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.     

Fe/Al2O3/Fe隧道结特性分析

用离子束溅射方法制备磁性隧道结(MTJ). 研究MTJ样品的隧道结磁电阻(TMR)效应.用X射线 光电子能谱分析了MTJ的软、硬磁层和非磁层及其界面的化学组成与微结构.研究了MTJ的微 结构对氧化铝势垒高度与有效宽度和TMR效应的影响. 关键词： 磁性隧道结 X射线光电子能谱 隧道结磁电阻     

Enhancement of photoluminescence intensity from Si nanodots using Al2O3 surface passivation layer grown by atomic layer deposition

Temperature-dependent photoluminescence (PL) from Si nanodots with Al₂O₃ surface passivation layers was studied. The Si nanodots were grown by low pressure chemical vapor deposition and the Al₂O₃ thin films were prepared by atomic layer deposition (ALD), respectively. The BOE (Buffer-Oxide-Etch) treatment resulted in the damaged surface of Si nanodots and thus caused dramatic reduction in the PL intensity. Significant enhancement of the PL intensity from Si nanodots after the deposition of Al₂O₃ thin films was observed over a wide temperature range, indicating the remarkable surface passivation effect to suppress the non-radiative recombination at the surface of Si nanodots. The results demonstrated that the Al₂O₃ surface passivation layers grown by ALD are effectually applicable to nanostructured silicon devices.     

磁性隧道结Ni80Fe20/Al2O3/Co的研究

用等离子体氧化形成中间绝缘层的方法可重复制备出具有隧道磁电阻（TMR)效应的Ni₈₀Fe₂₀/Al₂O₃/Co磁性隧道结.光透射谱等实验结果表明等离子体氧化能可控制地制备较致密的Al₂O₃绝缘层.样品的TMR比值在室温下最高可达6.0％,反转场可低于800A/m,相应的平台宽度约为2400A/m.结电阻R_j的变化范围从百欧到几百千欧,并且TMR比值随零磁场结偏压增大单调减小. 关键词：     

Al2O3绝缘层的AlGaN/GaN MOSHEMT器件研究

在研制AlGaN/GaN HEMT器件的基础上,采用ALD法制备了Al₂O₃ AlGaN/GaN MOSHEMT器件.通过X射线光电子能谱测试表明在AlGaN/GaN异质结材料上成功淀积了Al₂O₃薄膜.根据对HEMT和MOSHEMT器件肖特基电容、器件输出以及转移特性的测试进行分析发现：所制备的Al₂O₃薄膜与AlGaN外延层间界面态密度较小,因而MOSHEMT器件呈现出较 关键词： 2O₃')" href="#">Al₂O₃ ALD GaN MOSHEMT     

Investigation of the chemical state of ultrathin Hf-Al-O films during high temperature annealing

Al₂O₃ incorporated HfO₂ films grown by atomic layer deposition (ALD) were investigated by high-resolution X-ray photoelectron spectroscopy (HRXPS). The core level energy state of a 15 Å thick film showed a shift to higher binding energy, as the result of a silicate formation and Al₂O₃ incorporation. The incorporation of Al₂O₃ into the HfO₂ film had no effect on silicate formation at the interface between the film and Si, while the ionic bonding characteristics and hybridization effects were enhanced compared to a pure HfO₂ film. The dissociation of the film in an ultrahigh vacuum (UHV) is effectively suppressed compared to a pure HfO₂ film, indicating an enhanced thermal stability of Hf-Al-O. Any dissociated Al₂O₃ on the film surface was completely removed into the vacuum by vacuum annealing treatment over 850 °C, while HfO₂ contributed to Hf silicide formation on the film surface.     

Effects of substrate on surface morphology, crystallinity, and photoluminescence properties of sputtered ZnO nano films

Effects of substrate on crystallinity, surface morphology, and luminescence properties of radio frequency sputtered zinc oxide (ZnO) thin films were investigated. A variety of materials such as Si (100), Si (111), Al₂O₃, quartz, and silicon carbide (SiC) wafers were examined as substrates for deposition of ZnO thin films. The results showed smooth and uniform growth of c-axis orientation films. The thickness of the layers was about 50 nm. The average grain sizes of films were about 10, 13, and 12 nm for Si (111), quartz, and SiC samples, respectively. The deposited film on Al₂O₃ showed the largest grain size, about 500 nm. Grazing incidence x-ray diffraction patterns of the samples revealed that sputtered layers on Al₂O₃ and quartz had better crystallinity with higher peak at (002) orientation compared to Si and SiC substrates. Moreover, the Al₂O₃ sample exhibited a weak peak at position of (100) planes of ZnO too. The photoluminescence spectra of the samples showed a typical luminescence behavior with a broad UV band, including a main peak at around 388 nm and a weak shoulder peak at around 381 nm, corresponding with bound excitonic recombination and free excitonic recombination, respectively. The luminescence peak revealed that the intensity of UV emission is not necessarily dependent on the grain sizes and the micro-structural quality of ZnO films.     

Microstructure and dielectric properties of (Ba0.6Sr0.4)TiO3 thin films grown on super smooth glazed-Al2O3 ceramics substrate

Modified substrates with nanometer scale smooth surface were obtained via coating a layer of CaO-Al₂O₃-SiO₂ (CaAlSi) high temperature glaze with proper additives on the rough-95% Al₂O₃ ceramics substrates. (Ba_0.6Sr_0.4)TiO₃ (BST) thin films were deposited on modified Al₂O₃ substrates by radio-frequency magnetron sputtering. The microstructure, dielectric, and insulating properties of BST thin films grown on glazed-Al₂O₃ substrates were investigated by X-ray diffraction (XRD), atomic force microscope (AFM), and dielectric properties measurement. These results showed that microstructure and dielectric properties of BST thin films grown on glazed-Al₂O₃ substrates were almost consistent with that of BST thin films grown on LaAlO₃ (1 0 0) single-crystal substrates. Thus, the expensive single-crystal substrates may be substituted by extremely cheap glazed-Al₂O₃ substrates.     

Optimized emitter contacting on multicrystalline silicon thin film solar cells

We present an optimized contacting scheme for multicrystalline silicon thin film solar cells on glass based on epitaxially crystallized emitters with a thin Al₂O₃ layer and a silver back reflector. In a first step a 6.5 µm thick amorphous silicon absorber layer is crystallized by a diode laser. In a second step a thin silicon emitter layer is epitaxially crystallized by an excimer laser. The emitter is covered by an Al₂O₃ layer with a thickness ranging from 1.0 nm to 2.5 nm, which passivates the surface and acts as a tunnel barrier. On top of the Al₂O₃ layer a 90–100 nm thick silver back reflector is deposited. The Al₂O₃ layer was found to have an optimal thickness of 1.5 nm resulting in solar cells with back reflector that achieve a maximum open‐circuit voltage of 567 mV, a short‐circuit current density of 27.9 mA/cm², and an efficiency of 10.9%. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Chemical bath deposition of hausmannite Mn3O4 thin films

A low-temperature chemical bath deposition (CBD) technique has been used for the preparation of Mn₃O₄ thin films onto glass substrates. The kinetic behavior and the formation mechanism of the solid thin films from the aqueous solution have been investigated. Structure (X-ray diffraction and Raman), morphological (atom force microscope), and optical (UV-vis-NIR) characterizations of the deposited films are presented. The results indicated that the deposited Mn₃O₄ thin films of smooth surface with nanosized grains were well crystalline and the optical bandgap of the film was estimated to be 2.54 eV.     

Al2O3 thin films by plasma-enhanced chemical vapour deposition using trimethyl-amine alane (TMAA) as the Al precursor

2 O₃ thin films by plasma-enhanced chemical vapour deposition (PECVD) using trimethyl-amine alane (TMAA) as the Al precursor. The thin films were deposited on both Si and quartz silica (SiO₂) substrates. Deposition rates were typically 60 Å min^-1 keeping the TMAA temperature constant at 45 °C. The deposited Al₂O₃ thin films were stoichiometric alumina with low carbon contamination (0.7–1.3 At%). The refractive index ranged from 1.54 to 1.62 depending on the deposition conditions. The deposition rate was studied as a function of both the RF power and the substrate temperature. The structure and the surface of the deposited Al₂O₃ thin films were studied using X-ray diffraction, atomic force microscopy (AFM) and scanning electron microscopy (SEM). Received: 20 May 1997/Accepted: 12 June 1997     

Ionized physical vapor deposited Al2O3 films: Does subplantation favor formation of α‐Al2O3?

The broad energy distributions of the condensing particles typically encountered in ion assisted vapor deposition techniques are often a drawback when attempting to understand the effect of the energetic bombardment on the film properties. In the current study, a monoenergetic Al⁺ beam generated by a filtered cathodic arc discharge is employed for the deposition of alumina (Al₂O₃) films at well defined Al⁺ ion energies between 4 eV and 200 eV at a substrate temperature of 720 °C. Structural analysis shows that Al⁺ energies of 40 eV or larger favor the formation of the thermodynamically stable α‐Al₂O₃ phase at the expense of other metastable Al₂O₃ polymorphs. The well defined ion energies are used as input for Monte‐Carlo based simulations of the ion–surface interactions. The results of these simulations reveal that the increase of the Al⁺ ion energy leads to an increase in the fraction of ions subplanted into the growing film. These findings underline the previously not considered role of subsurface processes on the phase formation of ionized physical vapor deposited Al₂O₃ films. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and structure study of ordered arrays of ZnSe nanodots

A novel approach is presented for synthesis of ZnSe nanodot arrays by physical vapor deposition on porous aluminum oxide templates with ordered channels. The structure of nanodots was studied by scanning electron microscopy and EXAFS spectroscopy. Data were obtained for the sizes of nanodots in the array and local atomic structure parameters, i.e., the interatomic distances and coordination numbers, in comparison with the data for the ZnSe film synthesized on a smooth surface of nonporous Al₂O₃.     

The film thickness dependent thermal stability of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>:Ag thin films as high-temperature solar selective absorbers

The monolayer Al₂O₃:Ag thin films were prepared by magnetron sputtering. The microstructure and optical properties of thin film after annealing at 700 °C in air were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and spectrophotometer. It revealed that the particle shape, size, and distribution across the film were greatly changed before and after annealing. The surface plasmon resonance absorption and thermal stability of the film were found to be strongly dependent on the film thickness, which was believed to be associated with the evolution process of particle diffusion, agglomeration, and evaporation during annealing at high temperature. When the film thickness was smaller than 90 nm, the film SPR absorption can be attenuated until extinct with increasing annealing time due to the evaporation of Ag particles. While the film thickness was larger than 120 nm, the absorption can keep constant even after annealing for 64 h due to the agglomeration of Ag particles. On the base of film thickness results, the multilayer Al₂O₃:Ag solar selective thin films were prepared and the thermal stability test illustrated that the solar selectivity of multilayer films with absorbing layer thickness larger than 120 nm did not degrade after annealing at 500 °C for 70 h in air. It can be concluded that film thickness is an important factor to control the thermal stability of Al₂O₃:Ag thin films as high-temperature solar selective absorbers.     

First nucleation steps of vanadium oxide thin films studied by XPS inelastic peak shape analysis

The initial states of deposition of vanadium oxide thin films have been studied by analysis of the peak shape (both inelastic background and elastic contributions) of X-ray photoemission spectra (XPS) after successive deposition experiments. This study has permitted to assess the type of nucleation and growth mechanisms of the films. The experiments have been carried out in situ in the preparation chamber of a XPS spectrometer. Thin films of vanadium oxide have been prepared on Al₂O₃ and TiO₂ by means of thermal evaporation, ion beam assisted deposition and plasma enhanced chemical vapour deposition. The thin films prepared by the first two procedures consisted of V₂O₄, while those prepared by the latter had a V₂O₅ stoichiometry. The analysis of the inelastic background of the photoemission spectra has shown that the films prepared by thermal evaporation on Al₂O₃ are formed by big particles that only cover completely the surface of the substrate when their height reaches 16 nm. By contrast, the thin films prepared with assistance of ions on Al₂O₃ or with plasma on TiO₂ consist of smaller particles that succeed in covering the substrate surface already for a height of approximately 4 nm. Thin films prepared by plasma-assisted deposition on Al₂O₃ depict an intermediate situation where the substrate is completely covered when the particles have a height of approximately 6 nm. The type of substrates, differences in the deposition procedure or the activation of the adatoms by ion bombardment are some of the factors that are accounted for by to explain the different observed behaviours.     

Metal-Oxide Interfaces in Magnetic Tunnel Junctions

Metal-oxide interfaces play an important role in spintronics—a new area of microelectronics that exploits spin of electrons in addition to the traditional charge degree of freedom to enhance the performance of existing semiconductor devices. Magnetic tunnel junctions (MTJs) consisting of spin-polarized ferromagnetic electrodes sandwiching an insulating barrier are such promising candidates of spintronic devices. The paper reviews recent results of first-principle density-functional studies of the atomic and electronic structure of metal-oxide interfaces in Co/Al₂O₃/Co and Co/SrTiO₃/Co MTJs. The most stable interface structures, O-terminated for fcc Co (111)/-alumina(0001) and TiO₂-terminated with oxygens on top of Co atoms for fcc Co (001)/SrTiO₃(001) were identified based on energetics of metal-oxide cohesion at the interface. The covalent character of bonding for both the Co/alumina and Co/SrTiO₃ interface structures has been determined based on the pattern of electron distribution across the interface. The Al-terminated Co/alumina interface that corresponds to an under-oxidized MTJ exhibits a metallic character of bonding. The unusual charge transfer process coupled with exchange interactions of electrons in Co results in quenching of surface magnetism at the interface and substantial reduction of work of separation. The electronic structure of the O-terminated Co/Al₂O₃/Co MTJ exhibits negative spin polarization at the Fermi energy within the first few monolayers of alumina but it eventually becomes positive for distances beyond 10 Å. The Co/SrTiO₃/Co MTJ shows an exchange coupling between the interface Co and Ti atoms mediated by oxygen, which results in an antiparallely aligned induced magnetic moment on Ti atoms. This may lead to a negative spin polarization of tunneling across the SrTiO₃ barrier from the Co electrode. The results illustrate the important fact that spin-polarized tunneling in magnetic tunnel junctions is not determined entirely by bulk density of states of ferromagnet electrodes, but is also very sensitive to the nature of the insulating tunneling barrier, as well as the atomic structure and bonding at the ferromagnet/insulator interface.     

Enhanced water vapor barrier properties for biopolymer films by polyelectrolyte multilayer and atomic layer deposited Al2O3 double-coating

Commercial polylactide (PLA) films are coated with a thin (20 nm) non-toxic polyelectrolyte multilayer (PEM) film made from sodium alginate and chitosan and additionally with a 25-nm thick atomic layer deposited (ALD) Al₂O₃ layer. The double-coating of PEM + Al₂O₃ is found to significantly enhance the water vapor barrier properties of the PLA film. The improvement is essentially larger compared with the case the PLA film being just coated with an ALD-grown Al₂O₃ layer. The enhanced water vapor barrier characteristics of the PEM + Al₂O₃ double-coated PLA films are attributed to the increased hydrophobicity of the surface of these films.     

Preparation and characterization of ferroelectric SrBi2Ta2O9 thin films on Si using Al2O3 buffer layers

SrBi₂Ta₂O₉ (SBT) thin films were prepared on p-type Si(100) substrates with Al₂O₃ buffer layers. Both the SBT films and the Al₂O₃ buffer layers were deposited by a pulsed laser deposition technique using a KrF excimer laser. An Al prelayer was used to prevent Si surface oxidization in the initial growth stage. It is shown that Al₂O₃ buffer layers effectively prevented interdiffusion between SBT and Si substrates. Furthermore, the capacitance–voltage (C-V) characteristics of the SBT/Al₂O₃/Si heterostructures show a hysteresis loop with a clockwise trace, demonstrating the ferroelectric switching properties of SBT films and showing a memory window of 1.6 V at 1 MHz. Received: 17 July 2000 / Accepted: 16 August 2000 / Published online: 30 November 2000     

不同生长环境下砷化镓纳米颗粒的应变场模拟

对于埋嵌在薄膜材料中的纳米颗粒,在其生长过程中总是不可避免地伴随着应变场的产生,而这种应变场的分布能反映纳米颗粒的结构变化,纳米颗粒结构与它的物理性能有重要的关系.研究埋嵌在不同薄膜材料中的纳米颗粒生长过程中的应变场分布对于调控纳米颗粒的物理性能有着重要的意义.本文利用有限元算法分别计算了埋嵌在非晶氧化铝薄膜和非晶二氧化硅薄膜材料中的砷化镓纳米颗粒生长过程中的应变场分布.砷化镓纳米颗粒在以上两薄膜材料生长过程中都受到非均匀偏应变作用.对于埋嵌在氧化铝薄膜中的砷化镓纳米颗粒,其生长过程中,纳米颗粒内部受到的应变大于纳米颗粒表面受到的应变;而对于埋嵌在二氧化硅薄膜中的砷化镓纳米颗粒,纳米颗粒内部受到的应变小于纳米颗粒表面受到的应变.选择砷化镓纳米颗粒生长的薄膜材料可以调控纳米颗粒生长过程中的应变场分布,从而进一步调控纳米颗粒的晶格结构和形貌及其物理性能.     

Optical simulation, optimized design and fabrication of (ZrO2)x-(Al2O3)1−x composite films with thin inserted TiO2 layers for ArF-line high transmission attenuated phase shift mask blank applications

The tunable optical constants of the stoichiometric (ZrO₂)_x-(Al₂O₃)_1−x composite films with thin inserted TiO₂ layers are simulated as π-phase shifters. The optimized composition range of the superlattices to be used as a high transmission attenuated phase shift mask (HT-APSM) blank is found. The absorption edge shifts to the longer wavelengths when the thickness fraction of the TiO₂ layer increases. The optimized film for ArF-line HT-APSM blank applications must have the lower inspection transmittance for the better inspection and the lower reflectance at the exposure wavelength for a better aerial image as π-phase shifters, and they will be easier to fabricate than a superlattice. In order to find such a film, (ZrO₂)_x-(Al₂O₃)_1−x composite films with various inserted TiO₂ layers are simulated. The optimal deposition processes of such a film are also determined. For example, a (ZrO₂)_0.187-(Al₂O₃)_0.813 composite film with two inserted TiO₂ thin layers is fabricated. The optical properties are as follows: a transmittance of 19.8%, a reflectance of 9.1%, a calculated phase shift of ∼181.5° at the exposure wavelength of 193 nm, and a transmittance of 18.9% at the inspection wavelength of 257 nm. Such a film should be used as an optimized HT-APSM blank.