Thermal Deposition Research Articles

Some properties of metal organic chemical vapor deposited (MOCVD) manganese nitride thin films (MnxNy) obtained using a single precursor of Tetraamminebis-(hexamethylenetetrammine) manganese (II) chloride [Mn (HMTA)2(NH3)4] Cl2

A single solid source precursor, tetraamminebis-(hexamethylenetetrammine) Manganese (II) Chloride [Mn (HMTA)2(NH3)4] Cl2 was prepared and thin films of manganese nitride MnxNy were grown on soda-lime glass substrates at varied temperature using Metal Organic Chemical Vapor deposition (MOCVD) technique. The Energy Dispersive X-ray (EDX) spectra showcased the thin film constituent's elements as Mn and N in weight ratios which further confirmed absolute stoichiometry. The Fourier Transform Infra-Red (FTIR) spectrometry carried out on the precursors revealed the presence of functional groups between 1600 and 3200 cm−1 in the precursors, and ligands were mostly removed by pyrolysis process of the MOCVD at a temperature range of 300–340 °C. Due to the thermal deposition technique employed, FTIR spectrographs of MnN thin films exhibit coalescences between grains and a clear bond disintegration. Structural characterization using X-ray diffraction (XRD) revealed that the synthesized MnN thin film possesses a simple cubic structure with crystallite sizes estimated by employing Scherer's formula and Hall–Williamson plots. The scanning electron microscopy (SEM) showed columnar pattern and mesopores with the substrate covered by smaller, spherical grain particles having an estimated size of 3–4 nm, and large, structured particles with an estimated size of 10.0–20.0 nm placed on top of the smaller grain size particles. The indirect optical bandgap value of the MnN thin film was confirmed by optical absorbance analysis to be 2.75 eV and 3.0 eV at temperatures of 300 and 340 °C, respectively.

Al2O3 Layers Grown by Atomic Layer Deposition as Gate Insulator in 3C-SiC MOS Devices.

Metal-oxide-semiconductor (MOS) capacitors with Al2O3 as a gate insulator are fabricated on cubic silicon carbide (3C-SiC). Al2O3 is deposited both by thermal and plasma-enhanced Atomic Layer Deposition (ALD) on a thermally grown 5 nm SiO2 interlayer to improve the ALD nucleation and guarantee a better band offset with the SiC. The deposited Al2O3/SiO2 stacks show lower negative shifts of the flat band voltage VFB (in the range of about -3 V) compared with the conventional single SiO2 layer (in the range of -9 V). This lower negative shift is due to the combined effect of the Al2O3 higher permittivity (ε = 8) and to the reduced amount of carbon defects generated during the short thermal oxidation process for the thin SiO2. Moreover, the comparison between thermal and plasma-enhanced ALD suggests that this latter approach produces Al2O3 layers possessing better insulating behavior in terms of distribution of the leakage current breakdown. In fact, despite both possessing a breakdown voltage of 26 V, the T-ALD Al2O3 sample is characterised by a higher current density starting from 15 V. This can be attributable to the slightly inferior quality (in terms of density and defects) of Al2O3 obtained by the thermal approach and, which also explains its non-uniform dC/dV distribution arising by SCM maps.

Non-Conjugated Poly(Diphenylene Phthalide)-New Electroactive Material.

In organic electronics, conjugated conductive polymers are most widely used. The scope of their application is currently very wide. Non-conjugated polymers are used much less in electronics and are usually used as insulation materials or materials for capacitors. However, the potential of non-conjugated polymers is much wider, due to the fact that new electronic materials with unique electronic properties can be created on the basis of non-conjugated polymers, as well as other inorganic dielectrics. This article demonstrates the possibilities of creating electrically conductive materials with unique electronic parameters based on non-conjugated polymers. The results of the study of the sensory properties of humidity are given as examples of the practical application of the structure. The abnormal electronic properties are realized along the interface of two polymer dielectrics with functional polar groups. The submicron films of polydiphenylenephthalide were used as a dielectric. It is shown that a quasi-two-dimensional electronic structure with abnormally large values of conductivity and mobility of charge carriers occurs along the interface. These structures are often called quasi-two-dimensional electron gas (Q2DEG). This article describes the manufacturing processes of multielectrode devices. Polymer films are deposited via the spin-coating method with polymer solutions in cyclohexanone. The metal electrodes were manufactured through thermal deposition in a vacuum. Three types of metal electrodes made of aluminum, copper and chromium were used. The influence of the electron work function of contacting metals on the electronic parameters of the structure was studied. It was established that the work function decrease leads to an increase in the conductivity and mobility of charge carriers. The charge carrier parameters were estimated based on the analysis of the current-voltage characteristics within the space-charge-limited current technique. The Richardson-Schottky thermionic emission model was used to evaluate values a potential barrier at metal/organic interfaces. It was established that the change in ambient humidity strongly affects the electronic transport properties along the polymer/polymer interface. It is demonstrated that the increase in conductivity with an increase in humidity occurs due to an increase in the mobility of charge carriers and a decrease in the height of the potential barrier at the three-dimensional metal contact with two-dimensional polymer interface. The potential barrier between the electrode and the bulk of the polymer film is significantly higher than between the electrode and the quasi-two-dimensional polymer structure.

Thermal laser separation and high-throughput layer deposition for edge passivation for TOPCon shingle solar cells

This work demonstrates the reduction of cutting-induced losses on tunnel-oxide passivated contact (TOPCon) shingle solar cells via edge passivation using high-throughput layer deposition. TOPCon shingle solar cells with a size of 26.46 mm × 158.75 mm are separated from industrial full-square TOPCon host cells either by laser scribing and mechanical cleaving (LSMC) from the emitter-free rear side or by thermal laser separation (TLS) from the front side. TLS yields up to 0.2%abs more efficient shingle cells directly after singulation in comparison to shingle cells that have been separated by LSMC. Passivated edge technology (PET) is applied by depositing aluminum oxide (Al2O3) layers using two different tools: thermal atomic layer deposition (T-ALD) in a lab-scale tool with a throughput of tens of shingle cells per hour and a high-throughput plasma-enhanced ALD (PE-ALD) prototype tool with a throughput of about 60,000 shingle cells per hour. The energy conversion efficiency of the edge-passivated shingle cells after T-ALD Al2O3 PET is found to be 0.4%abs higher than directly after separation. This gain is the same regardless of whether LSMC or TLS is used for cell separation. For PE-ALD Al2O3 and TLS, a gain of 0.5%abs is measured after PET. Stringing tests with electrically conductive adhesive so far indicate that Al2O3 layers do not negatively affect the resistance of cell to cell interconnections. Thus, low-damage cell cutting in combination with high-throughput Al2O3 layer deposition for edge passivation is a very promising approach to maintain high efficiency for industrial TOPCon solar cells in shingled modules.

ALD deposited bipolar HfOx films for silicon surface passivation

Hafnium oxide thin films consist of trap states which can degrade or enhance the device performance depending upon the application. These trap states play a crucial role in silicon surface passivation when using HfOx films. This paper investigates the dependence of crucial surface passivation parameters on different film growth components of thermal ALD process. Our study is focused on understanding different oxide charges present at the HfOx/Si interface using capacitance-voltage and constant voltage stress studies; particularly trap states introduced during thermal atomic layer deposition process. This study is performed for different film growth conditions to understand the origin of traps states. We show that the interfacial layer (IL) grows during the film deposition and therefore two interfaces are formed, i.e., HfOx/SiOx and SiOx/Si. Acting as the tunnelling oxide, this interlayer consists of trap states which are intrinsic in origin. The investigation on MOS structures fabricated using n and p type silicon substrates gives an understanding towards amphoteric nature of the trap states. Their nature (acceptor/donor) depends on the substrate doping type (n-Si/p-Si) giving it bipolar characteristic. However, the interaction of such trap states with the majority carrier band edge of the substrate strongly depends on the IL thickness. Additionally, the trap charge density increases with metal pulsing duration, suggesting that the metal precursor may be the source of these trap charges rather than the oxidant. By shedding light on the nature and behaviour of trap states in HfOx films, our study contributes to a deeper understanding of their impact on device performance. This knowledge can aid in optimizing surface passivation strategies and improving the overall performance of HfOx-based devices in various applications.

Parylene-coated SiO2 aerogel with controlled thermal conductivity

The thermal properties of two types of SiO2 aerogels (waterglass and tetraethylorthosilicate (TEOS)) were investigated before and after parylene (parylene-N) coating using thermal deposition and plasma deposition methods. The surface morphology and the pore structure of the aerogels was analyzed using scanning electron microscopy and Brunauer–Emmett–Teller (BET) analyzer. After thermal deposition of parylene coating, the specific surface area of SiO2 aerogel was decreased to be –69.3% (for waterglass-based one) and –93.1% (for TEOS-based one). In the case of plasma deposition of parylene coating, the specific surface area of SiO2 aerogel was decreased only –21.9% (for waterglass-based one) and –16.8% (for TEOS-based one). The influence of the plasma-deposited parylene coating on the thermal conductivity was investigated by calculating the thermal conductivity from differential scanning calorimetry (DSC) analysis. After parylene coating by plasma-deposition, the thermal conductivity was decreased from 0.016 ± 0.001 W/m·K to 0.009 ± 0.001 W/m·K (from 0.035 ± 0.004 W/m·K to 0.025 ± 0.002 W/m·K) for TEOS-based (waterglass-based) SiO2 aerogel with the parylene coating thickness of 0–195 nm (0–181 nm), which represented the improved thermal insulating property after parylene coating. In the case of thermal deposition of parylene coating, the thermal conductivity was observed to change in the reversed-direction. The thermal properties of the two types of SiO2 aerogels were strongly influenced by the deposition methods of parylene. These results demonstrate that the parylene in different deposition methods could be effectively used to control the thermal conductivity of SiO2 aerogels synthesized from waterglass as well as TEOS.

Photoresponse and noise characteristics of in-situ fabricated NiPc nanowire photodetectors

The interface between organic nanowires and metal layers plays a key role in determining the photoresponse and noise characteristics of organic nanowires. Herein, nickel phthalocyanine (NiPc) nanowires are self-aligned along parallel nanogrooves on a sapphire surface, and then photodetectors are fabricated in situ without post-growth transfer and alignment steps. This in-situ fabrication eliminates unpredictable factors associated with post-growth processing steps and allows us to focus on studying the influence of different nanowire-metal interfaces. Two different electrodes prepared by thermal evaporation deposition (TED) and etching-assisted transfer printing (ETP) are compared. While both electrodes ensure that NiPc nanowires exhibit a sensitive photoresponse in the 380–800 nm spectrum, the ETP electrodes result in higher sensitivity but an order of magnitude slower response due to the increased nanowire-metal interfacial capacitance. The noise power spectral density (PSD) confirms that for both photodetectors, the frequency-dependent 1/f noise dominates at frequencies below 10 kHz while the frequency-independent white noise increases significantly at higher frequencies. However, while the noise PSD of the photodetectors with TED electrodes remains stable with increasing temperature and bias, the noise PSD of the photodetectors with ETP electrodes increase by four to twelve orders of magnitude due to significantly increased electromigration and structural damage.

Compact Wideband Groove Gap Waveguide Bandpass Filters Manufactured with 3D Printing and CNC Milling Techniques.

This paper presents for the first time a compact wideband bandpass filter in groove gap waveguide (GGW) technology. The structure is obtained by including metallic pins along the central part of the GGW bottom plate according to an n-order Chebyshev stepped impedance synthesis method. The bandpass response is achieved by combining the high-pass characteristic of the GGW and the low-pass behavior of the metallic pins, which act as impedance inverters. This simple structure together with the rigorous design technique allows for a reduction in the manufacturing complexity for the realization of high-performance filters. These capabilities are verified by designing a fifth-order GGW Chebyshev bandpass filter with a bandwidth BW = 3.7 GHz and return loss RL = 20 dB in the frequency range of the WR-75 standard, and by implementing it using computer numerical control (CNC) machining and three-dimensional (3D) printing techniques. Three prototypes have been manufactured: one using a computer numerical control (CNC) milling machine and two others by means of a stereolithography-based 3D printer and a photopolymer resin. One of the two resin-based prototypes has been metallized from a silver vacuum thermal evaporation deposition technique, while for the other a spray coating system has been used. The three prototypes have shown a good agreement between the measured and simulated S-parameters, with insertion losses better than IL = 1.2 dB. Reduced size and high-performance frequency responses with respect to other GGW bandpass filters were obtained. These wideband GGW filter prototypes could have a great potential for future emerging satellite communications systems.

A Platform for Atomic Fabrication and In Situ Synthesis in a Scanning Transmission Electron Microscope.

The engineering of quantum materials requires the development of tools able to address various synthesis and characterization challenges. These include the establishment and refinement of growth methods, material manipulation, and defect engineering. Atomic-scale modification will be a key enabling factor for engineering quantum materials where desired phenomena are critically determined by atomic structures. Successful use of scanning transmission electron microscopes (STEMs) for atomic scale material manipulation has opened the door for a transformed view of what can be accomplished using electron-beam-based strategies. However, serious obstacles exist on the pathway from possibility to practical reality. One such obstacle is the in situ delivery of atomized material in the STEM to the region of interest for further fabrication processes. Here, progress on this front is presented with a view toward performing synthesis (deposition and growth) processes in a scanning transmission electron microscope in combination with top-down control over the reaction region. An in situ thermal deposition platform is presented, tested, and deposition and growth processes are demonstrated. In particular, it is shown that isolated Sn atoms can be evaporated from a filament and caught on the nearby sample, demonstrating atomized material delivery. This platform is envisioned to facilitate real-time atomic resolution imaging of growth processes and open new pathways toward atomic fabrication.

Alloying bulk-immiscible metals at the nanoscale: An XPS/STM study of bimetallic Ag-Pt/HOPG nanoparticles

The intentional tailoring of surface structure in bimetallic nanoparticles is of high interest for academic research and industry, and many attempts have been made to improve the control over the distribution mode of the constituent elements which ranges from homogeneously mixed nanoalloys to core–shell nanostructures. However, some metal combinations exhibit a wide miscibility gap in the bulk, which nonetheless could be overcome under definite conditions at the nanoscale due to size effects. Here we present the detailed XPS/STM investigation of alloying capability of bulk-immiscible metals on the example of the Ag-Pt/HOPG bimetallic system prepared by thermal vacuum deposition. We found out that partial alloying of Ag and Pt occurs already at the preparation stage, and the following thermal annealing of the Ag-Pt/HOPG samples at 300–400 °C does not help to enhance the alloying degree owing to thermodynamically driven surface segregation of silver. Increasing the annealing temperature ruins the structure of Ag-Pt bimetallic nanoparticles due to silver sublimation, while even longer annealing time leads to partial phase separation. Our results demonstrate a limited alloying capability of Pt and Ag at the nanoscale which will be relevant for further research on the design and functioning of bimetallic catalysts containing bulk-immiscible metals.

Quantitative PEEM and Raman Study of Nanorough Au SERS-Active Substrates for Molecular Sensing Applications

Surface-enhanced Raman scattering (SERS) is a well-established surface-sensitive technique for detecting trace amounts of molecular analytes. While the impact of surface singularities on plasmonic materials has been widely studied, the fabrication of cost-effective, efficient SERS substrates remains a challenge. In this paper, we present the study of large-area nanorough Au SERS-active substrates, elaborated by thermal evaporation deposition by photoemission electron microscopy (PEEM), a high-resolution near-field mapping technique, to access the statistical properties of the hot-spot distribution. We experimentally demonstrate that the near-field PEEM and far-field Raman statistical signatures of nanorough Au surfaces are quantitatively correlated when used for molecular sensing. The maximum of the SERS signal of thiophenol (TP) molecules diluted to 10–6 M is observed near the film percolation threshold for which the hot-spot density is maximum. Finally, SERS measurements from solutions of TP, crystal violet, and rhodamine B molecules at 10–8 M demonstrated the sensitivity of our substrates for molecular sensing.

In Situ H-Radical Surface Treatment on Aluminum Gallium Nitride for High-Performance Aluminum Gallium Nitride/Gallium Nitride MIS-HEMTs Fabrication.

In this work, we demonstrated a low current collapse normally on Al2O3/AlGaN/GaN MIS-HEMT with in situ H-radical surface treatment on AlGaN. The in situ atomic pretreatment was performed in a specially designed chamber prior to the thermal ALD-Al2O3 deposition, which improved the Al2O3/AlGaN interface with Dit of ~2 × 1012 cm-2 eV-1, and thus effectively reduced the current collapse and the dynamic Ron degradation. The devices showed good electrical performance with low Vth hysteresis and peak trans-conductance of 107 mS/mm. Additionally, when the devices operated under 25 °C pulse-mode stress measurement with VDS,Q = 40 V (period of 1 ms, pulse width of 1 μs), the dynamic Ron increase of ~14.1% was achieved.

All-Solution-Processed Perovskite Light-Emitting Diodes Based on a Thiol-Modified ZnO Electron-Transporting Layer.

All-solution-processed perovskite light-emitting diodes (LEDs) have the potential to be inexpensive and easily manufactured on a large scale without requiring vacuum thermal deposition of the emissive and charge transport layers. Zinc oxide (ZnO), which possesses superior optical and electronic properties, is commonly used in all-solution-processed optoelectronic devices. However, the polar solvent of ZnO inks can corrode the perovskite layer and cause severe photoluminescence quenching. In this work, we report the successful dispersion of ZnO nanoparticles in nonpolar n-octane by controlling the surface ligands from acetates to thiols. The nonpolar ink prevents the destruction of perovskite films. In addition, thiol ligands upshift the conduction band energy level, which also helps inhibit exciton quenching. Consequently, we demonstrate the fabrication of high-performance all-solution-processed green perovskite LEDs with a brightness of 21 000 cd/m2 and an external quantum efficiency of 6.36%. Our work provides a ZnO ink for fabricating efficient all-solution-processed perovskite LEDs.

ПОДВИЖНОСТЬ НОСИТЕЛЕЙ ЗАРЯДА ВДОЛЬ ГРАНИЦЫ РАЗДЕЛА ПОЛИМЕР/ПОЛИМЕР

Organic thin-film transistors are increasingly being used in various electronic devices, successfully replacing transistors on silicon and other traditional semiconductors. The advantages of such electronic devices are particularly noticeable in the development of flexible electronic devices. However, one of the intractable problems of organic devices is the low mobility of charge carriers, often not exceeding 10-3 cm2/Vs. Obviously, this significantly limits the scope of their application. In this paper, a new approach to the formation of a transport layer in an organic field-effect transistor is proposed. This approach is based on the use of anomalous transport properties occurring along the interface of two dielectrics. Along such a boundary, a layer of quasi-two-dimensional electron gas with abnormally large values of conductivity and mobility of charge carriers can occur. In this regard, polymer heterostructures representing a field-effect transistor with a transport layer made in the form of an interface between two films of an unconjugated (dielectric) polymer, polydiphenylene phthalide, were investigated in this work. Along such a boundary, a layer of quasi-two-dimensional electron gas with abnormally large values of conductivity and mobility of charge carriers can occur. In this regard, polymer heterostructures representing a field-effect transistor with a transport layer made in the form of an interface between two films of an unconjugated (dielectric) polymer, polydiphenylene phthalide, were investigated in this work. The paper describes the technology of creating a multielectrode device. Polymer films were made by centrifugation from a polymer solution in cyclohexanone. The metal electrodes were manufactured by thermal deposition in vacuum. Measurements of the electrophysical characteristics of an organic field-effect transistor have been carried out. It is established that the main charge carrier along the interface are electrons. Estimates of the mobility of charge carriers were carried out using two different techniques. At zero potential at the gate, an injection model of currents limited by a volumetric charge was used. In the presence of a potential on the gate, the mobility assessment was made within the framework of the field effect model. Comparison of the obtained estimates showed satisfactory agreement of the mobility values. From this fact, it was concluded that it is possible to use an injection model to estimate the mobility of charge carriers when they move along the polymer/polymer interface.

Comparative Study of Thermal and Plasma-Enhanced Atomic Layer Deposition of Iron Oxide Using Bis(N,N'-di-butylacetamidinato)iron(II).

Only a few iron precursors that can be used in the atomic layer deposition (ALD) of iron oxides have been examined thus far. This study aimed to compare the various properties of FeOx thin films deposited using thermal ALD and plasma-enhanced ALD (PEALD) and to evaluate the advantages and disadvantages of using bis(N,N'-di-butylacetamidinato)iron(II) as an Fe precursor in FeOx ALD. The PEALD of FeOx films using iron bisamidinate has not yet been reported. Compared with thermal ALD films, PEALD films exhibited improved properties in terms of surface roughness, film density, and crystallinity after they were annealed in air at 500 °C. The annealed films, which had thicknesses exceeding ~ 9 nm, exhibited hematite crystal structures. Additionally, the conformality of the ALD-grown films was examined using trench-structured wafers with different aspect ratios.

Characteristics of phosphorescent organic light-emitting devices with interfacial nanolayers of acid molecule-doped tris(4-aminophenyl)amine

Here we report that 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA)-doped tris(4-aminophenyl)amine (TAPA) can act as an interfacial layer for hole injection in phosphorescent organic light-emitting devices (OLEDs) and deliver improved device stability upon electric fields. The acid-base reaction between TAPA and AMPSA was carried out using 2-methoxy ethanol solvent with various molar ratios (0–300 mol. %). The resulting TAPA:AMPSA layers (1–10 nm thick) were spin-coated on indium-tin-oxide (ITO)-glasses and selectively annealed before the thermal deposition of organic small molecular multilayers in a vacuum. The doping reaction between TAPA and AMPSA gave rise to a new absorption peak at a wavelength of ca. 880 nm. The work function of TAPA:AMPSA layer-coated ITO-glasses increased with the molar ratio, but the highest luminance and efficiency of OLEDs were achieved at 100 mol. % (AMPSA to TAPA). The thickness control and thermal treatment process of TAPA:AMPSA layers (100 mol. %) could further enhance the luminance (from ca. 5000 cd/m2 (t = 10 nm) to 15,500 cd/m2 (t = 2 nm)) with relatively high device stability upon electric field compared to the pristine TAPA layers.

Study on the Deposition Characteristics of Molybdenum Thin Films Deposited by the Thermal Atomic Layer Deposition Method Using MoO2Cl2 as a Precursor

In this study, we conducted research on manufacturing molybdenum (Mo) thin films by a thermal atomic layer deposition method using solid MoO2Cl2 as a precursor. Mo thin films are widely used as gate electrodes and electrodes in metal-oxide semiconductor field-effect transistors. Tungsten (W) has primarily been used as a conventional gate electrode, but it suffers from reduced resistivity due to the residual fluorine component generated from the deposition process. Thus, herein, we developed a Mo thin film with low resistivity that can substitute W. The MoO2Cl2 precursor used to deposit the Mo thin film exists in a solid state. For solid precursors, the vapor pressure does not remain constant compared to that of liquid precursors, thereby making it difficult to set process conditions. Furthermore, the use of solid precursors at temperatures 600 °C and above has many limitations. Herein, H2 was used as the reactive gas for the deposition of Mo thin films, and the deposition temperature was increased to 650 °C, which was the maximum processing temperature of the aluminum nitride heater. Additionally, deposition rate, resistivity change, and surface morphology characteristics were compared. While resistivity decreased to 12.9 μΩ∙cm with the increase of deposition temperature from 600 °C to 650 °C, surface roughness (Rq) was increased to 0.560 nm with step coverage of 97%. X-ray diffraction analysis confirmed the crystallization change in the Mo thin film with increasing process temperature, and a certain thickness of the seed layer was required for nucleation on the initial wafer of the Mo thin film. Thus, the molybdenum nitride thin film was deposited after the 4 nm deposition of Mo thin film. This study confirmed that crystallinity of Mo thin films must be increased to reduce their resistivity and that a seed layer for initial nucleation is required.

Scalable production of stretchable conductive fibers for textile electronics

Stretchable conductive fibers are key building blocks for constructing textile electronics. In this Preview, we highlight the scalable production of stretchable conductive fibers based on multimaterial thermal drawing and chemical deposition. The resulting fibers exhibit initial electrical conductivities up to 4,415 S/cm while retaining more than 500% stretchability. They can be further made into multifilaments, driving the development of textile electronics toward real-world applications. Stretchable conductive fibers are key building blocks for constructing textile electronics. In this Preview, we highlight the scalable production of stretchable conductive fibers based on multimaterial thermal drawing and chemical deposition. The resulting fibers exhibit initial electrical conductivities up to 4,415 S/cm while retaining more than 500% stretchability. They can be further made into multifilaments, driving the development of textile electronics toward real-world applications. Stretchable and conductive fibers fabricated by a continuous method for wearable devicesMa et al.Cell Reports Physical ScienceFebruary 21, 2023In BriefMa et al. develop a continuous approach for fabricating stretchable and conductive fibers, which are suitable for being twisted into textile yarns, woven and knitted into textile fabrics, or braided and stitched onto textile structures. These textiles can be assembled into breathable and washable devices for wearable electronic applications. Full-Text PDF Open Access

Controlled Growth of Indium Oxide Nanowires for Gas Sensing Application.

The In2O3 nanowires have attracted enormous attention for gas sensor application due to their advantageous features. However, the controlled synthesis of In2O3 nanowires for gas sensors is vital and challenging because the gas sensing performance of the nanowires is strongly dependent on their characteristics. Here in this patent, we fabricated In2O3 nanowires on SiO2/Si substrate via a simple thermal vapor deposition method with the Au thin film as the catalyst. The growth temperatures were controlled to obtain desired nanowires of small size. The grown In2O3 nanowires were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The ethanol gas sensing properties were tested under the dynamic flow of dry air and analytic gas. The synthesized In2O3 nanowires have the potential for use in ethanol gas sensor application. In2O3 nanostructures grown at different temperatures ranging from 600 to 900oC have different morphologies. The sample grown at 600oC had a morphology of nanowire, with a diameter of approximately 80 nm and a length of few micrometers. Nanowires grown at 600°C were composed of oxygen (O) and indium (In) elements, with the atomic ratio of [O]/[In] = 3/5. The nanowire was a single phase cubic structure of In2O3 crystal. The In2O3 nanowire sensor showed typical n-type semiconducting sensing properties. The response decreased from 130 to 75 at 100 ppm when the working temperature decreased from 450°C to 350°C. The nanowires grown at 600°C by the thermal vapor deposition method had the best morphology with a small diameter of about 80 nm and a length of few micrometers. The In2O3 nanowires had a good ability to sense ethanol at varying concentrations in the range of 20 ppm to 100 ppm. The In2O3 nanowires can be used as building blocks for future nanoscale gas sensors.

Morphological and Compositional Analysis on Thermal Deposition of Supercritical Aviation Kerosene in Micro Channels.

The integration of active cooling systems in super or hypersonic aircraft using endothermic hydrocarbon fuels is considered an effective way to relieve the thermal management issues caused by overheating. When the temperature of aviation kerosene exceeds 150 °C, the oxidation reaction of fuel is accelerated, forming insoluble deposits that could cause safety hazards. This work investigates the deposition characteristic as well as the morphology of the deposits formed by thermal-stressed Chinese RP-3 aviation kerosene. A microchannel heat transfer simulation device is used to simulate the heat transfer process of aviation kerosene under various conditions. The temperature distribution of the reaction tube was monitored by an infrared thermal camera. The properties and morphology of the deposition were analyzed by scanning electron microscopy and Raman spectroscopy. The mass of the deposits was measured using the temperature-programmed oxidation method. It is observed that the deposition of RP-3 is highly related to dissolved oxygen content (DOC) and temperature. When the outlet temperature increased to 527 °C, the fuel underwent violent cracking reactions, and the structure and morphology of deposition were significantly different from those caused by oxidation. Specifically, this study reveals that the structure of the deposits caused by short-to-medium term oxidation are dense, which is different from long-term oxidative deposits.