Thin 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.

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.

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).

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.

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.

AgSbTe2 semi-nanocrystalline thin films as a multifunctional platform for optoelectronic and diode applications

The synthesis of the nanosized multifunctional thin film provides new solutions for many technological issues and consider a great step for miniaturized technology. Toward these goals, AgSbTe2 semi-nanocrystalline thin films of different thicknesses were synthesized by the thermal evaporation technique. The structural features were investigated by X-ray diffraction, and selected area electron diffraction (SAED) yielding a semi-nanocrystalline thin film of grain size ranging from 9.98 to 21.38 nm. The energy-dispersive X-ray spectroscopy (EDAX) verified the high purity and stoichiometry of the deposited films. For optoelectronic application, many optical parameters, including band gap (Eg), Urbach energy (Eu), Refractive index (n), dispersion energy (Ed), electronic polarizability (αe), and interband transition strength (JCV) were extensively discussed. The optical band gap reduced from 1.41 to 1.04 eV upon increasing the thickness from 150 to 550 nm. The temperature dependence of the electrical resistivity (ρ) of nanosized thin film was measured and the activation energy was estimated and it was found that the resistivity increased up to 450 K asserting the semiconductor behavior of the films. As for diode application, The Ag/2D-MoS2/p-AgSbTe2 (550 nm)/n-Si/Al heterostructure diode was constructed by thermal evaporation and all the diode parameters alongside conduction mechanism were studied in detail. AgSbTe2-based diode showed a low rectification ratio; however, the ideality factor (n) and zero bias barrier height (Φb) had optimal values of about 1.40 and 0.75 at room temperature, respectively.

Effects of Film Thickness on the Residual Stress of Vanadium Dioxide Thin Films Grown by Magnetron Sputtering.

Vanadium dioxide (VO2) thin films of different thicknesses were prepared by regulating the deposition time (2, 2.5, 3, and 3.5 h). The impact of deposition time on the microstructure, surface morphology, and cross-section morphology was investigated. The results showed that the grain size increased with the film thickness. Meanwhile, the influence of film thickness on the residual stress was evaluated by X-ray diffraction. The phenomenon of "compressive-to-tensile stress transition" was illustrated as the thickness increased. The change of dominant mechanism for residual stress was used for explaining this situation. First, the composition of residual stress indicates that growth stress play a key role. Then, the effect of "atomic shot peening" can be used to explain the compressive stress. Lastly, the increased grain size, lower grain boundary density, and "tight effect" in the progress of film growth cause tensile stress.

Thermal annealing of superconducting niobium titanium nitride thin films deposited by plasma-enhanced atomic layer deposition

Next-generation superconducting radio frequency (SRF) cavities, based on tailored thin films, would allow for more efficient and sustainable accelerators operating at higher accelerating gradients. In particular, superconductor–insulator–superconductor (SIS) multilayers are proposed as a potential alternative to bulk Nb. In this context, NbTiN stands out as a superconducting candidate. Here, we report our studies on NbTiN thin films grown by plasma-enhanced atomic layer deposition (PEALD) in a supercycle approach on AlN in situ deposited on planar silicon substrates. In detail, different ternary compound compositions and thicknesses have been investigated concerning the elemental composition, the superconducting properties, and the crystallinity of the deposited thin films. Two different post-deposition thermal treatments have been applied to Nb0.75Ti0.25N thin films of different thicknesses. Their effect on the film properties has been evaluated. It has been demonstrated that an optimized post-deposition thermal annealing procedure significantly improves the quality of our PEALD deposited Nb0.75Ti0.25N thin films, achieving the highest superconducting critical temperature (Tc) of 15.9 K obtained for films deposited by atomic layer deposition (ALD) so far and a lower critical field (Hc1) of 213 mT, which overpasses the bulk Nb intrinsic limit of 200 mT. Our studies are a promising first stepping stone on the path toward tailored thin films based SRF cavities.

Dependence of WAL effect and enhancement of spin-orbit coupling effect in Bi1.2Sb0.8Te0.4Se2.6 low-temperature magnetic transport

The strong spin-orbit coupling and time-reversal symmetry in topological insulators (TIs) produce a new quantum state known as the topological surface state (TSS). The study of low-temperature magnetic transport in the TSS provides opportunities to explore exotic physical phenomena such as the spin Hall effect and the topological phase transition. An important goal in obtaining intrinsic TI systems is to eliminate internal defects and thereby reduce the contributions of metallic states in transport measurements. In this work, we are committed to overcoming this difficulty by elemental alloying. This paper reports the successful preparation of high-quality and stoichiometrically stable Bi1.2Sb0.8Te0.4Se2.6 (BSTS) thin films by innovatively combining the hybrid target structure with the laser molecular beam epitaxy (LMBE) system and low-temperature magnetic transport tests conducted on BSTS thin films of different thicknesses. Due to stronger spin-orbit coupling, we observed a weak anti-localization (WAL) effect, and the strength of the effect was affected by the film thickness and temperature in the low-temperature magnetic transport study. The dependence of the WAL effect provides a way to regulate the TSS.

Preparation and electrical properties of ultra-thin Bi2212 films by sol-gel method

In order to achieve flexible applications of superconducting thin film materials in devices, the surface quality of the film is critical. The thickness of the film is one of the important factors affecting its surface quality. In this paper, Bi2212 superconducting thin films of different thicknesses were prepared on LaAlO3(100) and SrTiO3(100) single crystal substrates by sol-gel method and the effects of film thickness and different heterogeneous structures on their crystallographic, morphological and superconducting properties were investigated. The results showed that the roughness gradually increased with increasing Bi2212 thickness at the initial stage of film growth and stabilized after reaching a certain thickness, while the superconducting properties were destroyed at very small sample thickness, which was consistent in both single-crystal substrate films. In the Bi2212/LaAlO3 structure, the surface quality of the sample was excellent with a roughness of 5.4 nm at a thickness of about 18 nm for Bi2212, and the growth of the precipitated phase was inhibited to a greater extent. The film also had good superconductivity. This work provided a further research basis for the preparation of high quality Bi2212 films and offers further possibilities for their practical application.

Pseudocapacitive performance of amorphous ruthenium oxide deposited by successive ionic layer adsorption and reaction (SILAR): Effect of thickness

Developing and fabricating effective, affordable electrode materials for supercapacitors is still a challenge. Electrical conductivity, a large surface area, dynamic faster electron transport, and other customizable qualities are present in metal oxide materials while being inexpensive to manufacture. In this work, successive ionic layer adsorption and reaction (SILAR) method was employed for deposition of amorphous ruthenium oxide (RuO2) thin films of different thicknesses on a stainless steel substrate. At 1.56 mg cm−2 thickness amorphous RuO2 achieved a maximum specific capacitance (Cs) of 1146 F g−1 at a scan rate of 5 mV s−1 with 87% capacitance retention up to 5000 cycles. These findings bolster the idea of cost effective deposition of amorphous RuO2 material for supercapacitor applications.

InSnO:N homojunction thin-film transistors fabricated at room temperature

Nitrogen-doped indium tin oxide (ITON) thin films of different thicknesses were deposited by radio frequency magnetron sputtering. The crystallinity, surface morphologies, and chemical compositions of the thin films were found to be influenced by film thickness, and changes in these factors eventually caused changes in the conductivity of the thin films. Therefore, we used ultrathin ITON thin films as channels and an 85-nm-thick ITON as the source/drain electrodes to fabricate thin-film transistors. The optimal device fabricated at room temperature (∼25 °C) has a threshold voltage of −2.5 V and a field-effect mobility of 10.31 cm2/(V∙s).

SERS Detection of Rhodamine-6G on Ion Beam Nanostructured Ultra-Thin Gold (Au) Films: A Correlation between Fractal Growth, Water Contact-Angle and Raman Intensity

SERS (Surface Enhanced Raman Scattering) detection of rhodamine-6G on gold nanostructures (Au–NS) of various sizes under ion beam irradiation is presented. On a glass substrate, Au thin films of different thicknesses (∼2, 3 and 5 nm) were deposited by thermal evaporation. Subsequent irradiation using 10 keV Ar+ at different fluences has been able to modify the size of Au-NS. Ion beam-induced sputtering and diffusion processes control the formation of Au-NS. The reduction in Au content during ion beam sputtering is confirmed by Rutherford Backscattering Spectroscopy (RBS), which also validates tuning the size and structures of Au-NS. The wettable characteristics of Au-NS surfaces are controlled by two competing statistical factors of sputtering and surface diffusion. A correlation between the water contact angle, rms roughness, and the detection of rhodamine-6G (R6G) by SERS is presented. The current study sheds light on the mechanism(s) of SERS chemical detection for wider metallic surfaces.

Investigations of dielectric properties of cadmium selenide thin films

Thin Films of different thickness of Cadmium Selenide (CdSe) were prepared by using thermal evaporation technique on a glass substrate, and investigation of dielectric properties as a function of frequency in the range up to 1 MHZ using Auto Lab Potentiostat/Galvanostat meter was conducted. Preliminary data for complex parameters i.e. complex dielectric constant (ε*), complex impedance (Z*), electric modulus (M*), tangent loss (δ) and conductivity (σ) has been calculated. All these properties are used to explore various processes that contribute to the dielectric spectroscopy investigation.

Analysis of current-voltage curves of ZnO thin films under dark and optical stimulus

In this work, we are reporting the current conduction mechanism in ZnO thin films of various thicknesses under the dark and optical stimulus. The ZnO thin films of different thicknesses (45, 70, 110, 160, 220 nm) were grown on a glass substrate at 250 °C using the spray pyrolysis method. For photoconductivity measurements, electrodes were made using silver paste by putting a ∼1 mm gap between the electrodes. The photocurrent under UV illumination increases with increasing film thickness. Linear fitting of the data suggests the major role of space charges in the film for the rise in the photocurrent. Therefore the obtained conduction mechanism is found to be space charge-limited conduction in ZnO thin films under UV illumination.

МЕТОДИЧНИЙ АСПЕКТ ПРОВЕДЕННЯ СПОСТЕРЕЖЕНЬ ЗА ЗМІНОЮ ОБ’ЄМНОЇ КОНЦЕНТРАЦІЇ РАДОНУ В ЗАЛЕЖНОСТІ ВІД ГЕОГРАФІЧНО-СЕЙСМІЧНИХ ПАРАМЕТРІВ У РЕГІОНІ

The paper describes one of the methods of investigation of galvanomagnetic phenomena compound thin film semiconductor system AIVBVI. The resulting current-voltage characteristics of thin films PbTe: Sb and analyzed the basic parameters for thin films of different thicknesses using the method of Hall. The dependence of the film thickness PbTe:Sb on the mobility and concentration of major carriers.

Effects of electric quadrupole interactions with tunable atomic mirrors

Recent studies have involved electric quadrupole effects in atoms interacting with the evanescent mode. This type of surface mode is usually produced by the total internal reflection in a dielectric-vacuum atz=0, and its intensity distribution is very close to the outer surface z>0 half-space. Coating the planar surface of a dielectric substrate with multilayer dielectric thin film of different thicknesses provides an enhanced in such evanescent modes. This type of mode can be used purely as an atomic mirror. We show that the use of such elements for atomic optics gives significant enhancement of the evanescent mode magnitude without degrading the quality of the atomic reflection process. In addition, the decay depth of the evanescent mode can be conveniently controlled by design parameters. This property keeps the atom-light interaction timeτ, and thus the probability of decay emission, very low, which means a high degree of coherence property.

Flexible Printed Circuit Board Strain Sensor Embedded in a Miniaturized Pneumatic Finger

A miniaturized pneumatic finger allows for safer grasping without damaging the surface of an object. A flexible strain sensor was developed and embedded in a miniaturized pneumatic finger to sense the finger’s self-deformation as a feedback control signal. The proposed flexible strain sensor comprised a Zr-based metallic glass sensing material and a flexible printed circuit board (FPCB) substrate. The properties of fabricated strain sensors with different patterns and with metallic glass thin films of different thicknesses were measured. The miniaturized pneumatic finger was fabricated from a highly elastic polymer by demolding. To integrate the flexible strain sensor and the miniaturized pneumatic finger, surface treatment was performed to improve the bonding strength. Measurements of the contact angle and peel-off force reveal that the treated surfaces have lower contact angles and higher bonding strength. This higher bonding strength between the flexible strain sensor and the miniaturized pneumatic finger prevented the destruction of the finger during bending. The developed flexible strain sensor embedded in the miniaturized pneumatic finger could sense the finger’s self-deformation by measuring changes in resistance.