the balance between juvenile and adult performance, which is known to have a crucial role in Daphnia population dynamics. We discuss the implications of these results for the dynamics of structured populations.

Temperature-Dependent Growth Characteristics and Competition of Pseudanabaena and Microcystis

Global warming has been considered to accelerate the expansion of cyanobacterial blooms, which are frequently composed of the bloom-forming genera, Microcystis and Pseudanabaena, in freshwater ecosystems worldwide. Nonetheless, the impact of changes due to toxin production or lack thereof on the growth of co-existing strains, both arising from increasing temperature, has remained unknown to date. We conducted competition experiments involving toxic Microcystis PCC7806, a non-toxic mcyB− mutant, and two strains of Pseudanabaena (TH-1 and DC-1) identified as P. mucicola. In mono-culture, the specific growth ratio of Pseudanabaena increased; nevertheless, the maximum cell density declined with increasing temperature. The maximum growth ratios of Pseudanabaena TH-1 and Pseudanabaena DC-1 were 0.512 day−1 in the 30 °C group and 0.440 day−1 in the 35 °C group, respectively. The optimum temperature for the growth of Pseudanabaena was 25 °C. Remarkably, there was no significant disparity in the maximum cell density of Microcystis PCC7806 and the mcyB− mutant across varied temperature groups, even though their maximum growth rates differed marginally, reaching 0.280 day−1 and 0.306 day−1 in the 30 °C group, respectively. In co-cultures, the growth of Pseudanabaena TH-1 was uniformly inhibited, whereas that of DC-1 was somewhat influenced by co-culturing with toxic and non-toxic Microcystis, except for the 35 °C group, where inhibition was absent amongst DC-1 and Microcystis. Moreover, the growth of Microcystis was promoted with a co-culture of TH-1 in the 20 °C groups. Conversely, the co-culture of Microcystis with Pseudanabaena DC-1 led to the inhibition of the former in the 30 °C and 35 °C groups. With a Lotka–Volterra competition model, the results showed that Microcystis dominated or co-existed with Pseudanabaena, conforming to expectations from the wild.

Temperature-dependent growth kinetic and crystallization behavior of the supercooled erythritol as a phase change material in long-term heat storage

Along with the development of long-term heat storage, the utilization of sugar alcohol with large supercooling has been valued in recent years. However, the heat release rate is not easy to control, and the supercooling would be easily influenced by accident factors. Different from the research of directly developing the composites to control the heat release rate and keep stable supercooling, this paper investigated the temperature-dependence crystal growth of erythritol coupled with diffusion-limited kinetics to find the mechanism for better understanding the utilization of supercooling upon different heat needs. The mean crystal growth rate (vm) on supercooled erythritol and the thermodynamic parameters were characterized experimentally. A nucleation factor J* was proposed to improve the modern Wilson-Frenkel equation, which enables a more accurate reflection of the nucleation effect on the practical vm. The sensitivity analysis indicates that the diffusion coefficient (D) and liquid–solid interfacial free energy (IFE1) have a great impact on vm, with 62% and 37% correlations. To verify this result, 0.1 wt% PVA was added to erythritol, which resulted in a significant reduction in the vm maximum by 33.3%. An oil seal was added to reduce the liquid–air interfacial free energy (IFE2) of erythritol, which significantly extended the supercooling duration to 5 days with a 12% cumulative crystallization fraction. Moreover, the crystal morphology analysis revealed that the maximum growth rate had preferred orientations of (211), the largest grain boundary size of 9.2 mm, and exhibited three-dimensional growth. This work can aid in the creation of a dependable heat release model for sugar alcohols in long-term heat storage systems.

Prevalence, Identity, Pathogenicity, and Infection Dynamics of Botryosphaeriaceae causing Avocado Branch Canker in California.

Botryosphaeria branch canker and dieback of avocado has expanded in avocado growing areas in recent years. Twenty-one avocado groves in major California producing regions were surveyed in 2018 and 2019. Monthly inoculations of wounded, green and lignified branches of 'Hass' and 'Lamb Hass' were conducted. Botryosphaeriaceae were the predominant fungi recovered from cankered tissues collected across traditional and high-density orchards, causing symptoms on all sampled cultivars. These fungi were also recovered in asymptomatic twigs and other organs, thus exist as potential reservoir for future infections. Molecular analyses of 173 isolates showed that Neofusicoccum luteum had the greatest incidences across sites and cultivars, with 83 and 29% recovered from 'Hass' and 'Lamb Hass', respectively. Pathogenicity tests on excised ('Hass', 'GEM', and 'Hass' mutants), attached shoots from potted ('Hass') and mature avocado trees ('Hass' and 'Lamb Hass') showed that all species were pathogenic on wounded, green, and mature branches. Monthly inoculations of wounded, green and lignified branches of 'Hass' and 'Lamb Hass' showed that both stem types were susceptible throughout the inoculation periods, regardless of the avocado phenological stage. In temperature-dependent growth and infection studies, growth of three Botryosphaeriaceae was higher between 20 and 30 °C, but only Lasiodiplodia theobromae significantly grew and caused external lesions at 35 °C. Lasiodiplodia theobromae also grew more on perseitol-amended media, all indicating its adaptation to warmer temperatures and capacity in metabolizing the avocado-produced sugar. Overall, this study extended our knowledge of the biology of Botryosphaeriaceae on avocados, which will be useful to tailor management strategies.

Molecular Layer Deposition of Organic–Inorganic Hafnium Oxynitride Hybrid Films for Electrochemical Applications

The molecular layer deposition (MLD) method can be used to deposit hybrid organic–inorganic films with precisely defined composition, flexible properties, and conformality on different substrates. In this study, hafnium-based organic–inorganic hybrid polymer films were studied as potential coatings for silicon nanoparticles (SiNPs) used in composite lithium-ion battery (LIB) anodes, an application which requires the film to be both flexible and stable under electrochemical conditions. Hf-hybrid films were successfully deposited by MLD using sequential exposure of the homoleptic tetrakis(dimethylamido) hafnium complex and ethanolamine as the reactants. The self-limiting surface reactions lead to a constant growth per cycle (GPC) of ∼2.0 Å/cycle at 120 °C. Temperature-dependent growth was observed, with the GPC decreasing from ∼2.5 to ∼1.1 Å/per cycle as the temperature was increased from 65 to 145 °C. Scanning transmission electron microscopy and electron energy loss spectroscopy mapping confirm that a thin, dense, and conformal Hf-based MLD layer is deposited on the SiNPs. The presence of expected C–N, C–O, and −CH2 moieties in the MLD films was confirmed by Fourier transform infrared spectroscopy. Hafnium nitride and hafnium oxide bonds within the hybrid thin films were identified by X-ray photoelectron spectroscopy. Characterization results indicated that the deposited hafnium-based organic–inorganic hybrid films contain both metal oxynitride bonds and organic bonds, including C–C, C–O, and C–N. This Hf-based MLD thin film was tested on LIB SiNP composite anodes as an artificial solid–electrolyte interphase, with results showing that the capacity retention increased by about 35% after 110 cycles in a LIB application.

Warmer temperatures favor slower-growing bacteria in natural marine communities

Earth's life-sustaining oceans harbor diverse bacterial communities that display varying composition across time and space. While particular patterns of variation have been linked to a range of factors, unifying rules are lacking, preventing the prediction of future changes. Here, analyzing the distribution of fast- and slow-growing bacteria in ocean datasets spanning seasons, latitude, and depth, we show that higher seawater temperatures universally favor slower-growing taxa, in agreement with theoretical predictions of how temperature-dependent growth rates differentially modulate the impact of mortality on species abundances. Changes in bacterial community structure promoted by temperature are independent of variations in nutrients along spatial and temporal gradients. Our results help explain why slow growers dominate at the ocean surface, during summer, and near the tropics and provide a framework to understand how bacterial communities will change in a warmer world.

Temperature dependent growth of InAs/InAsSb superlattices by molecular beam epitaxy for HOT mid-wavelength infrared detectors

High-quality InAs/InAs1-xSbx type-II superlattices (T2SLs) were grown on GaSb substrates by molecular beam epitaxy for high operating temperature (HOT) mid-wave infrared detectors. The optimal growth conditions for T2SLs were obtained by determining the temperature dependence of defects formation and the effect of V/III fluxes ratio on strain and composition. The material properties of proposed T2SLs grown with various temperature and Sb/In flux ratios were investigated using standard characterization methods, including high-resolution X-ray diffraction, atomic force microscopy, and photoluminescence (PL). The zero-order peak full width at half maximum (FWHM) of 18.4 arcsec, surface roughness less than 3 Å, strain balance, and distinct PL intensity is achieved in InAs/InAs0.65Sb0.35 T2SL. Temperature-dependent PL, ranging from 70 K to 240 K, shows a slight peak shift from 4.74 μm to 5.14 μm. The temperature-sensitive parameter α extracted from Varshni fitting is smaller than those of InAs/GaSb and bulk InAsSb, indicating the promising perspective of InAs/InAs1-xSbx T2SLs for HOT mid-wave infrared photodetectors.

Control of Al composition of mist chemical vapor deposition grown α-(AlGa)2O3 alloy thin films by acetylacetonation of Al ion

We investigated the dominant factors affecting the Al composition of α-(AlGa)2O3 alloy thin films in mist CVD, focusing on the acetylacetonation of the source solutions. The Al–acetylacetonate (acac) complex formation time was evaluated using Fourier-transform IR spectroscopy to examine the effectiveness of heating during stirring of the source solutions. Then, α-(AlGa)2O3 alloy thin films were grown in source solutions in which the state of the acac complex was changed by adding ammonia water and/or hydrochloric acid, and the Al composition increased with increasing the pH value due to the acceleration of acetylacetonation. The growth-temperature dependence of the Al composition was also experimentally investigated. The Al composition decreased with increasing growth temperature. The reasons are due to the strength of the Al–O bond or the dissociation of the Al–acac ligand.

Species composition of micromycetes at the Progress, Vechernyaya Gora, and Novolazorevskaya stations (East Antarctica)

The survival of fungi in Antarctica is a consequence of both ecological selection and evolutionary adaptation expressed at the physiological, metabolic, structural, and genetic levels. The study of the biological diversity of Antarctic micromycetes will help us to better understand the pathways of fungal dispersal in the biosphere, as well as to broaden our understanding of their role in extreme ecosystems. In addition, micromycetes of extreme habitats are the promising objects of biotechnology.The purpose of the work is to study the biological diversity of microscopic fungi on natural and anthropogenically introduced substrates in the East Antartica research areas of Progress, Novolazarevskaya, and Mount Vechernyaya stations.Traditional isolation methods were used to isolate micromycetes in culture. To determine the species composition, microbiological and molecular genetic methods were used. As a result of mycological analysis, 46 species of micromycetes from 22 genera and 3 phylum were identified. The taxonomic analysis was made and the dominant genera of micromycetes were identified: Thelebolus, Penicillium, Acremonium, Aspergillus, Cladosporium, Geomyces, Cadophora, Rhodotorula, Cryptococcus. The temperature-dependent growth features of micromycetes were analyzed: most of the isolated species were psychrotrophic. The greatest species diversity of micromycetes was noted in soils with plant and animal inclusions, the smallest – on stony substrates.

Temperature-Dependent Growth and Spore Germination of Fungi Causing Grapevine Trunk Diseases: Quantitative Analysis of Literature Data.

Grapevine trunk diseases (GTDs) are serious threats in all viticultural areas of the world, and their management is always complex and usually inadequate. Fragmented and inconsistent information on the epidemiology and environmental requirements of the causal fungi is among the reasons for poor disease control. Therefore, we conducted a quantitative analysis of literature data to determine the effects of temperature on mycelial growth and the effects of temperature and moisture duration on spore germination. Using the collected information, we then developed mathematical equations describing the response of mycelial growth to temperature, and the response of spore germination to temperature and moisture for the different species and disease syndromes. We considered 27 articles (selected from a total of 207 articles found through a systematic literature search) and 116 cases; these involved 43 fungal species belonging to three disease syndromes. The mycelial growth of the fungi causing Botryosphaeria dieback (BD) and the esca complex (EC) responded similarly to temperature, and preferred higher temperatures than those causing Eutypa dieback (ED) (with optimal temperature of 25.3, 26.5, and 23.3°C, respectively). At any temperature, the minimal duration of the moist period required for 50% spore germination was shorter for BD (3.0 h) than for EC (17.2 h) or ED (15.5 h). Mathematical equations were developed accounting for temperature-moisture relationships of GTD fungi, which showed concordance correlation coefficients ≥0.888; such equations should be useful for reducing the risk of infection.

Investigation on the temperature-dependent diffusion growth of intermetallic compounds in the Mg-Al-Zn system: Experiment and modeling

With the rapid development of Mg alloys, deeper understanding to the thermodynamic and diffusional kinetic behavior of intermetallic compounds (IMCs) is important for studying the effect of alloying elements to the microstructure evolution. Specially, a systematic quantitative investigation on the diffusional growth of IMCs is of great necessity. However, the works studying the elemental diffusion behaviors of multiple-element IMCs are rare in magnesium alloy systems. The current work takes the ternary Mg-Al-Zn system as research target, and combines the diffusion couple technique, phase stability diagrams, in-situ observation technique and numerical inverse method to investigate the temperature-dependent kinetic coefficients. The parabolic growth constant (PGC) and interdiffusion coefficients for Mg solid-solution phase and γ-Mg17Al12, β-Mg2Al3, ε-Mg23Al30, MgZn2, Mg2Zn3, τ-Mg32(Zn, Al)49 and ϕ-Mg5Zn2Al2 IMCs in the Mg-Al-Zn alloy system are determined. By comparing the current experimental with calculation results, the rate-controlling factor of the temperature-dependent diffusion growth of ϕ, τ and ε ternary IMCs in the Mg-Al-Zn system is further discussed in detail.

Study on temperature-dependent growth characteristics of germanium oxide film by plasma-enhanced atomic layer deposition

Germanium oxide (GeOx) films were grown by plasma-enhanced atomic layer deposition (PE-ALD) at 70, 130, 190 and 250 °C, using tetrakis (dimethylamino)-germanium as a precursor and O2 plasma as a reactant. For GeOx film grown at 250 °C, a relatively low growth-per-cycle (GPC) of 0.55 Å/cycle and high refractive index of 1.73 was observed as compared to the GPC and refractive index for the films grown at 70, 130, and 190 °C.Meanwhile, the areal portion of the germanium monoxide (GeO) peak to germanium dioxide (GeO2) in the Ge 3d core-level spectra of X-ray photoelectron spectroscopy increased proportional to the refractive index of the film. When estimating the mean molar mass of the GeOx films from the Lorentz-Lorenz equation, low molar mass was obtained from the GeOx film grown at 250 °C indicating germanium monoxide bond formation in the film.As the PE-ALD grown GeOx films exhibited high densities of about 3.5 g/cm3 almost close to the typical density value (3.6 ∼ 3.7 g/cm3) of germanium oxide film, low water-etch rates of 5 ∼ 10 nm/s were achieved for the PE-ALD grown GeOx films, compared to the reported etch rates of 60 ∼ 100 nm/s for germanium dioxide films. In summary, PE-ALD process for growing GeOx films has the advantage of obtaining high film density with controllable water-etch rate.

Analysis of reported substrate-misorientation and growth-temperature dependences of alloy composition in metalorganic vapor-phase epitaxially grown c-plane InGaN

Reported substrate-misorientation and growth-temperature dependences of alloy composition in metalorganic vapor-phase epitaxially grown c-plane InGaN were successfully analyzed by applying least-squares regression to relationships derived in the kink segregation model. The analysis gave a reasonable result that the equilibrium indium content at the kink site decreased with growth temperature T due to increased desorption of indium adatoms. The analysis also revealed that the relaxation time for the indium content at the step-edge site (i.e., the length of time before the indium content at the step-edge site reaches its equilibrium value) was reduced with increasing T (i.e., 34 ms at 780 °C and 21 ms at 820 °C). The analysis can be improved by more experimental results for various T and contribute to practical predictions of compositional variation in alloy semiconductors.