Influence Of Growth Temperature Research Articles

Influence of growth temperature of transparent conducting oxide layer on Cu(In,Ga)Se 2 thin-film solar cells

We have studied the influence of growth temperature ( T G) in the deposition of an indium tin oxide (ITO) transparent conducting oxide layer on Cu(In,Ga)Se 2 (CIGS) thin-film solar cells. The ITO films were deposited on i-ZnO/glass and i-ZnO/CdS/CIGS/Mo/glass substrates using radio-frequency magnetron sputtering at various T G up to 350 °C. Both the resistivity of ITO and the interface quality of CdS/CIGS strongly depend on T G. For a T G ≤ 200 °C, a reduction in the series resistance enhanced the solar cell performance, while the p–n interface of the device was found to become deteriorated severely at T G > 200 °C. CIGS solar cells with ITO deposited at T G = 200 °C showed the best performance in terms of efficiency.

The influence of growth temperatures on the characteristics of GaN nanowires

This paper presents the investigation of the properties of GaN nanowires synthesized from Ni-catalyzed chemical vapour deposition method under various growth temperatures. The influence of the growth temperatures on the morphological, structural and optical characteristics of the synthesized GaN nanowires was investigated in this work. Field-emission scanning electron microscopy images revealed that the 950 °C was the optimal growth temperature for synthesizing uniform, straight and smooth morphology of GaN nanowires. X-ray diffraction results demonstrated that the synthesized low dimensional GaN structures have the hexagonal wurtzite structure. Ultraviolet and blue emissions were detected from photoluminescence measurements. In addition, phonon replicas with the energy separation of 90 meV have been observed at the lower energy of the blue emission region in photoluminescence spectra.

GaAs-based long-wavelength InAs bilayer quantum dots grown by molecular beam epitaxy

Molecular beam epitaxy growth of a bilayer stacked InAs/GaAs quantum dot structure on a pure GaAs matrix has been systemically investigated. The influence of growth temperature and the InAs deposition of both layers on the optical properties and morphologies of the bilayer quantum dot (BQD) structures is discussed. By optimizing the growth parameters, InAs BQD emission at 1.436 μm at room temperature with a narrower FWHM of 27 meV was demonstrated. The density of QDs in the second layer is around 9 × 109 to 1.4 × 1010 cm−2. The BQD structure provides a useful way to extend the emission wavelength of GaAs-based material for quantum functional devices.

Growth temperature influence on the GaN nanowires grown by MOVPE technique

GaN nanowires (NWs) were successfully grown by Vapor-Liquid-Solid (VLS) growth mechanism on GaN template using metal-organic vapor phase epitaxy (MOVPE) with diameters ranging from 20 to 200 nm and length up to few microns. The characterization by scanning electron microscopy (SEM) reveals an optimum growth temperature at 790°C and X-ray diffraction (XRD) investigations indicates oriented crystallinity of grown NWs.

Influence of growth temperature on AlGaN multiquantum well point defect incorporation and photoluminescence efficiency

The dependence of (Al)GaN/AlGaN multiquantum well (MQWs) optical efficiency and defect incorporation on the growth temperature (Tg) of the optically active region was investigated. Marked increase in MQW photoluminescence (PL) intensity was observed for increasing Tg. Correspondingly, increasing Tg also significantly reduced point defect incorporation under QW growth conditions, as determined by deep level optical spectroscopy. It is suggested that enhanced MQW PL with increasing Tg resulted from improved nonradiative lifetime through reduced nonradiative defect density in the MQW region.

Influence of growth temperatures on the quality of InGaAs/GaAs quantum well structure grown on Ge substrate by molecular beam epitaxy

Molecular beam epitaxy growth of an InxGa1−xAs/GaAs quantum well (QW) structure (x equals to 0.17 or 0.3) on offcut (100) Ge substrate has been investigated. The samples were characterized by atomic force microscopy, photoluminescence (PL), and high resolution transmission electron microscopy. High temperature annealing of the Ge substrate is necessary to grow GaAs buffer layer without anti-phase domains. During the subsequent growth of the GaAs buffer layer and an InxGa1−xAs/GaAs QW structure, temperature plays a key role. The mechanism by which temperature influences the material quality is discussed. High quality InxGa1−xAs/GaAs QW structure samples on Ge substrate with high PL intensity, narrow PL linewidth and flat surface morphology have been achieved by optimizing growth temperatures. Our results show promising device applications for III—V compound semiconductor materials grown on Ge substrates.

Influence of growth temperature on the optical and structural properties of ultrathin ZnO films

This study investigates the effect of growth temperature on the optical and structural properties of ultrathin ZnO films on the polished Si substrate. Thickness of the ultrathin ZnO films deposited by atomic layer deposition (ALD) method was about 10 nm. Photoluminescence (PL), X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques were used to measure the properties of ultrathin ZnO films. Experimental results showed that the ultrathin ZnO film deposited at 200 °C had excellent ultraviolet emission intensity, and the average roughness of the film surface was about 0.26 nm.

Influence of growth temperature on the structure, composition and bonding character of nitrogen-doped multiwalled carbon nanotubes

Abstract

Fabrication of densely packed arrays of GaN nanostructures on nano-imprinted substrates

We have grown GaN on patterned Si (1 1 0) substrates prepared using a nano-imprinting technique and investigated the influence of growth temperature and the nano-pattern on the morphology of the nanostructure. Although {1 1̄ 0 2} facets were preferentially formed as sidewalls at a growth temperature of 650 °C, {1 1̄ 0 0} facets became dominant at substrate temperatures above 700 °C. We found that closely packed hexagonal GaN nanostructures, which are quite promising for future high efficiency light emitting devices, can be formed by the correct choice of not only the alignment between the pattern and the in-plane crystalline orientation of the substrate but also the period of the triangular lattice array of Si nano-pillars. The formation of this unique structure can most probably be attributed to the self-inhibited growth of GaN on the sidewall facets.

Vapor-Liquid-Solid Growth of Cadmium Telluride Nanowires by Close-Space-Sublimation for Photovoltaic Applications

ABSTRACTArrays of CdTe nanowires have been grown on conductive, flexible Mo substrates by the vapor-liquid-solid technique. A method of forming the arrays on a largely continuous CdTe film is described. For producing nanowire solar cells, this structure provides the advantage of preventing shunts. Nanowires having diameters in the range 100-500 nm and lengths up to 100 μm were generated. The influence of growth temperature, time and pressure on the morphology of deposited layers was investigated, and a mechanism for the generation of layer/nanowire combinations is postulated. Characterization by SEM, TEM and low temperature photoluminescence is presented.

Influence of growth temperature on the production of antibody Fab fragments in different microbes: A host comparative analysis

Microorganisms encounter diverse stress conditions in their native habitats but also during fermentation processes, which have an impact on industrial process performance. These environmental stresses and the physiological reactions they trigger, including changes in the protein folding/secretion machinery, are highly interrelated. Thus, the investigation of environmental factors, which influence protein expression and secretion is still of great importance. Among all the possible stresses, temperature appears particularly important for bioreactor cultivation of recombinant hosts, as reductions of growth temperature have been reported to increase recombinant protein production in various host organisms. Therefore, the impact of temperature on the secretion of proteins with therapeutic interest, exemplified by a model antibody Fab fragment, was analyzed in five different microbial protein production hosts growing under steady-state conditions in carbon-limited chemostat cultivations. Secretory expression of the heterodimeric antibody Fab fragment was successful in all five microbial host systems, namely Saccharomyces cerevisiae, Pichia pastoris, Trichoderma reesei, Escherichia coli and Pseudoalteromonas haloplanktis. In this comparative analysis we show that a reduction of cultivation temperature during growth at constant growth rate had a positive effect on Fab 3H6 production in three of four analyzed microorganisms, indicating common physiological responses, which favor recombinant protein production in prokaryotic as well as eukaryotic microbes.

Influence of growth temperature and measuring temperature on isoprene emission, diffusive limitations of photosynthesis and respiration in hybrid poplars

Acclimatory and direct responses of photosynthesis (A), stomatal (gs) and mesophyll (gm) conductance, light (RL) and dark (RD) respiration, and isoprene emission, measured at different temperatures, were compared in one-year-old Populus × euramericana saplings grown at 25 °C, 35 °C, and in the saplings grown initially at 35 °C and then exposed for two weeks at 25 °C. Results show that A, gs and gm were significantly lower at 35 °C, than at the other growth temperatures. This resulted in a downward acclimation of these parameters over the range of measuring temperatures. Both RL and RD also showed a considerable downward acclimation. However, the respiration to photosynthesis ratio increased with high temperatures, for RL and RD were more responsive to increasing growth temperatures than A at all measuring temperatures. This type of acclimation would lead to a shift in the carbon balance between photosynthesis and respiration under changing climatic conditions. Isoprene emission was greatly affected by temperature treatments and showed a downward acclimation to higher temperatures. Respiration and isoprene emission rates were directly related, independently of growth and measuring temperatures. These findings may be likely relevant to predict the emissions of isoprenoid in globally changing environmental conditions.

Fever temperature enhances mechanisms of survival of Streptococcus agalactiae within human endothelial cells

Group B streptococci (GBS) are the most common cause of pneumonia and sepsis during the neonatal period. However, the pathogenesis of invasive infection is poorly understood. We investigated the ability of GBS grown at 37 degrees C and 40 degrees C to adhere and invade human umbilical vein endothelial cells (HUVECs) at different periods of incubation (0, 0.5, 1, 2, 18 and 24 h). All strains tested, except strain 88641-vagina survived for 24 h in the intracellular environment at 40 degrees C. For serotype III grown at 40 degrees C, both strains (80340-vagina and 90356-liquor) showed increased adherence and intracellular survival when compared to bacteria grown at 37 degrees C (P<0.01). GBS serotype V strains (88641-vagina and 90186-blood) showed ability to survive inside HUVECs until 2 and 24 h post-infection at 40 degrees C and 37 degrees C, respectively (P<0.01). Influence of growth temperature in bacterial interaction with endothelial cells was partially dependent of serotypes and the clinical origin of strains. Serotypes III and V strains grown at both temperatures remained viable within acidic endothelial vacuoles which acquired Rab7 and LAMP-1 endosomal markers. The data emphasize the influence of temperature on cellular events of phagocytosis and pathogenesis of GBS diseases.

Gold-free growth of GaAs nanowires on silicon: arrays and polytypism

We report growth by molecular beam epitaxy and structural characterization ofgallium-nucleated GaAs nanowires on silicon. The influences of growth temperature andV/III ratio are investigated and compared in the case of oxide-covered and oxide-free substrates.We demonstrate a precise positioning process for Ga-nucleated GaAs nanowires using ahole array in a dielectric layer thermally grown on silicon. Crystal quality is analyzed byhigh resolution transmission electron microscopy. Crystal structure evolves from purezinc blende to pure wurtzite along a single nanowire, with a transition region.

Longevity and temperature response of pollen as affected by elevated growth temperature and carbon dioxide in peanut and grain sorghum

It is important to understand the effects of environmental conditions during plant growth on longevity and temperature response of pollen. Objectives of this study were to determine the influence of growth temperature and/or carbon dioxide (CO 2) concentration on pollen longevity and temperature response of peanut and grain sorghum pollen. Plants were grown at daytime maximum/nighttime minimum temperatures of 32/22, 36/26, 40/30 and 44/34 °C at ambient (350 μmol mol −1) and at elevated (700 μmol mol −1) CO 2 from emergence to maturity. At flowering, pollen longevity was estimated by measuring in vitro pollen germination at different time intervals after anther dehiscence. Temperature response of pollen was measured by germinating pollen on artificial growth medium at temperatures ranging from 12 to 48 °C in incubators at 4 °C intervals. Elevated growth temperature decreased pollen germination percentage in both crop species. Sorghum pollen had shorter longevity than peanut pollen. There was no influence of CO 2 on pollen longevity. Pollen longevity of sorghum at 36/26 °C was about 2 h shorter than at 32/22 °C. There was no effect of growth temperature or CO 2 on cardinal temperatures ( T min, T opt, and T max) of pollen in both crop species. The T min, T opt, and T max identified at different growth temperatures and CO 2 levels were similar at 14.9, 30.1, and 45.6 °C, respectively for peanut pollen. The corresponding values for sorghum pollen were 17.2, 29.4, and 41.7 °C. In conclusion, pollen longevity and pollen germination percentage was decreased by growth at elevated temperature, and pollen developed at elevated temperature and/or elevated CO 2 did not have greater temperature tolerance.

Epitaxial Heusler alloy Co2FeSi films on Si(1 1 1) substrates grown by molecular beam epitaxy

The influence of growth temperature on the structural and magnetic properties of Heusler alloy Co2FeSi films grown on Si(1 1 1) substrates has been studied. Reflection high energy electron diffraction, double crystal x-ray diffraction (DCXRD) and transmission electron microscopy (TEM) measurements revealed that Co2FeSi layers were epitaxially grown on Si(1 1 1) substrates in an optimized growth temperature range 150 °C < TG < 200 °C. From DCXRD measurements and TEM, it was shown that in the optimized temperature range the Co2FeSi/Si(1 1 1) films crystallize in the B2 + L21 structures. All layers are ferromagnetic and well-ordered films on Si(1 1 1) show high magnetic moments with an average value of (1140 ± 250) emu cm−3, which is in good agreement with the value of bulk Co2FeSi at 300 K. The magnetic anisotropy is correlated with the structural properties of the layers.

Influence of growth temperature on the stoichiometry of InSb nanowires grown by vapor phase transport

We report on the influence of growth parameters on the stoichiometry of indium antimonide nanowires grown by vapor phase transport. Using electron microscopy and composition analysis, we show that there is an optimum growth temperature window for growing stoichiometric indium antimonide (InSb) nanowires. The choice of the metal catalyst, evaporation and growth temperature are all critical parameters affecting the morphology and stoichiometry of the growing crystal. By controlling the growth temperature, it was possible to grow either stoichiometric InSb nanowires or In nanowires that contained no Sb within detectable limits. Electrical transport measurements of single InSb nanowires with two ohmic contacts demonstrate n-type conduction persisting from room temperature to 15 K.

Influence of growth temperature and starvation state on survival and DNA damage induction in the marine bacterium Sphingopyxis alaskensis exposed to UV radiation

Despite the considerable volume of literature describing the individual effects of temperature or UV light on aquatic bacteria, little is known about their combined effects. The current study was conducted to learn about the effects of growth temperature and duration of starvation on the response of a marine bacterium, Sphingopyxis alaskensis to UV-B or simulated solar radiation. Cells grown at 12 °C or 24 °C, and harvested at early or late stationary phase, were exposed to UV-B or simulated solar radiation (>290 nm). The predominant forms of UV-induced DNA damage, namely cyclobutane pyrimidine dimers (CPDs) and (6-4) photoproducts (6-4PPs), were quantified using a HPLC–mass spectrometry. While the commonly accepted view that DNA damage induced by UV-B radiation is temperature-independent, we observed in S. alaskensis that the yield of photoproducts for 12 °C was generally lower than for cells grown at 24 °C. The relative distribution of DNA photoproducts also varied with growth temperature, with an increased formation of TC 6-4PP for late compared to early stationary phase cells. In contrast, with the exception of cultures grown at 12 °C exposed to simulated solar radiation, the duration of stationary phase had no effect on total photoproduct formation. Collectively, these data indicate that growth temperature has more effect than duration of starvation on the formation of photoproducts in S. alaskensis.

Influence of the growth temperature of AlN buffer on the quality and stress of GaN films grown on 6H–SiC substrate by MOVPE

The influence of AlN buffer growth temperature on the quality and stress of 4.5 μm GaN epilayer on 6H–SiC substrate by organometallic vapor phase epitaxy (MOVPE) has been investigated. The crystalline quality and the atomic surface morphology were improved, the density of the pits and the stress of the GaN epilayer were reduced by increasing the growth temperature of the AlN buffer in the range from 950 °C to 1100 °C. By employing the optimized 1100 °C growth temperature of AlN buffer, very high quality of GaN epilayer was achieved. The X-ray full width of half maximums (FWHMs) of (0 0 2) and (1 0 2) reflection rocking curves of the GaN epilayer have been improved to 159 arcsec and 194 arcsec, respectively, and the surface RMS to only 0.31 nm in the 5 μm × 5 μm atomic force microscopy (AFM) scan. The stress of GaN epilayer was investigated by X-ray diffraction and Raman scattering as well. The degree of the tensile stress in GaN epilayer could be suppressed by increasing the growth temperature of AlN buffer. Finally, a high quality of crack-free 4.5 μm thick GaN epilayer was obtained on 6H–SiC substrate using the optimized 1100 °C AlN growth temperature.

Doping Concentration and Surface Morphology of 4H-SiC C-Face Epitaxial Growth

This research is focused on the influence of high C/Si ratios and low pressure on n-type doping concentration and surface defects of 4H-SiC C-face epilayers. N-type doping concentration decreases as C/Si ratio increases from 3.0 to 4.0 and pressure reduces from 100 mbar to 50 mbar; defect densities decrease as pressure increases at both C/Si ratios of 3.0 and 4.0. RMS roughness is about 0.21 nm for all C-face samples, independent of C/Si ratios of 3.0 and 4.0 and pressure from 50 mbar to 100 mbar. However, the influence of growth temperature on doping concentration and surface defects can not be clearly observed in this work.