Search Results (145)

The study explores the optical and transport properties of polycrystalline ZnO thin films prepared using reactive pulsed mid-frequency sputtering with RF electron cyclotron wave resonance (ECWR) plasma. This deposition method increases the ionization degree of sputtered particles, the dissociation of reactive gas and the plasma density of pulsed reactive magnetron plasma. Optical absorption spectra reveal a sharp Urbach edge, indicating low valence band disorder. Lattice disorder and deep defect concentration are more likely to occur in samples with higher roughness. PL analysis at low temperature reveals in all samples a relatively slow (μs) red emission band related to deep bulk defects. The fast (sub-ns), surface-related blue PL band was observed in some samples. Blue PL disappeared after annealing in air at 500 °C. Room temperature Hall effect measurements confirm n-type conductivity, though with relatively low mobility, suggesting defect-related scattering. Persistent photoconductivity was observed under UV illumination, indicating deep trap states affecting charge transport. These results highlight the impact of deposition and post-treatment on polycrystalline ZnO thin films, offering insights into optimizing their performance for optoelectronic applications, such as UV detectors and transparent conductive oxides. Full article

A simple two-step approach was proposed to obtain hBN thin films with high crystalline quality, meaning that the films were initially prepared by using an RF magnetron sputtering technique and subsequently followed by a post-annealing process at a high temperature. In the case of introducing Al₂O₃ nanoparticles, the effects of annealing temperature from 1000 °C to 1300 °C and annealing time from 0.5 h to 1.5 h on the recrystallization process of the grown hBN films were systematically studied by using XRD and SEM technologies. The introduction of Al₂O₃ impurities during the annealing process successfully reduced the transition temperature of hexagonal phase BN by more than 300 °C. The crystalline quality of hBN films grown by RF magnetron sputtering could be effectively enhanced under annealing at 1100 °C for 1 h. The DUV detectors were prepared using the hBN films before and after annealing, and showed a notable improvement in detector performance by using annealed films. It has significant application value in further enhancing the performance of DUV photodetectors based on high-quality hBN films. Full article

Heat flow sensors allow the straightforward measurement of the heat flow emitted from an object by attaching the sensor to the object. However, the inability of this method to control the surface emissivity of the sensor over a wide range lowers the measurement accuracy of a heat flow sensor. This study introduces a flexible heat flow sensor whose surface emissivity can be adjusted over a wide range. This sensor integrates a heat flow detector (HFD), which harnesses the Seebeck effect of a carbon nanotube/polymer composite to convert heat flow into voltage. This conversion exhibits a linear relationship with the heat flow, characterized by a proportional coefficient of 0.6556 mV·W⁻¹. The sensor features an emissivity-controlling layer (ECL), comprising a thin Al film deposited on a flexible polymer film substrate. The surface emissivity of the layer can be adjusted between 0.06 and 0.88 by modulating the thickness of the Al coating. The ECL can be easily attached to and detached from the HFD. The proposed sensor enables the measurement of heat flow from heat sources with various emissivities by simply affixing it to the source. This study shows that the deployment of such sensors is useful for the advanced thermal management of diverse facilities. Full article

β-Ga₂O₃ holds significant promise for use in ultraviolet (UV) detectors and high-power devices due to its ultra-wide bandgap. However, the cost-effective preparation of large-area thin films remains challenging. In this study, β-Ga₂O₃ thin films are prepared using an inorganic solution reaction spin-coating method followed by post-annealing. The structures, surface morphologies, and optical properties of the films are then characterized using X-ray diffraction, scanning electron microscopy, and ultraviolet–visible spectrophotometry. A low-cost Ga metal was used to produce NH₄Ga(SO₄)₂, which was then converted into a precursor solution and spin-coated onto sapphire and quartz substrates. Ten cycles of spin coating produced smoother films, although higher annealing temperatures induced more cracks. The films on the (0001) sapphire subjected to spin-coating and preheating processes that were repeated for ten cycles, followed by annealing at 800 °C, had a preferred orientation in the [–201] direction. All the films showed high transmittances of 85% in ultraviolet–visible light with wavelengths above 400 nm. The films on the (0001) sapphire substrate that were annealed at 800 °C and 1000 °C exhibited bandgaps of 4.8 and 4.98 eV, respectively. The sapphire substrates demonstrated a superior compatibility for high-quality Ga₂O₃ film fabrication compared to quartz. This method offers a cost-effective and efficient approach for producing high-quality β-Ga₂O₃ films on high-temperature-resistant substrates with promising potential for optoelectronic applications. Full article

This paper focuses on the search for the desired thickness of the ¹⁰${\mathrm{B}}_4$C thin-film coating, as well as the macrostructuring of the aluminum foil substrate used as a cathode in the production of a multiwire gas detector of thermal neutrons. The impact of the ¹⁰${\mathrm{B}}_4$C film thickness from 1.0 to 2.5 $\mathsf{\mu }$m and of the 0.05 mm thick $\mathsf{\Lambda }$-shaped macrostructured aluminum foil substrate with an angle at the $\mathsf{\Lambda }$-vertex from 10 to 45 degrees, with a height from 0.5 to 4 mm and a distance between the $\mathsf{\Lambda }$-structures from 0.1 to 0.8 relative units on the neutron registration efficiency 1.8Å, was investigated. Numerical modeling of the electrostatic field was carried out using the Elcut software package. The interaction of neutrons with the ¹⁰${\mathrm{B}}_4$C thin-film coating was modeled using the Monte Carlo method in the Geant4 program. The optimal values of the geometrical parameters for the best neutron registration efficiency were determined. Full article

Grazing incidence small- and wide-angle X-ray scattering (GISAXS, GIWAXS) has been widely applied for the study of functional thin films, be it for the characterization of nanostructured morphologies in block copolymers, nanocomposites, and nanoparticle assemblies, or for the packing and orientation of aromatic molecules or conjugated polymers. Solution-processed thin films are typically uniaxial powders, with a specific crystallographic plane oriented parallel to the substrate surface while ordered domains assume random orientations laterally. The convenient GISAXS/GIWAXS scattering geometry facilitates obtaining complete information about thin film structure as well as the ability to study samples in well-defined sample environments, as controlled by temperature, exposure to solvent vapor and drying, or coating processes. Moreover, with suitable X-ray sources and detectors, information about the ordering kinetics and phase transitions can be obtained down to the millisecond scale. The scattering geometry and an interactive graphical tool to index such scattering patterns will be discussed here. Furthermore, it will be demonstrated that proper indexing of the X-ray scattering patterns can provide deep insight into thin film structure–property relationships and the kinetics of structure formation. Recent examples of nanostructures and molecular organization in thin films will be discussed, as well as self-assembly processes leading to such structures. Full article

A four-tether silicon microthermocycler for point-of-care PCR analytical systems is proposed. Substituting the commonly employed platinum with titanium in the fabrication of thin film resistance temperature detectors and heaters enabled the realization of a smaller device without compromising temperature accuracy or increasing heater lead power losses. The device was extensively analyzed through analytical modeling and FEM numerical simulations using a 3-D thermo-mechanical simulation model in COMSOL. Numerical simulations revealed that the four-tether design provides a 460% improvement in mechanical strength and a 57% reduction in the thermal time constant compared with a similar three-tether design, with a trade-off of a 22% increase in heat losses. Detailed structural and thermal analyses of crucial design parameters guided the optimization of the final geometry, leading to the successful fabrication of prototypes. It was shown that the current of 60 mA was sufficient to heat the fabricated solid and hollow silicon structure to 132 °C and 134 °C in 10 s for an applied heater power of 510 mW and 525 mW, respectively. Full article

Acetone detection is of significant importance in various industries, from cosmetics to pharmaceuticals, bioengineering, and paints. Sensor manufacturing involves the use of different semiconductor materials as well as different metals for doping and functionalization, allowing them to achieve advanced or unique properties in different sensor applications. In the healthcare field, these sensors play a crucial role in the non-invasive diagnosis of various diseases, offering a potential way to monitor metabolic conditions by analyzing respiration. This article presents the synthesis method, using chemical solutions and rapid thermal annealing technology, to obtain Al-functionalized and Ni-doped copper oxide (Al/CuO:Ni) nanostructured thin films for biosensors. The nanocrystalline thin films are subjected to a thorough characterization, with examination of the morphological properties by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) analysis. The results reveal notable changes in the surface morphology and structure following different treatments, providing insight into the mechanism of function and selectivity of these nanostructures for gases and volatile compounds. The study highlights the high selectivity of developed Al/CuO:Ni nanostructures towards acetone vapors at different concentrations from 1 ppm to 1000 ppm. Gas sensitivity is evaluated over a range of operating temperatures, indicating optimum performance at 300 °C and 350 °C with the maximum sensor signal (S) response obtained being 45% and 50%, respectively, to 50 ppm gas concentration. This work shows the high potential of developed technology for obtaining Al/CuO:Ni nanostructured thin films as next-generation materials for improving the sensitivity and selectivity of acetone sensors for practical applications as breath detectors in biomedical diagnostics, in particular for diabetes monitoring. It also emphasizes the importance of these sensors in ensuring industrial safety by preventing adverse health and environmental effects of exposure to acetone. Full article

To explore the bending process and theory of the free-boundary aerodynamic film forming method for curved detectors, this study integrates practical forming structures with theoretical analysis and establishes a simulation model to investigate stress, strain, and morphological changes during bending. The analysis indicates that the shift from “projection” to “wrapping” in forming theory is due to the release of boundary degrees of freedom. The forming process can be summarized as the mold’s arc characteristics, originating from the chip’s corners, gradually replacing the chip’s rectangular characteristics along the diagonal, resulting in corresponding stress and strain changes. The “wrapping” bending theory of this method has significant advantages over traditional methods and represents a crucial direction for achieving higher curvature in the future. However, this study found that the use of film pressure can only inhibit out-of-plane deformation to a certain extent, and the buckling phenomenon will still occur when the thinner chip is bent. It prevents the use of thinner chips in the thinning–bending method, so avoiding out-of-plane deformation during the molding process is the direction that needs to be broken in the future. Full article

This paper presents a comprehensive study of hydrogenated amorphous silicon (a-Si)-based detectors, utilizing electrical characterization, Raman spectroscopy, photoemission, and inverse photoemission techniques. The unique properties of a-Si have sparked interest in its application for radiation detection in both physics and medicine. Although amorphous silicon (a-Si) is inherently a highly defective material, hydrogenation significantly reduces defect density, enabling its use in radiation detector devices. Spectroscopic measurements provide insights into the intricate relationship between the structure and electronic properties of a-Si, enhancing our understanding of how specific configurations, such as the choice of substrate, can markedly influence detector performance. In this study, we compare the performance of a-Si detectors deposited on two different substrates: crystalline silicon (c-Si) and flexible Kapton. Our findings suggest that detectors deposited on Kapton exhibit reduced sensitivity, despite having comparable noise and leakage current levels to those on crystalline silicon. We hypothesize that this discrepancy may be attributed to the substrate material, differences in film morphology, and/or the alignment of energy levels. Further measurements are planned to substantiate these hypotheses. Full article

Pt thin-film resistance temperature detectors (RTDs) have been fabricated by magnetron sputtering on various substrates, including silica, polyimide (PI) and LaAlO₃ (LAO) (100) single crystal. The influences of different substrates on the performance of Pt thin-film RTDs have been studied. It is revealed that the substrates exhibit a significant dependence on the temperature coefficient of resistance (TCR). Silica, PI and LAO substrates yield TCRs of 3.2 × 10⁻³, 2.7 × 10⁻³ and 3.4 × 10⁻³ /K, respectively. The Pt thin-film RTDs on LAO substrate exhibit a significantly larger TCR, compared to most of the other reported values. These devices also demonstrate a fast response time of 680 μs, which is shorter than that of many other reported RTDs. Furthermore, Pt thin-film RTDs on PI substrates could serve as flexible detectors, maintaining a consistent linear relationship between resistance and temperature even when bent. Full article

Sn-doped Ga₂O₃ thin films and metal–semiconductor–metal (MSM) ultraviolet detectors were prepared using the co-sputtering method to enhance their photoelectric performance. The results revealed that Sn doping can effectively change the optical and electrical properties of thin films, greatly improving the photoelectric responsiveness of the devices. Through microstructure testing results, all of the thin film structures were determined to be monoclinic beta phase gallium oxide. At a DC power of 30 W, the thickness of the Sn-doped thin film was 430 nm, the surface roughness of the thin film was 4.94 nm, and the carrier concentration, resistivity, and mobility reached 9.72 × 10¹⁸ cm⁻³, 1.60 × 10⁻⁴ Ω·cm, and 45.05 cm³/Vs, respectively. The optical results show that Sn doping clearly decreases the transmission of thin films and that the bandgap can decrease to 3.91 eV. Under 30 W DC power, the photo dark current ratio of the detector can reach 101, time responses of t_r = 31 s and t_f = 22.83 s were obtained, and the spectral responsivity reached 19.25 A/W. Full article

Lithium tantalate crystals, as a type of pyroelectric material, stand out from many other pyroelectric materials due to the advantages of high Curie temperature, large pyroelectric coefficient, high figure of merits, and environmental friendliness. Due to the pyroelectric effect caused by their spontaneous polarization, lithium tantalate crystals have broad application prospects in wide spectral bandwidth and uncooled pyroelectric detectors. This article reviews the pyroelectric properties of lithium tantalate crystals and evaluates methods for pyroelectric properties, methods for modulating pyroelectric properties, and pyroelectric detectors and their applications. The prospects of lithium tantalate thin films, doped lithium tantalate crystals, and near stoichiometric lithium tantalate crystals as response components for pyroelectric detectors are also discussed. Full article

Transition-edge sensor (TES) microcalorimeters are advanced cryogenic detectors that use a superconducting film for particle or photon detection. We are establishing a new production line for TES detectors to serve as cryogenic anticoincidence (i.e., veto) devices. These detectors are made with a superconducting bilayer of titanium (Ti) and gold (Au) thin films deposited via electron beam evaporation in a high vacuum condition on a monocrystalline silicon substrate. In this work, we report on the development of such sensors, aiming to achieve stable sensing performance despite the effects of aging. For this purpose, patterned and non-patterned Ti/Au bilayer samples with varying geometries and thicknesses were fabricated using microfabrication technology. To characterize the detectors, we present and discuss initial results from repeated resistance–temperature (R–T) measurements over time, conducted on different samples, thereby augmenting existing literature data. Additionally, we present a discussion of the sensor’s degradation over time due to aging effects and test a potential remedy based on an easy annealing procedure. In our opinion, this work establishes the groundwork for our new TES detector production line. Full article

Although perovskite has great potential in optoelectronic devices, the simultaneous satisfaction of material stability and high performance is still an issue that needs to be solved. Most perovskite optoelectronic devices use quantum dot spin coating or the gas-phase growth of perovskite thin films as the photoelectric conversion layer. Due to stability limitations, these materials often experience a significant decrease in photoelectric conversion efficiency when encountering liquid reagents. The self-assembled growth of hybrid perovskite crystals determines superior lattice ordering and stability. There are three types of ionic liquids—[Emim]BF4, EMIMNTF2, and HMITFSI—that can effectively enhance the X-ray photoelectric conversion performance of hybrid perovskite crystal CH₃NH₃PbI₃ (MAPbI₃), and the enhancement in the photocurrent leads to an improvement in the sensitivity of X-ray detectors. We soak the perovskite crystals in an ionic liquid and perform two treatment methods: electrification and dilution with ETOH solution. It is interesting to find that MAPbI₃ perovskite single crystal materials choose the same optimized ionic liquid species in X-ray detection and photovoltaic power generation applications, and the effect is quite the opposite. Compared with untreated MAPbI₃ crystals, the average photocurrent density of Electrify-HMITFSI MAPbI₃ increased by 826.85% under X-ray excitation and the sensitivity of X-ray detectors made from these treated MAPbI₃ crystals significantly increased by 72.6%, but the intensity of the PL spectrum decreased to 90% of the untreated intensity. Full article