Search

Diamond containing nitrogen‐vacancy centers (NV−) is one of the most investigated materials for quantum technologies, because of this system's exceptional spin properties. Although the NV− optical transition is very bright, it suffers from spectral diffusion and weak zero‐phonon line, and is in the visible range. This limits integration into quantum photonic structures and interfacing with optical fiber networks. In contrast, rare earth (RE) ions exhibit extremely narrow and stable optical transitions, including erbium's 1.5 µm telecom wavelength. Combining RE with NV− properties through short‐range interactions is however challenging as RE do not readily enter the diamond lattice. In this work, a thin‐film‐based architecture in which RE and NV− centers can interact while preserving their unique properties is introduced. Thin films of Er3+:Y2O3 are grown by chemical vapor deposition on diamond substrates with well‐crystallized and highly textured structures. An extensive spectroscopic study of Er3+ transitions at room and low temperatures further reveals that photoluminescence spectra and decays are close to bulk materials. It is also shown that Y2O3 thin film deposition has no detrimental effects on NV− optical and spin properties. RE thin films deposited on diamond can thus be suitable for building hybrid materials for new functionalities in quantum sensing, communication, and processing. [ABSTRACT FROM AUTHOR]

Transparent conducting oxides are crucial in the field of optoelectronics, and SrNbO 3 has emerged as a promising candidate because it can outperform commonly used indium tin oxides due to its novel functionality. However, experimental investigations of SrNbO 3 are challenging because it undergoes topotactic phase transition to exhibit insulating behavior. Here, we investigate the pivotal role of SrNbO 3 stoichiometry to enhance its performance as a transparent conducting oxide. Results indicate the optoelectronic properties of SrNbO 3 are highly dependent on its intrinsic lattice parameters and stoichiometry. Films with lattice parameters close to those of pure SrNbO 3 exhibit excellent conductivity and transmittance in the visible range, while off-stoichiometry diminishes optoelectronic properties. Our stoichiometric sample demonstrates a record-high figure of merit for SrNbO 3, considerably surpassing that of indium tin oxide by an order of magnitude. Thus, this study paves the way for production of high-quality SrNbO 3 and leveraging its novel functionalities in optoelectronic applications. [ABSTRACT FROM AUTHOR]

Perovskite nanocrystals (NCs) are emerging as a next generation display technology. In this regard, exploring the structural and optical stability when subjected to radiation is crucial for expanding their application in aerospace and radiation detection technologies. In this study, we investigated the effects of gamma radiation on CsPbBr 3 heterojunction thin films through a comprehensive analysis of their structural and optical characteristics. The thin films of CsPbBr 3 were subjected to varying doses of gamma radiation, ranging from 100 krad to 1 Mrad, followed by thorough examination using X-ray diffraction (XRD) and optical spectroscopy techniques. Our findings unveil significant changes in the crystal structure of CsPbBr 3 thin films when exposed to gamma radiation, including shifts in diffraction peak positions from cubic to monoclinic phases, broadening of peaks, and variations in peak intensities due to induced surface defects. The optical properties, such electroluminescence (EL) and photoluminescence (PL) intensity slightly drops at the moderate irradiation dose of 300 krad, while at an irradiation dose of 1 Mrad deteriorated severely. Notably, 300 krad is equivalent to the radiation dose accumulated by satellites in low-Earth orbit over 10 years. The findings in this work suggest the fabricated CsPbBr 3 thin film has the potential to be used in space applications. [ABSTRACT FROM AUTHOR]

Polycrystalline zinc oxide (ZnO) thin films were deposited on soda-lime glass substrates using the chemical spray pyrolysis method at three different substrate temperatures: 400, 450, and 500 °C. The solvents used in the precursor solution consisted of either ethanol or methanol. The effects of these solvents on the compositional, structural, morphological, electrical, and optical properties were studied with different techniques, including Rutherford Backscattering Spectrometry (RBS), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), four-point method, and Ultraviolet and Visible Spectroscopy (Uv-Vis). The results show that both temperature and the type of solvent modify the properties of the materials. An essential outcome of the study was that at 500 °C, the ZnO thin films prepared with either ethanol or methanol exhibited almost the same high-quality crystallinity, stoichiometry, average crystallite size, energy band gap, and resistivity. These findings contribute to our understanding of the properties of these materials and their potential applications. [ABSTRACT FROM AUTHOR]

Perovskite oxides, renowned for their adaptable structure and optoelectronic characteristics, hold significant potential for applications in catalysis and photoelectrochemical (PEC) processes. In this research, the preparation of praseodymium iron oxide (PrFeO3) by spin coating and the impact of incorporating a calcium (Ca) dopant on its PEC efficacy as photocathodes are investigated. Spin coating of a polymer containing sol–gel yields thin films with uniform morphology and porosity, facilitating effective semiconductor/electrolyte interactions, as characterized by scanning electron microscopy analyses. Evaluation of transient photocurrent responses reveals that introducing Ca at a 5 at% doping level significantly enhances the PEC activity of PrFeO3, resulting in an optimal photocurrent of −124 μA cm−2 at +0.43 V vs. a reversible hydrogen electrode (VRHE) under simulated sunlight conditions. This enhancement is accompanied by an incident photon‐to‐current efficiency (IPCE) of 3.8% at +0.43 VRHE and 350 nm, along with an onset potential of +1.1 VRHE. Ultraviolet and visible spectroscopy analyses indicate an increase in light‐absorption capabilities in the Ca‐doped films and a noticeable reduction in bandgap compared to the undoped counterparts, further supported by IPCE measurements. In the findings, the significant role of dopants in augmenting the photocurrent performance of stable perovskite oxides, highlighting their potential in advancing photon conversion technologies, is underscored. [ABSTRACT FROM AUTHOR]

The objective of this study is to elaborate SiC thin film as a humidity sensing element and study its behavior towards tritiated water vapor, to apply it for radiation protection purposes. Silicon carbide was chosen as a material because of its remarkable properties and its capacity to be applied in harsh environments. The thin layers of SiC were deposited on the Si substrate by the magnetron sputtering technique. Their morphological, structural, and optical properties were examined by scanning electron microscopy, X-ray diffraction, and UV visible spectroscopy, respectively. The obtained thin films were examined by X-ray fluorescence and Auger electron spectrometry to get the elemental and chemical state information. The film's sensitivity was carried out by current–voltage measurements of SiC/pSi(100)/Cu Schottky diode structure before and after exposure to tritiated water steam for 10 and 38 days in an airtight container. The impedance measurements were performed in air, at room temperature, with frequencies ranging from 10-5 Hz to 0.1 Hz. The current showed an increase in forward bias after exposure to the super-heavy water vapor, which implies that the obtained amorphous SiC thin films could have an application as a tritiated water vapor sensing element at room temperature. [ABSTRACT FROM AUTHOR]

In this work, CdS thin films were prepared on glass substrates using the chemical bath deposition method. The samples were used as a gas sensor for NO2 in the range of 5–50 ppm and H2S in the range of 10–50 ppm. The sensor was operated at room temperature and activated by UV LED illumination of 395 nm. The morphology, optical, and electrical properties of this nanostructure were examined using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, spectroscopic ellipsometry, UV–Vis spectroscopy and 3D optical profilometry. The films are highly sensitive to NO2 and H2S with a response of 75 and 52% at 50 ppm respectively. Furthermore, they showed good long duration stability and short response/recovery times. The sensor response to NO2 gas increases linearly with increasing gas concentration, while for H2S gas the rate of increase of the sensor response becomes greater from 20 ppm. The results obtained suggest that the developed sensor may have great application potential to detect toxic gases such as H2S and NO2 at room temperature. [ABSTRACT FROM AUTHOR]

The article presents the results of a study of the elemental composition, surface morphology, optical and electronic properties of Mg2Si thin films formed on Si (111). Both samples containing films were formed in layers by the method of reactive epitaxy, but at different heating temperatures of the substrates. The formed films consisting of alternating layers of Mg and Si at a ratio of 3:1, according to electron Auger spectroscopy, contain Mg and Si atoms in the associated layers. The Raman light scattering method established the presence of peaks on the graphs of samples at a shift of 258 and 348cm-1 belonging to Mg2Si. Infrared spectroscopy data also indicate the presence of magnesium silicide in the films. The thickness of Mg2Si films was estimated from the data of the known dependence of the amplitude of absorption peaks at 272 cm-1 on the absorption coefficient, which gave the values of the thicknesses of the grown films. Based on the results of the study of samples in the infrared-ultraviolet range and on the basis of geometric calculations, the width of the Mg2Si band gap was determined.

In this work, tungsten oxide (WO3) films were deposited at room temperature and annealed for 2 h at 400°C. The electrochromic and electrochemical properties were studied for two different electrolytes. The films were deposited at different oxygen flow rates of 2, 4, and 6 standard cubic centimeters per minute (SCCM). X-ray diffraction analysis revealed structural characterization of amorphous and crystalline phases. UV-visible spectroscopy optical transmittance revealed 91% transmittance, and energy-dispersive x-ray spectroscopy (EDS) analysis revealed the absence of impurities and the presence of W and O. An electrochemical analyzer was used to characterize the deposited and annealed WO3 films immersed in the two different electrolyte solutions (H2SO4 and LiClO4 with oxygen flow rates ranging from 2 SCCM to 6 SCCM). It was found that the H2SO4 electrolyte of an annealed WO3 thin film at 2 SCCM demonstrated high coloring efficiency of 50.18 cm2/C, and the LiClO4 electrolyte of an annealed WO3 thin film at 4 SCCM demonstrated high coloring efficiency of 20.06 cm2/C. [ABSTRACT FROM AUTHOR]

The acousto-optic modulation over a broad near-infrared (NIR) spectrum with high speed, excellent integrability, and relatively simple scheme is crucial for the application of next-generation opto-electronic and photonic devices. This study aims to experimentally demonstrate ultrafast acousto-optic phenomena in the broad NIR spectral range of 0.77–1.1 eV (1130–1610 nm). Hundreds of GHz of light modulation are revealed in an all-optical configuration by combining ultrafast optical spectroscopy and light–sound conversion in 10–20 nm-thick bismuth selenide (Bi2Se3) van der Waals thin films. The modified optical transition energy and the line shape in the NIR band indicate phonon–photon interactions, resulting in a modulation of optical characteristics by the photoexcited interlayer vibrations in Bi2Se3. This all-optical, ultrafast acousto-optic modulation approach may open avenues for next-generation nanophotonic applications, including optical communications and processing, due to the synergistic combination of large-area capability, high photo-responsivity, and frequency tunability in the NIR spectral range. [ABSTRACT FROM AUTHOR]

In this work, we primarily aimed to study the Nb(V) doping effect on the surface activity and optical and electrical properties of nanocrystalline TiO2 obtained through flame-spray pyrolysis. Materials were characterized using X-ray diffraction, Raman spectroscopy and IR, UV and visible spectroscopy. The mechanism of surface reaction with acetone was studied using in situ DRIFTs. It was found that the TiO2-Nb-4 material demonstrated a higher conversion of acetone at a temperature of 300 °C than pure TiO2, which was due to the presence of more active forms of chemisorbed oxygen, as well as higher Lewis acidity of the surface. Conduction activation energies (Eact) were calculated for thin films based on TiO2-Nb materials. The results of the MB photobleaching experiment showed a non-monotonic change in the photocatalytic properties of materials with an increase in Nb(V) content, which was caused by a combination of factors, such as specific surface area, phase composition, concentration of charge carriers as well as their recombination due to lattice point defects. [ABSTRACT FROM AUTHOR]

In this work, we synthesized a family of three structurally related chiral oligothiophenes containing a 1,4‐diketo‐3,6‐diarylpyrrolo[3,4‐c]pyrrole (DPP) unit as the central core; functionalized with the same (S)‐3,7‐dimethyl‐1‐octyl chains on the nitrogen atoms of lactam moieties, they only differ in the number of lateral thiophene units. The aggregation modes of these π‐conjugated chiral systems were evaluated by means of UV–Vis absorption and ECD spectroscopies in conditions of solution aggregation (CHCl3/MeOH mixtures) and as thin films, describing in particular the impact of the π‐conjugation length on the chiroptical properties. Interestingly, we found that the variable number of thiophene units attached to the DPP core affects not only the propensity to aggregation but also the aggregates' helicity. ECD revealed information about the supramolecular arrangement of these molecules, that one would not obtain by using conventional optical spectroscopy and microscopy techniques. Thin film samples revealed very different aggregation modes with respect to solution aggregates, casting doubts on the common assumption that these latter may serve as simple models of the former ones. [ABSTRACT FROM AUTHOR]

Tin oxide (SnO2) nanoparticles were prepared by green synthesis process using extract of leaf from buckthorn and tin (IV) chloride pentahydrate (SnCl4·5H2O). The materials calcined at 400 °C for 3 h to produce of SnO2 NPs. SnO2 nanoparticles were characterized by X-ray diffraction, scanning electron microscope, optical microscope, and optical spectroscopy techniques.The result of XRD showed formation tin oxide nanoparticles with tetragonal crystal structure. The optical properties were enhanced with rising concentration from 1.25gm/100 ml to 5gm/100 ml. The optical absorbance (A) enhanced of 42.3% at λ = 340 nm (UV-spectrum), 55.8% at λ = 540 nm (VIS-spectrum) and 53.3% at λ = 840 nm (NIR-spectrum). The energy gap is reduced from 3.31 eV to 3.16 eV while the SnO2 concentration increases from 1.25gm/100 ml to 5gm/100 ml. The obtained results showed that SnO2 thin film are appropriate for numerous electronic, photocatalytic and photonics fields. The SnO2 thin film employed for self cleaning against organic dyes. The results indicate that the SnO2 NPs are very important to apply as a coating nanolayer for self cleaning to obtain on cleaning environment. [ABSTRACT FROM AUTHOR]

We investigated the correlation between the crystallite size, resistance to oxidation, and phase transition of Ge-doped Fe3O4 nanocrystalline thin films. We prepared thin films on water-cooled glass substrates by radiofrequency sputtering with Ge-tipped α-Fe2O3 ceramic disks as targets. The addition of Ge caused a reductive phase transition from α-Fe2O3 with a corundum structure to Ge-doped Fe3O4 with an inverse spinel structure, resulting in a crystallite size of <10 nm. We annealed three samples with average sizes of 5, 8, and 10 nm by changing Ge addition concentrations at 673 K in air for up to 323 days until reaching near-thermal equilibrium. All samples maintained their magnetization at almost a constant value over long-term heat treatment. The results of Raman spectroscopy and optical transmittance spectroscopy suggest that there was a phase transition to Ge-doped γ-Fe2O3 at 5 nm, Ge-doped Fe3−δO4 with iron vacancies δ at 8 nm, and Ge-doped Fe3O4 at 10 nm. In other words, we retained Fe3O4 down to a relatively small crystallite size of 10 nm because of the improved oxidation resistance imparted by Ge doping. [ABSTRACT FROM AUTHOR]

We investigated the correlation between the crystallite size, resistance to oxidation, and phase transition of Ge-doped Fe3O4 nanocrystalline thin films. We prepared thin films on water-cooled glass substrates by radiofrequency sputtering with Ge-tipped α-Fe2O3 ceramic disks as targets. The addition of Ge caused a reductive phase transition from α-Fe2O3 with a corundum structure to Ge-doped Fe3O4 with an inverse spinel structure, resulting in a crystallite size of <10 nm. We annealed three samples with average sizes of 5, 8, and 10 nm by changing Ge addition concentrations at 673 K in air for up to 323 days until reaching near-thermal equilibrium. All samples maintained their magnetization at almost a constant value over long-term heat treatment. The results of Raman spectroscopy and optical transmittance spectroscopy suggest that there was a phase transition to Ge-doped γ-Fe2O3 at 5 nm, Ge-doped Fe3−δO4 with iron vacancies δ at 8 nm, and Ge-doped Fe3O4 at 10 nm. In other words, we retained Fe3O4 down to a relatively small crystallite size of 10 nm because of the improved oxidation resistance imparted by Ge doping. [ABSTRACT FROM AUTHOR]

Glow discharge optical emission spectroscopy (GDOES) is a useful technique for qualitative plasma characterization. It also enables depth profiling of solid materials upon exposure of samples to energetic positively charged ions from gaseous plasma, providing specifics of both surface- and gas-phase collision phenomena that are considered. The early stages of developing GDOES useful for the determination of surface composition and depth profiling of solid materials are reviewed and analyzed, stressing the contribution of early authors. The advantages as well as drawbacks of the GDOES technique are presented and discussed. The recent applications of this technique for depth profiling of various materials are presented, and the directions for constructing a laboratory-scale device are provided. [ABSTRACT FROM AUTHOR]

Porous TiO2 thin films were prepared via electrochemical anodization of commercial-grade titanium foils in baths containing variable amounts of ethylene glycol. X-Ray diffraction, scanning electron microscopy, and UV/visible spectroscopy were employed to assess the effect of ethylene glycol on the nature of TiO2 layers. Emphasis is given to the modification of pore size and anatase-to-rutile ratio since these characteristics strongly affect the catalytic performance of TiO2. To simplify the scaling up of the process, a single-step anodization process was employed on a commercial grade 2 titanium foil in constant-current mode without the use of fluorides—conditions that are easily replicable on an industrial scale. We point out some interesting relationships among operating parameters, such as bath composition and current densities, and the characteristics of the anodization layers evidence that the pore size and anatase-to-rutile ratio can be strictly controlled. Increasing the amount of ethylene glycol stimulated the formation of a thinner and less porous TiO2 layer, richer in rutile phase, and characterized by reduced-diameter pores. These results demonstrate the effectiveness and, to some extent, the tunability of the morphology and mineralogic composition of titanium anodization in fluoride-free and ethylene-glycol-bearing acidic solutions. [ABSTRACT FROM AUTHOR]

The paper presents the application of the acousto-optic tunable filter (AOTF) in surface plasmon resonance (SPR) spectroscopy to measure the optical thickness of thin dielectric coatings. The technique presented uses combined angular and spectral interrogation modes to obtain the reflection coefficient under the condition of SPR. Surface electromagnetic waves were excited in the Kretschmann geometry, with the AOTF serving as a monochromator and polarizer of light from a white broadband radiation source. The experiments highlighted the high sensitivity of the method and the lower amount of noise in the resonance curves compared with the laser light source. This optical technique can be implemented for nondestructive testing in the production of thin films in not only the visible, but also the infrared and terahertz ranges. [ABSTRACT FROM AUTHOR]

Nonstoichiometric NiO x thin films were grown on single crystal substrates of c -plane (0001) sapphires by ion-beam sputter-deposition (IBSD) of a Ni metal target in a mixed argon and oxygen atmosphere. Structural characterization was carried out by X-ray diffraction and scanning electron microscopy. All samples grew (111) -oriented out-of-plane and with a defined in-plane orientation relationship relative to the crystalline substrate. The chemical bonding information of the films was examined by X-ray photoelectron spectroscopy showing that the composition x could be varied by adjusting the oxygen-to-argon ratio in the IBSD process. However, a growth anomaly was detected for a certain range of synthesis parameters, standing out due to an enhanced growth rate, nickel excess, and unusually elongated surface structures. With joint solid-state and plasma diagnostic tools, the underlying processes on the atomic scale were studied. An increased proportion of atomic oxygen species in the intermediate range of the oxygen-to-argon gas flux ratio was identified to be responsible for an enhanced generation of NiO x species. Optical emission spectroscopy was found to be a tool especially well-suited, since the in situ examination of various locations of interest (plasma, ion beam, and vicinity of the target) is feasible nonintrusively. [ABSTRACT FROM AUTHOR]

Nonstoichiometric NiO x thin films were grown on single crystal substrates of c -plane (0001) sapphires by ion-beam sputter-deposition (IBSD) of a Ni metal target in a mixed argon and oxygen atmosphere. Structural characterization was carried out by X-ray diffraction and scanning electron microscopy. All samples grew (111) -oriented out-of-plane and with a defined in-plane orientation relationship relative to the crystalline substrate. The chemical bonding information of the films was examined by X-ray photoelectron spectroscopy showing that the composition x could be varied by adjusting the oxygen-to-argon ratio in the IBSD process. However, a growth anomaly was detected for a certain range of synthesis parameters, standing out due to an enhanced growth rate, nickel excess, and unusually elongated surface structures. With joint solid-state and plasma diagnostic tools, the underlying processes on the atomic scale were studied. An increased proportion of atomic oxygen species in the intermediate range of the oxygen-to-argon gas flux ratio was identified to be responsible for an enhanced generation of NiO x species. Optical emission spectroscopy was found to be a tool especially well-suited, since the in situ examination of various locations of interest (plasma, ion beam, and vicinity of the target) is feasible nonintrusively. [ABSTRACT FROM AUTHOR]

Solution-processed ZnO-based TCOs generally exhibit greater resistivity and lesser transparency when compared to those processed by vapour-based techniques such as sputtering, PLD or ALD. This is mainly because of defects, lack of preferred orientation, partial segregation of dopants near grain boundaries and sometimes impurities such as partially decomposed precursors. The properties can be improved by improving crystallinity and reducing scattering from grain boundaries and defects, improving mobility. Doping with aluminium increases the carrier concentration; however, it introduces defects that hamper transparency and mobility. Here, we have utilized quick radiative annealed (10 s at 480°C) in 5%H2+Ar atmosphere to achieve resistivity as low as ~ 2 × 10− 3 Ωcm with ~ 94% transparency at 550 nm wavelength for 2% Al-doped ZnO films in spray-deposited thin film. The fast radiative annealing improved the mobility of all the films while simultaneously increasing the carrier concentration by as much as 10 times. XRD and SEM showed improved orientation and crystallinity on quick radiative annealing. PL and Raman spectroscopy revealed that the hydrogen passivated the defects (Zni and VO) and grain boundaries resulting in improved mobility and transparency. XPS and UV visible spectroscopy revealed activation of greater amounts of Al dopants, at the same time, passivating VO by partial H+ substitution, increased carrier concentration and wider optical bandgaps. [ABSTRACT FROM AUTHOR]

Inductively coupled plasma with an argon/hydrogen (Ar/H2) mixture is a potential solution to many surface treatment problems, especially when encountering carbon contamination in optical X-ray and extreme ultraviolet instruments. Removing carbon contamination on multilayer thin films with Ar/H2 plasma extends the lifetime of the above devices. To further investigate the reaction between plasma and carbon, both optical emission spectroscopy and finite element method with multiphysics fields were employed. The results demonstrated that the intensities of the Balmer lines were in good agreement with the densities of the radical hydrogen atoms from the simulation model, showing a dependence on the mixing ratio. At an electrical input power of 165 W and a total pressure of 5 Pa, an optimum mixing ratio of about 35 ± 5 % hydrogen produced the highest density of hydrogen radicals, coinciding with the highest carbon removal rate. This shows that the carbon removal with Ar/H2 plasma was mainly controlled by the density of hydrogen radicals, and the mixing ratio showed a significant impact on the removal rates. [ABSTRACT FROM AUTHOR]

The main task of the work was to determine the peculiarities of structure formation of the copper films with a thickness of 100-300 nm on glass substrates obtained by thermal sputtering and to study the effects of optical resonances in thin metal copper films using absorption and Raman scattering spectra. The research of the atomic crystal structure of thin copper films was carried out using X-ray diffractometry. The formation mechanism of insular thin films was analysed. The result of the structure transformation is determined by the interaction energy of atoms in film with each other and with the substrate, as well as physical and technological parameters of condensation and subsequent processing regime of deposition and annealing. Optical resonances of copper films on glass substrates were identified using absorption and Raman scattering spectra. [ABSTRACT FROM AUTHOR]

Plasma synthesis of thin films by physical vapour deposition (PVD) enables the creation of materials that drive significant innovations in modern life. High value manufacturing demand for tighter quality control and better resource utilisation can be met by a digital twin capable of modelling the deposition process in real time. Optical emission spectroscopy (OES) was combined with process parameters to monitor all stages of both high power impulse magnetron sputtering and conventional magnetron sputtering processes to provide a robust method of determining process repeatability and a reliable means of process control for quality assurance purposes. Strategies and physics-based models for the in-situ real-time monitoring of coating thickness, composition, crystallographic and morphological development for a CrAlYN/CrN nanoscale multilayer film were developed. Equivalents to the ion-to-neutral ratio and metal-to-nitrogen ratios at the substrates were derived from readily available parameters including the optical emission intensities of Cr I, N2 (C–B) and Ar I lines in combination with the plasma diffusivity coefficient obtained from the ratio of substrate and cathode current densities. These optically-derived equivalent parameters identified the deposition flux conditions which trigger the switch of dominant crystallographic texture from (111) to (220) observed in XRD pole figures and the development of coating morphology from faceted to dense for a range of magnetron magnetic field configurations. OES-based strategies were developed to monitor the progress of chamber evacuation, substrate cleaning and preventative chamber wall cleaning to support process optimisation and equipment utilisation. The work paves the way to implementation of machine learning protocols for monitoring and control of these and other processing activities, including coatings development and the use of alternative deposition techniques. The work provides essential elements for the creation of a digital twin of the PVD process to both monitor and predict process outcomes such as film thickness, texture and morphology in real time. [ABSTRACT FROM AUTHOR]

In this work, high crystalline copper zinc tin sulfide (CZTS) thin films optimized using various stabilizers were fabricated using a low-cost non-vacuum-based spin coating method. The structural and optical properties of these films were characterized by XRD, FESEM, Raman spectroscopy, XRF and PL. Kesterite CZTS structure and its composition were confirmed by XRD and XRF, respectively. Trace secondary phase peaks were found using Raman spectroscopy and an optical band gap of 1.53 eV was obtained using photoluminescence measurements. In addition, density functional theory calculations were performed to understand the role of stabilizers in the formation of thin films. The results indicated variation in the crystallinity of the films upon changing the stabilizers. Photocatalytic degradation performance and photocurrent response were estimated to assess the crystallinity-property relationship. The thin film obtained using cyclohexylamine (CHA) stabilizer showed the highest methylene blue (MB) degradation i.e. 97% in 180 min with a reaction rate constant of 0.019 min−1 which is 73% greater than the thin films without stabilizers. The photocurrent response of this film was found to be 29 μA/cm2, which was twice that of CZTS thin films without stabilizers. It was found the use of a cyclohexylamine stabilizer in CZTS thin film preparation improved the structural and optical characteristics of thin films. This study is significant in the context of obtaining high-quality CZTS thin films for efficient solar photovoltaic, photocatalysis and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

Atmospheric-pressure plasma-enhanced spatial atomic layer deposition (PE-s-ALD) is considered a promising technique for high-throughput and low-temperature deposition of ultrathin films for applications where volume and costs are particularly relevant. The number of atmospheric-pressure PE-s-ALD processes developed so far is rather limited, and the fundamental aspects of their growth mechanisms are largely unexplored. This work presents a study of the atmospheric-pressure PE-s-ALD process of Al2O3 using trimethylaluminum [TMA, Al(CH3)3] and Ar–O2 plasma within the temperature range of 80–200 °C. Thin-film analysis revealed low impurity contents and a decreasing growth-per-cycle (GPC) with increasing temperature. The underlying chemistry of the process was studied with a combination of gas-phase infrared spectroscopy on the exhaust plasma gas and optical emission spectroscopy (OES) on the plasma zone. Among the chemical species formed in the plasma half-cycle, CO2, H2O, CH4, and CH2O were identified. The formation of these products confirms that the removal of CH3 ligands during the plasma half-cycle occurs through two reaction pathways that have a different temperature dependences: (i) combustion reactions initiated by O2 plasma species and leading to CO2 and H2O formation and (ii) thermal ALD-like reactions initiated by the H2O molecules formed in pathway (i) and resulting in CH4 production. With increasing temperature, the dehydroxylation of OH groups cause less TMA adsorption which leads to less CO2 and H2O from the combustion reactions in the plasma step. At the same time, the higher reactivity of H2O at higher temperatures initiates more thermal ALD-like reactions, thus producing relatively more CH4. The CH4 can also undergo further gas-phase reactions leading to the formation of CH2O as was theoretically predicted. Another observation is that O3, which is naturally produced in the atmospheric-pressure O2 plasma, decomposes at higher temperatures mainly due to an increase of gas-phase collisions. In addition to the new insights into the growth mechanism of atmospheric-pressure PE-s-ALD of Al2O3, this work presents a method to study both the surface chemistry during spatial ALD to further extend our fundamental understanding of the method. [ABSTRACT FROM AUTHOR]

The control of thin film deposition is an important issue in a wide range of applications, ranging from optoelectronic devices to active components in energy storage technologies. In this sense, the successive ionic layer adsorption and reaction (SILAR) technique has gained increasing interest from the scientific community for its simplicity, efficiency, and versatility in depositing several types of thin film materials of great technological interest over a variety of substrates, with tunable properties depending on the deposition parameters. Regarding the limitations and problems induced by using the conventional manual SILAR process, we present the design and implementation of a new automatic low-cost SILAR system for further developing and improving thin film deposition quality and reproducibility while avoiding operator fatigue. Our designed system relies on a motorized mobile platform with 1.8 degrees of freedom equipped with a multiple substrate holder, a control board in order to regulate the horizontal and vertical axis speed, and finally, an improved graphical user interface for controlling and monitoring the main parameters such as displacement speed in x and y directions, growth cycles, immersion, and rise time for each beaker. More particularly, the present study aims to improve the system's programming in order to allow the motor to reach its maximum speed at start-up, reduce the cycle time, make it more controllable, and overcome the problem of time delay between cycles. The performance of the system was assessed by depositing crystalline zinc oxide (ZnO) thin film. Scanning electron microscopy, X-ray diffraction, and ultraviolet/visible spectroscopy demonstrated a good correlation between the evolution of the number of deposition cycles with the crystallite/grain size and film thickness. Moreover, controlling the instrument allows obtaining thin films with good adhesion and homogeneity. All these advantages make this technology promising at the industrial scale. [ABSTRACT FROM AUTHOR]

Nickel oxide (NiO) is a transparent conductive oxide material that has interesting physical properties, making it one of the most promising materials for a variety of modern technological applications. The interest of this work is to study the structural and optical properties of pure and Li doped NiO thin films deposited using spray pyrolysis on glass substrates. The samples were prepared at 480 °C with various concentrations of Li doping (1, 2, 3, and 5%). X-Ray Diffraction (XRD) was employed to study the structural characteristics including the crystallite size, dislocation density, and lattice strain. Meanwhile, UV visible spectroscopy was used to study the optical properties. The results revealed a polycrystalline cubic structure with (200) crystal plan being the preferred orientation for the produced films. On the other hand, (Li: NiO) films have shown a high transmittance ranging between 60 and 80%. Also, the bandgap values (Eg), were found to be significantly affected by the Li doping ratios to take values from 3.38 to 3.66 eV. Furthermore, diverse linear and nonlinear optical properties were examined. It was found that the nonlinear properties values of χ1, χ3, and n2 to were improved when lithium doping is incorporated into the NiO lattice. [ABSTRACT FROM AUTHOR]

Four sets of samples of anodically prepared ZnO thin films were tested as potential photocatalysts for degradation of methyl orange (MO). The results show that the best properties belong to the samples prepared by anodization in oxalic acid and subsequently annealed 3 hours at 341°C. The dependences of the rate of the reaction on the time of use of the photocatalyst, the temperature of the decomposition reaction, the pH of the solution and the illumination were investigated too. The activation energies of the reactions were derived from the dependence of the rate of the reaction on the temperature. The properties of the acquired ZnO anodic films, as well as their compositions and structures were investigated by various analytical techniques, as follows: Attenuated Total Reflection Fourier Transformation Infrared Spectroscopy (ATR-FTIR), X-ray Diffractometry (XRD), Atomic Force Microscopy (AFM), Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP-OES), Scanning Electron Microscopy (SEM) and UV-VIS Spectrophotometry. [ABSTRACT FROM AUTHOR]

In the past, terahertz spectroscopy has mainly been performed based on terahertz time-domain spectroscopy systems in a transmission or a window/prism-supported reflection configuration. These conventional approaches have limitations in regard to characterizing opaque solids, conductive thin films, multiple-layer structures, and anisotropic materials. Ellipsometry is a self-reference characterization technique with a wide adaptability that can be applied for nearly all sample types. However, terahertz ellipsometry has not yet been widely applied, mainly due to the critical requirement it places on the optical setting and the large discrepancy with regard to traditional terahertz spectroscopy and conventional optical ellipsometry. In this Tutorial, we introduce terahertz time-domain spectroscopic ellipsometry from the basic concept, theory, optical configuration, error calibration to characterization methods. Experimental results on silicon wafers of different resistivities are presented as examples. This Tutorial provides key technical guidance and skills for accurate terahertz time-domain spectroscopic ellipsometry. [ABSTRACT FROM AUTHOR]

Creating gradients of nanostructure on the surface has found broad applications such as enhanced optical spectroscopy, optical storage of information, and broadband solar energy harvesting. Here, a facile strategy is presented for fabricating gradient nanoparticle arrays with tunable size. It takes a ZnO:Ga microwire as the starting material, and the Ga3+ doping gradient along the microwire is induced by the high voltage applied. Such a doping gradient facilitates the formation of a temperature gradient in a Joule heating process. And this temperature gradient produced by this technique can be as high as 800 °C/mm, which could be later used for gradient annealing of thin metal films. After annealing, the thin metal films turn to gradient nanoparticle arrays. The obtained gradient nanoparticle arrays are confirmed effective in multi-wavelength surface enhanced Raman scattering enhancement. [ABSTRACT FROM AUTHOR]

Dense cauliflower type nanostructured hematite ($\alpha $ -Fe2O3) thin films were grown by plasma-enhanced chemical vapor deposition (PECVD) using ferrocene (Fe(C5H5)2) as precursor. The influence of the plasma parameters on the layer composition and growth rate was investigated and correlated with the plasma used during the deposition process. Optical emission spectroscopy (OES) data from the plasma in conjunction with scanning electron microscopy (SEM), energy dispersive spectrometry (EDX) and Raman spectroscopy showed that plasma power of about 50–120 W with an O2 content of 10%–15% in the carrier gas Ar favors the growth of hematite rather than maghemite. The thickness of the thin films is position dependent due to the plasma reactor geometry. The growth rate can reach a very high value, up to 440 nm/min. [ABSTRACT FROM AUTHOR]

• Ring-shaped crystallization is possible under the action of cylindrical light beams. • Cylindrical beams provide more uniform crystallization of GST225 than HG 00 mode. • Images brightness analysis shows a gradual crystallization consistent with intensity. • Raman spectra study correlate with image brightness analysis. Chalcogenide phase-change materials are promising for optical technologies, since they allow rapid (tens of nanoseconds) reversible switching between the amorphous and crystalline phase states characterized by significantly different electrical and optical parameters. In this work we experimentally studied the local optical transition of as-deposited amorphous Ge 2 Sb 2 Te 5 thin films into the crystalline state under the action of structured continuous-wave laser beams. For cylindrical laser beams with an annular intensity profile obtained through the phase singularity or through the axially symmetric polarization distribution, significantly more efficient crystallization was observed in comparison with the commonly used fundamental Hermite–Gaussian HG 00 mode. The numerical simulation showed that the annular intensity distribution results in a more uniform temperature profile inside the irradiated region, which is necessary for more uniform crystallization. To analyze the degree of crystallinity we used Raman spectroscopy and optical microscopy, enhanced with digital brightness filtering for characterization of the reflectance within the modified region. [ABSTRACT FROM AUTHOR]

Ga-atoms dynamic in an Ar/N 2 magnetron sputtering discharge for GaN deposition is explored employing plasma diagnostic techniques such as optical emission spectroscopy and microwave interferometry. Through the assessment of gas temperature, electron temperature and density measured from the abovementioned diagnostics, we estimated both the flux and average energy of Ga-atoms impinging on the substrate. Emphasizing the working pressure as a pivotal factor, this study uncovers a correlation between the Ga-atoms flux, their average energy, and the growth rate and crystallinity of the GaN films extracted from ex-situ characterizations. Notably, the pressure value (6.6 Pa) at which both the growth rate and crystalline fraction are the greatest is also the condition at which both the flux and energy of Ga-atoms impinging on the target are maximal. The findings pave the way for improving the understanding and control of the complex interplay between plasma conditions and resulting film properties in the sputtering process. • Correlation between gas phase species (Ga-atoms) and surface properties of GaN thin films. • Analysis of Ar/N 2 plasma facing Ga target using in situ analysis. • The pressure value of 6.6 Pa is the condition at wich the growth rate crystalline fraction are the greatest. [ABSTRACT FROM AUTHOR]

Ge2Sb2Te5 (GST225) looks to be a promising material for rewritable memory devices due to its relatively easy processing and high optical and electrophysical contrast for the crystalline and amorphous phases. In the present work, we combined the possibilities of crystallization and anisotropic structures fabrication using femtosecond laser treatment at the 1250 nm wavelength of 200 nm thin amorphous GST225 films on silicon oxide/silicon substrates. A raster treatment mode and photoexcited surface plasmon polariton generation allowed us to produce mutually orthogonal periodic structures, such as scanline tracks (the period is 120 ± 10 μm) and laser-induced gratings (the period is 1100 ± 50 nm), respectively. Alternating crystalline and amorphous phases at the irradiated surfaces were revealed according to Raman spectroscopy and optical microscopy studies for both types of structures. Such periodic modulation leads to artificial optical and electrophysical anisotropy. Reflectance spectra in the near infrared range differ for various polarizations of probing light, and this mainly results from the presence of laser-induced periodic surface structures. On the other hand, the scanline tracks cause strong conductivity anisotropy for dc measurements in the temperature range of 200–400 K. The obtained results are promising for designing new GST225-based memory devices in which anisotropy may promote increasing the information recording density. [ABSTRACT FROM AUTHOR]

The pulsed laser deposition (PLD) technique has been proved to be able to grow oxide thin films with high structural quality with precisely controlled composition and thickness to achieve designed optical and electronical properties established in alloyed semiconductors and heterostructures. In this Letter, inorganic halide perovskite CsPb(IxClyBr1−x−y)3 epitaxial alloyed films on (001)-SrTiO3(STO) substrates were grown by PLD. The film crystal quality, phase stability, and the epitaxial relationship between the film and substrate were characterized with a detailed x-ray diffraction technique like high-resolution reciprocal spatial mapping and ϕ-scan. In addition, the photocarrier dynamics of the alloyed epitaxial films were investigated by photophysics spectroscopy, including steady and femtosecond transient optical absorption spectroscopy and temperature-dependent and time-resolved photoluminescence spectroscopy. The bandgap of the CsPbX3 films was tuned from 1.75 to 2.98 eV by substituting X with I/Br/Cl and their mixture of different ratios. Free exciton emissions were observed at a low temperature photoluminescence spectrum (PL, 10 K), which confirmed the high crystal and optical quality of the epitaxial perovskite alloyed films except the CsPbI3 film. The femtosecond transient absorption spectra also showed that such perovskite films are of very low concentration of exciton trap states. These results indicated that PLD is a powerful technology for growing high quality inorganic halide perovskite films with a tunable bandgap covering the full visible light range, which provided more options for CsPbX3 based panchromatic LED and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

We report electrical transport and optical spectroscopy measurements on LuN thin films variously doped with nitrogen vacancies along with the computed band structures of stoichiometric and nitrogen vacancy doped LuN. LuN has been the subject of several recent computational studies; however, the most recent experimental studies regarding its electronic properties are already over four decades old. Here, we bridge the void between computation and experiment with a combined study of LuN focusing on its electronic properties. We find that LuN is a semiconductor with an optical bandgap of ∼1.7 eV. Its conductivity can be controlled by nitrogen vacancy doping, which results in defect states at the conduction band minimum and valence band maximum. These results not only provide information on LuN but also help underpin understanding of the electronic properties of the entire rare-earth nitride series. [ABSTRACT FROM AUTHOR]

This study presents the development of a high-power LC circuit for generating arc plasma in a vacuum, utilizing argon as the working gas. Arc plasma is generated by applying 900 W of high power to two pin–plate electrodes, resulting in powerful electric fields that excite and ionize argon particles. The system's I–V characteristics were investigated. Optical emission spectroscopy is a technique for diagnosing plasma formation that calculates electron temperature and density for various powers at varying pressures. This design allowed for a high deposition rate within an exceptionally short time, up to 25 s. Thin films of 229, 346, 468, and 592 nm thicknesses are deposited on glass at 100, 300, 600, and 900 W deposition powers. This design's key characteristic is used in the production of electrodes that are deposited on the glass. The electrical resistivity of films has been studied as a function of film thickness. The 4-point probe technique was used to assess those parameters. For the ranges investigated, the film's resistivity decreases linearly with its thickness. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO2) thin films grown on hexagonal boron nitride (hBN) flakes show three orders of magnitude resistance change due to metal–insulator transition (MIT). The MIT property of VO2 thin films is strongly dependent on the metallic domain size, which should be identified to derive the resistance change owing to the single metallic domain. In this study, we investigated the relationship between the metallic domain size and the device-size-dependent MIT property of VO2 thin films grown on hBN. We observed by temperature-dependent Raman spectroscopy and optical microscopy the emergence of the metallic domains and determined the metallic domain size in VO2 thin films grown on hBN. The metallic domain size of the VO2 thin films grown on hBN was determined to be ∼500 nm on average in length and up to sub-micrometer scale. Electric transport measurements revealed that VO2/hBN microwires exhibit multi-level step-like resistivity changes that change by one to two orders when the length and width are ∼2 μm owing to the confined metallic domains in the micrometer scale. Our results open a way for VO2 devices, showing a steep and large resistance change even in the micrometer scale. [ABSTRACT FROM AUTHOR]

• A low-cost synthesis method for nontoxic, promising alternative as PV absorber. • Simple facile, solution processed synthesis route to obtain pure phase BiSI. • Experimental measurements validated the potential of the material as PV absorber. • Suggested methods to improve film morphology. • Excellent optoelectronic characterization to establish experimental method and property correlation. Bismuth sulphoiodide (BiSI) is considered as an excellent absorber material for toxicity-free photovoltaics (PV). Nevertheless, its applications in thin-film PV are often limited by the lack of pure phase thin-film fabrication techniques. Here, we design a novel precursor composition to fabricate pure phase thin-films by conventional spin-coating route. The as-prepared thin-films are characterized by X-ray diffraction studies, optical absorption spectroscopy, X-ray photoelectron spectroscopy, and transmission electron spectroscopy to confirm the phase purity. The thin-films also exhibit decent photoconductivity which demonstrate its potential as a non-toxic, air-stable absorber materials for PV. [ABSTRACT FROM AUTHOR]

Using optical spectroscopy in solution and thin film, and supported by quantum chemical calculations, we investigated the aggregation process of the donor-acceptor type molecule p-DTS(FBTTH2)2. We demonstrate that cooling a solution induces a disorder-order phase transition that proceeds in three stages analogous to the steps observed in semi-rigid conjugated polymers. By analyzing the spectra, we are able to identify the spectral signature of monomer and aggregate in absorption and emission. From this we find that in films, the fraction of aggregates is near 100% which is in contrast to films made from semi-rigid conjugated polymers. [ABSTRACT FROM AUTHOR]

Using optical spectroscopy in solution and thin film, and supported by quantum chemical calculations, we investigated the aggregation process of the donor-acceptor type molecule p-DTS(FBTTH2)2. We demonstrate that cooling a solution induces a disorder-order phase transition that proceeds in three stages analogous to the steps observed in semi-rigid conjugated polymers. By analyzing the spectra, we are able to identify the spectral signature of monomer and aggregate in absorption and emission. From this we find that in films, the fraction of aggregates is near 100% which is in contrast to films made from semi-rigid conjugated polymers. [ABSTRACT FROM AUTHOR]

The control and arguably the tailoring aspect of technologies like pulsed laser deposition (PLD) rises from understanding the chemistry hidden by the laser generated plasma. With the continuous transition towards thin films with complex structures and geometries, the comprehension of the fundamental processes during the film deposition becomes critical. During the PLD of Mo and Eu-doped Lu2O3, optical emission spectroscopy was implemented for in-situ plasma monitoring. The spatial distribution of individual elements revealed the structuring of a stoichiometric plasma while the formation of LuO molecule within the plasma plume is seen as being induced by the addition of a minimum 1 Pa of O2. The energy of the ejected particles was controlled through doping and O2 pressure. The effect of O2 pressure over the plasma energy revealed a transition from an atomic dominated region towards a molecular dominated one. The properties of the resulted films were analyzed by XRD, AFM, and photoluminescence techniques and show a strong correlation between the dynamical regime of the plasma and their structural properties. [ABSTRACT FROM AUTHOR]

The control and arguably the tailoring aspect of technologies like pulsed laser deposition (PLD) rises from understanding the chemistry hidden by the laser generated plasma. With the continuous transition towards thin films with complex structures and geometries, the comprehension of the fundamental processes during the film deposition becomes critical. During the PLD of Mo and Eu-doped Lu2O3, optical emission spectroscopy was implemented for in-situ plasma monitoring. The spatial distribution of individual elements revealed the structuring of a stoichiometric plasma while the formation of LuO molecule within the plasma plume is seen as being induced by the addition of a minimum 1 Pa of O2. The energy of the ejected particles was controlled through doping and O2 pressure. The effect of O2 pressure over the plasma energy revealed a transition from an atomic dominated region towards a molecular dominated one. The properties of the resulted films were analyzed by XRD, AFM, and photoluminescence techniques and show a strong correlation between the dynamical regime of the plasma and their structural properties. [ABSTRACT FROM AUTHOR]

Atomistic defect engineering through the pulsed laser epitaxy of perovskite transition metal oxides offers facile control of their emergent opto‐electromagnetic and energy properties. Among the various perovskite oxides, EuTiO3 exhibits a strong coupling between the lattice, electronic, and magnetic degrees of freedom, which is highly susceptible to atomistic defects. In this study, we investigated the magnetic phase of EuTiO3 epitaxial thin films via systematic defect engineering. A magnetic phase transition from an antiferromagnet to a ferromagnet was observed when the unit cell volume of EuTiO3 expanded due to the introduction of Eu–O vacancies. Optical spectroscopy and density functional theory calculations show that the change in the electronic structure as the ferromagnetic phase emerges can be attributed to the weakened Eu–Ti–Eu super‐exchange interaction and the introduction of the ferromagnetic Eu–O–Eu interaction. Facile defect engineering in EuTiO3 thin films facilitates understanding and tailoring of their magnetic ground state. [ABSTRACT FROM AUTHOR]

Copper Zinc Tin Sulfide (CZTS) has emerged as a promising photo absorber material for thin film solar cell applications. However, the efficiency of CZTS based solar cell is predominantly governed by the presence and absence of various secondary phases. Identification and estimation of these phases are very crucial for understanding the parameters controlling the formation of these phases. In this work, CZTS thin films are prepared on soda lime glass by magnetron co-sputtering of Cu, Zn, and Sn followed by sulfurization. Precursor composition is varied to control the secondary phase formation during the growth of CZTS layer. Study of various secondary phases formed is done using XANES spectroscopy. Other analyses, like XRD, Raman spectroscopy and optical absorption spectroscopy are used to confirm the results from XANES. It is observed that precursor composition plays a vital role in the selective formation of secondary phase during the growth of CZTS layer. An interesting observation is that bandgap of the secondary phase vis-à-vis CZTS plays a key role in determining the device efficiency. This study highlights that different secondary phases deteriorate the device efficiency in different manner. Secondary phase with much higher band gap then absorber layer deteriorates the device efficiency less compared to the secondary phase having bandgap closer to absorber layer. This also brings out the importance of identification of secondary phase that impact the device efficiency to a greater extent and process parameter that controls its formation. • Formation and quantity of secondary phases controlled by precursor composition. • Estimation of Secondary phases in CZTS layer by XANES spectroscopy. • Effect of secondary phases on CZTS solar cell device. • Secondary phases with a bandgap closer to CZTS deteriorate device efficiency drastically. [ABSTRACT FROM AUTHOR]