Low Sublimation Temperature Research Articles

Hydrophobic evaporable fullerene indanone ketone with low sublimation temperature and amorphous morphology for inverted perovskite solar cells.

A hydrophobic evaporable indano[60] fullerene ketone with low sublimation temperature (CF3-FIDO) was successfully synthesized, providing the fullerene mono-adduct derivative with the lowest sublimation temperature reported to date. The amorphous characteristic of the evaporated film was confirmed by grazing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). Perovskite solar cells using CF3-FIDO as the electron transport layer (ETL) achieved long-term device stability retaining 60% of their initial PCE after 500 h in air.

Application of Individual Quick Freezing (IQF) Technology for Freezing The Raw Materials of Sambal at UD Dede Satoe

The price of chili raw materials in Indonesia is influenced by several factors. These factors include erratic harvest seasons, the nature of perishable raw materials, poor post-harvest handling, and also supply and demand at the market. This is the cause of frequent fluctuations in the price of chili raw materials. Fluctuations in the price of chili raw materials are a problem in the chili production process at UD Dede Satoe. Thus, an inventory system is needed to store and freeze ingredients during rising material prices. The inventory system is an IQF refrigerator with dry ice freezing media. Dry ice is usually added to the cooling media because the ability to absorb the heat of a material by dry ice is greater than ordinary ice media. The use of dry ice in the freezing process aims to reduce the temperature of the material more quickly due to the large heat absorption ability caused by the low sublimation temperature point of dry ice, which is around -78.5oC. Thus, the material frozen with IQF refrigerators can extend the shelf life because it restrains microbial growth, maintains its nutritional and sensory quality.

Modeling snowline locations in protostars: The impact of the structure of protostellar cloud cores

Context. Snowlines during star and disk formation are responsible for a range of effects during the evolution of protostars, such as setting the chemical composition of the envelope and disk. This in turn influences the formation of planets by changing the elemental compositions of solids and affecting the collisional properties and outcomes of dust grains. Snowlines can also reveal echoes of past accretion bursts, providing insight into the formation process of stars. Aims. The objective is to identify which parameters (e.g., luminosity, gas density, and presence of disk) dictate the location of snowlines during the early, deeply embedded phase and to quantify how each parameter changes the observed snowline location. Methods. A numerical chemical network coupled with a grid of cylindrical-symmetric physical models was used to identify what physical parameters alter the CO and H2O snowline locations. The investigated parameters are the initial molecular abundances, binding energies of CO and H2O, heating source, cloud core density, outflow cavity opening angle, and disk geometry. Simulated molecular line emission maps were used to quantify the change in the snowline location with each parameter. Results. The snowline radius of molecules with low sublimation temperatures (≲30 K), such as CO, shift outward on the order of 103 AU with an order of magnitude increase in protostellar luminosity. An order of magnitude decrease in cloud core density also shifts the CO snowline position outward by a few 103 AU. The presence of disk(-like) structures cause inward shifts by a factor of a few, and mainly along the disk mid-plane. For molecules that sublimate at higher temperatures, such as H2O, increasing the protostellar luminosity or decreasing the cloud core density by an order of magnitude shifts the snowline position outward by a factor of a few. The presence of a disk concentrates molecules with high sublimation temperatures to compact regions (a few 10 AU) around the protostar by limiting the outward shift of snowline positions. Successful observational measurements of snowline locations are strongly dependent on spatial resolution, the presence or lack thereof of disk(-like) structures, and the inclination of the disk(-like) structure. Conclusions. The CO and H2O snowline locations do not occur at a single, well-defined temperature as is commonly assumed. Instead, the snowline position depends on luminosity, cloud core density, and whether a disk is present or not. Inclination and spatial resolution affect the observability and successful measurement of snowline locations. We note that N2H+ and HCO+ emission serve as good observational tracers of CO and H2O snowline locations. However, constraints on whether or not a disk is present, the observation of additional molecular tracers, and estimating envelope density will help in accurately determining the cause of the observed snowline position. Plots of the N2H+ and HCO+ peak emission radius versus luminosity are provided to compare the models with observations of deeply embedded protostars aiming to measure the CO and H2O snowline locations.

Volatilisation of Trace Elements During Evaporation to Dryness of HF‐Dissolved Silicates (BHVO‐2, AGV‐1, BIR‐1, UB‐N): Open‐ Versus Closed‐System Conditions

This work characterises the volatilisation of trace elements during evaporation to dryness of HF‐dissolved silicate rock reference materials (BHVO‐2, AGV‐1, BIR‐1, UB‐N). In open‐system conditions, sublimation at 80 °C remained small (≤ 3%) for most elements with the exception of boron. Conversely, during closed‐system evaporation in a PTFE elbow, volatilisation loss could exceed 3% for Te, Au, Se, Ru, B, Re, As, V and Ge; 100 μg g−1 for Pt, Cd, Ag, Mo and Ti; and 10 μg g−1 for many refractory elements including Nb, Hf, U and Yb. Higher volatilisation loss in the closed‐system results from the higher vapour pressure of HF that allows for the formation of highly fluorinated species with lower sublimation temperature, or unstable species such as rare earth tetrafluorides for which sublimation competes with thermal decomposition. Increasing the temperature from 50 to 100 °C promotes the formation and sublimation of highly fluorinated species (VF5, GeF4, SeF6). Conversely, some refractory elements (Hf, Zr, Yb, U, Cu, Zn, Rb, Ba and Sr) seem to preferentially sublimate at 50 °C possibly through the formation of hydrated fluorides. Our results indicate that closed‐system evaporation must be used with caution for quantitative analyses.

A Look at Outbursts of Comet C/2014 UN271 (Bernardinelli–Bernstein) near 20 au

Cometary activity may be driven by ices with very low sublimation temperatures, such as carbon monoxide ice, which can sublimate at distances well beyond 20 au. This point is emphasized by the discovery of the Oort cloud comet C/2014 UN271 (Bernardinelli–Bernstein) and its observed activity out to ∼26 au. Through observations of this comet’s optical brightness and behavior, we can potentially discern the drivers of activity in the outer solar system. We present a study of the activity of comet Bernardinelli–Bernstein with broad-band optical photometry taken at 19–20 au from the Sun (2021 June to 2022 February) as part of the LCO Outbursting Objects Key (LOOK) Project. Our analysis shows that the comet’s optical brightness during this period was initially dominated by cometary outbursts, stochastic events that ejected ∼107 to ∼108 kg of material on short (<1 day) timescales. We present evidence for three such outbursts occurring in 2021 June and September. The nominal nuclear volumes excavated by these events are similar to the 10–100 m pit-shaped voids on the surfaces of short-period comet nuclei, as imaged by spacecraft. Two out of three Oort cloud comets observed at large pre-perihelion distances exhibit outburst behavior near 20 au, suggesting such events may be common in this population. In addition, quiescent CO-driven activity may account for the brightness of the comet in 2022 January to February, but that variations in the cometary active area (i.e., the amount of sublimating ice) with heliocentric distance are also possible.

Ultra-Hard (41 GPa) Isotopic Pure 10BP Semiconductor Microwires for Flexible Photodetection and Pressure Sensing.

An urgent demand for electronic and optoelectronic devices able to work in extreme environments promotes a series of research studies on semiconductor materials. Cubic boron phosphide (BP) as a semiconductor material with excellent characteristics shows great application potential. However, since the synthesis conditions required are difficult to achieve and the growth mechanism of BP is still unclear, there are few reports on the basic properties of BP and pure isotope BP, resulting in a narrow understanding of their special physical properties. Here, we successfully obtained highly pure isotopic 10BP crystals by a vapor-liquid-solid (VLS) method unconventionally designed, which successfully overcomes the thermodynamic conflict between the high melting point of the boron element and low sublimation temperature of the phosphorus element. The 10BP achieved owns an aspect ratio as high as 104 and a hardness up to 41 GPa. Besides, as an indirect bandgap semiconductor, it has ultrawide red emission spectra, a p-type conductivity with extremely low resistivity, and excellent photoelectronic and piezoelectric characteristics. Furthermore, compared with other superhard semiconductors like cubic BN and diamond, 10BP has an obvious advantage of lower growth temperature (1200 °C). All these characteristics confirm the prospects owned by 10BP in its applications to the field of high-conductivity, optoelectronic, strain-sensing, and superhard semiconductors.

Quinizarin: a large aromatic molecule well suited for atomic layer deposition.

Atomic layer deposition (ALD) is a remarkable synthesis tool due to the vast array of materials that can be deposited and the complexity of structures that can be designed. The low-temperature layer-by-layer approach even allows organic and inorganic components to be combined as hybrid or composite materials. The technique is then called molecular layer deposition (MLD). This opens the door for deposition of advanced optical materials using highly absorbing aromatic molecules. Unfortunately, most large aromatic molecules are difficult to sublime or have insufficient reactivity. This is a major barrier for ALD when designing with the use of organic components for dye-sensitized solar cells, luminescence, visible light photochemistry, chemical sensors and organic electronics. In this work, we introduce a well-known orange dye molecule, quinizarin. This molecule has a large conjugated aromatic system with strong absorption of visible light and shows strong luminescence both in solutions and as a complex together with aluminium ions. Interestingly, quinizarin also shows surprisingly good properties for film deposition due to reactive -OH groups and low sublimation temperature (130 °C). Strongly coloured pink hybrid films were deposited with trimethylaluminium and quinizarin at 175 °C with a growth rate of 0.28 nm per cycle. These films were not luminescent although their optical absorption spectra are similar to those of the corresponding solution. An attempt was made to dilute quinizarin through partial replacement with pentaerythritol as a multilayer structure or simultaneous co-pulsing, although this also did not produce luminescent films. The low sublimation temperature, good reactivity and large conjugated system of quinizarin open the way for exploration of solid-state hybrid and organic films based on this molecule along many different technological pathways.

Tidal fragmentation as the origin of 1I/2017 U1 (‘Oumuamua)

The first discovered interstellar object (ISO), `Oumuamua (1I/2017 U1) shows a dry and rocky surface, an unusually elongated short-to-long axis ratio $c/a \lesssim 1/6$, a low velocity relative to the local standard of rest ($\sim 10$ km s$^{-1}$), non-gravitational accelerations, and tumbles on a few hours timescale. The inferred number density ($\sim 3.5 \times 10^{13} - 2 \times 10^{15}$ pc$^{-3}$) for a population of asteroidal ISOs outnumbers cometary ISOs by $\geq 10^3$, in contrast to the much lower ratio ($\lesssim 10^{-2}$) of rocky/icy Kuiper belt objects. Although some scenarios can cause the ejection of asteroidal ISOs, a unified formation theory has yet to comprehensively link all `Oumuamua's puzzling characteristics and to account for the population. Here we show by numerical simulations that `Oumuamua-like ISOs can be prolifically produced through extensive tidal fragmentation and ejected during close encounters of their volatile-rich parent bodies with their host stars. Material strength enhanced by the intensive heating during periastron passages enables the emergence of extremely elongated triaxial ISOs with shape $c/a \lesssim 1/10$, sizes $a \sim 100$ m, and rocky surfaces. Although volatiles with low sublimation temperature (such as CO) are concurrently depleted, H$_2$O buried under surfaces is preserved in these ISOs, providing an outgassing source without measurable cometary activities for `Oumuamua's non-gravitational accelerations during its passage through the inner Solar System. We infer that the progenitors of `Oumuamua-like ISOs may be km-sized long-period comets from Oort clouds, km-sized residual planetesimals from debris disks, or planet-size bodies at a few AU, orbiting around low-mass main-sequence stars or white dwarfs. These provide abundant reservoirs to account for `Oumuamua's occurrence rate.

Improved Configuration and LSPR Response of Platinum Nanoparticles via Enhanced Solid State Dewetting of In-Pt Bilayers

Noble metallic nanoparticles (NPs) can exhibit valuable properties such as localized surface plasmon resonance (LSPR) and large surface to volume ratio, which can find various optoelectronic and catalytic applications. In this work, the improved configuration and uniformity of platinum (Pt) NPs are demonstrated by using a sacrificial indium (In) layer via the enhanced solid state dewetting of In-Pt bilayers on sapphire (0001). In a sharp contrast to the conventional dewetting of intrinsic Pt film, the introduction of In component can significantly enhance the global dewetting process and thus can result in the fabrication of well-defined Pt NPs with the improved uniformity. This can be due to the fact that In possess high diffusivity, low surface energy and low sublimation temperature. Upon annealing, the intermixing of In and Pt atoms can occur at the interface due to the inter-diffusion, which forms In-Pt alloy system. As a result, the overall diffusivity and dewetting degree of system can be significantly improved and this can produce more isolated, uniform and semispherical Pt NPs at much lower temperatures as compared to the pure Pt film dewetting. Conveniently, the In atoms preferentially can be removed from the NP matrix by the sublimation even at relatively low temperatures. These Pt NPs exhibit dynamic LSPR band in the UV-visible wavelength based on the excitation of dipolar, quadrupolar and higher order resonance modes. Specifically, the LSPR wavelength can be tuned between ~480 and 580 nm by the fabrication of small to large size Pt NPs with the distinct configuration and interparticle spacing. Furthermore, at a constant Pt thickness, the size, spacing and density of Pt NPs can be readily tuned by the control of In layer thickness. The introduction of sacrificial In component can enable an additional flexibility for the control of surface morphologies of metallic NPs with the low diffusivity materials.

Stable Sodium Storage of Red Phosphorus Anode Enabled by a Dual-Protection Strategy.

Red phosphorus is appealing for anode use in sodium-ion batteries. However, the synthesis of electrochemically stable red P anodes remains challenging due to a notable volume variation upon (de)sodiation, and limited synthetic methods arising from the low ignition and sublimation temperatures. To address the above problems, we herein successfully develop an industrially adaptable process for scalable synthesis of affordable phosphorus/carbon (APC) anode materials with an excellent electrochemical performance at a significantly reduced cost. The key to our success is a delicately designed, self-organized, strongly interactive porous P/C structure filled with sodium alginate binder, which maintains the structural integrity of anode and enhances the electrical contact of red P upon its volume variation via a dual protection from porous structure and strong surface interactions. The APC anodes hence present ultrahigh initial Coulombic efficiency (86.2%), excellent cycling stability, and superior rate capability. The industrially adaptable process and excellent electrochemical performance endow the novel APC nano/microspheres with promising applications in high-performance Na-ion batteries.

Effect of Sublimation Temperature on the Photovoltaic Properties of Amorphous Carbon Thin Films from Fullerene

This paper presents the effects of sublimation temperature of C60 fullerene on the photovoltaic properties of amorphous carbon (a-C) films synthesized by remote plasma cracking. Here, we show that the deposition rate increases rapidly,Raman peak intensity corresponding to disordered fullerene becomes strong and the optical band gap increases with increasing the sublimation temperature. The photovoltaic devices with structure of Al/C60/a-C/ITO glass are fabricated with different sublimation temperatures and therelationship between the photovoltaic properties and the material properties of a-C films are discussed. It is shown that the improvementof power conversion efficiency is explained by low component of disorderedC60in amorphous carbon at lower sublimation temperature.

Carbon nanotubes or carbon globules: Optimization of the pyrolytic synthesis parameters and study of the magnetic properties

We report the optimized parameters necessary for the synthesis of carbon nanotubes (CNTs) and carbon globules during the pyrolysis of benzene in a closed reactor. The precursor concentration and sublimation temperature were controlled to tune the growth of carbon nanostructures. A low sublimation temperature leads to the formation of globular carbon aggregates while a high sublimation temperature (∼ 600 °C) favours the growth of carbon nanotubes. A set of optimized parameters allows the growth of CNTs or carbon globules, selectively or simultaneously. The carbon globules and the CNTs contain embedded magnetic nanoparticles, which makes them suitable electronic and magnetic material for various applications.

Self-assembly of dodecaphenyl POSS thin films

The self-assembly abilities of Dodecaphenyl Polyhedral Oligomeric Silsesquioxane thin films on Si(1 0 0) surfaces were studied. Due to their thermal properties – relatively low sublimation temperature and preservation of molecular structure – cage type silsesquioxanes are ideal material for the preparation of a thin films by Physical Vapor Deposition. The Ultra-High Vacuum environment and the deposition precision of the PVD method enable the study of early stages of thin film growth and its molecular organization. X-ray Reflectivity and Atomic Force Microscopy measurements allow to pursuit size-effects in the structure of thin films with thickness ranges from less than a single molecular layer up to several tens of layers. Thermal treatment of the thin films triggered phase change: from a poorly ordered polycrystalline film into a well-ordered multilayer structure. Self-assembly of the layers is the effect of the π−stacking of phenyl rings, which force molecules to arrange in a superlattice, forming stacks of alternating organic-inorganic layers.

Growth and physical properties of large MoO3 single crystals

Molybdenum trioxide (MoO3) is an interesting material for smart windows, electrodes for batteries, and gas sensors. So far, it is known that the growth of large single crystal of MoO3 is elusive because of the rapid changing of activation energy at 650 °C. Small MoO3 crystals can be made by sublimation. In this study, we successfully grew large MoO3 single crystals through the modified vertical Bridgman method, which can prevent the sublimation of MoO3. Similar structural and optical properties were measured like those of nano/micro-crystalline MoO3. This study can provide evidence to contribute to the creation of large single crystals, which have a lower sublimation temperature than melting temperature.

Pathways for synthesis of new selenium-containing oxo-compounds: Chemical vapor transport reactions, hydrothermal techniques and evaporation method

Due to the low and close melting and sublimation temperatures (340 and 350°C, respectively), the crystal growth of selenates and/or selenites is generally achieved using either chemical vapor transport routes, hydrothermal methods due to the good solubility and reactivity of (SeO3)2− anions or isothermal evaporation synthesis. Here we report examples many new crystal structures obtained using these synthesis routes. Particularly, description of each process is given with theoretical and practical information assorted with description of selected structures.

(Invited) Quality Improvement and Mapping Analysis of Single Crystal 4H SiC Grown with Purified Beta-SiC Powder Source

The most important consideration when growing single crystal silicon carbide by the physical vapor transport method is to minimize defects. To minimize defects caused by temperature gradient, we used β phase SiC powder, which has a low sublimation temperature, and purified the β phase SiC powder to improve the purity of single crystal SiC. Furthermore, we performed thermodynamic computational simulations based on compositions of purified and non-purified β-SiC powders to study the impact of metallic impurities within SiC powder on the composition of single crystal SiC. We grew SiC at temperatures about 200 °C lower than the previous growth temperature using purified β-SiC powder and mapped the phase change behavior of SiC according to different growth temperatures. Moreover, we compared and analyzed the characteristics of SiC polytype formation and crystallinity according to growth temperature. We compared the distribution of defects and dislocations of single crystal 4H SiC grown from purified and non-purified β-SiC powder to study the impact of source purification on defect generation. We also investigated the effect of metallic impurities on the formation of defects and dislocations through content analysis of metallic impurities.

Study the efficiency of single crystal CdTe/ZnCdS solar cell at various temperatures and illumination levels

Abstract CdTe is the best suited semiconductor for solar cells due to its band gap value 1.47 eV which is close to solar spectrum, low sublimation temperature and high absorption coefficient in the range of solar spectrum. To improve the photovoltaic performance of CdS/CdTe thin film solar cells, the CdS window layer is alloyed with different concentration of ZnS to reduce the resistivity and increase the band gap values. The single crystal CdTe based solar cell devices were prepared by vacuum evaporation method and have undergone for different temperature at various illumination levels to enhance the cell efficiency. We have achieved 14.37% efficiency and increased short circuit current density and open circuit voltage by reducing series resistance of the cell.

Functionalized thienoacridines: synthesis, optoelectronic, and structural properties

The preparation and characterization of hexylated, brominated, and 5-hexyl-2-thienyl-substituted tetrathienoacridine (TTAc) is described. Comparative electrochemical, optical, computational, and solid-state studies with their thienoanthracene (TTAn) analogs demonstrate that replacement of CH with nitrogen leads to an overall lowering of the frontier molecular energy levels and decrease in the HOMO–LUMO energy gap. While the brominated TTAc and TTAn derivatives are isostructural, as indicated by X-ray diffraction studies, the lower sublimation temperature and thermochromic behaviour exhibited by bromo-TTAc is attributed to an additional dipole−dipole interaction resulting from the dipole moment afforded by carbon/nitrogen substitution in the core aromatic ring. This work represents a fundamental study of heteroatom substitution in 2-D conjugated small molecules and investigates how inclusion of an electron deficient aromatic ring into the molecular framework (i.e., acridine versus anthracene) can influence the physical properties.

Mapping analysis of single crystal SiC polytypes grown from purified β-SiC powder

The most important consideration when growing single crystal silicon carbide by the physical vapor transport method is to minimize defects. To minimize defects caused by temperature gradient, we used β phase SiC powder, which has a low sublimation temperature, and purified the β phase SiC powder to improve the purity of single crystal SiC. Furthermore, we performed thermodynamic computational simulations based on compositions of purified and non-purified β-SiC powders to study the impact of metallic impurities within SiC powder on the composition of single crystal SiC. We grew SiC at temperatures about 200 °C lower than the previous growth temperature using purified β-SiC powder and mapped the phase change behavior of SiC according to different growth temperatures. Moreover, we compared and analyzed the characteristics of SiC polytype formation and crystallinity according to growth temperature. We compared the distribution of defects and dislocations of single crystal 4H SiC grown from purified and non-purified β-SiC powder to study the impact of source purification on defect generation. We also investigated the effect of metallic impurities on the formation of defects and dislocations through content analysis of metallic impurities.

Studies of dodecaphenyl polyhedral oligomeric silsesquioxane thin films on Si(1 0 0) wafers

In this work the spectroscopic and microscopic studies of dodecaphenyl POSS thin films are presented. Thin films have been deposited using molecular beam technique. Due to thermal properties – relatively low sublimation temperature and preservation of molecular structure – cage type silsesquioxanes are perfect to fabricate a thin film by means of physical vapor deposition.PhT12 thin films with thickness varying from 40nm up to 100nm, deposited on a Si(100) surface, were studied under high vacuum conditions. The research was focused on the influence of post deposition annealing (from 100°C up to 200°C) on molecular structure as well as thin film roughness and optical properties.A wide range of measuring methods were applied for thin film studies. Fourier Transform Infrared Spectroscopy (FTIR) was used in order to learn molecular structure and stability, Ellipsometry for thin film thickness and uniformity, Grazing Incidence X-ray Diffraction (GIXD) for thin film long range order investigation and finally Atomic Force Microscopy (AFM) for visual confirmation of drawn conclusions.