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The In x Ga 1 − x A s y Sb 1 − y alloy was studied in epilayers and photodiodes grown lattice matched to GaSb across a comprehensive composition range, 0 ⩽ x ⩽ 0.3 , as a promising technology to support the extended short-wave infrared region ∼ 1.7 − 3 µ m. Low background carrier concentrations between 6 × 10 14 and 1 × 10 15 cm − 3 were achieved in all samples, reducing with In fraction. Both the absorption coefficient and external quantum efficiency were found to increase with indium fraction, up to ∼ 10 4 cm − 1 and 70% without an AR coating, respectively. Counter to the fundamental bandgap dependence, leakage current density initially reduced with the addition of low In and As fractions, before rising as the fractions increased and the bandgap reduced further. These properties resulted in specific detectivity reaching a maximum in the sample with x = 0.043, before decreasing towards higher alloy fractions. It is concluded that for moderate In fractions, the InGaAsSb alloy offers clear potential to improve on the disappointing material and photodiode properties of GaSb and support emerging SWIR sensing applications. However, development of fabrication and passivation technology is required to fully exploit this potential. [ABSTRACT FROM AUTHOR]

In fabricating passivated emitter and rear contact (PERC) solar cells, creating small openings on the SiN x coated silicon substrate to establish metal contacts necessitates using a nanosecond pulsed green laser for ablation. However, the thermal nature of laser ablation poses a challenge. Excessive nitrogen diffusion from SiN x into the silicon substrate can compromise the electrical performance of solar cells. Therefore, this study aims to comprehensively understand how laser parameters impact the electrical properties of such solar cells. PERC solar cell precursors were initially fabricated by ablating the SiN x layer at four laser fluences, each corresponding to different regimes: solid, liquid, vapor, and phase explosion. Subsequently, various optical, chemical, and electrical characterizations were conducted on the solar cell precursors. Complete PERC solar cells were also fabricated to measure quantum efficiency (QE). In the solid regime, SiN x removal is precise, with minimal thermal damage, resulting in a nitrogen concentration of approximately 0.15%. Photoluminescence count and carrier lifetime are notably higher by 21% in the solid regime compared to the explosive regime. The QE measurement at 984 nm quantitatively assesses rear-side recombination losses. Notably, 26% of the area exhibits a 56% QE in the solid state, while this number drops to around 22% in the explosive state. This decline can be attributed to increased thermal damage in the explosive regime, which augments recombination centers and diminishes the solar cell performance. PERC solar cells ablated in the solid regime showcase lower subsurface damage, superior electrical characteristics, and higher performance than those ablated in the explosive regime. [ABSTRACT FROM AUTHOR]

All-angle wideband electromagnetic (EM) transparency for dual polarizations is desired for many practical applications. Conventionally, surface-mount anti-reflection materials or films are usually used to reduce the reflection and thus enhance transparency. In this paper, we propose to achieve wideband EM transparency under extreme angles for both TE- and TM-polarizations using embedded anti-reflection metasurface. The metasurface is composed of a pair of long and short metallic strips, which can introduce both plasma and lattice modes into the original half-wave wall. The plasma mode can create an angle-stable transmission peak at a lower frequency while the lattice mode renders a transmission peak under extreme angles at a higher frequency due to scattering cancellation between short strips and the substrate. By synergizing the plasma, half-wave, and lattice modes consecutively, wide-band transparency can be achieved under extreme angles for TE polarization. Due to the anisotropy of the metasurface, wideband transparency under TM-polarization is maintained. This finally enables us to obtain wideband EM transparency for dual polarizations under extreme angles. More importantly, the metasurface can also be customized to operate best under any given incident angle. Prototypes were designed, fabricated, and measured. Both the simulation and experiment results verify our method. This work provides an efficient route to wideband EM transparency under extreme angles and may find wide applications in communication, radar, and others. [ABSTRACT FROM AUTHOR]

With chemical stability under high temperatures, dielectric materials can be idealized thermal emitters for different energy applications. However, dielectric materials do not support surface waves at near-infrared ranges for longer-distance thermal photon tunneling, which limits their applications in near-field thermal radiation. It is demonstrated in this study that thermal field amplification at near-infrared wavelengths at dielectric surfaces could be achieved through asymmetric Fabry–Perot resonance with anti-reflection coatings or 1D photonic crystal type structures. ⩾100 nm near-infrared thermal photon tunneling can be achieved when these thin film structures are added to the emitter and the collector surfaces. Among these two thin film structures, 1D photonic crystal type periodic structures constructed with the same high refractive index material as the emitter/collector material allow near-field thermal photon tunneling at large parallel wavenumbers. Moreover, the field amplification can be increased by adding more 1D photonic crystal layers to achieve even longer distances near field thermal photon tunneling. [ABSTRACT FROM AUTHOR]

The thermal stability of antireflective moth-eye topographical features fabricated by nanoimprint lithography on poly (methyl methacrylate) (PMMA) incorporating TiO2 nanoparticles is explored. The effect of nanoparticle load on the relaxation dynamics of the moth-eye nanostructure is evaluated via grazing incidence small angle x-ray scattering measurements by in situ monitoring the structural decay of the nanopatterns upon thermal annealing. It is demonstrated that the incorporation of TiO2 nanoparticles to the imprinted surface nanocomposite films delays greatly the pattern relaxation which, in turn, enhances the stability of the patterned topography even at temperatures well above the polymer glass transition (Tg). The improved thermal behavior of the antireflective films will significantly enhance their functionality and performance in light-trapping applications where temperatures typically rise, such as solar devices or solar glass panels. [ABSTRACT FROM AUTHOR]

Localized surface plasmon resonances in metallic nanostructures have been extensively harnessed for light absorption enhancement in various solar cells, including perovskite solar cells (PSCs). For stabilization and functionalization, plasmonic metal nanostructures are often coated with dielectric shells. In this work, we numerically investigate the effects of dielectric coated plasmonic metal nanoparticles (NPs) on solar absorption enhancement in perovskite thin films. To our surprise, a further absorption enhancement compared with the films embedding bare Ag NPs can be achieved when using thin dielectric coating of high refractive index, while an absorption reduction in comparison with bare perovskite thin films may take place when the embedded Ag NPs are coated with thick dielectric shells of low refractive index. The physics behind is addressed within classic electrodynamics. These anomalous effects extend our knowledge of PSCs, providing guidelines for optimized design of plasmonic solar cells. [ABSTRACT FROM AUTHOR]

Plasmon-induced transparency phenomena in the mid-infrared caused by the coupling behavior between dipole (bright element) and higher-order modes (dark element) in graphene as well as black phosphorus (BP) nanoribbons are investigated. The transparent windows can be adjusted flexibly by varying the carrier concentration of graphene and BP. It is also shown that the carrier mobility and refractive index of the substrate are the key factors affecting destructive interference. Obvious group delays are obtained near the transparent windows so that the slow light effect can be achieved. Our results allow a better understanding of efficient exploration of surface plasmons with integrated properties of building blocks from a family of two-dimensional materials, with the aim of expanding both photonic bands and functionalities. [ABSTRACT FROM AUTHOR]

A new method for modification of planar multilayer structures to create nanostructured aluminum oxide anti-reflection coatings is reported. The method is non-toxic and low-cost, being based on treatment of the coating with heated de-ionized water after the deposition of aluminum oxide. The results show that the method provides a viable alternative for attaining a low reflectance ARC. In particular, a low average reflectivity of ∼3.3% is demonstrated in a broadband spectrum extending from 400 nm to 2000 nm for ARCs deposited on GaInP solar-cells, the typical material used as top-junction in solar cell tandem architectures. Moreover, the process is compatible with volume manufacturing technologies used in photovoltaics, such as ion beam sputtering and electron beam evaporation. [ABSTRACT FROM AUTHOR]

A novel fiber-end antireflection method for reducing the reflection noise in ultra-weak fiber Bragg grating (FBG) sensing systems is proposed in this study. The principle of fiber-end antireflection is analyzed and simulated theoretically, and then an antireflection structure is designed and fabricated. In this method, the fiber end is cut into an inclined surface and covered directly with an ellipsoid photosensitive ultraviolet (UV) glue drop, whose refractive index is similar to that of the fiber core. Under the online monitoring of the fiber-end reflection with the ultra-weak FBG interrogator, the refractive index of the glue drop is adjusted by controlling the UV curing time to achieve optimal reflection suppression. Results show that this method can reduce fiber-end reflection to less than −60 dB and effectively eliminate the influence of fiber-end reflection noise on the last sensor. The proposed method thus provides an excellent solution for the fiber-end processing of ultra-weak FBG sensing systems. [ABSTRACT FROM AUTHOR]

Advances in science and technology have increased the demand for greater temperature measurement accuracy. Radiation thermometry is a mature technology that is applicable to various industrial fields. In special environments (e.g. a high ambient temperature), background radiation reflected by the target surface is superimposed with the radiation from the target itself, which affects the measured radiation temperature. In this study, different radiation thermometry methods were evaluated. The errors of single-spectral, colorimetric, and multispectral temperature measurements of targets in a high-temperature environment have been discussed. Based on this, we propose a multi-wavelength temperature measurement method with reflection correction to reduce the impact of high-temperature environment. Experiments show that this method can reduce the uncertainty in the multispectral temperature measurement from 4.16% to 0.26% under the experimental conditions. [ABSTRACT FROM AUTHOR]

The structural, optical, and mechanical properties of TiO2 nanolaminate films grown by plasma-enhanced atomic layer deposition are discussed. Several TiO2/Al2O3 and TiO2/SiO2 compositions have been investigated to study the effect of the relative number of ALD oxide cycles on the film properties to obtain a high refractive index coating with low optical losses, low roughness, and low mechanical stress. The formation of crystalline TiO2 observed at high deposition temperature, or film thickness was inhibited by periodically introducing ultra-thin amorphous layers into the film. Only 4 ALD cycles of Al2O3 (corresponding to ca. 0.5 nm) between 335 ALD cycles of TiO2 (ca. 11 nm) form a closed, distinct layer suppressing the crystallization in TiO2 film. Consequently, the roughness of the pure TiO2 film is reduced from ca. 20 nm rms to 1 nm rms in the 335/4 nanolaminate, with only a slight decrease of the refractive index from 2.46 to 2.44 in 100 nm pure TiO2 and the nanolaminate, respectively. The refractive indices of the nanolaminates in various compositions vary between 2.38 and 2.50 at 632 nm, and the corresponding optical losses from the films are low. The mechanical stress was reduced to about 140 MPa in several TiO2/Al2O3 nanolaminates; however, lower mechanical stress has not been obtained with the studied compositions. The nanolaminate structure is preserved up to 600 °C annealing temperature. After annealing at 800 °C, the individual layers interdiffuse into each other so that no distinct nanolaminate structure is detected. By using TiO2/Al2O3 nanolaminates with reduced mechanical stress, a narrow bandpass filter was realized on various substrates, including half-ball and aspherical lenses. [ABSTRACT FROM AUTHOR]

Bio-inspired anti-reflective (AR) coatings with porous graded refractive index structures are known to considerably reduce the reflectance of light at optical interfaces, however, research is lacking for thin-film cell application. Ray Tracing software coupled with the Effective Medium Theory were used to simulate the reflectance of nanostructured coatings placed above a thin-film system. The most optimal coating was paraboloid-shaped, with 300 nm nipple heights and spacings of 15%. The non-zero refractive index 'step' aids light trapping and energy absorption. This coating reduced reflectance in the λ = 300–800 nm range by an average of 2.665% and 11.36% at 0∘ and 80∘ incident light, respectively, whilst increasing annual energy output by 4.39% and 5.39% for standard UK roof and vertical window tilts, respectively. Significant wide angle reflectance capabilities are demonstrated at specifically λ = 300 nm and 80∘ incident light, with a reflectance reduction of 19.192%. There are now many promising manufacturing techniques for these porous nanostructures, such as AR or wavelength filtering coatings for photovoltaics. Further understanding of the exact parameters needed to replicate these nanostructures must be explored to proceed. [ABSTRACT FROM AUTHOR]

Magnetic fields and mechanical forces can change the deformation and stability of magnetic emergent crystals (MECs) such as Bloch skyrmion crystal (SkX), Néel SkX and Anti-SkX. Due to the tensor nature of strains, mechanical loads provide more fruitful ways to manipulate the MECs, while their effect on MECs other than the Bloch SkX is hitherto unclear. We construct a thermodynamic model for noncentrosymmetric ferromagnets in all possible point groups when subjected to coupled magnetoelastic fields. Compared with classic theories, we include terms coupling the elastic strains, the magnetization, and its derivatives in the free energy, which lead to strain-induced Dzyaloshinskii–Moriya interaction anisotropy. For epitaxial thin films in three types of point groups (T, C3v, D2d) hosting Bloch SkX, Néel SkX and Anti-SkX, we find the newly added terms always deform the MECs and eventually lead to their instability as the misfit strains increase. Specifically, for Bloch SkX in group T materials and Néel SkX in group C3v materials, a novel magnetic phase called paired-skyrmion crystal (pSkX) appears. Our theory lays the path to study deformation and phase transitions of different MECs, and to explore novel states of MECs in chiral magnets when subjected to magnetoelastic fields. [ABSTRACT FROM AUTHOR]

Investigation into the cause of the furnace effect, encountered in the realization of high-temperature fixed points (HTFPs), was conducted at the copper point. Modifications of the cavity design reduced the furnace effect, which indicates that the furnace effect is caused by the interaction between the furnace and the cavity through reflection at the cavity side wall, linked to the design of the HTFP cells. It was shown that the effect could be mitigated by applying a small aperture at the cavity opening. The difference of the realized temperature from that in the absence of the furnace effect was considered, and it was shown that the effect at the copper point in a HTFP furnace was estimated to be around 14 mK or less, the realized temperature being lower than the true temperature. [ABSTRACT FROM AUTHOR]

The present study investigates processing routes to obtain highly conductive and transparent electrodes of silver nanowires (AgNWs) on flexible polyethylene terephthalate (PET) substrate. The AgNWs are embedded into a UV-curable polymer to reduce the electrode roughness and enhance its stability. For the purpose of device integration, the AgNWs must partially protrude from the polymer, which demands that their embedding is followed by a transfer step from a host substrate to the final substrate. Since the AgNWs require some sort of curing (thermal or plasma) to reduce the electrode sheet resistance, a thermally stable host substrate is generally used. This study shows that both thermally stable polyimide, as well as temperature-sensitive PET can be used as flexible host substrates, combined with a gentle, AgNW plasma curing. This is possible by adjusting the fabrication sequence to accommodate the plasma curing step, depending on the host substrate. As a result, embedded AgNW electrodes, transferred from polyimide-to-PET and from PET-to-PET are obtained, with optical transmittance of ∼80% (including the substrate) and sheet resistance of ∼13 Ω/sq., similar to electrodes transferred from glass-to-glass substrates. The embedded AgNW electrodes on PET show superior performance in bending tests, as compared to indium-tin-oxide electrodes. The introduced approach, involving low-cost flexible substrates, AgNW spray-coating and plasma curing, is compatible with high-throughput, roll-to-roll processing. [ABSTRACT FROM AUTHOR]

The strong chiroptical effect is highly desirable and has a wide range of applications in biosensing, chiral catalysis, polarization tuning, and chiral photo detection. In this work, we find a simple method to enhance the reflection circular dichroism (CDR) by placing the planar anisotropic chiral metamaterials (i.e., Z-shaped PACMs) on the interface of two media (i.e., Z-PCMI) with a large refractive index difference. The maximum reflection CDR from the complex system can reach about 0.840 when the refractive index is set as ntop = 4.0 and nbottom = 1.49, which is approximately three times larger than that of placing the Z-shaped PACMs directly on the substrate (i.e., Z-PCMS). While the minimum reflection CDR is 0.157 when the refractive index is set as nbottom = 1.49. So we can get a large available range of reflection CDR from –0.840 to –0.157. Meanwhile, the transmission CDT remains unchanged with the refractive index ntop increment. Our in-depth research indicates that the large reflection CDR is derived from the difference of non-conversion components of the planar anisotropic chiral metamaterials' reflection matrices. In short, we provide a simple and practical method to enhance the chiroptical effect by changing the refractive index difference between two media without having to design a complex chiral structure. [ABSTRACT FROM AUTHOR]

In this manuscript, we demonstrate the potential of replacing the standard bottom anti-reflective coating (BARC) with a polymethylglutarimide (PMGI) layer for wafer-scale nanofabrication by means of deep-UV displacement talbot lithography (DTL). PMGI is functioning as a developable non-UV sensitive bottom anti-reflective coating (DBARC). After introducing the fabrication process using a standard BARC-based coating and the novel PMGI-based one, the DTL nanopatterning capabilities for both coatings are compared by means of the fabrication of etched nanoholes in a dielectric layer and metal nanodots made by lift-off. Improvement of DTL capabilities are attributed to a reduction of process complexity by avoiding the use of O2 plasma etching of the BARC layer. We show the capacity of this approach to produce nanoholes or nanodots with diameters ranging from 95 to 200 nm at a wafer-scale using only one mask and a proper exposing dose. The minimum diameter of the nanoholes is reduced from 118 to 95 nm when using the PMGI-based coating instead of the BARC-based one. The possibilities opened by the PMGI-based coating are illustrated by the successful fabrication of an array of nanoholes with sub-100 nm diameter for GaAs nanowire growth on a 2″ GaAs wafer, a 2″ nanoimprint lithography (NIL) master stamp, and an array of Au nanodots made by lift-off on a 4″ silica wafer. Therefore, DTL possess the potential for wafer-scale manufacturing of nano-engineered materials. [ABSTRACT FROM AUTHOR]

Antireflection (AR) film is a widely used technology to enhance the performance of photovoltaic devices that require transparent electrodes in the photovoltaic industry. At present, several AR films including monolayer MgF2 or multilayered composite films, textured polydimethylsiloxane (PDMS) and porous SiO2 have been successfully applied due to their excellent properties. Nevertheless, all of the above-mentioned AR films have some minor drawbacks to overcome, for instance, the cost or thermal durability. Herein, we report a cost-effective and low-temperature method to fabricate a mesoporous aluminum oxide (meso-Al2O3) layer as the AR coating with high thermal durability, which will meet the fabrication condition of various photovoltaic devices. Briefly, the process begins at magnetron sputtering a compact Al2O3 film, which shows no AR effect, followed by a hot water treatment at 80 °C to turn the compact film into a mesoporous film with graded-index and AR effect. The application of meso-Al2O3 AR film enhances the maximum transmittance of our laboratory-used fluorine-doped tin oxide (FTO) from 84% to 89%, which is in good agreement with our theoretical simulation named graded-index approximation. Taking perovskite solar cells (PSCs) as an example, planar PSCs with meso-Al2O3 AR film deliver excellent photon conversion efficiency of 21.5%, which is higher than that of cells without meso-Al2O3 AR film (20.9%). [ABSTRACT FROM AUTHOR]

Nanostructured Anti-Reflective (AR) surfaces have attracted a focused attention during the last few years and offer an alternative to AR coatings. Recent nanopatterning approaches have allowed fabrication of bioinspired nanostructured surfaces with unprecedented broadband and omnidirectional AR properties. However, nanofabrication methods face major challenges for reaching industrial maturity including high capital expenditure cost, scalability, reliability and adaptability of the technologies. Block copolymer (BCP) films provide one way to overcome some of these limitations by offering scalable and versatile masks to fabricate well-defined, uniform and tunable nanostructures on a variety of substrates at a modest price. This article aims at highlighting recent efforts for assembling such AR nanostructured surfaces with BCP films and the challenges yet to tackle prior to commercialization of the technology. [ABSTRACT FROM AUTHOR]

The extinction ratio and insertion loss of spatial light modulator are subject to the material problem, thus limiting its applications. One reflection-type silicon-based spatial light modulator with high reflective materials outside the Fabry–Perot cavity is demonstrated in this paper. The reflectivity values of the outside-cavity materials with different film layer numbers are simulated. The reflectivity values of 6-pair Ta2O5/SiO2 films at 1550 nm are experimentally verified to be as high as 99.9%. The surfaces of 6-pair Ta2O5/SiO2 films are smooth: their root-mean-square roughness values are as small as 0.53 nm. The insertion loss of the device at 1550 nm is only 1.2 dB. The high extinction ratio of the device at 1550 nm and 11 V is achieved to be 29.7 dB. The spatial light modulator has a high extinction ratio and low insertion loss for applications. [ABSTRACT FROM AUTHOR]

We show that reflections of self-collimated beams at the boundaries of a finite-size coupled zigzag-box resonator, which is designed to slow down the speed of self-collimated beams in a photonic crystal, can be minimized by introducing antireflection structures. The optimal values of design parameters for minimal reflection can be obtained by using one-dimensional antireflection coating theory and finite-difference time-domain simulations. It is shown that the optimized antireflection structures significantly reduce unnecessary finite-size effects, such as strong Fabry–Pérot oscillations in the transmission spectrum and variations in the group velocity curve. Our results could be useful in implementing devices to control self-collimated beams in the time domain. [ABSTRACT FROM AUTHOR]

In this paper, multilayer antireflection coatings are designed by modifying the thickness of two and three paired layer distributed Bragg reflector (DBR) structure. Our proposed DBR-based structures show antireflection behaviors, in spite of the reflection treatment in traditional DBR structures. Firstly, the proposed structures are designed to be equivalent to the theoretical ideal triple-layer (TL) antireflection coating (ARC). Therefore, the problem of finding a suitable material for the middle layer of triple structure is solved. Simulation results show the significant equivalency for the reflectance of proposed structures to the ideal TL ARC at the same wavelengths and incident angles. Also, the design of the structure is changed in order to present the constant reflectance coefficient over a wide range of wavelengths. This structure enhances the omni-directionality of the multilayer ARC. [ABSTRACT FROM AUTHOR]

This paper proposes an ultraviolet nanoimprint lithography (UV-NIL) roll-to-roll (R2R) process with argon and oxygen (Ar–O2) plasma ashing and coating of a dilute perfluorodecyltrichlorosilane (FDTS) layer to fabricate the large-area moth-eye-like surface morphology on a polyethylene terephthalate substrate. By using Maxwell-Garnett's effective medium theory, the optimal dimensions of the moth-eye-like surface morphology was designed and fabricated with UV-NIL R2R process to obtain maximum transmittance ratio. In addition, the base angle (θ = 30.1°) of the moth-eye-like surface morphology was modified with Ar–O2 plasma ashing and coated with a dilute FDTS layer to possess both superhydrophobic and air-retention properties. This increases both the transmittance ratio of 4% and contact angle to 153°. [ABSTRACT FROM AUTHOR]

Continuous-wave laser properties of Nd :GYSGG crystal based on the transition from 4F3/2 to 4I13/2 are investigated. With different output couplers, single or multiple wavelength lasers operating at 1321, 1336, 1404 and 1424 nm are obtained, which provide new options in these wavelength bands. In the 1.3μm region, the maximum output power is 2.5W, corresponding to the conversion efficiency of 18.5%. In the 1.4μm region, the maximum output power at 1424 nm is 707mW, corresponding to the conversion efficiency of 6.8%. The output power and conversion efficiency can be improved with better anti-reflection coatings for the laser crystal. [ABSTRACT FROM AUTHOR]

In this paper we analyze the influence of active layer thickness on the light absorption processes of c-Si solar cells by the finite-difference frequency-domain (FDFD) method and show that the ideal c-Si active layer thickness range is from 10 to 20 μm. By evaluating the absorption enhancement factor, we find that c-Si solar cells with thicknesses within this range can give full play to the synergistic effects of back reflectors and antireflection coatings. By using a simple light trapping scheme, which is composed of a Ag back reflector, a bilayer antireflection coating and a one-dimensional photonic crystal front surface texture structure with rectangular profile, a c-Si solar cell with an active layer thickness of 12 μm can obtain a higher photocurrent density of 32.6 mA cm−2 for normally incident sunlight and a broader acceptance angle range of −60°–60° for obliquely incident sunlight. [ABSTRACT FROM AUTHOR]

Thin-film interference is a well-known effect, and it is commonly observed in the colored appearance of many natural phenomena. Caused by the interference of light reflected from the interfaces of thin material layers, such interference effects can lead to wavelength and angle-selective behavior in thin-film devices. In this work, we describe the use of interfacial nanostructures to eliminate interference effects in thin films. Using the same principle inspired by moth-eye structures, this approach creates an effective medium where the index is gradually varying between the neighboring materials. We present the fabrication process for such nanostructures at a polymer-silicon interface, and experimentally demonstrate its effectiveness in suppressing thin-film interference. The principle demonstrated in this work can lead to enhanced efficiency and reduce wavelength/angle sensitivity in multilayer optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this study, theoretical and experimental investigations have been carried out to explore the suitability of graphene layers as an antireflection coating. Microwave plasma enhanced chemical vapor deposition and chemically grown graphene layers deposited on polished and textured silicon surfaces show that graphene deposition results in a large decrease in reflectance in the wavelength range of 300-650 nm, especially in the case of polished silicon. A Si3N4=textured silicon reference antireflection coating and graphene deposited polished and textured silicon exhibit similar reflectance values, with the graphene/Si surface showing lower reflectance in the 300-400 nm range. Comparison of experimental results with the finite difference time domain calculations shows that the graphene along with a SiO2 surface layer results in a decrease in reflectance in the 300-650 nm range, with a reflectance value of <5% for the case of graphene deposited textured silicon surfaces. The monolayer and inert character along with the high transmittance of graphene make it an ideal surface layer. The results of the present study show its suitability as an antireflection coating in solar cell and UV detector applications. [ABSTRACT FROM AUTHOR]

Quantitative analysis of the contribution from different physics mechanisms induced by nanocone gratings (NCG) to the efficiency of crystalline Si thin-film solar cells is systematically demonstrated through the performance comparison of such a nanotextured Si solar cell, an equivalent reflection planar Si solar cell, an equivalent volume planar Si solar cell and an actually planar Si solar cell, when their back-interface is a perfect-matched layer or air and their thickness is 1µm or 10µm. The results indicate that the contribution of each physics mechanism to the ultimate efficiency and their total contribution are significantly influenced by the thickness of their active layer. When the height of the NCG structure is comparable to the thickness of the active layer, the contribution from each physics mechanism to the efficiency must be considered. In that respect, the contribution from the guided-mode resonance effect is the largest, and even surpasses the contribution of the active layer itself. When the active layer is significantly thicker than the height of the NCG structure, the contribution from antireflection induced by such a nanostructure rises up to the most, and the volume reduction effect can be ignored. In addition, the cavity-resonance effect exhibits a weak contribution and seems to be insensitive to the active layer thickness and interface reflection. Such an investigation provides a methodology to optimize nanostructure-textured thin-film solar cells. Furthermore, the comparison of efficiency between a 1µm thick NCG-textured solar cell and a 10µm thick planar solar cell indicates that higher efficiency can be achieved in a thinner Si solar cell by the use of the optimized NCG structure, which just fulfils the expectation of third generation of Si solar cells. [ABSTRACT FROM AUTHOR]

Thin film solar cells have the potential to significantly reduce the cost of photovoltaics. Light trapping is crucial to such a thin film silicon solar cell because of a low absorption coefficient due to its indirect band gap. In this paper, we investigate the suitability of surface plasmon resonance Ag nanoparticles for enhancing optical absorption in the thin film solar cell. For evaluating the transmittance capability of Ag nanoparticles and the conventional antireflection film, an enhanced transmittance factor is introduced. We find that under the solar spectrum AM1.5, the transmittance of Ag nanoparticles with radius over 160 nm is equivalent to that of conventional textured antireflection film, and its effect is better than that of the planar antireflection film. The influence of the surrounding medium is also discussed. [ABSTRACT FROM AUTHOR]

The design and fabrication of graded-refractive-index (GRIN) antireflection (AR) coatings with wide-angle and broadband characteristics are demonstrated. The optimization of the graded-index profiles with a genetic algorithm is used in the design of the GRIN AR coatings. The average reflectance over a wavelength range from 400 nm to 800 nm and angles of incidence from 0° to 80° could be reduced to only 0.1% by applying an optimized AR coating onto BK7 glass. The optimization of step-graded GRIN AR coating is then further investigated in detail. A two-layer AR coating was deposited by electron beam evaporation with glancing angle deposition technology, and the positional homogeneity was improved by depositing the film from two opposite directions. The microstructure of the AR coating was investigated by scanning electron microscopy, and the residual reflectances of the coating sample are in agreement with theoretical calculations. The optimized GRIN AR coatings are beneficial to increasing the efficiency of light utilization. [ABSTRACT FROM AUTHOR]

We report on the results of an extensive campaign of optical and mechanical characterization of the ion-beam sputtered oxide layers (Ta2O5, TiO2, Ta2O5–TiO2, SiO2) within the high-reflection coatings of the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors: refractive index, thickness, optical absorption, composition, density, internal friction and elastic constants have been measured; the impact of deposition rate and post-deposition annealing on coating internal friction has been assessed. For Ta2O5 and SiO2 layers, coating internal friction increases with the deposition rate, whereas the annealing treatment either erases or largely reduces the gap between samples with different deposition history. For Ta2O5–TiO2 layers, the reduction of internal friction due to TiO2 doping becomes effective only if coupled with annealing. All measured samples showed a weak dependence of internal friction on frequency [ϕc(f) = afb, with −0.208 < b < 0.140 depending on the coating material considered]. SiO2 films showed a mode-dependent loss branching, likely due to spurious losses at the coated edge of the samples. The reference loss values of the Advanced LIGO and Advanced Virgo input (ITM) and end (ETM) mirror HR coatings have been updated by using our estimated value of Young’s modulus of Ta2O5–TiO2 layers (120 GPa) and are about 10% higher than previous estimations. [ABSTRACT FROM AUTHOR]

The fabrication of nanotips has been driven by the increasing industrial demands in developing high-performance multifunctional nanodevices. In this work, we proposed a controlled, rapid as well as low cost nanomolding-necking technology to fabricate gold nanotips arrays. The geometries of gold nanotips having cone angle range of ∼28–77° and curvature radii of <5 nm can be prepared by tailoring the diameters of raw nanorods in nanomolding process or modulating the necking temperature. Molecular dynamics simulation reveals that the formation of the nanotip geometry is determined by the interplay between dislocation-based and diffusion-based deformation mechanisms, intrinsically arising from the nonlinear dependence of atom diffusion on temperature and sample size. The good controllability, mass production and low cost of the developed nanomolding-necking technology make it highly promising in developing nanodevices for a wide range of applications, such as probing, sensing, antireflection coating and nanoindentation. [ABSTRACT FROM AUTHOR]

We report a systematic study of the fabrication and chemical and structural characterization of epitaxial Cr films and Pt/Cr bilayers on MgO substrates. Cr films of different thicknesses were grown by molecular beam epitaxy at 373 K and then post-annealed at different temperatures. These films are chemically stable, present a well-ordered tetragonal structure, with only a low degree of oxidation distributed throughout the films. The lattice parameter can be finely tuned by varying the film thickness and the post-annealing temperature, as the elastic energy is progressively relaxed by edge dislocations, so that the film can approach the structural and electrical properties of bulk chromium. Moreover, the chemical and structural properties of Cr are not affected by a Pt capping layer, which grows in a well-ordered Pt[1 1 0]||Cr[1 0 0] orientation, holding potential for applications in recently proposed Pt/Cr-based antiferromagnet spintronics and for the realization of epitaxial Pt films on MgO by using a thin buffer layer of chromium. [ABSTRACT FROM AUTHOR]

Magneto-optic Kerr effect (MOKE) microscopy involves the surface-sensitive probing of magnetisation at micron-sized lateral resolution. Here, we present a low-temperature, focused polar MOKE microscope for simultaneous magneto-optic and magneto-transport measurements which has a temperature range of 1.6–300 K and is equipped with a magnet capable of delivering a field of up to 9 T. In this microscope, all optical components are integrated in a free-standing probe, allowing for straightforward incorporation into many non-optical cryostat systems. Two-dimensional magnetisation scans on patterned ferromagnetic [CoFeB/Pt]n films demonstrate a magnetisation sensitivity of 10 µrad (Kerr angle) and a spatial resolution of 2.2 µm. The combination of optical and electrical measurements provides complementary temperature-dependent information, as demonstrated by the study of magnetic topological insulator thin films with out-of-plane magnetic anisotropy. Using this complementary approach, we study the effects of a secondary phase in Cr and V co-doped Sb2Te3 thin films, which show a combination of weak antilocalisation and anisotropic magnetoresistance effects above 70 K. Our results highlight the virtue of MOKE and electrical transport to optimise exotic topological magnetic materials, paving the way for energy-efficient spintronic devices. [ABSTRACT FROM AUTHOR]

A multifunctional antireflective (AR) thin film is always a prerequisite for growing high-tech applications. Herein we proposed a surface modification technique to transform the hydrophilic behaviour of HfO2 AR nanofilms into hydrophobic without influencing the nanostructure, morphology, refractive index (η) or AR efficacy of HfO2 nanofilms. Our experimental results demonstrate that the fabricated HfO2 AR nanofilms retain its AR efficiency after surface modification to <1% in the visible wavelength range (450–700 nm) on FTO and sapphire. HfO2 AR nanofilms show hydrophilic behaviour before surface modification with a water contact angle (WCA) of 29° on FTO and 22° on sapphire. However, after surface treatment, they display hydrophobic nature θw > θ > 90° with a contact angle of (127°–130°). The experimental result demonstrates that the η of the thin layers fabricated at deposition angle 0°, 80°, and 88° before and after modification remains almost the same. HfO2 AR nanofilms exhibit long term AR permanency as AR efficiency measured within a year practically displays the equivalent reflectance curves similar to as deposit AR thin films, i.e. <1% in the wavelength range of 450–700 nm. We proposed a cost-effective procedure to make hydrophilic AR films to show non-wetting behaviour for its long-term exposure in a moist, damp environment without affecting the refractive index of AR thin film. [ABSTRACT FROM AUTHOR]

Single-layer, anti-reflective coatings prepared via the sol–gel method can be scaled to large-area applications (e.g. solar collectors). In the specific case of evacuated tube solar thermal collectors, there are often three glass–air or glass–vacuum interfaces which can cause reflection. Thus, in the absence of any anti-reflective technology (i.e. most commercial products), a steep 15% or 22% reflective loss (e.g. transmission ~0.92N, where N  =  2 or 3) occurs in evacuated tube solar collectors. Porous MgF2-based materials have been shown to provide low refractive index as a single layer, but they have not yet been applied to solar thermal collector technology—which requires elevated temperature stability and spectrum transmission. Importantly, these should be low cost at the m2 scale. Further, since solar technologies are considered ‘green’, the materials used in their manufacturing should be carefully considered. In this study, we have employed trifluoroacetic acid (instead of hydrofluoric acid) as the fluorine source to produce single-layer porous MgF2 coatings. These coatings were designed and modeled with OpenFilters, fabricated with dip-coating, and characterized with ellipsometetry, x-ray diffraction, Raman spectroscopy, and focused ion beam/transmission electron microscopy to validate the OpenFilters model. For high transmission substrates, the dip coated films produced in this study can reach a solar-weighted reflectance of 2.3%. Additionally, to test if these films are suitable for solar thermal collectors, durability tests were conducted, which revealed acceptable heat resistance. However, without a water-resistant outer layer, the films did not pass an ASTM D870-09 water immersion test. Overall, this study presents a low-cost approach to developing anti-reflective coatings which are suitable for large-area solar thermal applications. [ABSTRACT FROM AUTHOR]

Transparent conductive electrodes (TCEs) are widely used in applications ranging from display devices to thin-film solar cells. It remains a challenge, however, for industry and academia to implement mass production of large-area TCEs at low cost and at high volumes. It is also difficult to fabricate TCEs with good electrical properties and high light transmittance levels. In this study, a novel large-area and high-performance TCE manufacturing method is demonstrated that combines the electric-field-driven fusion direct printing technique and the liquid bridge transfer method. The master molds of the TCEs are fabricated by the electric-field-driven fusion direct printing technology, then soft lithography and the liquid bridge transfer processes are used to form the TCEs on different substrates. The relationships between process parameters, and their effects on the fabrication of the TCEs are explored through experiments, and the optimal process parameters are established. Using these methods, grid and stripe TCEs on the glass substrates with an area of 50 mm  ×  50 mm, an average line width of 4 µm, a spacing of 200 µm, a transmittance effectiveness of 88.94% and 88.15% which was nearly same as the bare glass, and a sheet resistance of 12 Ω sq−1 were successfully manufactured. These results illustrate the feasibility of mass producing large-area TCEs with high performances and at low cost. [ABSTRACT FROM AUTHOR]

In this work, the patterned aluminium nitride (AlN) ceramic has been designed to achieve reflection reduction over a broad frequency band. This is implemented by simply drilling holes in the AlN ceramic. Unlike absorbing materials, the reflection reduction arises from the out of phase cancellation of the reflected fields from the patterned AlN ceramic. Both simulations and measurements indicate that the proposed AlN ceramic has a broadband reflection reduction performance with the efficiency larger than 10 dB in the backward direction and is of polarization insensitivity. Due to the high decomposition temperature and good oxidation resistance of AlN ceramic materials, our proposal works well at high temperatures all the same and this is demonstrated experimentally. It is therefore expected that the result here provides an alternative candidate for the electromagnetic application under the high-temperature conditions. [ABSTRACT FROM AUTHOR]

In continuation of our recent report on molybdates [Appl. Phys. A124, 44 (2018)], the structural, electronic, elastic, and optical properties of ZMoO3 (Z = Ba and Sr) molybdates are investigated under pressure (10 GPa–50 GPa) comprehensively by deploying the density functional theory. Our investigations show that the studied compounds exhibit stable cubic phase with metallic attributes. The thermodynamic parameters such as enthalpy of formation, Debye, and melting temperatures of the compounds are observed to increase with pressure. While the Grüninsen parameter and the coefficient of super-plastic deformation decrease as the pressure increases. Mechanical properties elucidate an increase in measured values of hardness, bulk, shear, and youngʼs moduli with pressure. Our results suggest that the studied compounds are useful in high pressure optoelectronic devices. The optical properties of BaMoO3 (BMO) and SrMoO3 (SMO) are computed for the radiation of up to 35 eV. The present compounds show beneficial optical applications in the anti-reflection coating, lenses, and the high avoiding solar heating applications in the variant applied pressure. [ABSTRACT FROM AUTHOR]

This work proposes a synthetic design for a microwave absorber and antireflection to achieve reduction of wideband scattering. Simultaneous control of the absorption and scattering pattern of metasurfaces can be achieved by theoretical analysis and calculation aimed at improving the reduction of backward reflection. With a topologically optimized design and antenna array synthesis, customized absorption and an optimal arrangement can be achieved over a broad spectrum within an integrative optimization procedure. To validate the design method, a wideband low radar cross-section metasurface is proposed, for which good agreement is observed between simulations and experiment with pronounced reflection suppression from 9 to 23.9 GHz. This work reveals the opportunity for use of a metasurface in effective manipulation of microwaves and a synthesis optimization method for designing a high-performance flexible low-scattering platform. [ABSTRACT FROM AUTHOR]

In this letter, we propose the design of anti-reflection (AR) lining for enhancing transmission of high-permittivity dielectric (HPD) plate based on locally modified Fresnel law. By applying metamaterial unit cells on the air-dielectric interfaces, the fields are distorted locally in the HPD, leading to split and tilted wave-vectors in sub-wavelength scale. Due to the tilted wave-vectors, the reflection and refraction on the interface are locally modified without violating Snell’s law, leading to reduced reflection and hence enhanced transmission according to Fresnel equations. As an example, we demonstrate two prototypes that enhance the transmission of a 3 mm thick alumina plate below and above the half-wavelength frequency. Both the simulation and measured results verify the good transmission enhancement performance in X and Ku bands. This work provides an effective alternative to the design of AR structures for especially HPD materials. [ABSTRACT FROM AUTHOR]

CdTe/CdS quantum dots (QDs) are fabricated on Si nanowires (NWs) substrates with and without Au nanoparticles (NPs). The formation of Au NPs on Si NWs can be certified as shown in scanning electron microscopy images. The optical properties of samples are also investigated. It is interesting to find that the photoluminescence (PL) intensity of CdTe/CdS QD films on Si nanowire substrates with Au NPs is significantly increased, which can reach 8-fold higher than that of samples on planar Si without Au NPs. The results of finite-difference time-domain simulation indicate that Au NPs induce stronger localization of electric field and then boost the PL intensity of QDs nearby. Furthermore, the time-resolved luminescence decay curve shows the PL lifetime, which is about 5.5 ns at the emission peaks of QD films on planar, increasing from 1.8 ns of QD films on Si NWs to 4.7 ns after introducing Au NPs into Si NWs. [ABSTRACT FROM AUTHOR]

Compared with conventional anti-reflective film, an anti-reflective sub-wavelength surface structure provides an ideal choice for a sapphire optical window especially in harsh environments. However, it is still a challenge to obtain a sapphire anti-reflective surface microstructure because of its high hardness and chemical inertness. In this paper, combined with optical simulation, we proposed a facile method based on the anodic oxidation of aluminum film and following epitaxial annealing. Al thin film was deposited on a sapphire substrate by magnetron sputtering, and anodic oxidation was then performed to prepare surface pore-like structures on the Al film. Followed by two-step annealing, both the anodic oxidized coating and underlying unoxidized Al film were transformed totally into alumina. The parameters of anodic oxidation were analyzed to obtain the optimal pore-like structures for the antireflection in the mid-infrared and visible spectrum regions, respectively. Finally, the optimized surface sub-wavelength nanostructure on sapphire can increase the transmittance by 7% in the wavelength range of 3000–5000 nm and can increase 13.2% significantly for visible spectrum region, respectively. Meanwhile, the surface wettability can be also manipulated effectively. The preparation of surface pore-like sub-wavelength structure by the annealing of anodic oxidized aluminum film on sapphire is a feasible, economical and convenient approach and can find the applications for various optoelectronic fields. [ABSTRACT FROM AUTHOR]

Indium tin oxide (ITO) thin films were sputter-deposited at ambient temperature on a glass-like substrate that was periodically nanostructured by UV nanoimprint lithography. Cross gratings of the corrugated and conformal ITO, with different periods and modulation depths, were tailored to exhibit light trapping or antireflection properties at specific spectral windows by combined optical simulations and experiments. For dense gratings, the light transmission in the 450–850 nm range was enhanced by 8% (absolute) compared to flat ITO films, which is one of the largest performance improvements reported in the literature for nanostructured transparent electrodes. Increasing the grating period shifts the threshold for diffraction coupling to waveguide modes in the visible and near infrared part of the spectrum, resulting in broad light trapping behaviour at wavelengths below this threshold. This work demonstrates a simple processing route at ambient temperature for the fabrication of high-performance transparent electrodes in order to fulfil different device requirements. [ABSTRACT FROM AUTHOR]

Refractive index inhomogeneity is one of the important characteristics of optical coating material, which is one of the key factors to produce loss to the ultra-low residual reflection coatings except using the refractive index inhomogeneity to obtain gradient-index coating. In the normal structure of antireflection coatings for center wavelength at 532 nm, the physical thicknesses of layer H and layer L are 22.18 nm and 118.86 nm, respectively. The residual reflectance caused by refractive index inhomogeneity (the degree of inhomogeneous is between −0.2 and 0.2) is about 200 ppm, and the minimum reflectivity wavelength is between 528.2 nm and 535.2 nm. A new numerical method adding the refractive index inhomogeneity to the spectra calculation was proposed to design the laser antireflection coatings, which can achieve the design of antireflection coatings with ppm residual reflection by adjusting physical thickness of the couple layers. When the degree of refractive index inhomogeneity of the layer H and layer L is −0.08 and 0.05 respectively, the residual reflectance increase from zero to 0.0769% at 532 nm. According to the above accuracy numerical method, if layer H physical thickness increases by 1.30 nm and layer L decrease by 4.50 nm, residual reflectance of thin film will achieve to 2.06 ppm. When the degree of refractive index inhomogeneity of the layer H and layer L is 0.08 and −0.05 respectively, the residual reflectance increase from zero to 0.0784% at 532 nm. The residual reflectance of designed thin film can be reduced to 0.8 ppm by decreasing the layer H of 1.55 nm while increasing the layer L of 4.94 nm. [ABSTRACT FROM AUTHOR]

A low filling ratio and enhanced absorption is needed to enable the full potential of Si nanowire (NW) arrays for optoelectronic applications. In this paper, we report a versatile, scalable fabrication technique that uses nanosphere lithography (NSL) patterning for the synthesis of vertically aligned Si and Si/SiO2 NW arrays. The optical reflection of the NW arrays can be substantially suppressed by the addition of the transparent shell. Meanwhile, by the finite-difference time-domain (FDTD) simulation, we find that the absorption enhancement in the core Si NW can be obtained by adding the transparent shell. The special absorption enhancement of the Si NW arrays with a core–shell structure can be theoretically understood by modal analysis. The absorption in such Si NW array structures is very sensitive to the thickness of transparent coating. By the addition of a SiO2 shell layer, the absorption in the inner Si NW array can be substantially enhanced. Furthermore, significant absorption enhancement and broadband anti-reflection effects can be achieved by the diluted Si NWs combined with the single dielectric shell. [ABSTRACT FROM AUTHOR]

In this paper, an inverted silicon (Si) nanopyramid (iSiNP) surface structure with low aspect ratio and remarkable antireflection is developed through sequential treatments of NaOH and HF/CH3COOH/HNO3 solutions to Si nanowire (SiNW)-textured Si wafers, which are prepared by traditional electroless chemical etching. The iSiNP/PEDOT:PSS hybrid solar cell is fabricated through conformally spin-coating poly(3.4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) onto the iSiNPs; it exhibits enhanced device performance owing to the improved junction and contact quality as compared to the SiNW/PEDOT:PSS counterpart. A power conversion efficiency (PCE) of 9.6% mainly contributed from an increased fill factor (FF) of 0.61 and improved open circuit voltage (Voc) of 0.53 V is delivered by the iSiNP/PEDOT:PSS solar cell. As a comparison, the SiNW/PEDOT:PSS structure delivers a 7.1% PCE with a FF of 0.45 and Voc of 0.46 V. Considering the submicro-scale characteristic dimensions, iSiNPs are expected to be applicable to highly efficient thin film Si/PEDOT:PSS hybrid solar cells. [ABSTRACT FROM AUTHOR]

Multi-layer optical coatings with complex spectrum requirements, such as multi-band pass filters, notch filters, and ultra-broadband antireflection coating, which usually contain very thin layers and sensitive layers, are difficult to be fabricated using a quartz crystal monitoring method or a single wavelength optical monitoring system (SWLOMS). In this paper, a broadband antireflection (AR) coating applied in the wavelength range from 800 nm to 1800 nm was designed and deposited by ion beam sputtering (IBS). Ta2O5 and SiO2 were chosen as high and low refractive index coating materials, respectively. The optimized coating structure contains 9 non-quarter-wave (QW) layers totally with ultra-thin layers and sensitive layers in this coating stack. In order to obtain high transmittance, it is very important to realize the thickness accurate control on these thin layers and sensitive layers. A broadband optical monitoring mixed with time monitoring strategy was successfully used to control the layer thickness during the deposition process. At last, the measured transmittance of AR coating is quite close to the theoretical value. A 0.6% variation in short wavelength edge across the central 180 mm diameter is demonstrated. A spectrum shift of less than 0.5% for 2 continuous runs is also presented. [ABSTRACT FROM AUTHOR]

The oxynitride materials present a high versatility, which enables their properties to be controlled by tuning their elemental composition. This is the case for silicon oxynitrides used for multilayer antireflective coatings (ARCs), where several thin films with various refractive indexes are needed. Different techniques allow for the modification of the thin film composition. In this paper, we investigate the reactive gas pulsing sputtering process to easily tune the thin film composition, from an oxide to a nitride, by controlling the averaged oxygen flow rate, without reducing the deposition rate, compared to a conventional reactive process (CP). We then demonstrated that the refractive indexes of films deposited by this pulsing process (PP) can be varied in the same range compared to films obtained by CP (from 1.83 to 1.45 at 1.95 eV), whereas their extinction coefficients remain low. Finally, the multilayer ARC has been simulated and optimized by a genetic algorithm for wavelength at 600 nm and for the silicon substrate. Various optimized multilayer (mono-, bi- and tri-layers) structures have been deposited by the PP technique and characterized. They are presented in good agreement with the simulated reflectivity. Hence, the PP allows for an easy depositing tri-layer system with a reasonable deposition rate and low reflectivity (8.1% averaged on 400–750 nm visible light range). [ABSTRACT FROM AUTHOR]

Surface plasmon polaritons have been proposed in the architectures of several solar cells as a way to enhance light collection and thus to increase their efficiency. Here, Ag nanoparticles (NPs) are embedded in a SiON antireflective layer using an electroless technique. The plasmonic effects are modeled and observed experimentally for NPs 5 to 200 nm in size. The systematic comparison of scattering and extinction efficiencies computed as a function of the NPs and surrounding medium properties allows establishing engineering rules, validated by the experimental measurements. The fact that Ag NPs larger than 30 nm mainly contribute to light scattering and therefore to optical path enlargement (green–red light), whereas those smaller than 15 nm absorb light by light trapping (blue–green), is demonstrated and physically explained. A physical barrier making it impossible to shift the dominant resonance beyond 650 nm is pointed out. [ABSTRACT FROM AUTHOR]