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Sol–Gel Spin-Coating Followed by Solvothermal Synthesis of Nanorods-Based ZnO Thin Films: Microstructural, Optical, and Gas Sensing Properties
摘要： Zinc oxide thin films with nanorod morphology were investigated for microstructural and optical properties as well as their performance as a liquid petroleum gas sensing material. A two-step synthesis procedure consisting of sol–gel spin-coating and solvothermal methods was employed where several factors such as rational utilization of metal precursors, solvent, stabilizing, and structure directing agents, a repetitive drying-coating process, as well as post-thermal annealing were found influential to obtain qualified nanorods and a final homogeneous thin film. Compositional and optical investigations were pursued to characterize features, namely morphology, poly crystallinity, porous structure, nanocrystallite size, lattice oriented growth, textural atomic ratio, lattice purity and transparency, phonon and exciton transitions, as well as the formed structural defects via field-emission scanning electron microscopy, x-ray diffraction, energy-dispersive x-ray, UV–Vis spectroscopy, Raman, and photoluminescence techniques. The as-prepared thin film was then used as an active LPG sensing material via a home-made gas sensor where the control sensing parameters were chamber testing temperature and gas concentration. Results showed a quantitative response of 92.7% as sensor sensitivity at an operation temperature of 250°C and a LPG concentration of 800 ppm in addition to fast response and recovery times of 44.1 s and 218.7 s, respectively.
关键词： Zinc oxide nanorods,thin film,optical characteristics,gas sensing,microstructural properties,liquid petroleum gas
更新于2025-09-23 15:23:52
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Optical Properties of Nanohole Arrays with Various Depths
摘要： Studies to imitate structural colors have been conducted with various methods, most of which are disadvantageous for mechanical stability and economic feasibility because of complexity or lack of reproducibility. Numerous alternatives to overcome these shortcomings have been proposed. One such method is the anodic oxidation of aluminum, which requires relatively simple equipment and techniques. The present study used the aluminum anodic oxidation process to fabricate nanohole arrays of various sizes. Furthermore, using the finding that the structure color is the most strongly influenced by the nanohole depth based on the Bragg's Law, this study fabricated nanoholes of various depths to identify the structural colors arising from varied depths. This study further identified the colors from the same color series occurring periodically at each interval of 250 nm using the CIE 1931 color coordinate system. Moreover, nanohole arrays with two different depths were fabricated on a single substrate to confirm the coexistence of different colors and their capacity for deformation into various shapes.
关键词： Nanohole array,Structural color,Bragg's law,Anodic aluminum oxidation,Thin film effect
更新于2025-09-23 15:23:52
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Tailoring metal film texture by use of high atomic mobility at metal-semiconductor interfaces
摘要： The difference in the microstructural and texture evolution of Al films grown on amorphous SiO2 (a-SiO2) and amorphous Ge (a-Ge) substrates have been investigated. Surprisingly, the a-Ge substrate was found to change the preferred orientation of Al grains from the conventional (1 1 1) to the unconventional (1 1 0). The effect of the high mobility of Ge atoms at the metal-semiconductor interface on the microstructural and texture evolution of the metal thin film was studied. The diffusion of the Al adatoms on the a-Ge substrate was suppressed owing to the segregation of Ge atoms at the film surface. The mobility of Al grain boundaries was also suppressed because of grain-boundary wetting by the Ge atoms. It is concluded that the a-Ge substrate could tailor the Al grain orientation from (1 1 1) to (1 1 0) owing to the change in the film-growth mode from three-dimensional to two-dimensional nucleation. The concept of interaction-induced island-growth model, which is based on the Volmer–Weber growth model, is also discussed here. This work thus demonstrates how the atomic mobility at the interface of the metal thin film and the semiconductor substrate controls the film microstructure and texture during deposition.
关键词： Substrate,Microstructure,Surface diffusion,Texture,Metal thin film,Grain-boundary wetting
更新于2025-09-23 15:23:52
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Design and fabrication of the ultrathin metallic film based infrared selective radiator
摘要： Selective radiators have received considerable research attention and been extensively applied in many areas, such as thermophotovoltaic systems, infrared cloaking and sensing. Herein, the design of the infrared selective radiator based on ultrathin metallic films was fully demonstrated. From the discussions on the radiative characteristic and growth law of the metallic film, it has been concluded that a continuous ultrathin metallic film can behave as a thermal radiation enhancer. Taking the radiative cooling technology as the application background, a multilayered broadband selective radiator, consisting of an ultrathin Ag film and dielectric Ge films is designed and fabricated. The proposed radiator, which can radiate selectively in the 8–13 μm atmospheric transparency window (ε5–8 μm = 0.21; ε8–13 μm = 0.84; ε13–25 μm = 0.39), achieves an average temperature reduction of 3.5 °C under outdoor conditions and exhibits potential application in radiative cooling technology. Moreover, for our proposed selective radiator, flexible tuning of radiative characteristics can be achieved via structural design, which paves the way for its application in various areas. Unlike the common metamaterial based thermal radiator, our selective radiator with a planar structure is free from the complicated process of lithography or etching and is scalable to realize large-area fabrication and application.
关键词： Structural design,Radiative cooling,Selective radiator,Ultrathin metallic film
更新于2025-09-23 15:23:52
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A simple, low cost ink system for Drop-On-Demand printing high performance metal oxide dielectric film at low temperature
摘要： We have successfully developed an ink system containing cheap raw materials through a simple process and have printed ZrOx dielectric film at a relatively low annealing temperature of 250 °C. The ZrOx dielectric film afforded a leakage current density of 5.4×10-6 A/cm2 at 1 MV/cm and a dielectric constant of 10, which shows promising future for flexible electronics. The ink system shows a temperature-induced gelation behavior and gel network is formed when temperature rises. A high concentration of oxide precursors is obtained near the network area through the absorption function of polymer groups, and thus oxide structure can be formed at a relatively low temperature due to the shorter diffusion path of precursor polymerization. The microstructure of printed ZrOx film was investigated by High Resolution Transmission Electron Microscope (HRTEM), Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), and the effect of annealing temperature on film structure was studied.
关键词： dielectric film,low temperature,Low cost,ink system,Drop-On-Demand printing
更新于2025-09-23 15:23:52
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Preparation of high-quality stress-free (001) aluminum nitride thin film using a dual Kaufman ion-beam source setup
摘要： We proposed and demonstrated a preparation method of (001) preferentially oriented stress-free AlN piezoelectric thin films. The AlN thin films were deposited by a reactive sputtering technique at substrate temperatures up to 330 °C using a dual Kaufman ion-beam source setup. We deposited the AlN on Si (100), Si (111), amorphous SiO2, and a (001) preferentially oriented Ti thin film and compared their crystallographic, optical, and piezoelectric properties. The AlN thin films deposited on the (001) preferentially oriented Ti thin films have the highest crystallographic quality. The stress-free AlN reached a high value of the piezoelectric coefficient d33 = (7.33 ± 0.08) pC·N?1. The properties of the AlN thin film prepared at such low temperatures are suitable for numerous microelectromechanical systems, piezoelectric sensors, and actuators monolithically integrated with complementary metal-oxide-semiconductor signal-processing circuits.
关键词： Ellipsometry,Aluminum nitride thin film,Optical properties,d33 piezoelectric coefficient,Kaufman ion-beam source,Ion-beam sputtering deposition,(001) preferential orientation,X-ray diffraction
更新于2025-09-23 15:23:52
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Diketopyrrolopyrrole based small molecular semiconductors containing thiazole units for solution-processed n-channel thin-film transistors
摘要： In this work, three diketopyrrolopyrrole-based conjugated small molecular semiconductors characterized by the combination of a diketopyrrolopyrrole (DPP) central core, thiazole π-conjugated moiety, and dicyanovinyl end group with different alkyl side chain substituents, 2TzDPPA1-2DCV, 2TzDPPA2-2DCV, and 2TzDPPA3-2DCV were synthesized. These small molecules have a similar narrow band gap of about 1.50 eV and deep LUMO energy level at -4.30 eV. Under ambient conditions, electron mobilities of 0.28 cm2 V-1 s-1, 0.13 cm2 V-1 s-1, 0.25 cm2 V-1 s-1 for solution processed thin films of 2TzDPPA1-2DCV, 2TzDPPA2-2DCV, and 2TzDPPA3-2DCV were obtained, due to high crystallinity and well-organized molecular stacking. Compared with the other two materials, thin films of 2TzDPPA1-2DCV enable the best OFET performance with desirable Ion / Ioff rates exceeding of 107, attribute to the coefficient of smoother film morphology and stronger crystallinity. These results reveal that introducing the thiazole unit into the DPP-based conjugated skeleton is conducive to enhance the crystallinity and tailor LUMO energy levels which ensure good performance and excellent stability of these molecules as active materials for n-channel electronic devices.
关键词： small molecules,solution-processed n-channel thin-film transistors,thiazole unit,diketopyrrolopyrrole,air stability
更新于2025-09-23 15:23:52
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Direct utilization of solar linear Fresnel reflector on multi-effect eccentric horizontal tubular still with falling film
摘要： The paper presents a multi-eccentric tubular desalination system heated directly by a linear Fresnel reflector (LFR) field to enhance the productivity. In this novel system, the solar radiation is sent directly into desalination unit. The configuration and working processes of the proposed design are described in details. The tube inner wall with absorbing coating were used as a receiver by placing in the cylindrical cavity to absorb concentrated solar energy and transfer it to a falling water film. To verify the performance of the system in different effects, an indoor experimental eccentric tubular still was fabricated and tested under different heating conditions from 400 to 1600 W respectively. The experimental results showed that the maximum accumulated yield of the 1st and 2nd effect are about 28.27 kg and 21.37 kg, respectively. The outdoor experimental results show that the cumulative output of the unit is about 11.35 kg, the maximum performance ratio (PR) is about 2.88 with an evacuated tube solar collector. A two-effect tubular desalination system for linear Fresnel reflector with a capacity of 63.68 kg/d was proposed according to the presented theoretical and experimental work. By taking solar linear Fresnel reflector heating mode, the cost of water production reaching about $6.16/ton.
关键词： Falling water film,Heat and mass transfer,Solar distillation,Horizontal tubular still,Multi-eccentric
更新于2025-09-23 15:23:52
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Combined effects of unsteady wake and free-stream turbulence on turbine blade film cooling with laid-back fan-shaped holes using PSP technique
摘要： Detailed film cooling effectiveness distribution for a gas turbine blade under the effects of unsteady wakes and oncoming free-stream turbulence intensities was obtained using pressure sensitive paint (PSP) technique. Tests were performed on a linear cascade at Reynolds number of 3.85 × 10^5 based on the blade chord at cascade exit. Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. The test blade has three rows of compound angled cylindrical film holes at the leading edge, five rows of laid-back fan-shaped holes on the pressure surface and three rows of laid-back fan-shaped holes on the suction surface. The wake Strouhal number was varied from 0 to 0.36 and three mass flux ratios were determined. The oncoming free-stream turbulence intensities are 2.7% and 26.9%, respectively. Results show that the effect of the mass flux ratio on the film cooling effectiveness decreases under the high turbulence intensity and unsteady wake conditions. In most regions of the blade surface, the film cooling effectiveness decreases with the increase of wake Strouhal number, and the free-stream turbulence superimposed on the unsteady wake reduces the film cooling effectiveness further. The effect of the unsteady wake decreases under the high free-stream turbulence conditions.
关键词： Turbulence intensity,Film cooling effectiveness,PSP,Wake,Mass flux ratio,Turbine blade,Strouhal number,Laid-back fan-shaped hole
更新于2025-09-23 15:23:52
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A Study on the Solvent Vapor Induced Film Formation of PS/AgNPs Composites
摘要： In this study, pyrene (P) tagged polystyrene (PS) latex dispersions and silver nanoparticles (AgNPs) were mixed at various weight fractions in the range between 0 and 50 wt%. The prepared mixtures were dropped on the glass substrates by considering drop casting method and were dried at the room temperature. The resultant powder films were then exposed to solvent vapor to monitor how film formation and morphological behaviors of PS/AgNPs composites are altered. Film formation behavior of composites was assessed via fast transient fluorescence (FTRF) which measures the ?uorescence lifetimes of P from its decay traces during vapor exposure process. It was observed that pyrene lifetimes decreased as vapor exposure time, t increased. A Stern–Volmer kinetic analysis was used for low quenching ef?ciencies to interpret the decrease in pyrene lifetimes. UV-Vis (UVV) technique was employed to monitor optical transparency of the films. In the range of 0-20 wt% of AgNPs content, smooth and transparent films were obtained. However, above this range, the films were seen that they have low transparency and poor film formation since the increment in AgNPs content was lead to aggregations. The Prager–Tirrel model was employed to the FTRF data to obtain back-and-forth frequencies, ν, of the reptating PS chains during vapor induced ?lm formation process. SEM images of the samples were taken after film formation process is completed and were found to be consistent with optical and fluorescence quenching data.
关键词： Polystyrene latex,film formation,reptation frequency,fluorescence lifetime,nanocomposites,crossing-density,Silver nanoparticles,vapor-induced
更新于2025-09-23 15:23:52