Silicon solar cells with Al2O3 antireflection coating

The paper presents the possibility of using Al₂O₃ antireflection coatings deposited by atomic layer deposition ALD. The ALD method is based on alternate pulsing of the precursor gases and vapors onto the substrate surface and then chemisorption or surface reaction of the precursors. The reactor is purged with an inert gas between the precursor pulses. The Al₂O₃ thin film in structure of the finished solar cells can play the role of both antireflection and passivation layer which will simplify the process. For this research 50×50 mm monocrystalline silicon solar cells with one bus bar have been used. The metallic contacts were prepared by screen printing method and Al₂O₃ antireflection coating by ALD method. Results and their analysis allow to conclude that the Al₂O₃ antireflection coating deposited by ALD has a significant impact on the optoelectronic properties of the silicon solar cell. For about 80 nm of Al₂O₃ the best results were obtained in the wavelength range of 400 to 800 nm reducing the reflection to less than 1%. The difference in the solar cells efficiency between with and without antireflection coating was 5.28%. The LBIC scan measurements may indicate a positive influence of the thin film Al₂O₃ on the bulk passivation of the silicon.     

Ab initio calculations of electric field gradients detected by impurities in TiO2, Al2O3 and CaCO3

We present ab initio calculations of electric field gradients (EFGs) at impurity sites in ionic crystals TiO₂, Al₂O₃ and CaCO₃. The electronic structure was calculated self-consistently by the KKR method in the framework of the local spin density approximation of the density functional theory. The system with a single impurity was simulated by the super cell method. It was found that EFGs for the transition metal impurities (Sc, Nb, Cd and Ta) in TiO₂ were well reproduced by the calculations if the charge state of them in TiO₂ was taken into account. The present method was applied to the determination of the implantation sites of N and O nuclei in TiO₂. The calculation of EFGs at a Si impurity in Al₂O₃ and at Ca site in CaCO₃ were used to derive the quadrupole moments of ²⁷Si and ³⁹Ca from their quadrupole coupling constants. This revised version was published online in August 2006 with corrections to the Cover Date.     

Al2O3单晶三明治结构的高温热激发电流

以Al2O3单晶和具有三明治结构的Al2O3单晶-Bi2O3-Al2O3单晶试样为研究对象,测量了在室温到750 ℃之间升温过程和降温过程中这两种试样的热激发电流,仅在三明治结构试样中检测到了热激发电流.随测量过程中升温速率的增大,降温过程中的热激发电流逐渐减小.认为热激发电流是由缺陷离子的扩散所引起,通过扩散活化能的计算发现有两种缺陷参与了热激发电流的形成.     

Dielectric loaded surface plasmon polariton properties of the Al_2O_3–Al nanostructure

Surface plasmons(SPs) in ultraviolet(UV) have attracted a great deal of attention because of their emerging applications in energy resources, environmental protection, and biotechnology. In this article, the dielectric loaded surface plasmon polariton(DLSPP) properties of the Al_2O_3–Al nanostructure are investigated theoretically. Sharp SP responses can be obtained in deep UV by setting an insulator grating on the aluminum film. It is found that the height of the grating element,the lattice parameter, and the filling factor can all modulate the DLSPPs of the Al_2O_3–Al nanostructure. We further find that this structure is sensitive to the embedding medium and can serve as a refractive index sensor in the UV region. The corresponding sensitivity increases with the decrease of the filling factor. The Al_2O_3–Al nanostructure may be useful for medical diagnostics and biotechnology in deep UV.     

Equilibrium faceting formation in vicinal Al2O3 (0001) surface caused by annealing

We report on a heat-induced transformation of the surface of α-alumina (0001) crystals which have an off-cut in the [1$\overline{2}$10] direction. Annealing the crystal causes the surface to transform into a regular array of (0001) and (1$\overline{2}$16) facets. The resultant faceted morphology represents the equilibrium state of the system. It is demonstrated that the average terrace periodicity is determined by the annealing temperature. Possible causes for the surface rearrangement are also discussed. This method could be used for producing templates with controlled periodicity for growth of nanostructure arrays.     

Polarization effects in thin layers of SiO2 and Al2O3

For film metal-dielectric-metal and hybrid-metal-dielectric-semiconductor systems based on pyrolytic fully grown films of SiO₂ and Al₂O₃ the dependence of the remanent polarization coefficient on the magnitude of the field in the films and the short circuit time was investigated. The nature of relaxation processes related to remanent polarization effects was analyzed.The authors take the opportunity to express their gratitude to A. S. Bashakidze for help in carrying out the measurements.     

Dispersion behavior and thermal conductivity characteristics of Al2O3–H2O nanofluids

Nanofluid is a kind of new engineering material consisting of solid nanoparticles with sizes typically of 1–100 nm suspended in base fluids. In this study, Al₂O₃–H₂O nanofluids were synthesized, their dispersion behaviors and thermal conductivity in water were investigated under different pH values and different sodium dodecylbenzenesulfonate (SDBS) concentration. The sedimentation kinetics was determined by examining the absorbency of particle in solution. The zeta potential and particle size of the particles were measured and the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to calculate attractive and repulsive potentials. The thermal conductivity was measured by a hot disk thermal constants analyser. The results showed that the stability and thermal conductivity enhancements of Al₂O₃–H₂O nanofluids are highly dependent on pH values and different SDBS dispersant concentration of nano-suspensions, with an optimal pH value and SDBS concentration for the best dispersion behavior and the highest thermal conductivity. The absolute value of zeta potential and the absorbency of nano-Al₂O₃ suspensions with SDBS dispersant are higher at pH 8.0. The calculated DLVO interparticle interaction potentials verified the experimental results of the pH effect on the stability behavior. The Al₂O₃–H₂O nanofluids with an ounce of Al₂O₃ have noticeably higher thermal conductivity than the base fluid without nanoparticles, for Al₂O₃ nanoparticles at a weight fraction of 0.0015 (0.15 wt%), thermal conductivity was enhanced by up to 10.1%.     

Two-photon imaging to a depth of 1000 microm in living brains by use of a Ti:Al2O3 regenerative amplifier

It is shown that two-photon fluorescence images can be obtained throughout almost the entire gray matter of the mouse neocortex by using optically amplified femtosecond pulses. The achieved imaging depth approaches the theoretical limit set by excitation of out-of-focus fluorescence.     

A study of lattice defects in solids belonging to Al2O3−B2O3 and Al2O3−SiO2 systems by thermoluminescence experiments

Summary Spectrally resolved thermoluminescent emission has been investigated in solids belonging to Al₂O₃−B₂O₃ and Al₂O₃−SiO₂ systems. These solids, which are characterized by a structure like that of alumino-silicate mullite, contain a high density of oxygen and aluminum or boron lacunae. This fact favours the occurrence of both-sign interstitial ions acting as carrier traps. The results show a close similarity with those obtained when studying, with the same experimental method, the thermoluminescent emission of alumina. The overall analysis of data allows for reliable conclusions on the nature of crystal defects in these materials.     

Silicon surface passivation by atomic‐layer‐deposited Al2O3 facilitated in situ by the combination of H2O and O3 as reactants

We investigate the effect of O₃ and H₂O oxidant pre‐pulse prior to Al₂O₃ atomic layer deposition for Si surface passivation. Interfacial oxide SiO_x formed by the O₃ pre‐pulse is more beneficial than that by H₂O to a high level of surface passivation. The passivation of thinner H₂O–Al₂O₃ films is more improved by this O₃ pre‐pulse. O₃ pre‐pulse for 10 nm H₂O–Al₂O₃ reduces saturation current density in boron emitter to 18 fA cm^–2 by a factor of 1.7. Capacitance–voltage measurements reveal this interfacial oxide plays a role of decreasing interface trap density without detrimental effect to negative charge density of Al₂O₃. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

冲击压缩下蓝宝石光学性质的晶向效应

本文基于第一性原理计算方法,研究了a向、c向和r向蓝宝石理想晶体和含氧离子空位点缺陷晶体在0-180 GPa冲击压力范围内的光学性质.波长在1550 nm处理想晶体的折射率数据表明,在蓝宝石Corundum、Rh2O3以及CalrO_3相区,其折射率分别表现出强、弱以及强的晶向效应.波长在0-250 nm范围内理想晶体的能量损失谱结果指明,在Corundum和Rh_2O_3结构相区,其晶向效应不明显;在CalrO_3结构相,主峰附近的波段范围内,蓝宝石的能量损失谱有一定的晶向效应:c和r向的主峰强度基本相同,但a向主峰强度明显高于c和r向主峰强度.缺陷晶体数据表明:氧离子空位点缺陷对蓝宝石折射率和能量损失谱晶向效应的影响较微弱.     

Buffer effects of titanium in the case of silver / a - Al 2 O 3(0001)

The influence of thin titanium layers on the growth of silver clusters on - Al ₂ O ₃ (0001) is investigated. We demonstrate through in situ RHEED measurements that titanium can relax stress in a growth mode where two lattice parameters show up simultaneously. Above a certain thickness, the lattice parameter closest to the bulk value of titanium dominates. Depending on the amount of stress in the titanium layer, silver films can either develop 3D textures or grow in epitaxy and form 2D like films.     

The chemisorption of H2O,HCOOH and CH3COOH on thin amorphous films of Al2O3

Inelastic electron tunneling spectroscopy (IETS) has been used to probe the irreversible chemisorption of H₂O, HCOOH, and CH₃COOH on a thin amorphous film of Al₂O₃. The “clean” Al₂O₃ film was also probed in a similar way. The measurement involves examining the second derivative of the I–V curve for electrons tunneling between the metal electrodes in an AlAl₂O₃Pb junction. When chemisorbed species are present on the Al₂O₃, the second derivative measurement is a representation of vibronic excitations of the chemical bonds in the adspecies, i.e. the tunneling spectra are analogous to IR spectra. A “clean” Al₂O₃ surface is found to possess free OH groups essentially equivalent to a surface exposed to large concentrations of H₂O. Saturation coverages of HCOOH and CH₃COOH yield similar spectra to each other, as expected. However, chemical shifts as well as variations in intensity among the equivalent bonds in the adsorbed HCOOH and CH₃COOH are noted. Tentative assignments are given for the observed peaks, and it is concluded that the acids adsorb as formate and acetate ions on the surface. Tunneling spectra for several submonolayer coverages of HCOOH (θ = 0.03, 0.08, 0.3 and 0.4) have been measured in addition to the spectrum corresponding to saturation coverage. Small shifts in certain vibronic transitions as a function of surface coverage have been noted. The shifts in the peak positions are related to variations in adsorbate-adsorbent and adsorbate-adsorbate interactions, and the variations in relative peak intensity are associated with the orientation of the adsorbed molecules. The kinetics of the chemisorption of HCOOH, i.e. the sticking probability as a function of surface coverage, has also been determined for surface coverages between 0.03 and 0.4 monolayer.     

ICP-AES同时测定铬质引流剂中的Cr2O3、Al2O3、Fe2O3和MgO

探讨了电感耦合等离子体-原子发射光谱法(ICP-AES)测定铬质引流剂中Cr2O3、Al2O3、Fe2O3和MgO的分析条件.试样经过氧化钠熔融分解,盐酸酸化,采用内标加入法,利用ICP光谱仪于所推荐的波长处,测量溶液中铬、铝、铁、镁元素对钇内标元素的相对强度,根据标准溶液绘制的校准曲线计算出待测元素氧化物的质量分数.对该方法进行精密度试验,相对标准偏差(RSD,n=8)均小于1.0％,本测试方法简单、快速、精度高,将该方法用于铬质引流剂中Cr2O3、Al2O3、Fe2O3和MgO含量的测定,取得满意效果.     

The effect of supports (Al2O3, Al2O3-CeO2 and Al2O3-CeZrO2) on the nature of gold-species in supported gold catalysts

This work is concerned with the study of Au specimens produced by gold deposition on nanosized mixed oxides (alumina, ceria, zirconia) prepared by the sol-gel method using organometallic precursors. According to X-ray absorption near edge structure, extended X-ray absorption fine structure, transmission electron microscopy data, and ultraviolet-visible and X-ray photoelectron spectroscopy measurements, mixed Al-Ce-Zr oxides are quite effective for stabilization of different gold specimens. The samples pre- treated in hydrogen at 150°C are characterized by the presence of gold Au³⁺ cations located on the surface in slightly disordered octahedral oxygen coordination. Metallic gold nanoparticles with a size of about 2 nm and gold clusters were found in the samples treated in hydrogen at 300°C.