Thin Fi Research Articles

In-Situ Confocal Microscopy to Analyze Volume Expansion of Solid State Microbatteries

The rise of embedded objects put great interests in miniaturized power supply solutions. Solid State Microbatteries (SSM) are the most promising, as they can safely store high energy and power density. SSM have the advantage of being all-solid (no liquid leakage and flammability), to have low self-discharge and good cyclability. Despite the strong interest in the field, the mechanisms of Li plating and stripping at the anode are not well observed and not yet fully understood [1]. The study of these phenomena would bring new insights to mechanical behavior during cycling and therefore may lead to optimization approaches at the cycle life level. In this purpose, we investigated the morphological change of SSM during the charge/discharge cycle. We looked at the influence of the cathode thickness and the packaging. Thick LiCoO2 layers were used for the study with thickness from 5 to 30 µm. Volume variations upon cycling were followed thanks to a Neox microscope 3D (Sensofar) and were correlated to charge/discharge capacity.Microbatteries are consisting of LiCoO2 (LCO) cathode and LiPON electrolyte. The anode-free configuration was adopted for integration compatibility. The anode is formed in-situ during the first charge operation. Wafers with different LCO thickness and back end level have been carried out. Confocal microscope was setup in Ar-filled glovebox to monitor the volume expansion during the charge and discharge operations. SSM cycling was operated through Biologic instruments. Figure 1 depicts a schematic representation of the SSM and the setup. Images were acquired during chrono-amperometric full charge at 4.2 V and galvanostatic full discharge at Idischarge = -3.5 µA within 3-4.2 V.Charge/discharge operations and corresponding in-situ thickness variations are presented in Figure 2 for the samples with different LCO thickness. The complete charge is achieved when current reaches a threshold of 0.5 µA. Charge capacity linearly increased with cathode thickness: Qcharge = 2.0 µA.h for the 5-µm-LCO and Qcharge = 9.6 µA.h for the 30-µm-LCO. Thickness variation increase follows the same evolution as capacity during charge and discharge. Regardless of the cathode thickness, same plating and stripping speed are observed during charge and discharge operation, respectively. According to the Qcharge and the volume variation, a theoretical lithium density at the anode side has been observed for all LCO thickness.Figure 3 depicts 2D images of 5-µm-LCO SSM at the onset of the charge. Pristine SSM presents a smooth surface (Fig. 3.a). Li plating is initiated with nucleated grains (Fig. 3.b). Then, grains grow and tend to coalesce with each other, forming a uniform and smooth Li layer (Fig. 3.c). Figure 4 reports 2D images of 30-µm-LCO SSM at different states of cycling. Bumps at the edge formed during the charge are due to SSM device architecture: electric field bends and the increased ion flux induces a more important Li accumulation on the edge. Otherwise, a uniform and fully dense Li metal deposition is realized in solid-state configuration under zero external pressure [2]. At the end of discharge, the battery thickness is higher than the pristine one (+ 3.7 µm). The Li plating non-reversibility phenomena after the first charge is due to low diffusion coefficient at low state-of-charge [3].Figure 5 shows the electrical behavior (Fig 5.a) and the volume expansion (Fig 5.b) of a SSM over 10 cycles. After the first cycle, cycling is performed at ≈100% coulombic efficiency, demonstrating high reversibility of the phenomena and so high cyclability of SSM [3].Finally, we followed the influence of the encapsulation layers on the volume variation. 2D images of the SSM reveals same volume variation for both samples. Those observations suggest that the encapsulation layers has no significant mechanical effect on the Li plating.In-situ confocal microscopy under Ar atmosphere has been proved efficient to study the volume expansion of SSM upon cycling and is a promising technique to investigate failure mechanisms of SSM.[1] J. Park et al., « In situ atomic force microscopy studies on lithium ( de ) intercalation-induced morphology changes in Li x CoO 2 micro-machined thin fi lm electrodes q », J. Power Sources, vol. 222, p. 417–425, 2013, doi: 10.1016/j.jpowsour.2012.09.017.[2] D. Cheng et al., « Freestanding LiPON: from Fundamental Study to Uniformly Dense Li Metal Deposition Under Zero External Pressure », arXiv.org, 8 août 2022. https://arxiv.org/abs/2208.04402v2.[3] J. Celè, S. Franger, Y. Lamy, et S. Oukassi, « Minimal Architecture Lithium Batteries: Toward High Energy Density Storage Solutions », Small Weinh. Bergstr. Ger., p. e2207657, janv. 2023, doi: 10.1002/smll.202207657. Figure 1

Designed and Produced the Rotary Substrate Holder and Its Optimized in Angular DC Magnetron Co-Sputtering System

We report the design approach of a home-built rotary substrate holder on simple rotation stages for low-pressure vacuum applications. The result of designing and fabricating the rotary substrate holder that it can be successfully used to rotate the substrate in a low-pressure vacuum application without pressure fl uctuations and leakage. Then we investigated the suitable thin fi lm deposition by fabricating optimal multilayer coatings under three variable operating conditions: Speed of substrate, deposition time, and discharge voltage. The thin film deposition result of three copper targets was mounted on each magnetron gun, providing a total of three magnetron guns. The thin fi lm was deposited on a glass slide at room temperature using a custom-built angular DC magnetron co-sputtering system. Analysis of variance for the response surface regression model of film thickness as a function of the three independent variables shows that substrate rotation speed, sputtering time, sputtering voltage, and coeffi cient of squared sputtering time are the most signifi cant factors in determining the optimum film thickness. The optimum thin-film deposition with substrate rotation speed, sputtering time, and sputtering voltage of 10 rpm, 8.61 min, and 200%V, respectively, maximizes the thickness of 72.036 nm.

Design and Manufacturing of Angular DC Magnetron Co- Sputtering System to Provide Multilayer Films

The research aims to design and produced a new vacuum chamber set of the angular multi-target magnetron sputtering system was supplied by three patterns of the process gas emissions in one system. One pattern supplies the gas directly in front of the target surface, while another pattern supplies the gas beside the chamber, and another pattern supplies the gas to the bottom of the lid. The vacuum chamber set was designed as a top-down sputtering process which has six major components is new designed and produced, consists of the base, the chamber with a window, the feedthrough for the anode pole, the lid, the magnetron target-holder gun, and the rotate substrate-holder set. When the system is completely assembled, then try to test the leakage and plasma ignition until both passes tested, and then a preliminary test of the sputtering process to provide a thin fi lm with sputtered one copper target which was mounted on one gun onto glass slide substrates for the gas emissions of three patterns. After that run sputtering process to provide the multilayers fi lms with three target materials include copper, aluminum, and brass, which was mounted on three guns onto the rotate glass slide substrates. The results of the thin fi lm thickness from the sputtering process was found this system can be used to build a thin fi lm for changing various sputtering voltages, including the system can be successfully used to provide multilayers fi lm and generate argon plasma which was supplied three patterns of the process gas emissions in one system.

Воздействие некоторых сложных хемостимуляторов и модификаторов на термооксидирование InP

Воздействие некоторых сложных хемостимуляторов и модификаторов на термооксидирование InP

Modeling Transition Layers at Boundaries of Thin-Film Coatings Using Ellipsometric Measurements

We consider the practical aspects of modeling monolayer thin-fi lm coating when interpreting ellipsometric measurement results. We have formulated the constraints imposed on the number and parameters of the layers in the model, the thickness of the skin layer, and the measurement uncertainty. The theoretical conclusions presented have been experimentally supported by investigations of thin fi lms of composition La0.7Sr0.3MnO3 and In2O3.

Modern Transportation and Photovoltaic Energy for Urban Ecotourism

This study proposes an innovative integrated transportation/photovoltaic energy system that will enable the Pompeii Municipality to develop a set of urban ecotourism policies and instruments for the preparation and adoption of an environmental sustainable mobility strategy to be applied in their future municipality urban plan. The innovative character of the study resides in two principal aspects: the technologies applied, namely, the use of thin fi lm photovoltaic (hereafter PV) panels (copper-indium-gallium-(di)selenide cells) on a fl exible support, and the way these technologies are applied. A combined energy/mobility approach based on ‘Zero km and zero emission energy production for zero emission electric transportation strategy’ to be implemented in the Public Urban Plan (Piano Urbanistico Comunale) of the town of Pompeii is presented. According to the technology to be adopted (thin PV fi lm on fl exible supports integrated in the parking shelters roofs), to the foreseen PV plant of 700 sqm parking lots, and to an innovative multifunctional design approach (bio-mimicking sun track roof), an improved yearly power production of 100.0 MWh is foreseen with a 20- 25% increase of power production with respect to standard fi xed PV panels of the same type.

EXPERIMENTAL DETERMINATION OF EFFECTIVENESS OF THERMAL INSULATION OF XPERIMENTAL DETERMINATION OF EFFECTIVENESS OF THERMAL INSULATION OF HEATING NETWORKS INVOLVING APPLICATION OF THIN-FILM COATINGS

The purpose of the paper is experimental evaluation of thermal characteristics in a heat insulating structure with a thin fi lm coating applied onto the same, such as conductive heat transmission capacity, radiation and convection, assessment of the extent of infl uence of each component on reducing heat fl ux density. Experimental studies have been held on determination of thermal conductivity factor, integral factor of emissivity and air permeability of the heat insulating structure. Investigation of thermal conductivity of the heat insulating structure with a thin fi lm coating has been carried out using the method of continuous heat fl ux passing through a sample of heat insulating structure under study. Investigation of thermal radiation of the heat insulating structure with a thin film coating consisted in determining the integral emissivity factor by the radiation method. The air permeability of the heat insulating structure with a thin fi lm coating has been determined by a method based on establishing the time of passage of a certain amount of air through the sample at a known air pressure. The results are presented of the infl uence produced by the thin fi lm coating in the design of thermal insulation of pipelines of heat networks on reducing heat losses through reducing heat fl ow density. It is found that the greatest eff ect on reducing heat fl ow density is produced by air permeability of the thermal insulation material after application of the thin fi lm coating to its surface, which generally enhances the effi ciency and reliability of thermal insulation structures of pipelines in heat supply systems.

Optical Studies of Poly(9,9-di-(2-ethylhexyl)-9H-fluorene-2,7-vinylene) and its Nanocomposites

Steady state and time-resolved spectroscopic measurements are carried out to understand the fl uorescent optical properties of the conjugated polymer poly(9,9-di-(2-ethylhexyl)-9H-fl uorene-2,7-vinylene) (PFV) in liquid phase and solid phase. Quite signifi cant color tuning is observed in the fl uorescence emission of PFV in the blue side of the spectra in the solid phase, especially in powder form, when the polymer is doped with 30B nanoclay (organically modifi ed Montmorillonite) and graphene nanoparticles. Interestingly, the average fl uorescence lifetime of PFVgraphene nanocomposite in thin fi lm is found to be much higher (8.1 ns) compared to that for PFV only in thin fi lm (3 ns). These novel nanocomposites may have potential applications in polymer optoelectronics industry.

Quantitative Characterization and Mechanism of Formation of Multilength-scale Bulk Heterojunction Structures in Highly Efficient Solution-Processed Small-Molecule Organic Solar Cells

In this study we used simultaneous grazing-incidence small- and wide-angle X-ray scattering (GISAXS and GIWAXS, respectively) to probe the multilength-scale structures of thin active layers comprising the linear A–D–A-type π-conjugated donor molecule TBDTCNR and the fullerene acceptor molecule PC61BM for use in solution-processed small-molecule-based organic solar cells (SMOSCs). We found that the pseudo-two-dimensional fractal-like networks in the bulk heterojunction (BHJ) structure were determined by mutual interactions between the small-molecule (SM) crystallites and the nanoscale PC61BM clusters during their formation and phase separation, and deduced quantitatively, at multiple length scales, the BHJ structures comprising these SM crystallites and PC61BM clusters. We also conducted in situ GIWAXS measurements to study the temporal behavior and kinetics of SM crystallization from solution to the solid film state. Our GISAXS/GIWAXS study revealed that the multilength-scale BHJ structures in the thin fi...

Effect of Preparation Conditions on the Fundamental Absorption Edge of Y2O3 Thin Films

The fundamental absorption edge of Y2O3 thin fi lms obtained by discrete evaporation and high-frequency (HF) onplasma sputtering in various atmospheres was studied using optical spectroscopy. It was ascertained that the optical bandgap Eg increased from 5.65 eV for Y2O3 fi lms obtained by discrete evaporation to 5.77 eV for fi lms obtained by HF sputtering in Ar to 5.90 eV for fi lms obtained by HF sputtering in O2. The effective reduced mass of free charge carriers was estimated. It was found that the concentration of free charge carriers in Y2O3 fi lms obtained by ionplasma sputtering in Ar with 50% O2 was N = 1.34·1017 cm–3 whereas sputtering in 100% O2 gave N = 1.38·1018 cm–3, which was typical of degenerate semiconductors. It was shown that the shift of the fundamental absorption edge in Y2O3 thin fi lms after addition of O2 to the sputtering atmosphere was most likely caused by the Burstein–Moss effect.

Features of the Photoalignment of Disodium Bis-[(4-Hydroxy-3-Carboxylate-6-Methyl)Phenylazo]-5,5′-Dioxobenzothiophene in Thin Films

UDC 539.23:547-304.4 E. A. Gracheva, and V. S. Mikulich Thin fi lms and multilayer thin-fi lm coatings based on the new dichroic azo dye disodium bis[(4-hydroxy-3carboxylate-6-methyl)phenylazo]-5,5�c -dioxobenzothiophene (FtF-1) were produced by the spin-coating method. The optical properties and morphology of the FtF-1 fi lms depended on the formation conditions and used solvents. Reversible photo-induced dichroism was observed in fi lms obtained by spin-coating of FtF-1 solutions in DMF and aqueous polyvinylpyrrolidone on quartz substrates upon irradiation with plane-polarized light (�� = 450 nm, I = 15 mW/cm 2 ). The anisotropic properties of the FtF-1 fi lms were caused by trans-cis-isomerization of the irradiated dye molecules.

Roles of Fullerene‐Based Interlayers in Enhancing the Performance of Organometal Perovskite Thin‐Film Solar Cells

To surmount these obstacles, conventional PHJ PVSCs with the confi guration of substrate/HTL (p)/perovskite (i)/fullerene derivative (n) has been developed. [ 9 ] PEDOT:PSS or NiO X are the commonly employed HTLs to date while the electron-transporting layers (ETLs) employed are mainly based on fullerene derivatives. [ 7c,9c,d,10 ] It is worth noting that room temperature and orthogonal solvent processability of fullerene derivatives can successfully prevent the degradation of the underlying perovskite layer. In addition, the decent electron mobility of most fullerene derivatives makes them promising ETLs for high-performance PVSCs. Guo et al. fi rst demonstrated the feasibility of such a conventional PHJ confi guration, realizing a PCE of 3.9% by employing a phenyl-C 61 -butyric acid methyl ester (PC 61 BM) ETL. [ 9c ] Although three different fullerene derivatives (C 60 , PC 61 BM, and indene-C 60 bisadduct (IC 60 BA)) were investigated as ETLs, the functions of these fullerene-based interlayers were not fairly explored due to the inferior quality of the perovskite thin fi lm grown atop them. Soon after, a PC 61 BM ETL was used in a similar PHJ structure by Lam et al. to further improve the device performance to 7.4% by optimizing the perovskite precursor solution concentration and the blending ratio of PbI 2 and methylammonium iodide (MAI). [ 9a ] Lately, Jen and co-workers have signifi cantly enhanced the PCE to 12%–13%, respectively, by optimizing perovskite deposition either by controlling annealing conditions or adding a solvent additive.[11] Most recently, Seok and co-workers have reported an over 14% PCE through solvent engineering and thickness optimization of PC 61 BM. [ 12 ]

Pore-Scale Controls on Reaction-Driven Fracturing

In this article we attempt to shed some light on the factors that determine whether volume-increasing reactions and growth in pores will reduce or increase permeability. We will start by describing fi eld-scale examples of reaction-driven fracturing, and use a Discrete Element Model (DEM) to analyze how the resulting pattern and the rate and progress of reaction depend on the initial porosity of the rock. Ultimately, however, stress generation is related to growth processes taking place at the pore scale. We will therefore zoom in and describe pore-scale growth processes and how these are associated with fracturing and the production of new reactive surface area and new transport channelways for migrating fl uids. Stress generation by growth in pores requires that crystals continue to grow even after having ‘hit’ the pore wall. This implies that the fl uid from which the crystals precipitate is not squeezed out from the reactive interface by the normal stress generated by the growth, but can be kept in place as a thin fi lm by opposing forces that operate at very small scales. To understand the dynamics of crystal growth against confi ning pore walls, we need to zoom in even further and examine interface processes taking place at the nanometer scale. Hence, the last part of this chapter focuses on the nanometer-scale morphology of the reacting interface and the mechanical and transport properties of the fl uids confi ned along reactive grain boundaries.

Occupancy of 4d-states in T (T: Mo, Nb) from NEXAFS L 3,2 Spectra of Nd-Fe-B-T Alloys

Introduction. Neodymium-iron-boron nanocomposite permanent magnets were developed in the early 1990s [1, 2]. Their low neodymium content, less than the stoichiometric amount of 12 at.%, made them cheaper and more corrosion resistant. Moreover, their higher boron content improves the amorphization ability. These systems, called exchange-spring magnets, exhibit interesting magnetic properties due to the exchange coupling between the hard and soft magnetic phases at nanoscale. The coexistence of both types of magnetic phases results in rema nence and magnetic energy product ((BH)max) enhancement. However, the presence of the soft phases reduces the coercivity. The use of alloying components such as Mn, Cu, Nb, Ti, and Mo, among others, helps to control the grain growth during the melt-spinning production of these kind of magnets, improving in this way the magnetic response of the material [3–5]. In particular, the addition of Mo and Nb was reported to be very effective for grain refi nement of nanocomposites, leading to the improvement of the coercivity after annealing [6]. However, the mechanisms that cause the suppression of α-Fe formation are not fully understood, as well as the role of Mo or Nb as an additive component that helps to stabilize the Nd2Fe14B phase (ϕ-phase). Urse et al. explained the coercivity enhancement by the pinning of domain walls at grain boundaries where the additive precipitates, in the case of Modoped Nd-Fe-B thin fi lms [7]. For Nb-doped ribbons, it was found that a higher concentration of this additive is required than in the case of Mo in order to obtain higher coercivities and (BH)max [8]. Thus, a study of the electronic state of these elements becomes appropriate to elucidate the role they play as additives in Nd-Fe-B magnets. Synchrotron radiation is a powerful tool that helps in this study. The information on the electronic structure of occupied/unoccupied 4d-electron states in these alloys was derived from near-edge X-ray absorption fine structure (NEXAFS) measurements. The purpose of the present work is to quantify, by X-ray absorption spectroscopy, variations in occupancy of the 4d-states of molybdenum and niobium added to NdFeB alloys produced by the melt spinning technique, both as quenched (AQ) and subsequently annealed (TT), and to identify correlations between these results and magnetic features of the alloys. Experimental. The starting ingots with nominal compositions of NdyFe(86–y–x)B14Tx (T: Mo, Nb; x = 2, 4; y = 7, 8) were prepared by arc melting of pure elements in argon atmosphere. The ribbons were produced by rapid solidifi cation of molten alloy (melt-spinning) with a roll speed of 20 m/s. Ribbons were sealed in quartz ampoules in a protective atmosphere of argon. Then, the overquenched ribbons were annealed at 973 K for 20 min. The thickness of the ribbons was about 20 μm. From here, the samples are identifi ed by their x and y values, namely, TxNdy (T: Mo, Nb). The measurements (fl uorescence mode) were carried out at the SXS beamline (source: D04A bending magnet) of the Laboratorio Nacional de Luz Sincrotron, Campinas, Brazil. X-ray absorption data were analyzed using standards procedures: a linear background was fi tted at the pre-edge region and then subtracted from the entire spectrum; the jump of the spectrum

Optically Tunable Magneto‐Capacitance Phenomenon in Organic Semiconducting Materials Developed by Electrical Polarization of Intermolecular Charge‐Transfer States

DOI: 10.1002/adma.201305965 formed in organic donor:acceptor composites under photoexcitation through charge transfer in organic materials. [ 15,16 ] In particular, changing photoexcitation intensity can largely modify the density of intermolecular CT states and thus forms an effective tuning method on magneto-capacitance generated from intermolecular CT states. In this paper, we demonstrate the optically-tunable magneto-capacitance by using intermolecular CT states in organic donor:acceptor composites. Essentially, our magneto-capacitance from optically generated CT states can be also named as magneto-photocapacitance. Furthermore, we fi nd that changing the density of intermolecular CT states can lead to a tuning on both magnitude and line-shape of magnetocapacitance. In particular, the line-shape tuning suggests that the interactions between intermolecular CT states can affect the spin-exchange interaction within individual intermolecular CT states in the development of magneto-capacitance. We use the N,N ′-diphenylN,N ′-bis(3-methylphenyl)-1,1′biphenyl-4,4′-diamine (TPD) as donor and the 2,5-bis(5tert butyl-2-benzoxazolyl)-thiophene (BBOT) as acceptor for the generation of intermolecular CT states under photoexcitation. To prepare high-quality thin fi lms for device fabrication, the TPD and BBOT were dispersed into an inert poly(methyl methacrylate) (PMMA) matrix. The devices for capacitance measurements were made by sandwiching TPD:BBOT:PMMA composite fi lms between two electrodes (see Experimental section). The good quality of the fabricated devices can be shown by no detectable leaking current or injection current under driving voltages between −1 V and +1 V (Figure S1 in the supporting information). Figure 1 a depicts the magneto-capacitance from the ITO/TPD:BBOT:PMMA/Al device under photoexcitation. It can be seen that a photoexcitation can lead to a magnetocapacitance in the device when an alternating bias of 50 mV is applied without a DC bias during the capacitance measurements. Specifi cally, the capacitance increases quickly and then saturates around 80 mT with applied magnetic fi eld under photoexcitation, while no magneto-capacitance is observed under dark condition. It is also noticed that the pure TPD and BBOT do not exhibit such magneto-capacitance phenomenon under either dark or photoexcitation. Therefore, the magnetocapacitance phenomenon observed from the photo-excited TPD:BBOT:PMMA composite can be attributed to the intermolecular CT states formed between TPD and BBOT molecules. In general, magneto-capacitance can be developed through two different channels: magnetic fi eld-dependent electrical polarization and magnetic fi eld-dependent electrical current, namely polarization-based and transport-based magneto-capacitance. [ 1,17,18 ] Here, when a magnetic fi eld changes the singlet/ triplet ratio in intermolecular CT states, the polarization-based Magneto-capacitance, which can be produced by magneticallydependent electrical polarization in functional materials, [ 1,2 ]

Highly Efficient Color Stable Inverted White Top‐Emitting OLEDs with Ultra‐Thin Wetting Layer Top Electrodes

In addition, these approaches attempt to compensate drawbacks introduced by a non-optimized semitransparent top contact without enhancing the optical properties of the contact itself. Here, we focus on improving the characteristics of the top electrode by employing a multi-layer thin fi lm metal electrode comprising an ultra-thin MoO 3 ‐Au wetting layer system below the actual Ag electrode. Compared to conventional, thicker metal top contacts, these electrodes feature considerably increased transmittance, while providing a comparable sheet resistance thus achieving a performance similar to ITO bottom contacts. In the past, multi-layer electrodes based on thick metal layers have already shown potential for electrode optimizations in non-inverted OLEDs. [ 10,15 ] To demonstrate the full potential of our wetting layer metal electrode system in terms of optical and electrical properties, it has been integrated into an inverted tandem white top-emitting OLED stack that provides high external quantum effi ciency (EQE). Especially for display applications, the use of such inverted stacks is often favorable due to the preferred use of n-doped silicon in the backplane electronics. The bottom-emitting reference OLEDs are based on the same stack but in noninverted geometry. This structure represents a highly effi cient, state-of-the-art OLED layout. [ 16,17 ]

Low‐Stress Silicon Nitride Platform for Mid‐Infrared Broadband and Monolithically Integrated Microphotonics

Implementation of mid-infrared (mid-IR) chip-scale microphotonic circuits is critical to advancing the science for applications such as (i) ultra-fast telecommunications that require wider bandwidth and (ii) integrated biochemical sensors which can fi nger-print using infrared absorption signatures. Though substantial progress has been made in the development of light sources and detectors, a monolithic mid-IR Si-CMOS-compatible platform remains a challenge. Here we experimentally demonstrate a sophisticated mid-IR microphotonics platform adopting engineered Si-rich and low-stress silicon nitride (SiN x ) thin fi lms where an extensive infrared transparency up to λ = 8.5 μ m is achieved. Furthermore, because of the designed low-stress property, the SiN x deposition is able to reach a thickness > 2 μ m that signifi cantly reduces mid-IR waveguide loss to less than 0.2 dB/cm. We show directional couplers functioning over a broad infrared spectrum, thus enabling monolithic mid-IR multiplexing schemes for integrated linear and nonlinear photonics leading to sophisticated label-free sensing.

Ultra‐High Optical Transparency of Robust, Graded‐Index, and Anti‐Fogging Silica Coating Derived from Si‐Containing Block Copolymers

www.advopticalmat.de Inevitable Fresnel refl ection from the interface between two optical media with different refractive indices ( η ) can decrease light absorption in photovoltaic devices and can cause undesirable glare in fldisplays. Thus, an effective antirefl ection coating (ARC) for a higher optical transmittance can contribute to the accomplishment of improved contrast and brightness in display devices and higher levels of energy conversion effi ciency in solar panels. Traditional ARCs improve optical transmittance by introducing destructive interference between refl ected light beams from the air-fi lm and fi lm-substrate interfaces. An ideal ARC should satisfy the requirements of a quarter-wavelength fi lm thickness and a fi lm η of ( η s ) 0.5 , where η s denotes the η of the substrate. [ 1 ] However, an ARC with a homogeneous η can achieve high transmittance only in narrow wavelength and incidence angle ranges, which are fi xed by its thickness and refractive index. In contrast, an ARC with a gradually changing η , also known as a graded index, can avoid the formation of an interface with a sharp contrast in η . As a result, the Fresnel refl ection can be effectively minimized in a wide wavelength range and high optical transparency can be achieved. In an ideal gradedindex anti-refl ection coating (GIARC), the η should gradually vary from that of the substrate material, onto which the GIARC is coated, to the η of air ( ∼ 1), necessitating the use of a material with a widely tunable η . Theoretical studies showed that a quintic profi le of η varying from that of the substrate (typically 1.5‐2) to 1 is best for achieving the lowest refl ectance (<0.1% in the visible range). [ 2 ] While dense materials generally have an η larger than ∼ 1.35, the extensive variability of indices has been demonstrated by nanoporous materials for the applications for GIARC. [ 2‐6 ] Various methods, such as lithography, obliqueangle deposition, catalytic etching, chemical vapor deposition, and a sol-gel process, have been reported. [ 2‐5 ] However, these methods may lack cost-effectiveness and high-throughput capabilities due to the requirements of vacuum processing, multiple etching steps, or because of the limited controllability of η . Recently, highly porous block copolymer (BCP) thin fi lms were applied to the fabrication of ARC due to the excellent low-cost solution processability and facile tunability of η when controlling the fraction of the pores generated by the selective removal of one block. [ 7‐11 ] Kim and co-workers reported a wide tuning range of η between 1.17 and 1.42 in nanoporous polystyrene (PS) thin fi lms obtained by removing poly(methyl methacrylate) (PMMA) in PS-PMMA BCPs. The stacking of three PS layers with gradually changing porosity achieved a minimum refl ectance of less than 0.1%. Han and coworkers demonstrated that a mixture of PS-PMMA BCPs and PMMA homopolymers led to a graded distribution of PMMA along the vertical direction of the thin fi lms and that a gradient η can be obtained for the remaining PS nanostructures after the removal of PMMA, which can reduce the number of processing steps including spin-coating and acid etching. However, these approaches may be associated with challenges related to the low chemical and mechanical stability of the porous organic thin fi lms and the

From Bare Metal Powders to Colloidally Stable TCO Dispersions and Transparent Nanoporous Conducting Metal Oxide Thin Films

06 Transparent conductive oxides (TCOs) are a technologically important class of materials. [ 1 ] Herein we describe a facile, universal, and green ‘one-pot’ approach to produce stable dispersions comprising TCO nanoparticles (NPs) such as SnO 2 , In 2 O 3 , ATO ( ≡ SnO 2 :Sb), ITO ( ≡ In 2 O 3 :Sn), and ZTO ( ≡ SnO 2 :Zn). The synthesis begins by etching the bare metal powder precursors (Sn, In, Sb, and Zn) with HCl and is completed by adding aqueous hydrogen peroxide below room temperature. No complex work-up or time-consuming purifi cation is required, only simple fi ltration. Moreover, this approach avoids organic surfactants, capping ligands and/ or organic solvents, metal halides like SnCl 4 or SbCl 3 , coordination compounds and sol–gel precursors like Sn(O t Bu) 4 , which are commonly used in all reported syntheses of TCOs NPs and which often contaminate and therefore complicate their subsequent utilization and purifi cation. [ 2 , 3 ] It is noteworthy that TCO nanoparticles have been synthesized in different reaction media including ionic liquids, [ 4 ] polyols, [ 5 ] and water. [ 6 ] The herein reported TCO NPs possess diameters of 3–6 nm, are colloidally stable, can be produced on a multigram scale and are well-suited for spin-coating nanoporous, transparent, and conductive TCO thin fi lms [ 7 ] (see Scheme 1 ) with potential utility in lithium ion batteries, solar and photoelectrochemical cells, electrochromics and sensors, fl at-panel displays, transparent thin-fi lm transistors, optoelectronic devices, and photonic crystal architectures. [ 8–12 ] Additionally,

Photocatalytic properties of transparent TiO2 coatings doped with neodymium

In this work photocatalytic properties of TiO2 thin fi lms doped with 8.51 at. % of Nd were described. The self-cleaning phenomenon of thin fi lms was discussed together with the structural, optical and surface properties of prepared thin fi lms. Transparent coatings based on titanium dioxide were manufactured by high-energy reactive magnetron sputtering process. Incorporation of Nd during sputtering process results in amorphous behavior, without a signifi cant infl uence on transparency and colour as compared to the undoped TiO2-rutile matrix. Nevertheless, doping with neodymium doubles the photocatalytic activity of the matrix due to higher quantity of photo-generated charge carriers and more effi cient mechanism of energy transfer.