Films Of Different Thicknesses Research Articles

Channeled spectroscopic ellipsometry enabled by physics-informed tandem untrained neural networks

Ellipsometry is a powerful metrology technique for characterizing the optical properties of various materials. Channeled spectroscopic ellipsometry (CSE) has shown great promise among the different types of ellipsometry due to its simple setup and rapid performance. Furthermore, CSE modulates the polarization parameters of thin films into a spectrum, thus transforming the measurement process into a demodulation problem. However, conventional CSE faces challenges in measurement accuracy and computational efficiency, with strict hardware and calibration requirements. Inspired by physics-informed machine learning, we propose CSE enabled by the physics-informed tandem untrained neural networks (PITUNN), which does not require training, exhibits high computational efficiency and partially alleviates the strict requirements for hardware and calibration accuracy. We also demonstrate the effectiveness of CSE enabled by the PITUNN and its ability to handle system errors and random noise through simulations and experiments on thin films of different thickness and materials.

Fabrication and application of two-dimensional tungsten disulfide thin film

To form a tungsten disulfide film, a tungsten trioxide film is deposited first and then hydrogen sulfide is injected into the furnace tube to sulfide the tungsten trioxide film in a high-temperature environment. Due to the need to accurately control the thickness of tungsten trioxide, the power of the RF sputtering machine was reduced as much as possible in a stable condition in the experiment and the bias voltage during each process was monitored. In this experiment, a sapphire substrate and a silicon substrate with 200[Formula: see text]nm silicon dioxide are used. Then use optical instruments such as Raman optics, ellipsometers and high-resolution electron transmission microscopes, atomic force microscopes and other instruments for further measurement. The analysis results show that we have successfully made tungsten disulfide films of different thicknesses. Moreover, two-dimensional tungsten disulfide thin film has a response to light, gas and pH and related devices have been successfully fabricated in experiments. Among them, comparing the single-layer film and the double-layer film, the film quality of the double-layer film is better. The quality of the film grown on the sapphire substrate is also better than the quality of the film grown on the silicon dioxide substrate.

Understanding photoacoustic signal formation in the presence of transparent thin films

Strain-induced variation of the refractive index is the main mechanism of strain detection in photoacoustic experiments. However, weak strain-optic coupling in many materials limits the application of photoacoustics as an imaging tool. A straightforward deposition of a transparent thin film as a top layer has previously been shown to provide signal enhancement due to elastic boundary effects. In this paper, we study photoacoustic signal formation in metal covered by thin transparent films of different thicknesses and demonstrate that in addition to boundary effects, the photoacoustic response is affected by optical effects caused by the presence of the top layer. The interplay of optical effects leads to a complex temporal signal shape that strongly depends on the thickness of the thin film.

In‐situ elemental reaction‐regulated Ag2S films enable the best thermoelectric performances

AbstractSilver sulfide thin film, with excellent thermoelectric properties, is few reported due to the complex and time‐consuming high‐temperature or high‐pressure synthesis process. Here, a fast ionic conductor n‐type Ag2S film with good crystallinity and uniform density is prepared by sputtering metal Ag films of different thicknesses on glass and then reacting in S precursor solution at low temperature. At 450 K, β‐Ag2S films can be obtained and underwent a phase transition from α‐Ag2S monoclinic, which had a significant effect on their electrical and thermal properties. The grain size of Ag2S films increases with the increase of film thickness. Before and after the phase transition, the carrier concentration and mobility cause obvious changes in the electrical properties of Ag2S. The carrier concentration of body‐centered cubic phase β‐Ag2S is about three orders of magnitude higher than that of monoclinic phase α‐Ag2S, and the mobility is also 2–3 times that of the latter. Especially, after the phase transition, the conductivity of β‐Ag2S rises exponentially from the zero conductivity of α‐Ag2S and increases with the increase of temperature. The Ag2S film shows the highest figure of merit of 0.83 ± 0.30 at 600 K from the sample with ∼1600 nm thickness, which is the highest record among Ag2S‐based thermoelectric materials reported so far.

Aggregation induced strong photoluminescence at room temperature in large-area C8BTBT thin films

Study of optical properties of 2,7-dioctyl[1]benzothieno[2,3-b]benzothiophene (C8BTBT) is promising for applications in low-cost and flexible optoelectronic devices. Here, we systematically investigated the thickness dependent structural and photophysical properties of large-area C8BTBT films. The large-area C8BTBT thin films of different thickness below 80 nm were prepared by off-centre spin coating method. Grazing incidence X-ray diffraction measurements confirm the highly crystalline nature of the thin films and reveal that crystal coherence length increases with increase of film thickness. The film morphology and its thickness were studied using atomic force microscopy. Further, optical absorption and emission behaviors of the thin films were analyzed. The results show strong ultraviolet (UV) emissions at room temperature. The photoluminescence behaviour of higher-thickness films differs from that of lower-thickness films. The thickness dependent UV emission spectra are explained in terms of defects and aggregation behavior of C8BTBT thin films. We determine the impact of thickness and aggregation (J- and H-type) on emission behaviors of the C8BTBT thin films. Our findings open a new avenue for the future optimization and prospective applications in photonics based on two-dimensional organic semiconductors.

Formation of thin Crsi2 films by the solid-phase ion-plasma method and their thermoelectric properties

ABSTRACT CrSi2 thin films with different thicknesses obtained on the Si(111) surface by magnetron sputtering method have been investigated using complex of electron spectroscopy and microscopy methods. The thin films’ composition, surface morphology, and cross-section, as well as the resistivity’s, Seebeck coefficient’s, and power factor’s temperature dependences have been studied for the first time. It has been established that, starting from a thickness of ~ 400 Å (deposition time ~ 60 sec), the SiO2/Si(111) surface is completely covered with an amorphous CrSi2 film. After heating the CrSi2/SiO2/Si(111) system at T ≈ 750 K, a homogeneous polycrystalline CrSi2/SiO2/Si(111) film is formed. It is shown that the resistivity ρ, the Seebeck coefficient S, and the power factor P of a CrSi2/SiO2/Si(111) film of different thicknesses (80 and 180 nm) change nonlinearly with increasing temperature. Their values for CrSi2 films of different thicknesses differ slightly from each other.

Controllable physicochemical properties of WOx thin films grown under glancing angle.

In this work, various physicochemical properties are investigated in nanostructured WOx thin films prepared by radio-frequency magnetron sputtering for optoelectronic applications. A glancing angle of 87° is employed to grow films of different thicknesses, which are then exposed to post-growth annealing. Detailed local probe analyses in terms of morphology and work function of WOx films are carried out to investigate thickness-dependent property modulations of the as-deposited and annealed films. The analyses show a reasonably good correlation with photoelectron spectroscopic measurements on the films and the bulk I-V characteristics acquired on a series of WOx/p-Si heterojunction diodes. The presence of a critical WOx thickness is identified to regulate the rectification ratio values at the WOx/p-Si heterostructures and increase in series resistance within the bulk of the films. The present study provides valuable insights to correlate optical, electrical, and structural properties of WOx thin films, which will be beneficial for fabricating WOx-based optoelectronic devices, including photovoltaic cells.

Hybrid periodic microstructures fabricated on chromium films by SLM-assisted nanosecond laser processing

An effective technique for preparing different hybrid periodic structures on chromium (Cr) films of different thicknesses using a 1064-nm nanosecond laser assisted by spatial light modulator (SLM) is proposed. For 1000-nm Cr films, by combining periodic modulated grating (MG) patterned by SLM with laser-induced periodic surface structures (LIPSS), regular dual-scale MG-LIPSS can be fabricated, with the morphological characteristics controlled by laser fluence, effective pulse number, and MG period. Due to diffraction effects of MG and LIPSS, MG-LIPSS patterned surfaces exhibit vivid anisotropic structural colors. In contract to MG-LIPSS, complex periodic structures consisting of MG and cracks (MGC) are fabricated on 200-nm Cr films due to the more significant thermal stress of a thinner film. Although the cracks of MGC distributed randomly, MGC show a long-range order characteristic with a certain transmittance, which can be utilized as a transmission grating with diffraction effects. These results demonstrate that optical field modulated laser machining based on SLM offers an efficient, cost-effective, and controllable method for fabricating large-area periodic structures on Cr films. Moreover, variations in film thickness can be employed to explore hybrid microstructures with specific properties, and thus utilized in diverse applications, such as optical components and anti-counterfeiting measures.

Electrochemical behaviour of sputter-coated titanium films on AZ31 magnesium alloy

Lightweight magnesium-based structural alloy AZ31 is normally prone to high corrosion in an aqueous environment. A detailed study is reported in this work on AZ31 Mg alloy coated with Ti thin films of different thicknesses by DC sputtering to investigate the capability of Ti coating to prevent corrosion of AZ31 under an aqueous environment similar to seawater. Ti films have been fabricated to 50, 100 and 150 nm thicknesses. Utilising grazing incidence-XRD and SEM, the films’ structure and microstructure were studied. The films were amorphous. Due to corrosion, interesting micro-structures evolved. Corrosion inhibition characteristics of the Ti films were characterised by electrochemical techniques such as potentiodynamic polarisation and impedance spectroscopy. Ti films with 100 nm and 150 nm thickness show a good inhibition capability. The corrosion mechanism was investigated using XPS and X-ray energy dispersive spectra.

Investigation of optical and electrical properties of TiO2, SiO2, and Ag single and multilayer thin films using spectroscopic ellipsometry and spectrophotometry methods: prepared by spin coating and DC magnetron sputtering

In this work, spectroscopic ellipsometry was used to study the optical and electrical properties of TiO2 and SiO2 thin films deposited by spin-coating at different coating rotation speeds and annealed at various temperatures. In addition, Ag thin films of different thicknesses were deposited by DC magnetron sputtering at ambient temperature. In this method, the optical band gap for TiO2 thin films is between 3.15–3.85 eV, and for SiO2 thin films, it is between 3.2–3.8 eV. The optical properties, including reflectance, transmittance, and absorbance, of TiO2, SiO2, and Ag thin films in the form of single and multilayer thin films in the wavelength range of 200–2500 nm, were investigated using an ultraviolet-visible-near infrared (UV–vis-NIR) dual-beam spectrophotometer. In the TiO2/Ag/SiO2 multilayer thin film, the rejection was 58.6% −73.6% in the NIR wavelength range (800–2500 nm), and a transmittance of 40%–45% was achieved in the visible light range (400–700 nm).

Development of highly sensitive and solar blind surface acoustic wave UV-C photodetector based on the In2O3/Ta2O5 nano-heterojunction and its interface electronics

A highly sensitive surface acoustic wave (SAW) ultraviolet-C (UV-C) sensor based on In2O3/Ta2O5 nano-heterojunctions and its interface electronics was developed to detect solar blind corona discharge near high voltage power lines. The SAW sensor, based on pristine In2O3 nanoparticles, exhibits a weaker and slower response to UV-C light. To improve the response to deep UV light, In2O3 nanoparticles/Ta2O5 heterojunctions were formed by depositing Ta2O5 films of different thicknesses (2–10 nm) around the In2O3 nanoparticles via atomic layer deposition (ALD) on the cavity between two interdigital transducers (IDTs) in the SAW delay line. The experimental results show a significantly enhanced sensor response towards UV-C light, which is attributed to a high surface-to-volume ratio, an inhibited recombination rate of the photogenerated electron-hole pairs on the surface of the sensing material owing to Ta2O5 conformal coverage, and well-matched energy bandgap engineering. An empirical mechanism was proposed to elucidate the enhanced sensing behavior of the heterostructure. To observe the frequency shifts in real-time on a PC display, portable interface electronics were developed on a single printed circuit board (PCB) for the SAW UV-C sensor, eliminating the effect of frequency shifts caused by ambient temperature and humidity changes. The sensor characteristics were evaluated based on the size and annealing conditions of the In2O3 nanoparticles and the thickness of the decorated Ta2O5, and the scientific and technical causes and analysis of the results were thoroughly investigated. In the selectivity test, the fabricated sensor exhibited a strong response to a UV-C light beam with a sensitivity of 368.3 (ppm (μW/cm2)−1 at 254 nm, and its spectral response to UV-C light was 3.3 times higher than that under UV-A 365 nm light.

Optical Properties of PS-MgO Thin Films

In this study, optical properties of thin films made of different volume ratios of polysulfone (PS) and magnesium oxide (MgO) thin film deposited on germania (GeO2 ) were studied as a function of wavelength in the range 0.3 – 1.1 μm using Matlab. Refractive indices, extinction coefficients, and absorption coefficients were investigated. The transmittance spectra of the PS-MgO thin films of different thicknesses deposited on the GeO2 substrate were also examined. The films were found to show an increase in transmittance with an increase in the MgO percentage the thin film. However, the absorbance of the film was found to be high in the ultraviolet. The results give good reason for the applications of MgO thin films in optoelectronic devices.

MOCVD of ZrN: Tuning Thin Film Properties Towards Catalytic Applications

Transition metal nitrides (TMN) have gained increasing attention over recent years as active materials for energy related applications including catalysis and energy storage. They feature high electrical conductivities, wide optical band gaps and superior chemical stability.[1] In particular, ZrN has been recently identified as a promising material for a range of potential applications that include plasmonic devices,[2] as a catalyst for the oxygen reduction reaction (ORR),[3] and as a catalyst for the nitrogen reduction reaction (NRR),[4] due to its appealing electronic properties, while being cheap and abundant compared to commonly used noble metals.[1,5] The fabrication of ZrN on large scale under moderate process conditions, with the required properties for catalytic applications, motivates the use of chemical vapor deposition (CVD) as the method of choice. Moreover, with the variation of process parameters that includes precursor choice and growth temperature, it is possible to tune the surface features as well as composition of the layers that are suitable for catalytic applications.In this study, we have employed metal organic chemical vapor deposition (MOCVD) to synthesize ZrN layers on Si and glassy carbon (GC) substrates in the temperature range of 550 – 850 °C. The influence of the nature of the precursor and deposition temperature on the structure, composition and surface morphology of the ZrN layers was systematically studied. Oriented ZrN layers with facetted grain morphology were obtained. ZrN films of different thickness were analyzed by complementary methods including X-ray diffraction (XRD) (Figure 1 a)), Raman spectroscopy, Rutherford backscattering spectrometry (RBS) (Figure 1 b)), nuclear reaction analysis (NRA), scanning electron microscopy (SEM) (Figure 1 c)), and X-ray photoelectron spectroscopy (XPS). Based on the detailed film analysis, catalyst surfaces were modeled by DFT calculations. The NRR activity and selectivity towards the competing hydrogen evolution reaction (HER) were evaluated by first principles simulations and electrochemical experiments. This preliminary study on material fabrication and theoretical investigations lays a foundation for the investigation of ZrN for NRR applications for future studies.

Modeling of sputter-based atomic layer deposition with altered parameters

Computational modeling of the sputtering process forming atomic layers of some technologically significant materials was performed based on sputter rate relation. Bismuth atomic layer deposition at different polar angles and ion fluence were shown. The atomic layers getting deposited were studied as a function of incident Argon ion energy at different pressure and a curve analogous to the Bragg curve was obtained. The sputtering parameters were varied to get different atomic layers of TiOx films and the variation of coverage with sticking coefficient was shown. The rate of change of partial sputtering yield with coverage was depicted in the sputter-based deposition of TiN films. The deposition pressure and time were varied to get films of different thicknesses. All the simulated results were correlated with experimental findings with features like variation of reactive gas pressure, electron aided momentum transfer in Bi, multilayer anatase and rutile formation in TiO2 and effect of process parameters on TiN.

Combined Retrieval of Oil Film Thickness Using Hyperspectral and Thermal Infrared Remote Sensing

An outdoor experiment was conducted to measure the thickness of oil films (0~3000 μm) using an airborne hyperspectral imager and thermal infrared imager, and the spectral response and thermal response of oil films of different thicknesses were analyzed. The classic support vector regression (SVR) model was used to retrieve the oil film thickness. On this basis, the suitable range for retrieving oil film thickness using hyperspectral and thermal infrared remote sensing was explored, and the decision-level fusion algorithm was developed to fuse the retrieval capabilities of hyperspectral and thermal infrared remote sensing for oil film thickness. The following conclusions can be drawn: (1) Based on airborne hyperspectral data and thermal infrared data, the retrieval accuracy of oil films of different thicknesses reached 154.31 μm and 116.59 μm, respectively. (2) The S185 hyperspectral data were beneficial for retrieving thicknesses greater than or equal to 400 μm, and the H20T thermal infrared data were beneficial for retrieving thicknesses greater than 500 μm. (3) The result of the decision-level fusion model based on a fuzzy membership degree was superior to those obtained using a single sensor (hyperspectral or thermal infrared), indicating that it can better integrate the retrieval results of hyperspectral and thermal infrared remote sensing for oil film thickness. Furthermore, the feasibility of using hyperspectral and thermal infrared remote sensing to detect water-in-oil emulsions of different thicknesses was investigated through spectral response and thermal response analysis.

Magnetic and anomalous Hall effect investigations of co-sputtered Co2MnGa Heusler alloy thin films

The cobalt-based full Heusler alloy Co2MnGa (CMG) is well known for exhibiting an exotic phenomenon such as magnetic Weyl semimetallic nature with a high Curie temperature of ∼700 K and a giant anomalous Hall effect. Here, we report a detailed study of structural, electrical, and magnetic properties of Co2MnGa thin films (thickness in the 40–10 nm range) grown on Si(100) by the direct-current magnetron co-sputtering technique using Co and MnGa targets. Structural analysis of the samples revealed the polycrystalline nature of these films with B2 type structural ordering. The damping parameter decreases with the increase in film thickness and reaches the minimum value of 6.1 × 10−3 for a 40 nm thin CMG film. These CMG films are magnetically isotropic and soft ferromagnetic in nature. A remarkably high value of anomalous Hall conductivity (AHC) of 1920 S/cm (2 K) is found for the 40 nm thin film, which is comparable to earlier reported values on highly ordered CMG films. Nearly 73% of this AHC value originates from the intrinsic contribution. The AHC and longitudinal conductivity both increase with the film thickness. Different scaling mechanisms are used to compute the intrinsic and extrinsic contributions playing a role in AHC. The analysis of advanced scaling [by Tian et al., Phys. Rev. Lett. 103, 1–4 (2009)] performed on these CMG films suggests the consistency in the enhanced intrinsic AHC value irrespective of the thickness and a decrease in skew scattering contribution with thickness. These results will enhance the understanding about the magnetic and transport properties of Co2MnGa thin films of different thicknesses and suggest it to be a promising material for topospintronic applications.

Gate voltage control of helicity-dependent photocurrent and polarization detection in (Bi1−xSbx)2Te3 topological insulator thin films

Optical helicity provides us with an effective means to control the helicity-dependent photocurrent in the spin-momentum-locked surface states of topological insulators (TIs). Also, the TIs show potential in polarization detection as an intrinsic solid-state optical chirality detector for easier integration and fabrication. However, the complex photoresponses with the circular photogalvanic effect, the linear photogalvanic effect, and the photon drag effect in the TIs prevent them from direct chirality detection of the elliptically polarized light. Here, by fitting with the theoretical models to the measured photocurrents, the microscopic origin of different components of the helicity-dependent photocurrent has been demonstrated. We show a comprehensive study of the helicity-dependent photocurrent in (Bi1−xSb x )2Te3 thin films of different thicknesses as a function of the light incident angle and the gate-tuned chemical potential. The observation of the light incident angle dependence of the helicity-dependent photocurrent provides us with a polarization detection strategy using a TI thin film without the use of any additional optical elements, and the detection accuracy can be enhanced by gate tuning. Additionally, the Stokes parameters can be extracted by arithmetic operation of photocurrents measured with different incident angles and gating voltages for complete characterization of the polarization states of a light beam. Using this means, we realize the polarization detection and the Stokes parameters analysis with a single device. Our work provides an alternative solution to develop miniaturized intrinsic polarization-sensitive photodetectors.

Post-aseptic adaptation and ex vitro propagation of Ukrainian cultivars of Paulownia Sieb. et Zucc.

Plantation forestry using highly productive and fast-growing plants involves the use of high-quality improved planting material for genetic constancy, which is solved by microclonal reproduction. However, the high survival rate and stability of plants obtained in vitro are realised as a result of post-aseptic adaptation of regenerants. Therefore, the research aims to improve the survival techniques of paulownia regenerants of the Ukrainian varieties “Feniks” and “Enerdzhy” ex vitro. The study was conducted in December 2021 on the Ukrainian paulownia varieties “Feniks” and “Enerdzhy”, cultivar “Feniks”. The survival rate, development of regenerants, and their damage by facultative saprophytic pathogens differed on substrates of organic (Eco Plus, La Flora, Jiffy, coconut peat, cotton wool) and mineral (vermiculite, perlite, sand) origin. The biological products “Rise P” and “Prestop” proved to be effective for the control of pathogenic microorganisms on substrates of organic origin. The technological feasibility of using perlite substrate is substantiated. The pathophysiology of ex vitro regenerants of paulownia under Fusarium is described. The thickness of the films used for sheltering influenced the regeneration, engraftment, microbial damage, and temperature of the wet chambers. Growing regenerants with covering films of different thicknesses showed a high survival rate in the variants with stretch films of 10 and 23 µm thickness. In the case of using polyethene films with thicknesses of 60, 80 and 100 µm, a sharp increase in temperature was observed, which was 48, 53 and 650C, respectively. At these high temperatures, most of the regenerants died, after which they were colonised by facultative saprophytes, and the tissues were completely macerated within two days. The optimal ratio of juvenility reduction and the acquisition of adaptive traits is characteristic of the second, third and fourth generation ex vitro. The expediency of propagation by stem cuttings up to the fourth generation, which preserves the regenerative ability of shoot cuttings, was substantiated. The practical results of the research are a protocol for growing paulownia plants in vitro and ex vitro on different types of substrates for use by institutions engaged in paulownia propagation

Scintillation properties of composite films based on CsPbBr3 nanocrystals embedded in PMMA

Transparent composite films of polymethylmethacrylate with embedded CsPbBr3 colloidal nanocrystals (CsPbBr3-PMMA) were obtained. The optical, photoluminescent, and scintillation properties of the composite films were studied. The CsPbBr3-PMMA films had an intense photoluminescence signal and a nanosecond-range photoluminescence decay time (2 ns). The scintillation characteristics of CsPbBr3-PMMA films of different thicknesses were studied upon excitation by α-radiation of radionuclides 239Pu (Eα = 5.15 MeV) and 238Pu (Eα = 5.46 MeV). The sensitivity and minimum detectable activity of the composite films were calculated from the pulse-height spectra. The estimation of the absolute light yield according to the IEC 62372:2021 standard (determining the intrinsic resolution of scintillator) and calculation of the light collection coefficient showed that the 200-μm thick composite film emitted about 860 photons per 1 MeV of absorbed energy. Under α-excitation, the films revealed a fast scintillation response with average decay time of about 1.4 ns.

Regularities of the Formation of Fractal Structures on the Surface of Metallic Films of Different Thicknesses

Regularities of the Formation of Fractal Structures on the Surface of Metallic Films of Different Thicknesses