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Nickel cobalt oxides (NCOs) are promising, non‐precious oxygen evolution reaction (OER) electrocatalysts. However, the stoichiometry‐dependent electrochemical behavior makes it crucial to understand the structure‐OER relationship. In this work, NCO thin film model systems are prepared using atomic layer deposition. In‐depth film characterization shows the phase transition from Ni‐rich rock‐salt films to Co‐rich spinel films. Electrochemical analysis in 1 m KOH reveals a synergistic effect between Co and Ni with optimal performance for the 30 at.% Co film after 500 CV cycles. Electrochemical activation correlates with film composition, specifically increasing activation is observed for more Ni‐rich films as its bulk transitions to the active (oxy)hydroxide phase. In parallel to this transition, the electrochemical surface area (ECSA) increases up to a factor 8. Using an original approach, the changes in ECSA are decoupled from intrinsic OER activity, leading to the conclusion that 70 at.% Co spinel phase NCO films are intrinsically the most active. The studies point to a chemical composition dependent OER mechanism: Co‐rich spinel films show instantly high activities, while the more sustainable Ni‐rich rock‐salt films require extended activation to increase the ECSA and OER performance. The results highlight the added value of working with model systems to disclose structure‐performance mechanisms. [ABSTRACT FROM AUTHOR]

Abstract Nickel cobalt oxides (NCOs) are promising, non‐precious oxygen evolution reaction (OER) electrocatalysts. However, the stoichiometry‐dependent electrochemical behavior makes it crucial to understand the structure‐OER relationship. In this work, NCO thin film model systems are prepared using atomic layer deposition. In‐depth film characterization shows the phase transition from Ni‐rich rock‐salt films to Co‐rich spinel films. Electrochemical analysis in 1 m KOH reveals a synergistic effect between Co and Ni with optimal performance for the 30 at.% Co film after 500 CV cycles. Electrochemical activation correlates with film composition, specifically increasing activation is observed for more Ni‐rich films as its bulk transitions to the active (oxy)hydroxide phase. In parallel to this transition, the electrochemical surface area (ECSA) increases up to a factor 8. Using an original approach, the changes in ECSA are decoupled from intrinsic OER activity, leading to the conclusion that 70 at.% Co spinel phase NCO films are intrinsically the most active. The studies point to a chemical composition dependent OER mechanism: Co‐rich spinel films show instantly high activities, while the more sustainable Ni‐rich rock‐salt films require extended activation to increase the ECSA and OER performance. The results highlight the added value of working with model systems to disclose structure‐performance mechanisms.

Quasi‐2D hybrid halide perovskites have drawn considerable attention due to their improved stability and facile tunability compared to 3D perovskites. The expansiveness of possibilities has thus far been limited by the difficulty in incorporating large ligands into thin‐film devices. Here, a bulky bi‐thiophene 2T ligand is focused on to develop a solvent system around creating strongly vertically‐aligned (2T)2(MA)6Pb7I22 (n = 7) quasi‐2D perovskite films. By starting with a poorly coordinating solvent (gamma‐butyrolactone) and adding a small amount of dimethylsulfoxide and methanol, it is found that vertical orientation and z‐uniformity is greatly improved. These are carefully examined and verified using grazing‐incidence wide‐angle X‐ray scattering analysis and advanced optical characterizations. These films are incorporated into champion solar cells that achieve a power conversion efficiency of 13.3%, with a short‐circuit current density of 18.9 mA cm‐2, an open‐circuit voltage of 0.96 V, and a fill factor of 73.8%. Furthermore, the quasi‐2D absorbing layers show excellent stability in moisture, remaining unchanged after hundreds of hours. In addition, 2T is compared with the more common ligands butylammonium and phenylethylammonium in this solvent system to develop heuristics and deeper understanding of how to incorporate large ligands into stable photovoltaic devices. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) in the form of thin films has attracted enormous attention for photocatalysis. It combines the fundamental properties of TiO2 as a large bandgap semiconductor with the advantage of thin films, making it competitive with TiO2 powders for recycling and maintenance in photocatalytic applications. There are many aspects affecting the photocatalytic performance of thin film structures, such as the nanocrystalline size, surface morphology, and phase composition. However, the quantification of each influencing aspect needs to be better studied and correlated. Here, we prepared a series of TiO2 thin films using a sol-gel process and spin-coated on p-type, (100)-oriented silicon substrates with a native oxide layer. The as-deposited TiO2 thin films were then annealed at different temperatures from 400 °C to 800 °C for 3 h in an ambient atmosphere. This sample synthesis provided systemic parameter variation regarding the aspects mentioned above. To characterize thin films, several techniques were used. Spectroscopic ellipsometry (SE) was employed for the investigation of the film thickness and the optical properties. The results revealed that an increasing annealing temperature reduced the film thickness with an increase in the refractive index. Atomic force microscopy (AFM) was utilized to examine the surface morphology, revealing an increased surface roughness and grain sizes. X-ray diffractometry (XRD) and UV-Raman spectroscopy were used to study the phase composition and crystallite size. The annealing process initially led to the formation of pure anatase, followed by a transformation from anatase to rutile as the annealing temperature increased. An overall enhancement in crystallinity was also observed. The photocatalytic properties of the thin films were tested using the photocatalytic decomposition of acetone gas in a home-built solid (photocatalyst)–gas (reactant) reactor. The composition of the gas mixture in the reaction chamber was monitored using in situ Fourier transform infrared spectroscopy. Finally, all of the structural and spectroscopic characteristics of the TiO2 thin films were quantified and correlated with their photocatalytic properties using a correlation matrix. This provided a good overview of which film properties affect the photocatalytic efficiency the most. [ABSTRACT FROM AUTHOR]

A zinc oxide (ZnO) thin film-based carbon dioxide ( CO 2 ) gas sensor is proposed and designed in the present research from the perspective of sensing CO 2 emissions from vehicle tailpipes. Different ZnO thin films (ZnO-TF) have been synthesized on a silicon substrate using the radio frequency sputtering technique. The characteristics of the fabricated ZnO-TFs have been analyzed by x-ray diffraction and field emission scanning electron microscopy by observing the crystalline structure and the microstructure images, respectively, of the deposited thin films. One ZnO-TF sample has been selected for electrode deposition and further electrical characterization. ZnO-TF with an interdigital electrode has shown very good characteristics while performing electrical characterization. The same device has been used for gas-sensing experiments. A portable and compact gas testing experimental setup has been designed and developed. We have used that indigenous setup to evaluate the performance of the fabricated ZnO-TF gas sensor device upon exposure to CO 2 gas with varying concentrations from 1445 ppm to 4631 ppm. We mounted a reference meter (Temtop M2000 second-generation air quality monitor) on the experimental setup to measure the CO 2 concentration, temperature, and humidity. Excellent sensitivity of 17.5%, 23.3%, 30.9%, 40.7%, and 47.3% was found in the fabricated sensor when exposed to CO 2 concentrations of 2775 ppm, 2929 ppm, 3770 ppm, 4452 ppm, and 4631 ppm, respectively. [ABSTRACT FROM AUTHOR]

• Non-contact Electrostatic Voltmeter (ESV) application for the PV industry. • Identification of PID-affected PV module. • Identification of poor-performing PV module in grid-connected PV system. Potential induced degradation (PID) is a significant reliability issue for photovoltaic modules in the field. Conventionally, to detect the PID-affected modules, all the modules in a string are individually disconnected and measured using I-V (current–voltage) tracers. It is extremely time-consuming, expensive and unsafe (if the module connectors are field aged) approach. In our approach, we aim detecting the PID-affected modules quickly, inexpensively and safely without disconnecting individual modules in the string. In this study, contactless electrostatic voltmeter's (ESV) strength was explored to detect the PID-affected cadmium telluride (CdTe) modules in a string. These contactless measurements on high-voltage PV strings could make this technique unique and preferable to detect PID-affected modules in a string compared to the I-V curve method. In this work, a CdTe module was stressed for PID using the Aluminum (Al) foil method in a walk-in environmental chamber, which resulted in a reduction of module's peak current (I max), peak voltage (Vmax), and fill factor (FF), and hence power (Pmax). Outdoor light I-V, EL, and ESV measurements were performed pre- and post-PID to determine the effectiveness of the non-contact ESV technique. The ESV technique successfully detected the change in V max, and hence Pmax, compared to the pre-and post-PID conditions. A difference of less than 2% was observed in the results of the non-contact and non-interruptive method compared to the conventionally used interruptive voltmeter or I-V tracer method. This technique and the test results demonstrate a significant promise to identify poor-performing modules in PV string without disconnection of individual modules in the string. [ABSTRACT FROM AUTHOR]

Different SrTiO3 thin films are investigated to unravel the nature of ultra‐low conductivities recently found in SrTiO3 films prepared by pulsed laser deposition. Impedance spectroscopy reveals electronically pseudo‐intrinsic conductivities for a broad range of different dopants (Fe, Al, Ni) and partly high dopant concentrations up to several percent. Using inductively‐coupled plasma optical emission spectroscopy and reciprocal space mapping, a severe Sr deficiency is found and positron annihilation lifetime spectroscopy revealed Sr vacancies as predominant point defects. From synchrotron‐based X‐ray standing wave and X‐ray absorption spectroscopy measurements, a change in site occupation is deduced for Fe‐doped SrTiO3 films, accompanied by a change in the dopant type. Based on these experiments, a model is deduced, which explains the almost ubiquitous pseudo‐intrinsic conductivity of these films. Sr deficiency is suggested as key driver by introducing Sr vacancies and causing site changes (FeSr and TiSr) to accommodate nonstoichiometry. Sr vacancies act as mid‐gap acceptor states, pinning the Fermi level, provided that additional donor states (most probably TiSr••\[{\rm{Ti}}_{{\rm{Sr}}}^{ \bullet \bullet }\]) are present. Defect chemical modeling revealed that such a Fermi level pinning also causes a self‐limitation of the Ti site change and leads to a very robust pseudo‐intrinsic situation, irrespective of Sr/Ti ratios and doping. [ABSTRACT FROM AUTHOR]

Total internal reflection (TIR) optical spectroscopies have been widely used for decades as non-destructive and surface-sensitive measurements of thin films and interfaces. Under TIR conditions, an evanescent wave propagates into the sample layer within a region approximately 50 nm to 2 μm from the interface, which limits the spatial extent of the optical signal. The most common TIR optical spectroscopies are fluorescence (i.e., TIRF) and infrared spectroscopy (i.e., attenuated total reflection infrared). Despite the first report of TIR Raman spectroscopy appearing in 1973, this method has not received the same attention to date. While TIR Raman methods can provide chemical specific information, it has been outshined in many respects by surface-enhanced Raman spectroscopy (SERS). TIR Raman spectroscopy, however, is garnering more interest for analyzing the chemical and physical properties of thin polymer films, self-assembled monolayers (SAMs), multilayered systems, and adsorption at an interface. Herein, we discuss the early experimental and computational work that laid the foundation for recent developments in the use of TIR Raman techniques. Recent applications of TIR Raman spectroscopy as well as modern TIR Raman instruments capable of measuring monolayer-sensitive vibrational modes on smooth metallic surfaces are also discussed. The use of TIR Raman spectroscopy has been on a rise and will continue to push the limits for chemical specific interfacial and thin film measurements. [ABSTRACT FROM AUTHOR]

Superconducting thin films are widely applied in various fields, including switching devices, because of their phase transition behaviors in relation to temperature changes. Therefore, it is important to quantitatively determine the optical constant of a superconducting material in the thin-film state. We performed a terahertz time-domain spectroscopy, based on a 10 femtoseconds pulse laser, to measure the optical constant of a superconducting GdBa2Cu3O7−x (GdBCO) thin film in the terahertz region. We then estimated the terahertz refractive indices of the 70 nm-thick GdBCO film using a numerical extraction process, even though the film thickness was approximately 1/10,000 times smaller than the terahertz wavelength range of 200 μm to 1 mm. The resulting refractive indices of the GdBCO thin film were consistent with the theoretical results using the two-fluid model. Our work will help to further understand the terahertz optical properties of superconducting thin films with thicknesses under 100 nm, as well as provide a standard platform for characterizing the optical properties of thin films without the need of Kramers–Kronig transformation at the terahertz frequencies.

Highlights • Functional plasma polymer was prepared on electrospun polymer nanofibrous mat. • Plasma polymerization run at atmospheric pressure in Ar/maleic anhydride/C 2 H 2 mixture. • Anhydride/carboxyl plasma polymer thin films coated uniformly the polymer nanofibers. • The coating penetrated deep into the nanofibrous mat. Abstract This work investigates for the first time the penetration depth, nanoscopic homogeneity and conformality of the plasma polymerization onto an electrospun nanofibrous mat. The study is carried out on the model example of atmospheric pressure plasma co-polymerization of anhydride-rich films onto polycaprolactone mats that can find a significant practical applications, for example in tissue engineering and regenerative medicine. Since the surface-to-volume ratio of nanofibrous mats is enormous and the structure of mats resembles extracellular matrix the successful plasma coating of each whole fiber and understanding the penetration of the polymerization into the mat structure are extremely important. The films with reactive anhydride groups were prepared by co-polymerization of maleic anhydride and acetylene using dielectric barrier discharge. The studies were accompanied by the quantification of anhydride groups directly on the PCL electrospun mat using the chemical derivatization with trifluoroethylamine and X-ray photoelectron spectroscopy. The nanoscopic homogeneity and conformality of the anhydride plasma polymer coating on the front side and backside of the nanofibrous mat, 30–40 μ m in thickness, did not differ according to the dynamic SIMS mapping. The films containing approximately 6 anhydride groups per 100 carbon atoms coated homogeneously the nanofibers deeper in the PCL mat. The characteristic penetration depth of the deposition was estimated as 46 ± 5 μ m. [ABSTRACT FROM AUTHOR]

Abstract The performance of an optical coating stack depends on thickness and refractive index of each layer. In situ spectroscopic ellipsometry (SE) can track coating properties in real-time, but ex situ SE characterization is limited by the large number of unknown sample properties. We review various SE characterization strategies for multilayer structures using 37-layer alternating high-low index stacks of Ta 2 O 5 and SiO 2. A "tooling factor" for each coating material is developed to inform how the actual layer thicknesses compare to nominal specifications. We also introduce tests for sources of error that can occur during multilayer processing. Process drift may produce a gradual change in film properties, such as a slight increase or decrease in coating thickness or optical constants. This is modeled by adding a gradient to each tooling factor. User-error is also considered, where incorrect parameter entry produces an unintentional stack design. An erroneous layer is identified by systematically testing each layer. A "blind" test was performed to determine SE sensitivity to such errors, where a single layer was intentionally altered within a 37-layer stack, and systematic testing was able to resolve the altered layer thickness and position in the stack. Graphical abstract Unlabelled Image Highlights • We present ex situ spectroscopic ellipsometry characterization of a 37-layer optical coating stack. • We developed new data analysis strategies to determine how coating thickness compares to nominal design using a "tooling parameter" for each material. • We augment the tooling factor with linear scaling to show that process drift can be captured with ex situ measurements. • We show results from a "blind" test where a single altered thickness is correctly identified. [ABSTRACT FROM AUTHOR]

Herein, we report thin films’ characterizations and photovoltaic properties of an organic semiconductor zinc phthalocyanine (ZnPc). To study the former, a 100 nm thick film of ZnPc is thermally deposited on quartz glass by using vacuum thermal evaporator at 1.5 × 10−6 mbar. Surface features of the ZnPc film are studied by using scanning electron microscope (SEM) with in situ energy dispersive x-ray spectroscopy (EDS) analysis and atomic force microscope (AFM) which reveal uniform film growth, grain sizes and shapes with slight random distribution of the grains. Ultraviolet-visible (UV-vis) and Fourier Transform Infrared (FTIR) spectroscopies are carried out of the ZnPc thin films to measure its optical bandgap (1.55 eV and 3.08 eV) as well as to study chemical composition and bond-dynamics. To explore photovoltaic properties of ZnPc, an Ag/ZnPc/PEDOT:PSS/ITO cell is fabricated by spin coating a 20 nm thick film of hole transport layer (HTL)—poly-(3,4-ethylenedioxythiophene) poly(styrene sulfonic acid) (PEDOT:PSS)—on indium tin oxide (ITO) substrate followed by thermal evaporation of a 100 nm layer of ZnPc and 50 nm silver (Ag) electrode. Current-voltage (I-V) properties of the fabricated device are measured in dark as well as under illumination at standard testing conditions (STC), i.e., 300 K, 100 mW/cm2 and 1.5 AM global by using solar simulator. The key device parameters such as ideality factor (n), barrier height ( ϕ b ), junction/interfacial resistance (Rs) and forward current rectification of the device are measured in the dark which exhibit the formation of depletion region. The Ag/ZnPc/PEDOT:PSS/ITO device demonstrates good photovoltaic characteristics by offering 0.48 fill factor (FF) and 1.28 ± 0.05% power conversion efficiency (PCE), η.

Indium tin oxide (ITO) is one of the most commonly used optically transparent conductors in applications, such as electro-optic antennas, displays, and optical coatings. However, their RF frequency-dependent electrical properties have not been reported in the literature. In this paper, we present measurements of the electrical properties (permittivity and conductivity) of ITO films in the 0.1-20-GHz frequency range. Measurements were carried out using an in-house open-ended coaxial probe technique employing a one-port reflection coefficient. As usual, calibration and numerical post-processing is needed to extract the electrical properties of the ITO film placed on a 0.5-mm-thick Eagle glass. The measured conductivity was on the order of 105 throughout the frequency range, and the real and imaginary parts of the permittivity were on the order of 106 at lower frequencies and 105 at higher frequencies.

Abstract Organic light-emitting diodes (OLEDs) continue to attract research interest due to their application in bright displays and solid-state lighting. The highest efficiency values are reached with multilayer devices. The morphology of these layers is important for device performance. A current field of development is the application of solution-based deposition techniques. In general, solution processed devices do not yet reach the performance of OLEDs with vapor deposited materials. In this study, we used typical OLED materials with a sulfur based small molecule host, which can be vapor deposited as well as solution processed, to prepare single and multilayer samples. Samples consisted of the host layer deposited on a hole transport and a buffer layer and were investigated with a combination of grazing incidence X-ray fluorescence (GIXRF) and X-ray reflectometry (XRR). Measurements were performed using a diffractometer with an added fluorescence detector. The angle curves obtained have been evaluated with the software package JGIXA. Significant differences between differently prepared samples have been observed for single layer and multilayer samples. Sulfur could be detected in the layers beneath the solution processed host layer, but not in the layers below the vapor deposited host. The obtained results demonstrate the combination of GIXRF and XRR as a suitable nondestructive analysis method for the characterization of organic thin films with little to no sample preparation required. Graphical Abstract Highlights • Nondestructive X-ray analysis of organic semiconductor layers on the nanometer scale • Combination of grazing incidence X-ray analytical methods for unambiguous results • Layer structure changes depending on manufacturing process despite same materials • No interface layer found between solution processed layers as previously suggested [ABSTRACT FROM AUTHOR]

Many biological lab-on-a-chip applications require electrical and optical manipulation as well as detection of cells and biomolecules. This provides an intriguing challenge to design robust microdevices that resist adverse electrochemical side reactions yet achieve optical transparency. Physical isolation of biological samples from microelectrodes can prevent contamination, electrode fouling, and electrochemical byproducts; thus this manuscript explores hafnium oxide (HfO 2 ) films - originating from traditional transistor applications – for suitability in electrokinetic microfluidic devices for biological applications. HfO 2 films with deposition times of 6.5, 13, and 20 min were sputter deposited onto silicon and glass substrates. The structural, optical, and electrical properties of the HfO 2 films were investigated using atomic force microscopy (AFM), X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, ellipsometry, and capacitance voltage. Electric potential simulations of the HfO 2 films and a biocompatibility study provided additional insights. Film grain size after corrosive Piranha treatment was observed via AFM. The crystalline structure investigated via X-ray diffraction revealed all films exhibited the (111) characteristic peak with thicker films exhibiting multiple peaks indicative of anisotropic structures. Energy dispersive X-ray spectroscopy via field emission scanning electron microscopy and Fourier transform infrared spectroscopy both corroborated the atomic ratio of the films as HfO 2 . Ellipsometry data from Si yielded thicknesses of 58, 127, and 239 nm and confirmed refractive index and extinction coefficients within the normal range for HfO 2 ; glass data yielded unreliable thickness verifications due to film and substrate transparency. Capacitance-voltage results produced an average dielectric constant of 20.32, and the simulations showed that HfO 2 dielectric characteristics were sufficient to electrically passivate planar microelectrodes. HfO 2 biocompatibility was determined with human red blood cells by quantifying the hemolytic potential of the HfO 2 films. Overall results support hafnium oxide as a viable passivation material for biological lab-on-a-chip applications. [ABSTRACT FROM AUTHOR]

An analytical study has been performed on the measurement capabilities of a 100-nm thin suspended membrane setup for the in-plane thermal conductivity measurements of thin film samples using the 3ω measurement technique, utilizing a COSMOL Multiphysics simulation. The maximum measurement range under observance of given boundary conditions has been studied. Three different exemplary sample materials, with a thickness from the nanometer to the micrometer range and a thermal conductivity from 0.4 W/mK up to 100 W/mK have been investigated as showcase studies. The results of the simulations have been compared to a previously published evaluation model, in order to determine the deviation between both and thereby the measurement limit. As thermal transport properties are temperature dependent, all calculations refer to constant room temperature conditions. [ABSTRACT FROM AUTHOR]

• Hybrid sol-gel coatings have been investigated with the non-destructive technique. • Thermal parameters of these thin coatings were determined depending on their composition. • Optical photoacoustic method was applied for experimental investigations. • Two layer model of the samples was used for interpretation of experimental results. This work presents results of studies of thermal parameters such as thermal diffusivity, thermal conductivity, thermal effusivity and volumetric heat capacity of thin hybrid sol-gel corrosion protective layers deposited on the aluminum substrate. In the studies two groups of samples were investigated. The first group was: TMZ.1, TMZ.2 and TMZ.3 (TMZ- Si/Zr-based hybrid sol-gel coatings), with different amount of zirconium, and the second group was: TMZ.1/Ce, TMZ.2/Ce and TMZ.3/Ce (TMZ/Ce - Ce-doped Si/Zr-based hybrid sol-gel coatings) with the same amount of zirconium and an addition of cerium. This work presents the influence of the content of zirconium and cerium on their thermal parameters. The possibility of using the nondestructive photoacoustic method (PA), with the microphone detection, to characterize this type of layers was analyzed theoretically and experimentally too. [ABSTRACT FROM AUTHOR]

The study of a multilayered and multicomponent system by spatially resolved X-ray fluorescence microscopy poses unique challenges in achieving accurate quantification of elemental distributions. This is particularly true for the quantification of materials with high X-ray attenuation coefficients, depth-dependent composition variations and thickness variations. A widely applicable procedure for use after spectrum fitting and quantification is described. This procedure corrects the elemental distribution from the measured fluorescence signal, taking into account attenuation of the incident beam and generated fluorescence from multiple layers, and accounts for sample thickness variations. Deriving from Beer-Lambert's law, formulae are presented in a general integral form and numerically applicable framework. The procedure is applied using experimental data from a solar cell with a Cu(In,Ga)Se2 absorber layer, measured at two separate synchrotron beamlines with varied measurement geometries. This example shows the importance of these corrections in real material systems, which can change the interpretation of the measured distributions dramatically. [ABSTRACT FROM AUTHOR]

Frequency and phase agile microstrip antenna applications require relatively thick Barium Strontium Titanate (BST) films for good tunability. In this work, Polymer (PEG-200) modified MOSD process route is developed to produce cracks free (Ba0.6, Sr0.4) TiO3Thick film on Low loss ST-X quartz substrate. Structural and electrical characteristics of the deposited films were investigated using Atomic Force Microscope, X-Ray Diffraction, C-V and C-F characterizations. XRD characterization conformed the single BST phase with polycrystalline nature of the film. AFM analysis depicted equiaxed shaped grains with average grain size and roughness of 120 nm and 4.15 nm respectively. Dielectric tunability, dielectric constant and loss tangent of the deposited films were 36.46%, 310 and 0.0213 respectively at 1 MHz frequency using MIM capacitive structure where conductive oxide LNO was used as bottom electrode. The applicability of polymer modified BST thick films over low loss substrate as composite substrate for tunable microstrip antenna applications at microwave frequency was demonstrated by design, fabrication and testing of a compact frequency tunable microstrip antenna in coplanar configuration. The tunability exhibited at X band frequency proves the suitability of developed processed route for tunable antenna applications. [ABSTRACT FROM PUBLISHER]

We report on a novel method to fabricate composition gradient, epitaxial La1-xSrxMnO3 thin films with the objective to alleviate biaxial film strain. In this work, epitaxial, composition gradient La1-xSrxMnO3, and pure LaMnO3 and La0.67Sr0.33MnO3 thin films were deposited by radio frequency (RF) magnetron sputtering. The crystalline and epitaxy of all films were first studied by symmetric θ-2θ X-ray diffraction (XRD) and low angle XRD experiments. Detailed microstructural characterization across the film thickness was conducted by high-resolution transmission electron microscopy and electron diffraction. Four compositional gradient domains were observed in the La1-xSrxMnO3 film ranging from LaMnO3 rich to La0.67Sr0.33MnO3 at the surface. A continuous reduction in the lattice parameter was observed accompanied by a significant reduction in the out-of-plane strain in the film. Fabrication of the composition gradient La1-xSrxMnO3 thin film was found to be a powerful method to relieve biaxial strain under critical thickness. Besides, the coexistence of domains with a composition variance is opening up various new possibilities of designing new nanoscale structures with unusual cross coupled properties. [ABSTRACT FROM AUTHOR]

Atmospheric pressure (AP) thermal CVD is used to deposit thin poly-Si films on glass substrates. Also produced are heterojunction solar cells carrying out the deposition on c-Si wafers. A batch-type hot-wall reactor, employing SiHCl3 as a precursor, H2 as a carrier and reaction gas, BBr3 as a p-type doping agent, and PCl3 as a n-type doping agent, is used. The films obtained are homogeneous and well-adhered to the substrate. Samples are structurally characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), reflectance spectroscopy in the UV-vis region, X-ray diffraction (XRD), and Raman spectroscopy (RS). The electrical characterization includes conductivity measurements as a function of temperature, and Hall effect measurements. For the p-doped samples, XRD reveals a strong (220) preferential orientation of the films, while the n-doped samples lack columnar structure or preferential orientation. RS and UV-reflectance confirm a high crystalline fraction. Dark conductivity measurements as a function of temperature show that the films can be grown intrinsic, p-type or n-type. Activation energies between 0.61 and ∼0 eV are obtained, with reasonable values for the carrier mobilities. For the solar cells, relatively high values of VOC(∼507 mV) and JSC (∼29.6 mA cm−2) are measured. In conclusion, these results demonstrate the feasibility of directly depositing doped poly-Si thin films on glass and c-Si substrates at intermediate temperatures, with interesting characteristics for photovoltaic applications. [ABSTRACT FROM AUTHOR]

PEDOT:PSS electron-blocking layer, and PEDOT:PSS + P3HT:PCBM stacked layers are fabricated by ultrasonic atomization and characterized by scanning electron microscopy (SEM) and optical profilometry. The measured thicknesses based on SEM and optical profilometry are quite different, indicating the incapability of measurement techniques for non-uniform thin films. The thickness measurements are compared against theoretical estimations and a qualitative agreement is observed. Results indicate that using a multiple pass fabrication strategy results in a more uniform thin film. It was also found that the film characteristics are a strong function of solution concentration and spraying passes, and a weak function of substrate speed. Film thickness increases with solution concentration but despite the prediction of theory, the increase is not linear, indicating a change in the film porosity and density, which can affect physical and opto-electrical properties. Overall, while spray coating is a viable fabrication process for a wide range of solar cells, film characteristics can be easily altered by a change in process parameters. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, we investigate amorphous Ta2O5 films prepared using different magnetron sputtering techniques at a constant average power but under various power delivery conditions in the context of their application as high index material in optical coatings. We used a broad range of pulse frequencies and pulse durations, discharge voltage and current levels. This allowed us to systematically assess the effect of the specific deposition conditions on the growth characteristics, surface morphology, as well as on the optical and mechanical properties. In particular, we show that the HiPIMS-deposited films exhibit enhanced properties such as low surface roughness (∼0.2nm), low residual stress (∼−50MPa), high refractive index (n 550 ∼2.22) and high hardness (∼7.8GPa). Some of these properties are found to be comparable with the values reported for fully dense thermally-grown films. The presented observations are discussed in terms of energetic conditions at the substrate level. [Copyright &y& Elsevier]

TiC at the diamond‑titanium interface is known to be a stable and beneficial layer for diamond based electronic devices. However, certain cleaning steps can alter the chemical composition of this interface. One such process is oxygen plasma etching, which terminates the surface of the diamond with oxygen. Oxygen is highly reactive with titanium, forming titanium oxides. Theoretically the titanium-diamond interface can be improved through sufficient annealing after device fabrication. To test this, we investigated the interface of oxygen-terminated polycrystalline B-doped diamond and titanium via XPS in an effort to determine if oxygen would rearrange away from the diamond surface and TiC would be formed through post-deposition annealing. After annealing at temperatures up to 900 °C, it was found that TiC was not detected at any point in this experiment. Oxygen-termination, despite its de-scumming capabilities, likely inhibits the formation of TiC at the diamond surface. [Display omitted] • The thermal stability of Ti on oxidized diamond is addressed. • Diamond surface oxide inhibits the formation of Ti-carbide during annealing. • The interface oxide is rearranged into the Ti layer during annealing. • Microfabrication de-scum must be carefully designed for low resistance contacts. [ABSTRACT FROM AUTHOR]

Abstract: The grazing emission X-ray fluorescence (GEXRF) technique was applied to the analysis of different Al films, with nominal thicknesses in the range of 1nm to 150nm, on Si wafers. In GEXRF the sample volume from which the fluorescence intensity is detected is restricted to a near-surface region whose thickness can be tuned by varying the observation angle. This is possible because of the refraction of the fluorescence X-rays and the quite long emission paths within the probed sample. By recording the X-ray fluorescence signal for different shallow emission angles, defined relatively to the flat, smooth sample surface, the deposited Al surface layers of the different samples could be well characterized in terms of layer thickness, layer density, oxidation and surface roughness. The advantages offered by synchrotron radiation and the employed wavelength-dispersive detection setup were profited from. The GEXRF results retrieved were confirmed by complementary measurements. The experimental setup, the principles and advantages of GEXRF and the analysis of the recorded angular intensity profiles will be discussed in details. [Copyright &y& Elsevier]

Abstract: This work shows a systematic approach using design of experiments (DoE) for the integration of the deposition process for polycrystalline 3C-SiC from 100mm to 150mm wafers in a vertical low pressure chemical vapor deposition furnace. The approach aims at developing n-doped SiC thin films on silicon substrates with low stress and low resistivity showing high uniformity of growth rate across boat and wafer. The 3C-SiC films are prepared using monomethylsilane (MMS) as the main precursor, dichlorosilane (DCS) as an additional Si source, ammonia (NH3) as dopant and hydrogen (H2) as diluting gas. The experimental parameters are temperature, pressure, DCS flow and NH3 flow. Flow rates of MMS and H2 are kept constant, resulting in a two factorial DoE approach of 16 experiments. The analyzed response parameters are thickness, stress, and resistivity, including the thickness uniformity across boat and wafer. A strong influence of NH3 (dopant) is found on the deposition rate, resistivity and stress of the film. Increasing the NH3 flow from 1 to 2sccm leads to a decrease in the deposition rate by a factor of three. The improved 3C–SiC film with the intended parameters obtained within the experiments showed a resistivity as low as 75mΩcm and a low stress of 306MPa with the lowest deposition temperature of 775°C. [Copyright &y& Elsevier]

Abstract: In recent years, the wavelet transform has proven to be an extremely powerful image-processing tool. Here, we have developed a wavelet-enhanced Bayesian methodology to analyze the AFM images of organic crystals, such as pentacene, using the Haar wavelet transform. This methodology segments and identifies structures in AFM data and extracts quantitative information such as grain size, perimeter, and orientation. This methodology relies on a Naïve Bayesian classification system, which determines whether each data point corresponds to a peak or a valley with a finite statistical probability based on analysis of a synthetic teaching image. In this work, we apply this technique to AFM images of organic crystal films deposited on three different substrates. [Copyright &y& Elsevier]

Abstract: High power pulsed magnetron sputtering is being intensively explored as a very promising approach for the fabrication of functional coatings with enhanced performance. However, a direct comparison of the results obtained in different systems is complicated given the variety of pulse power supplies with different pulse shape, voltage and current characteristics. In this study, we systematically investigate and compare sputtering processes above a niobium target operated in the same reactor using two commercially available power supplies: (i) a shorter (200μs) square voltage pulse generator permitting higher cathode voltage values, and (ii) a modulated pulse power generator with longer (800–300μs) custom-shaped pulses. In addition, target sputtering using a conventional DC power supply is also analyzed for comparison purposes. The pulsed discharges are characterized by time-resolved current and voltage probes and optical emission spectroscopy. The deposition rate, the microstructure, and the mechanical stress of the fabricated Nb coatings are evaluated and compared. Finally, the effect of the power delivery management is discussed in terms of discharge characteristics and coating properties. [Copyright &y& Elsevier]

Abstract: The properties of hydrogenated amorphous germanium (a-Ge:H) are studied as a function of near-substrate plasma density and hydrogen partial pressure at fixed temperature. Near substrate plasma density is varied by using an unbalanced magnetron and an external magnetic field, and characterized using a guard ring flat probe and a cylindrical Langmuir probe. Films are characterized by infrared absorption, optical transmission, dark conductivity, activation energy, and photoconductivity. A major effect of increasing the near-substrate plasma density is to increase the dihydride component content of the films. The photoconductivity of these films is lower than those whose hydrogen content is increased by increasing the hydrogen partial pressure during deposition, implying a degradation in film properties with increasing near-substrate plasma density. These results show that chemical effects, as well as ion bombardment effects, need to be considered in the plasma-based deposition of a-Ge:H. [Copyright &y& Elsevier]

Abstract: The thickness evolution of multilayer film is investigated by focused ion beam (FIB) in the domain of polymer multilayers. This method, currently used in the modification and the characterization of integrated circuits, proves it is possible to determine the polymer film thickness. Sample cutting and its observation of the cross-section are performed in the FIB without leaving the vacuum chamber. Two main conclusions can be drawn: (1) the roughness of the film increases with the number of layer deposit, (2) the film growth changes from nonlinear (called exponential) to linear beyond 300nm (70 layers). [Copyright &y& Elsevier]

Abstract: It is demonstrated that a careful X-ray diffraction analysis represents an effective way to determine imperfections and their density in complex oxide epitaxial thin films. A method for simulating X-ray intensities of the (00ℓ) reflexes is developed and demonstrated for the model system YBa2Cu3O7−δ . In a first step, the δ dependence of the intensities of the different (00ℓ) reflexes is simulated and compared to literature data of perfect YBa2Cu3O7−δ thin film and bulk samples with different oxygen content. In a second step, it is demonstrated that the δ dependence of the intensities of the different (00ℓ) reflexes depends strongly on the type of defects in case of imperfect YBa2Cu3O7−δ . Different types of defects (e.g., cation disorder, cation substitution, Cu deficiency) are discussed. Finally, the method is applied to low-pressure sputtered YBa2Cu3O7−δ thin film. It is shown that according to this analysis and in contrast to previous assumptions, Cu(1) deficiency seems to be responsible for the elongation of the c-axis and the reduction of the superconducting transition temperature. [Copyright &y& Elsevier]

The theory of deposition of TiN by dc magnetron sputtering for wear protection of the surfaces is well known using different ferrous substrates. This theory apparently, is not so true for other non-ferrous materials. The present work shows the study of some characteristics of TiN deposition on a ternary copper alloy (Cu–3% Ti–1% Cr) with the purpose of modifying their superficial properties, and in this way allowing to enlarge the alternatives of use of this alloy. The wear, microhardness and adhesion of the films deposited have been studied under different conditions of applied current, Ar/N2 flow ratio and bias voltage by means of dc planar magnetron sputtering.By this study we concluded that, unlike the case of steel, for increasing the wear resistance of the alloy it is advisable not to use bias voltage during TiN deposition. It is desirable to obtain an open columnar structure in order to increase the wear resistance and the critical load in scratch testing. [Copyright &y& Elsevier]

Thin layers of ZnS–CuInS2 mixed crystals (called ZCIS) may be promising absorber materials for thin film solar cell applications. The ZCIS films studied here have been grown on (0 0 1) GaP, SiO2 and (0 1 2) CeO2/Al2O3 substrates with different stoichiometries by pulsed laser deposition (PLD). In order to optimize the film deposition process the thickness, stoichiometry and crystallinity of the films were determined by means of Rutherford backscattering spectrometry (RBS), particle induced X-ray emission (PIXE) and RBS/channeling using a 2 MeV He+ ion beam. Furthermore the stoichiometry of the targets used for the PLD was determined with backscattering spectrometry and PIXE using a 2 MeV H+ ion beam. A large variation in film thickness was observed and the film stoichiometry did not agree with the PLD-target stoichiometry in general. The element transfer efficiencies from the PLD-target to the deposited film varied substantially for the individual elements. Furthermore, on some films deposited on (0 0 1) GaP a remarkable out-diffusion of Cu into the substrate was found with RBS and confirmed by secondary neutral mass spectroscopy and transmission electron microscopy. RBS/channeling measurements show that mono-crystalline films can be grown on (0 0 1) GaP and (0 1 2) CeO2/Al2O3 substrates, however, they are characterized by a large defect density. [Copyright &y& Elsevier]