Substrate Thickness Research Articles

Study on the performance of thin-film VCSELs on composite metal substrate

Thin film p-side up vertical-cavity surface-emitting lasers (VCSELs) with 940 nm wavelength on a composite metal (Copper/Invar/Copper; CIC) substrate has been demonstrated by twice-bonding transfer and substrate removing techniques. The CIC substrate is a sandwich structure with a 10 µm thick Copper (Cu) layer/30 µm thick Invar layer/10 µm thick Cu layer. The Invar layer was composed of Iron (Fe) and Nickel (Ni) with a proportion of 70:30. The thermal expansion coefficient of the composite CIC metal can match that of the GaAs substrate. It results that the VCSEL layers can be successfully transferred to CIC metal substrate without cracking. At 1 mA current, the top-emitting VCSEL/GaAs and thin-film VCSEL/CIC had a voltage of 1.39 and 1.37 V, respectively. The optical output powers of VCSEL/GaAs and VCSEL/CIC were 21.91 and 24.40 mW, respectively. The 50 µm thick CIC substrate can play a good heat dissipation function, which results in improving the electrical and optical characteristics of thin film VCSELs/CIC. The VCSEL/CIC exhibited a superior thermal management capability as compared with VCSEL/GaAs. The obtained data suggested that VCSELs on a composite metal substrate not only affected significantly the characteristics of thin film VCSEL, but also improved considerably the device thermal performance.Graphical

Design and Analysis of Microstrip Patch Antenna Array and Electronic Beam Steering Linear Phased Antenna Array with High Directivity for Space Applications.

This study proposes an E-shaped microstrip patch antenna array (MSPAA). The substrate is RT/Duroid5880. Its 2.2 dielectric constant gives it a larger bandwidth than substrate materials with higher dielectric constants. The periphery dimension of a single E patch is 50 × 41 mm2. The areas of 2 × 2 and 3 × 3 MSPAAs are 120 × 96 and 180 × 144 mm2, respectively. Array members are 10 and 7 mm apart horizontally and vertically, respectively. MTM technology builds the projected MSPAA. This work looks at the effects of gain, reflection coefficient (return loss), directivity, bandwidth, and VSWR on proposed 2 × 2 and 3 × 3 MSPAAs with different patch lengths of 30, 40, and 60 mm, patch widths of 40, 50, and 60 mm, and substrate thicknesses of 0.8 and 1.6 mm. Also, this study compares the performance of existing E-shaped MSPAAs with proposed 2 × 2 and 3 × 3 MSPAAs. The suggested MSPAA performs better than the existing E-shaped MSPAA. The series network analyzer measures the prototype MSPAA's experimental outcomes. The polynomial is recommended for estimating the antenna array area with odd and even rows and columns. CST Studio Suite software analyzes and designs antenna arrays, and simulation findings are compared with hardware results. The main benefit of the proposed 2 × 2 MSPAA is that it reduces sidelobes. It has a gain of 8.9 dBi, a directivity of 8.95 dBi, a VSWR of 1.02, a return loss of -32.91 dB, and a bandwidth of 0.1 GHz at both 1.6 and 0.8 mm substrate material thicknesses. Across its operating range of 3.8-4.2 GHz, the recommended array antenna has a radiation gain of 7.01-7.81 dB and an efficiency of 68.51-71.11%. At 4 GHz, this study looks at how electronic steering affects the phase angle of the excitation signal, the number of elements, and the distance between elements in the beam steering linear phased antenna array (BSLPAA) using MATLAB.

Упругие резонансы в структуре: тонкая магнитная пленка – толстая упругая подложка

The task about excitation of connected magnetic and elastic vibrations in flat-parallel-structure consisted of thin magnetic film applied on thick nonmagnetic substrate is considered. For the solution of this task the model of propagation periodic boundary regime is proposed. This solution allowed to build the amplitude-frequency characteristics of magnetic and elastic vibrations. In this case the characteristic of magnetic vibrations has the view as wide bell-like maximum on which is put by equidistance net of narrow elastic resonances which divided one to another on the frequency elastic resonance along the substrate thickness. It is executed the model presentation of superposition elastic resonances on magnetic using the system of two connected oscillators which frequencies differs in some orders. It is supposed the mechanism of superposition elastic resonances on magnetic characteristic which consist of coincidence wave phase after two-path wave passage through the substrate thickness and phase of initial excitation. It is investigated the influence of elastic wave dissipation on the structure of amplitude-frequency characteristics of magnetization and elastic displacement. It is found the critical value of elastic dissipation parameter. It is shown that below of this value the elastic vibrations have resonance character and higher become non-periodical. It is found the inversion value of dissipation parameter which determined the transition from symmetrical distribution of elastic resonances on magnetic characteristic to anti-symmetrical. It is shown that the inversion value of dissipation parameter more (on two-three orders) smaller that critical value. It is found the phenomenon of second elastic resonance which is consist of exceeding frequency maximum rounding of elastic resonance net over the frequency of maximum magnetization characteristic. It is found the connected with dissipation second resonance splitting which take place near the neighbouring of inversion value dissipation parameter.

CNR performance of semiconductor materials for X-ray imaging of breast calcifications

We present the results of a GAMOS/GEANT4 computer simulation of a standard X-ray mammography system, which consists of a Tungsten 28 kVp polychromatic X-ray source with a 50 μm Rh filter, a mammography phantom with Al2O3 spherical specks of different diameters, and a generic pixel detector (55 μm × 55 μm pixel size) with different types of semiconductor sensors. The number of photons simulated is calibrated to produce similar entrance surface dose (ESD) as the one used by a standard clinical mammography screening. Estimates of Contrast to Noise Ratio (CNR) as a function of ESD, sensor thickness and microcalcification diameter are presented for four different sensor materials: Silicon (Si), Cadmium Telluride (CdTe), Gallium Arsenide (GaAs) and Perovskite (MAPbI3). For the X-ray energy spectrum and pixel size considered, and an ESD dose of 4 mGy, our study shows that, with the exception of Si, these sensors, as thin as 200 μm, are able to resolve (with at least 3 standard deviations above background) Al2O3 spherical specks up to a minimum diameter of 180 μm, having statistically compatible CNR performance. The increase in substrate thickness has a substantial improvement in the CNR values provided by the Si sensor, while for the other cases the enhancement of CNR is marginal and consistent with statistical uncertainties with the thinnest case considered.

A coded aperture with sub-mean free-path thickness for neutron implosion geometry imaging on inertial confinement fusion and inertial fusion energy experiments.

Inertial confinement fusion and inertial fusion energy experiments diagnose the geometry of the fusion region through imaging of the neutrons released through fusion reactions. Pinhole arrays typically used for such imaging require thick substrates to obtain high contrast along with a small pinhole diameter to obtain high resolution capability, resulting in pinholes that have large aspect ratios. This leads to expensive pinhole arrays that have small solid angles and are difficult to align. Here, we propose a coded aperture with scatter and partial attenuation (CASPA) for fusion neutron imaging that relaxes the thick substrate requirement for good image contrast. These coded apertures are expected to scale to larger solid angles and are easier to align without sacrificing imaging resolution or throughput. We use Monte Carlo simulations (Geant4) to explore a coded aperture design to measure neutron implosion asymmetries on fusion experiments at the National Ignition Facility (NIF) and discuss the viability of this technique, matching the current nominal resolution of 10 µm. The results show that a 10mm thick tungsten CASPA can image NIF implosions with neutron yields above 1014 with quality comparable to unprocessed data from a current NIF neutron imaging aperture. This CASPA substrate is 20 times thinner than the current aperture arrays for fusion neutron imaging and less than one mean free-path of 14.1MeV neutrons through the substrate. Since the resolution, solid angle, and throughput are decoupled in coded aperture imaging, the resolution and solid angle achievable with future designs will be limited primarily by manufacturing capability.

Electron-enhanced atomic layer deposition of Ru thin films using Ru(DMBD)(CO)3 and effect of forming gas anneal

Ruthenium (Ru) thin films were deposited utilizing electron-enhanced atomic layer deposition (EE-ALD). Sequential exposures of Ru(DMBD)(CO)3 (DMBD = 2,3-dimethylbutadiene) and low-energy electrons at ∼125 eV were used to grow the Ru films at temperatures ≤160 °C. The electrons were obtained from a hollow cathode plasma electron source that provided an electron current of ∼200 mA over a surface area of ∼4 cm2. Low-energy electrons can desorb surface ligands derived from Ru(DMBD)(CO)3, such as CO, through electron-stimulated desorption. The desorbed surface ligands leave chemically reactive sites for subsequent Ru(DMBD)(CO)3 precursor absorption. Ru EE-ALD film growth was monitored utilizing in situ spectroscopic ellipsometry (SE). The electron exposures resulted in rapid Ru film nucleation and growth. Under saturation conditions at 160 °C, the growth rate for Ru EE-ALD was 0.2 Å/cycle. The electron efficiency factor for Ru EE-ALD was ∼21 500 electrons/deposited Ru atom. There was no film growth without electron exposures. Ru growth was observed on various substrates including silicon with native oxide and titanium. Ru growth was also obtained on insulating substrates such as 400 nm thick thermal SiO2 substrates. XPS analysis measured <1 at. % oxygen in the deposited Ru films. XRD, x-ray reflectivity, and SE were used to characterize the Ru films before and after forming gas anneal (FGA). FGA successfully removed carbon impurities from the as-deposited Ru films. The resistivity of the Ru EE-ALD films after FGA was determined to be as low as 17 μΩ cm for a film thickness of 6.7 nm. SE measurements of the imaginary part of the pseudodielectric function, 〈ɛ2〉, were utilized to characterize the as-deposited Ru films and the high purity Ru films after FGA. The low resistivity of the Ru films after FGA was consistent with a prominent Drude absorption in the ⟨ε2⟩ spectrum at ≤1 eV. Various reactive background gases such as H2, NH3, and H2O were utilized during EE-ALD to attempt to remove the carbon from the as-deposited Ru EE-ALD films.

Вторичный магнитоупругий резонанс в структуре: тонкая магнитная пленка – толстая упругая подложка

The task about excitation of connected magnetic and elastic vibrations in flat-parallel structure consisted of normal magnetized thin magnetic film applied on thick nonmagnetic substrate is considered. As a result of estimated task solution the amplitude-frequency characteristics of magnetic and elastic vibrations are found. It is shown that in conditions when the ferromagnetic resonance frequency is higher then own elastic vibration of the structure on the amplitude-frequency characteristics of magnetic vibrations applied the equidistance net of elastic resonances of structure. For the interpretation of observed resonance net it is proposed the model of phase synchronization between initial excitation and elastic wave which experience two passages along the thickness of structure. It is shown that the frequency of maximum elastic vibrations rounding exceeds frequency of maximum magnetization characteristic. The existence of own rounding elastic vibrations characteristic is named the second elastic system resonance. It is investigated the dependence of maximum second resonance characteristic from value of magnetoelastic interaction constant. It is shown that by increasing of this constant the frequency distance between both characteristic maxima increases. As a hypothesis of this increasing it is proposed the analogy with splitting of amplitude-frequency characteristic of system consisted of two connected resonators. It is investigated the amplitude-frequency characteristics magnetic and elastic vibrations in wide frequency region. On the equidistance elastic resonances net amplitude-frequency characteristic it is found the narrow equidistance disposed resonance depressions which are correspond to decreasing of amplitude more then two orders of value. It is shown that the frequency interval between neighbouring depressions is back proportional to distance between point of elastic vibrations registration and surface of substrate opposite to magnetic film. For the interpretation of depressions formation it is proposed the model which takes into account the phase opposition in registration point between wave which goes out of the excitation point and wave which is reflected from the opposite end of structure. Briefly noted some physical analogies of investigated phenomena.

An improved method for measuring epi-wafer thickness based on the infrared interference principle: Addressing interference quality and multiple interferences in double-layer structures

The precise measurement of the thickness of substrate and epitaxial layers in epi-wafers is essential in the semiconductor chip fabrication process. This study presents a new method for measuring the thickness of epi-wafers using Fourier Transform Infrared (FTIR) technology, which allows for precise, simultaneous, and fast measurement of both substrate and epitaxial layers. To address the low accuracy of traditional FTIR techniques, a novel VMD-LSP algorithm is introduced, capable of precisely extracting frequency components from the original spectral signal to calculate the precise thickness of the substrate and epitaxial layers. This study also introduces an adaptive spectral excision algorithm and a high-precision thickness extraction algorithm to handle variations in the infrared light absorption of different epi-wafer materials, leading to weakened interference signals, and the challenges that stem from the unique double-layer structure of the wafer. These algorithms efficiently reduce the impact of poor spectral quality and multiple interferences on measurement results, resulting in improved measurement accuracy and stability. During the experimental phase, we compared our results obtained by ellipsometry as truth to evaluate the accuracy and stability of our proposed method. The results show an 85% reduction in measurement error and a 65% improvement in stability compared to traditional methods. As a result, our method meets the need for fast and efficient epi-wafer thickness measurement in semiconductor chip manufacturing, providing a feasible and effective solution to the challenge of epi-wafer thickness measurement.

In-situ laser metal deposition of nitinol and the effect of Ni4Ti3 phase concentration on its pseudoelasticity

Pseudoelasticity is one of the major properties of nitinol. It is highly altered by the presence of nickel-rich Ni4Ti3 phase in the nitinol matrix. Hence it is significant to make an attempt to study the connection between Ni4Ti3-concentration and the matrix-pseudoelasticity. In this work, the connection of pseudoelasticity of nitinol with the concentration of Ni4Ti3 in the matrix was investigated. A 0.5 mm thick preplaced layer of a powder mixture of nickel and titanium (55 % and 45 % by weight, respectively) on a 4 mm thick nitinol substrate was laser scanned with a laser power of 1000 W, scan speeds of 200, 400, 600, 800 and 1000 mm/min and a laser spot diameter of 3 mm under a shielding of argon gas stream. The various phases formed during the process at different scan speeds were quantified by Rietveld quantitative phase analysis. Further, load-displacement curves were obtained with nano-indentation to estimate the pseudoelastic recovery of the matrix and to show the pseudoelastic connection of the matrix with its constituent Ni4Ti3 concentration. The laser scanned tracks (with the scan speeds of 600, 800 and 1000 mm/min) having a higher concentration of Ni4Ti3 showed a higher amount of pseudoelastic recovery. On the other hand, the tracks (with the scan speeds of 200 and 400 mm/min) having a lower concentration of Ni4Ti3 showed a lower amount of pseudoelastic recovery.

Elastic stability of viscoelastic liquid films flowing on a porous substrate

This paper investigates the linear stability of viscoelastic liquid films flowing down an inclined porous substrate analytically and numerically. It focuses on the Stokes flow of viscoelastic films and uncovers two unstable modes triggered by elasticity. The elastic surface mode with a long wave number is solved analytically and numerically. Our results also indicate elasticity can trigger an elasto-porous mode at small incline angle and ratio of film thickness to substrate thickness. The Oldroyd-B model is used for the constitutive relation between the strain and polymer stress. The classical Beavers–Joseph condition is applied to describe the boundary conditions at the fluid-porous interface (Beavers and Joseph, 1967). This condition represents the linear relationship between velocity gradient of fluid layer and velocity difference between two layers, ∂zu=ακ(u−um), where α is the Beavers–Joseph coefficient, representing slip flow at the interface; κ is the permeability of the porous medium. Effects of porous medium properties, including permeability and depth ratio, as well as the impact of slip flow at the interface on the unstable modes are examined.

An analysis for support loss of micro-cantilever beam based on PML method

Support loss is the phenomenon where part of the vibration energy of a micro-cantilever is transferred to the support structure in the form of elastic waves and dissipated. Since the support loss is coupled with other dissipations, it is difficult for the experimental operator to analyze it experimentally. In this paper, the support loss of micro-cantilever beam is investigated using the perfectly matched layer method, and the support loss is calculated by using the two-dimensional and three-dimensional models, separately. Then we find that both models are consistent with the corresponding theoretical analysis, and the three-dimensional model is closer to the actual situation. In addition, we investigate the contribution of the thickness of the support substrate and the size of the micro-cantilever beam to the support loss. The result shows that the thicker the support substrate and the slimmer the micro-cantilever beam, the smaller the support loss.

Fabrication of flat stainless steel substrates with improved oxidation behavior for metal-supported solid oxide cells using aqueous tape casting

An aqueous tape casting procedure was developed and optimized to fabricate thick, flat tapes for use as porous stainless-steel substrates for metal-supported solid oxide cells (MS-SOCs). Curling tape is one of the main challenges when using aqueous based slurry formation. This work demonstrated that the sedimentation problem can be solved by increasing solid loading rather than adding excessive binder to raise viscosity. The effect of various casting surfaces on tape curling was also investigated. Materials that allow easy tape release resulted in flatter tapes once the water was evaporated. In addition, substrate oxidation resistance at high temperature was evaluated with respect to starting powder size, sintering extent, and pore former types. High sintering extent that removes or encloses the porosity between steel particles while retaining porosity left by pore formers can effectively prevent breakaway oxidation due to local chromium depletion. Carbon residue in the steel substrates from the slurry organic content can be decreased when formulating the slurry to prevent Cr-rich phase formation in the steel, which severely compromises the substrate oxidation resistance and ductility. By dwelling the substrate in high purity hydrogen, the sensitization can be reversed, but more detailed investigation of the reaction dynamics is needed. By combining the strategies described, this work produced crack-free, flat, 400–500 μm thick stainless steel substrates with 28.7 vol% porosity and improved oxidation resistance compared to previous substrates fabricated by dry pressing of fine powders.

Highly Improved PID Stability for Cu(In,Ga)Se2 Solar Modules Due to a Filled P1 Groove

Two types of Cu(In,Ga)Se2 (CIGS) thin-film solar modules, differing only in the patterning procedures, were exposed to a high voltage (1 kV) across the thickness of the soda-lime glass substrate. Both module types utilized a cell stack, and in particular, a molybdenum back contact, which was optimized for CIGS solar cells with enhanced stability against potential-induced degradation (PID). A standard module with regular patterning lines for monolithic interconnection consists of P1, P2, and P3 lines, with P1 separating the back contact, P2 establishing the contact between the front contact TCO of one cell to the Mo back contact of the next cell, and P3 isolating the front contact from one cell to the next cell. However, modules employing this cell stack with regular patterning lines P1, P2, and P3 suffered considerably from PID while modules with a P1 groove filled with an insulator showed greatly enhanced stability similar to the pure single cell without P1 patterning. PID manifests once a specific quantity of charge has been transmitted through the soda-lime glass substrate, while the molybdenum back contact of the cell functions as the cathode, maintaining a negative bias relative to the substrate’s backside. As a consequence of PID, sodium is increased in the adsorber for susceptible cells. Therefore, inhibiting sodium transport through the P1 groove by filling it with an insulating material enhances the PID stability of the modules considerably. As a result, the modules with a filled P1 groove showed similar stability to the single solar cells with an improved PID stable cell stack, while modules without a filled P1 patterning were much more susceptible to PID, although a cell stack with greatly enhanced PID stability was used. In summary, the presented strategy to fill the P1 groove offers a viable and novel path to improved PID stability of CIGS modules.

Effects of Pb nanosheets substrates on the optical and electrical properties CrSe thin films

Herein the effects of lead nanosheets substrates on the optical and electrical properties of chromium selenide thin films were studied. Chromium selenide thin films were grown by vacuum thermal evaporation technique onto glass and 100 nm thick lead nanosheets substrates. The effects of Pb nanosheets on the structural, morphological, compositional, optical and electrical properties was explored. While films grown onto glass substrates showed compositional stoichiometry forming CrSe2 phase those coated onto Pb substrates preferred the growth CrSe phase. Both films were of amorphous structure and exhibited direct and indirect allowed optical transitions. Pb nanosheets enhanced the optical absorption of chromium selenide in the visible and ultraviolet ranges of light. Formation of films onto Pb nanosheets resulted in band gaps and band tails narrowing and decreased the room temperature electrical conductivity () as well. Deep analyses of the variations in the range of 25–340 K showed that the electronic transport is dominated by the thermal excitation and variable range hopping of charge carriers. It was observed that Pb nanosheets increased the average hopping energy and hopping range, decreased the density of localized states near the Fermi level and increased the degree of state disorder. The features of glass/CrSe2 and Pb/CrSe films are promising for using then in optoelectronic technology.

Research on the core factors affecting the temperature rise of dichroic mirrors in wavelength beam combination system under high-power CW laser

The wavelength beam combination is considered an important method for improving the source power of high-energy laser weapons while maintaining high beam quality. The dichroic mirror is the key component that decisively determines the laser beam quality of the wavelength beam combining system. However, the temperature rise of the dichroic mirror due to continuous high-power laser irradiation can significantly deteriorate the beam quality and decrease the efficiency of the systems. Along these lines, in this work, the factors that influence the temperature rise of the dichroic mirror under high power CW laser were systematically examined. The temperature field equation of the dichroic mirror under transmission and reflection laser was also calculated. The variation of the dichroic mirror temperature by the laser power, laser spot size, diameter, and thickness of substrates, as well as material of substrates and thin-film absorption was simulated. The simulated results were verified by performing experiments on both sapphire and quartz substrates. The transmittance absorption was proved to be the main cause of the temperature rise and the laser power had a linear relationship with the maximum temperature. Interestingly, the temperature decreased with the thermal conductivity and the laser spot size. As a result, the optimization of the substrate size can significantly reduce the temperature of the dichroic mirror. Our work provides valuable insights into the design and increase in performance of dichroic mirrors in the wavelength combination system.

Automatic high depth-resolvability inspection of TBC debonding defects using nonlinear frequency modulation photothermal radar

In this article, a novel nonlinear frequency modulation (NLFM) photothermal radar whose instantaneous frequency curve is a concave quadratic function is proposed and further combines K-means clustering image segmentation algorithm to achieve automatic high depth-resolvability inspection of debonding defects in thermal barrier coating (TBC) structure. Firstly, a 3-dimensional (3D) photothermal finite element (FE) model of TBC structure is established, where the extrapolated Beer-Lambert model is introduced to describe the spatially volumetric heat source within the ceramic coating. Afterwards, the superior depth resolvability of the proposed NLFM photothermal radar is demonstrated compared to conventional waveforms using the established FE model. Meanwhile, its depth resolvability dependence on the thickness and thermal diffusivity of the ceramic coating is also investigated. Finally, the photothermal experiments of the TBC structure containing artificial debonding defects are conducted, and the influence of the coating thickness and metal substrate on the non-destructive testing (NDT) detection of TBC structure by NLFM photothermal radar combining K-means clustering is also experimentally studied. The results reveal that NLFM photothermal radar combining K-means clustering can achieve automatic high depth-resolvability inspection of debonding defects in TBC structure and the coating thickness and metal substrate have also a great influence on the photothermal NDT of the debonding defects of TBC structure.

The effect of magnetic proof masses on the energy harvesting bandwidth of piezoelectric coupled cantilever array

In order to explore the ability of magnetic force in improving energy harvesting bandwidth, a novel energy harvester of piezoelectric coupled cantilever array (PCCA) was proposed which introduces nonlinear magnetic force (damping) to differentiate the natural frequencies of PCCs and widen energy harvesting bandwidth of PCCA. Meanwhile, the design of PCCA can increase the number of voltage peaks of each PCC at the cost of decreasing the voltage peaks of its neighbouring PCCs at resonance. The effect of some significant factors, such as PCC interval, PCS length, PCC number, and PCC substrate thickness, on PCC voltage, PCC natural frequency, and PCCA bandwidth are deeply studied and analyzed by experiments and simulations. The results demonstrate that the bandwidth for the proposed PCCA can achieve 73 Hz by the standard of >15 V pp. voltage in the excitation of 1 g acceleration amplitude. Based on the experiment and simulation results, a series of theoretical models are derived to compute PCC voltage, PCC natural frequency, and bandwidth of PCCA with different design parameters, these theoretical models give a reliable instruction for the design of PCCAs to match environmental vibration with different frequency such as machine, wind, wave, and so on.

Precise channel temperature prediction in AlGaN/GaN HEMTs via closed-form empirical expression

In this study, we introduced a closed-form empirical expression for estimating the channel temperature in AlGaN/GaN HEMTs. This model incorporates parameters such as substrate thickness, gate length, gate width, and temperature-dependent thermal conductivity. The model's validity was rigorously established through comprehensive comparisons involving the channel temperature measurement procedure (DC) and TCAD device simulations. The outcomes exhibited a noteworthy alignment with the observed model data, reinforcing its credibility. The model yields a notably improved accuracy in channel temperature estimation compared to assumptions based on constant thermal conductivity. This observation holds particular significance for GaN/Sapphire HEMTs. The utilization of the closed-form expression enables the simultaneous optimization of both electrical and thermal properties, utilizing conventional computer-aided design tools.

Optical Characterization of Semiconducting Thin Films Using UV-VIS-NIR Spectroscopy: A Review

The review article focuses on the growth of thin film and its characterization by UV-Vis-NIR spectroscopy. For UV-Vis-NIR spectroscopy of thin films, they are usually deposited on translucent quartz glass surfaces. The article reports the extraction of various thin film optical parameters viz., absorption coefficient (α), Urbach energy (Eu), optical band gap (Eg), refractive index (n), extinction coefficient (k), dielectric constants, dissipation factor (tanδ) and optical conductivity (σoptical) by using optical spectra (absorption(A)/transmittance (T)/reflectance (R)). Furthermore, the effect of thin film substrate temperature (Ts) and/or thickness (d) and/or post-deposition annealing temperature (Ta) on various optical parameters is discussed in detail.

A High-Temperature Superconducting Wideband Bandpass Filter at the L Band for Radio Astronomy

In order to ensure the normal operation of radio astronomy observations, an extremely sensitive receiver system needs to be equipped in front of the large radio telescope. An 8-pole wideband high-temperature superconducting (HTS) filter using a Coplanar Spiral Resonator Structure with a passband of 1160∼1670 MHz is developed to suppress strong radio interference. The filter is fabricated on a 36 mm × 14 mm YBCO HTS film, which is deposited on a 0.5 mm thick MgO substrate. The minimum insertion loss measured in the liquid nitrogen temperature region is 0.03 dB, and the first parasitic passband appears at 2600 MHz. The measured results are in good agreement with the simulations. The filter can be used in radio telescope receivers for the observation of neutral hydrogen and pulsars, as well as in high-sensitivity satellite navigation instruments.