Abstract Background Aim is to analyze alterations in third and fourth corneal higher-order aberrations using a ray tracing aberrometer (iTrace) induced by SMILE (small incision lenticule extraction) refractive surgery on Algerian patients; and also to investigate how corneal aberrations vary with spherical equivalent (SE), corneal central thickness (CCT), and age. Design Prospective, non-randomized case series that were carried out at the Chiali Smile Center, Algiers, Algeria. Participants A total of 219 eyes from 110 myopic patients, with and without astigmatism, successfully concluded the ultimate follow-up. Participants exhibited an average age of 32.48 years, with preoperative mean corneal high-order aberrations (CHOA) measuring 0.005 ± 0.036 μm. Methods A tracking trend analysis of high-order aberrations (HOAs) was conducted on the three groups of patients, assessing total corneal high-order aberrations after SMILE over periods of two, six, and twelve months. Results A substantial increase in total corneal high-order aberrations following SMILE, with a P value < 0.05. Conversely, there was a noteworthy and significant decrease in vertical trefoil for all groups (P value = 0.000). Interestingly, the corneal higher-order aberrations were more pronounced after two months compared to the six and twelve-month intervals. Spherical aberration demonstrated a significant increase with the extent of preoperative myopia and preoperative spherical equivalent both before and after SMILE surgery (P < 0.05), particularly in cases of high myopia. Moreover, there were significant reductions in preoperative and postoperative vertical coma (P = 0.047, P = 0.004, respectively) corresponding to the degree of preoperative myopia, with a more substantial decrease in vertical coma observed in cases of low myopia. Conclusion In the post-SMILE period, a notable increase in vertical coma and spherical aberrations was observed, accompanied by a significant decrease in vertical trefoil across all eyes. These aberration changes were identified to be closely associated with the spherical equivalent.

Objectives:The shift from outdoor play to prolonged use of electronic devices among children, exacerbated by the COVID-19 pandemic, has raised concerns about its impact on visual health. This study explores the relationship between the excessive use of digital devices and the development of various refractive errors in children. This study aims to investigate the association between excessive screen time (including smartphones, tablets, computers, and televisions) with different types of refractive errors and axial length (AL) elongation in a cohort of school-aged children in North-West Algeria. It is a cross-sectional analysis focused on a representative sample from this region. Methods:Over a 1-year period, 208 schoolchildren (416 eyes), aged 6-18 years (mean age: 6.21±3 years), underwent comprehensive eye examinations at the ophthalmic service of the pediatric hospital EHS Canastel, Oran. Cycloplegic measurements assessed the refractive errors, while A-scan ultrasonography measured the ocular biometry. The study also evaluated children's technology usage patterns, including daily screen time, types of devices used, and time spent outdoors. Results:The study revealed a significant decrease in mean spherical equivalence (SE) in both eyes over the 1-year period. In the right eye (RE), SE dropped from -0.96 D to -1.48 D, and in the left eye (LE) from -0.70 D to -1.39 D. Myopic astigmatism was the most prevalent condition, affecting 51% of children, especially younger screen users (p<0.001). Axial length (AL) increased in both eyes, with an average elongation of 0.54 mm in the RE and 0.57 mm in the LE. There was a strong correlation between excessive screen use and the progression of myopic astigmatism, along with changes in spherical equivalence. Factors such as device type, screen time, and reduced outdoor activity were significantly associated with the progression of refractive errors and AL elongation (p<0.005). Conclusion:Prolonged use of digital screens is significantly correlated with increased risks of myopic astigmatism, AL elongation, and changes in spherical equivalent values. These findings emphasize the urgent need for further research and public health measures to address the impact of prolonged digital device use on children's vision.

The plasma-assisted Vapor-Liquid-Solid technique has been used to grow Silicon nanowires (SiNWs) on different substrates coated with 1 nm of tin and indium, to study the impact of the surface energy of the substrates on the morphology and structure of the NWs. The characteristics of the prepared Si NWs were analyzed by field emission scanning electron microscopy, X-ray diffraction (XRD) and Raman spectroscopy. The morphological characteristics differ in the density, diameter and length of the synthesized SiNWs. The mean diameters of these SiNWs range from 36 to 51 nm at the bottom and from 15 nm to 34 nm at the tip, while their average length varies from 0.2 mu m up to 0.54 mu m depending on the substrate and catalyst. The presence of strong peaks in all XRD patterns indicates that the as-grown SiNWs are highly crystalline. The XRD and Raman characteristics of the Sn and In catalyzed SiNWs formed on different substrates show that the crystalline grain size is influenced by the substrate nature and catalyst material, which can be related to the substrate surface energy. In particular shorter NWs with improved crystallinity (larger grain size) are obtained when using Sn as a catalyst on an amorphous silicon-germanium (a-SiGe) substrates, while the small grains were obtained on the same substrate when indium was used as a catalyst.

Zinc oxide (ZnO) is one of the commonly used materials in antireflective coating (ARC) due to its optical, physical, and chemical properties. In order to enhance optical transmittance, an ARC is essential. Refractive index and film thickness are the key parameters to get an efficient ARC The aim of this work is to study deposition parameters' effects on thickness evolution and film quality. Spin-coated ZnO film thickness was measured and controlled according to revolutions per minute (rpm) and spin time (t). For this purpose, a sol-gel derived film containing &hydrate Zinc Acetate (ZAD) and ethanolamine was used to be spin-coated on a glass substrate. 77rermogravimetric analysis (TGA) was carried out in order to study the film thermal behavior and was followed by X-Ray Diffiaction (XRD) measurement en order to confirm the crystallization of ZnO. The film thickness was deduced from its mass measured by a microbalance and its' centrifugal spread over the substrate was checked by an optical microscope. By optimizing the deposition parameters, good film spread was obtained up to 4000 rpm with a spin time of 90 seconds at least. We found that the rpm affects strongly film thickness, in contrast to the spin time which affects the film spread.

Étudier les réponses des mouvements verticaux obtenues par une faible prismation en fonction de la dominance oculaire à l'aide d'un nouveau vidéoculographe Gazelab. Les mouvements verticaux de vergence ont été enregistrés dans trois conditions, en fixation binoculaire sans prisme (VN), avec un prisme de 2 Δ base inférieure sur l'œil dominant (POD) et l'œil non dominant (POND) sur sept patients. Les résultats révèlent que le mouvement induit par un prisme de 2 Δ base inférieure à une distance de 150 cm est plus significatif sur l'œil non dominant que sur l'œil dominant. En supraversion PPOD = 0,094 et PPOND = 0,004. En position primaire PPOD = 0,172 et PPOND = 0,045. En infraversion PPOD = 0,084 et PPOND = 0,038. Les réponses oculomotrices de la vergence verticale sont modulées par la dominance oculaire. To study the responses of vertical movements given by low prismation according to the ocular dominance using new videooculograph Gazelab. The vertical movements of vergence have been recorded in three conditions, in binocular fixation without prism (NV), with prism of 2 Δ base down on the dominant eye (PDE) and the non-dominant eye (PNDE) on seven patients. The results reveals that movement induced by a prism of 2 Δ base-down at a distance of 150 cm is more significant on the non-dominant eye than the dominant eye In supraversion PPDE = 0,094 and PPNDE = 0,004. In primary position PPDE = 0,172 and PPNDE = 0,045. In infraversion position PPDE = 0,084 and PPNDE = 0,038. The oculomotor responses of vertical vergence are modulated by ocular dominance.

La2/3Sr1/3MnO3 (LSMO) thin films of various thicknesses (6, 8, 10, 20, and 30 nm), capped by 7 nm‐thick Pt layer, are grown by pulsed laser deposition on SrTiO3 (001) substrates. X‐ray diffraction revealed that LSMO films are (001) oriented. Vibrating sample magnetometer is used to determine the magnetization at saturation and the magnetic dead layer thickness. This latter is around 3.4 nm, significantly thicker compared with the one induced at interfaces of Pt with ferromagnetic transition metals. Microstrip line ferromagnetic resonance (MS‐FMR) is used to extract the gyromagnetic ratio, which is found to increase with LSMO thickness. MS‐FMR revealed that the in‐plane magnetic anisotropy is dominated by a uniaxial contribution for the Pt capped film, whereas the noncapped 10 nm‐thick LSMO layer shows a fourfold anisotropy. Furthermore, the thickness dependence of the effective magnetization reveals the existence of a second‐order perpendicular anisotropy term, which is thickness‐dependent, and of a weak uniaxial interface anisotropy. The Gilbert damping coefficient is found to vary linearly with the inverse of the effective LSMO thickness due to spin pumping leading to relatively low spin mixing conductance of LSMO/Pt interface.

The perpendicular magnetic anisotropy (PMA) and the interfacial Dzyaloshinskii-Moriya interaction (iDMI) are investigated in as grown and 300 °C annealed Co-based ultrathin systems. For this, Co films of various thicknesses (0.8 nm ⩽ t Co ⩽ 5.7 nm) were deposited by magnetron sputtering on thermally oxidized Si substrates using Pt, W, Ir, Ti, Ru and MgO buffer or/and capping layers. X-ray diffraction was used to investigate their structural properties and vibrating sample magnetometry (VSM) was used to determine the magnetic dead layer thickness and the magnetization at saturation (M s). VSM revealed that the M s for the Pt and the Ir buffered and capped films is the largest. Microstrip line ferromagnetic resonance (MS-FMR), used to extract the gyromagnetic ratio of the thicker Co films, revealed the existence of a second order PMA term, which is thickness dependent. Brillouin light scattering (BLS) in the Damon-Eshbach configuration was used to investigate the thickness dependence of the iDMI effective constant from the spin wave vector dependence of the frequency difference between Stokes and anti-Stokes lines. BLS and MS-FMR techniques were combined to measure the spin wave frequency variation as a function of the in-plane applied magnetic field (where the second order PMA contribution vanishes). The thickness dependence of the effective magnetization was then deduced and used to investigate PMA. For all the systems, PMA results from interface and volume contributions that we determined. The largest interface PMA constants were obtained for Pt- and Ir-based systems due to the electron hybridization of Co with these heavy metals having high spin orbit coupling. Annealing at 300 °C increases both the interface PMA and iDMI for the Pt/Co/MgO most probably due to de-mixing of interpenetrating oxygen atoms from the Co layer and the formation of a sharp Co/O interface.

PURPOSE:To report the practice of orthokeratology (OK) in Algeria and to investigate the visual outcomes, safety and subjective responses with this technique in myopes. METHODS:A retrospective chart review of 48 participants using OK lenses since January 2010 were included in the study. Lenses were selected and fitted according to the manufacturer's recommendations using their respective software and the number of lenses required for a successful fit was recorded. Visual acuity (VA) in logMAR units and biomicroscopic findings were recorded for each visit. Subjective ratings was determined with analogue rating scale was filled in by the investigator, the participants were divided into Group 1 (> 4.00D) and Group 2 (< 3.75D) myopic groups for analysis. RESULTS:First lens fitting success rate of 64.58%. There was also a significant difference between the BCVA at baseline and VA at Day 1 (P < 0.05), and no significant difference at Day 7, Day 30 and the final visit (P = 0.51, P = 0.93, P = 0.62, respectively), for Group 2. There was a significant difference between the BCVA at baseline and VA at Day 1, 7, 30 and the final visit (P < 0.05), for Group 1. the patients of the second group were happier but the results from the survey were not statistically significant (P = 0.10), no serious complication was reported. CONCLUSION:the technique was efficient and safe as we didn't have any serious complication, with a high success rate for first lens fitting.

Highly crystallized hydrogenated silicon layers were obtained via the treatment of hydrogenated polymorphous silicon films in a molecular hydrogen ambient. This contrasts other postdeposition studies that obtained nanocrystalline silicon films but necessitated either a plasma activation or high‐temperature annealing. The structure of the samples was analyzed by Raman spectroscopy to determine the crystallite volume fraction, which was found to increase up to 80% within 1 hour of treatment. Atomic force microscopy (AFM) showed that the roughness of the surfaces was found to increase after the H2 treatment. Optical transmission and spectroscopic ellipsometry revealed the pronounced porosity of the films characterized by a static refractive index that is below three, which is a low value for hydrogenated silicon films and a void fraction that is around 15% in the bulk of the films. The effect of the hydrogen molecules on the structure of the films was discussed in terms of the compressive stress exerted by the molecules, trapped in structural inhomogeneities, on the amorphous tissue. It is suggested that for this process to take effect, the films need to be porous and that the amorphous network needs to be in a “relaxed” state.

Evolved gas analysis (EGA), infrared attenuated reflection (ATR), and Raman spectroscopy experiments are used to study hydrogen evolution in hydrogenated microcrystalline silicon carbide (μc-Si1−xCx:H) films prepared by plasma-enhanced chemical vapor deposition. The results are compared with microcrystalline silicon (μc-Si:H). The effused hydrogen and carbon-hydride groups (CH, CH2, and CH3) are measured up to 800 °C. Their EGA curves have a peak at 410 °C, attributed to the methyl groups incorporated in the amorphous matrix during the deposition process. Moreover, hydrogen evolution curves show narrow and sharp peaks centered at 425 and 520 °C, corresponding to hydrogen desorbing from silicon hydrides at grain boundaries. While its content is more important than hydrogen bonded to silicon in the amorphous and denser crystalline regions of μc-Si1−xCx:H, but remains lower than in the μc-Si:H film. Raman and ATR data indicate that the μc-Si1−xCx:H film is composed of small size silicon crystallites embedded in a hydrogenated amorphous silicon carbide matrix and confirmed that carbon is incorporated in the amorphous matrix as methyl groups (CH3), inducing a decrease in SiHx groups compared to the μc-Si:H film.

Hydrogenated nanocrystalline silicon, while being non-charged and non-polar, could be an ideal candidate for the non-covalent and orientation-controlled immobilization of biomolecules thanks to local electric fields around nanocrystals. To that effect, the adsorption of bovine serum albumin on substrates with different densities of nanocrystals, revealed by Raman spectroscopy and X-ray diffraction, was studied using infrared spectroscopy and atomic force microscopy. It was found that the protein–surface interactions followed different mechanisms depending on the nanostructure at the surface: hydrophobic on the non-crystalline part of the surface and electrostatic around the crystalline part. These electrostatic interactions were driven by the electric fields that arose at the junction between crystalline and amorphous structures. These electric fields were found to be strong enough to interact with the amide dipoles, thereby reorienting the adsorbed protein molecules on this part of the surface. Nevertheless, the adsorbed proteins were found to be denatured, which was due to the surface chemistry, and not affected by the nanostructure.

[Pt(1.5 nm)/Co(tCo)/W(1.5 nm)]N multilayers of different Co thicknesses (tCo) and number of repeats (N) have been grown by sputtering on Si substrates, and their magnetic properties have been studied. The x-ray reflectivity has been used to measure thicknesses of each layer as well as their roughness. The dependence of the magnetic moment on tCo and N (as determined by vibrating sample magnetometry) indicates the existence of a magnetic dead layer, which increases with N and reaches its maximum values for N ≥ 3. A similar N dependence of the magnetization at saturation is found. Ferromagnetic resonance and Brillouin light scattering have been used to investigate perpendicular magnetic anisotropy, damping, and interfacial Dzyaloshinskii-Moriya interaction (iDMI) vs Co thickness and the number of Pt/Co/W sequence repeats. We show that these parameters result from interface contributions that vary in a similar way with N, confirming that the first two Pt/Co/W trilayers are of lower quality. We thus conclude that for these systems, the increase of N improves the quality of interfaces and the volume of the stack, leading to the enhancement of the magnetic properties. Moreover, the measured weak iDMI constant, even for the higher N values, suggests that most probably, this iDMI results mainly from the Pt/Co interfaces.

The crystallization enthalpy measured in a large series of amorphous silicon (a-Si) materials varies within a factor of 2 from sample to sample (Kail et al 2011 Phys. Status Solidi RRL 5 361). According to the classical theory of nucleation, this variation should produce large differences in the crystallization kinetics leading to crystallization temperatures and activation energies exceeding 550 °C and 1.7 eV, respectively, the 'standard' values measured for a-Si obtained by self-implantation. In contrast, the observed crystallization kinetics is very similar for all the samples studied and has no correlation with the crystallization enthalpy. This discrepancy has led us to propose that crystallization in a-Si begins in microscopic domains that are almost identical in all samples, independently of their crystallization enthalpy. Probably the existence of microscopic inhomogeneities also plays a crucial role in the crystallization kinetics of other amorphous materials and glasses.

This paper reports on work performed in the FP7 European project HELATHIS. It presents the development of a TCO-glass combining a low iron-content substrate with a SnO2-layer with enhanced carrier mobility and therefore higher optical transmission, achieving in average 7.4% single junction module efficiency in TSolar standard production. First results of the further optimization of the fabrication process with this TCO glass indicate an increase of the single junction module efficiency in the future to nearly 8% in the stabilized state. Lightsoaking experiments of modules present very similar stabilized efficiency in the investigated i-layer thickness range between 140 to 260 nm, therefore, decreasing the i-layer thickness permits to increase the factory production capacity from about 55 up to about 75 MW/year. Investigation of the deposition of Al-doped ZnO layers by rf-sputtering from rotatable targets for the back reflector indicates improvement in the Isc and Voc. Implementation of such targets allows to expand the target life time and to reduce the maintenance time in comparison to standard planar targets. Ga-doped ZnO layers, when implemented in the back reflector, present similar cell performance compared with Al-doped ZnO.

The European project HELATHIS, executed by the five project partners signing this article, is dedicated to the improvement of the efficiency of very large area (5.7m 2 ) silicon thin film photovoltaic (PV) modules. Optical confinement has been identified by the project partners as a major source for efficiency improvement of thin film silicon PV modules. One reason of the performance gap between highly efficient laboratory solar cells and industrial modules is the poorer electrical and optical performance of the industrial TCO-covered front glass substrate (TCO glass) which is investigated in this work. The glass substrate in industrial PV modules is about 3 times thicker than in laboratory solar cells where frequently Asahi U-type TCO glass (about 1 mm thick) is used. Therefore, the glass quality has an important impact on the transmission of industrial TCO glass. Reducing the iron-content in the float glass substrate increases the integrated transmission in the wavelength range from 400-800nm by nearly 2%. The electrical properties, namely the electrical carrier mobility, of the industrial TCO layer of AGC has been increased by about 15% by improving the industrial deposition process, resulting in a thinner TCO layer with higher transmission by maintaining the sheet resistance of about 9-10 /sq. Combining both developments the integrated transmission of industrial TCO glass has been increased by more than 2%. The TCO layer properties of Asahi U-type and standard industrial TCO glass (AGC AN10) have been investigated by SEM, AFM, XRD and ARS, showing that the Asahi U TCO scatters red light more effectively into larger angles.

The Expert Opinion is written by a distinguished scientist and presents his personal view on important and relevant new results of research, highlighting their significance and putting the work into perspective for a broader audience. Please send comments to pss.rapid@wiley‐vch.de or to the author. The text by D. A. Drabold refers to the Rapid Research Letter by F. Kail et al., published in this issue of Phys. Status Solidi RRL 5 (10–11), 361–363 (2011). (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The structural relaxation of pure amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) materials, that occurs during thermal annealing experiments, has been analysed by Raman spectroscopy and differential scanning calorimetry. Unlike a-Si, the heat evolved from a-Si:H cannot be explained by relaxation of the Si-Si network strain, but it reveals a derelaxation of the bond angle strain. Since the state of relaxation after annealing is very similar for pure and hydrogenated materials, our results give strong experimental support to the predicted configurational gap between a-Si and crystalline silicon.

We study hydrogen stability and its evolution during thermal annealing in nanostructured amorphous silicon thin films. From the simultaneous measurement of heat and hydrogen desorption, we obtain the experimental evidence of molecular diffusion in these materials. In addition, we introduce a simple diffusion model which shows good agreement with the experimental data.

Hydrogen diffusion is a crucial step in film growth by chemical vapor deposition of both hydrogenated amorphous silicon (a-Si:H) and hydrogenated microcrystalline silicon (µ-Si:H) materials. To gain an insight into the correlation between hydrogen diffusion and the amorphous to microcrystalline transition, we have exposed freshly deposited intrinsic, boron- and phosphorus-doped a-Si:H thin films to hydrogen (or deuterium) plasma in conditions of µc-Si:H deposition by chemical transport. Using both in-situ and ex-situ characterizations techniques, we examined the kinetics of hydrogen excess evolution during the plasma exposure. Solution of the partial differential equation for the diffusion of mobile H atoms with a specific boundary condition that accounts for the reduction of atomic H flux with the growth of the µc-Si:H layer supports the theory that the out-diffusion is a consequence of the growth of the µc-Si:H layer.