Charge-trapping characteristics of Al2O3/Cu/Al2O3 nanolaminate structures prepared through atomic layer deposition

The nanolaminate Al2O3/Cu/Al2O3 structures were constructed on p-type Si (001) substrates using atomic layer deposition (ALD) process with the aim to fabricating nonvolatile charge-trap memories. Low temperature Cu thin layers were deposited through plasma-enhanced atomic layre depositon of Cu aminoalkoxide (Cu(dmamb)2) combined with hydrogen plasma and Al2O3 layers were prepared by thermal atomic layer deposition of trimethylaluminum (TMA) combined with H2O. Nonvolatile features were confirmed using capacitance-voltage (C-V) measurements. The copper film functions as a charge-trapping layer and the Al2O3 thin layers were employed as tunneling and control oxide layers. Line shapes and binding energies of Cu metal and the thin layer of 6 nm Cu in nanolaminate structures were observed in the X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (TEM) image. The V(FB) shift width of the Al2O3 (28 nm)/Cu (6 nm)/Al2O3 (4.2 nm)/Si laminate structure is found to be 4.75 V in voltage sweeping between -10 and +10 V, leading to the trap density of 1.68 x 10(18) cm(-3).     

AZ91D镁合金在NaHCO_3薄液膜下的腐蚀行为

镁合金大气腐蚀的研究十分重要,而目前有关侵蚀性离子HCO_3~-在薄液膜下对镁合金腐蚀行为的研究报道较少。通过阴极极化曲线和电化学阻抗谱研究了AZ91D镁合金在NaHCO_3薄液膜下的腐蚀行为,详细讨论了液膜厚度、NaHCO_3浓度和时间等参数的影响,并用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)进行了表征。结果表明:随着液膜厚度的降低,阴极和阳极过程均受到限制,AZ91D镁合金腐蚀速率变小;NaHCO_3浓度增加会加剧AZ91D在薄液膜下的腐蚀;浸泡24.0 h后,本体溶液中腐蚀表现为均匀腐蚀,主要腐蚀产物为MgCO_3和Al_2O_3,而薄液膜下则表现为局部腐蚀,主要腐蚀产物为MgCO_3,Al_2O_3,MgCO_3·2H_2O和Mg_5(CO_3)_4(OH)_2·5H_2O。     

Quantitative SIMS Tiefenprofil Analyse

Quantitative secondary ion mass spectrometry (SIMS) Today, thin surface coatings have become an integral construction element in mechanical engineering, optics, electronics, automotive, etc.. The layer thicknesses range from a few nanometers, e.g. in optical filters or low‐E coating systems, via micrometerrange coatings for friction and wear reduction, to thick galvanic coatings or spray coatings of up to 100 microns thickness or more. Crucial for the development and application of such layers is the availability of analytical methods, which are capable of characterizing e.g. chemical composition of layers with high lateral and depth resolution. Only with knowledge of the internal composition coating systems can be systematically optimized and errors in coating processes can be identified. Quantitative SIMS depth profile analysis is a method that can determine the chemical composition of single or multi‐layer systems with a depth resolution in the nanometer range, making it an indispensable tool in the coating and surface technology. This article explains the technical basics of secondary ion mass spectrometry (SIMS) and shows several practical examples from industry.     

Al2O3 and TiO2 atomic layer deposition on copper for water corrosion resistance

Al(2)O(3) and TiO(2) atomic layer deposition (ALD) were employed to develop an ultrathin barrier film on copper to prevent water corrosion. The strategy was to utilize Al(2)O(3) ALD as a pinhole-free barrier and to protect the Al(2)O(3) ALD using TiO(2) ALD. An initial set of experiments was performed at 177 °C to establish that Al(2)O(3) ALD could nucleate on copper and produce a high-quality Al(2)O(3) film. In situ quartz crystal microbalance (QCM) measurements verified that Al(2)O(3) ALD nucleated and grew efficiently on copper-plated quartz crystals at 177 °C using trimethylaluminum (TMA) and water as the reactants. An electroplating technique also established that the Al(2)O(3) ALD films had a low defect density. A second set of experiments was performed for ALD at 120 °C to study the ability of ALD films to prevent copper corrosion. These experiments revealed that an Al(2)O(3) ALD film alone was insufficient to prevent copper corrosion because of the dissolution of the Al(2)O(3) film in water. Subsequently, TiO(2) ALD was explored on copper at 120 °C using TiCl(4) and water as the reactants. The resulting TiO(2) films also did not prevent the water corrosion of copper. Fortunately, Al(2)O(3) films with a TiO(2) capping layer were much more resilient to dissolution in water and prevented the water corrosion of copper. Optical microscopy images revealed that TiO(2) capping layers as thin as 200 ? on Al(2)O(3) adhesion layers could prevent copper corrosion in water at 90 °C for ~80 days. In contrast, the copper corroded almost immediately in water at 90 °C for Al(2)O(3) and ZnO films by themselves on copper. Ellipsometer measurements revealed that Al(2)O(3) films with a thickness of ~200 ? and ZnO films with a thickness of ~250 ? dissolved in water at 90 °C in ~10 days. In contrast, the ellipsometer measurements confirmed that the TiO(2) capping layers with thicknesses of ~200 ? on the Al(2)O(3) adhesion layers protected the copper for ~80 days in water at 90 °C. The TiO(2) ALD coatings were also hydrophilic and facilitated H(2)O wetting to copper wire mesh substrates.     

EPMA‐Analyse dünner PVD‐ und CVD‐Schichten

EPMA analysis of thin PVD and CVD layers Electron Probe Micro Analysis (EPMA) is an X‐ray spectroscopic method for determining the chemical composition of solid substances in the near‐surface region. It has a high detection sensitivity, a high spatial resolution, an adjustable depth of analysis and is easy and accurate to quantify. Less well known is the fact that the EPMA is also able to analyze the chemical composition and layer thicknesses of thin multi‐layer systems non‐destructively and with only one single measurement. In particular, it is possible to determine, for example, the composition and thickness of a layer buried under one or more other layers. Conversely, with a known film thickness, the density of thin layers can be determined, a quantity that is generally difficult to access with thin layers. The following article describes the physical basics of EPMA analysis and compares them with energy dispersive X‐ray spectroscopy (EDX) and X‐ray fluorescence analysis (XRF), which are also widely used. The principle of so‐called thin film analysis for multilayer systems is explained, and the possibilities and limitations of this method are illustrated by a number of industrial application examples.     

以Al2O3为过渡层脉冲激光法制备PZT铁电薄膜

为实现PZT铁电薄膜与半导体衬底的直接集成引入Al2O3为过渡层，首先用真空电子束蒸发法在Si(100)，多昌金刚石（111）衬底上生长约20nm厚的Al2O3过渡层，接着在上述衬底上采用脉冲激光淀积（PLD）法淀积PZT薄膜，衬底温度为350-550℃。X光电子能谱（XPS）测试表明，在高真空下，电子束蒸发Al2O3固态源能获得化学配比接近蒸发源的Al2O3薄膜。X射线衍射（XRD）测试说明，不论衬底是硅还是多晶金刚石，当衬底温度为550℃时，PZT在Al2O3过渡层上呈现（222）取向的焦绿石相结构，当衬底是金刚石时，通过如下工艺：（1）较低温度（350℃）淀积；（2）空气氛围650℃快速退火5min，可以在Al2O3过渡层上获得高度（101）取向的钙钛矿结构的铁电相PZT薄膜，最后AFM测试显示，在硅衬底上，PZT薄膜的表面均方根粗糙度为9.78nm；而在多晶金刚石衬底上，PZT薄膜的表面均方根粗糙度为17.2nm。     

Effect of Ta nanobarrier in magnetron sputtering of Nd-doped SrBi2Ta2O9 thin films

SrBi2Ta2O9 (SBT) is a bismuth layered perovskite with attractive ferroelectric properties for random access memory applications. Our previous studies showed that Nd-doped SBT (SNBT) thin films exhibited an improved remnant polarization and reduced coercivity. This paper concentrates on the effect of Ta nanobarrier in between the SNBT and the Pt layers. Without the nanobarrier, severe bismuth diffusion is revealed by the secondary ion mass spectroscopy. However, with a nano layer (up to 2 nm) of Ta metal, the interfacial diffusion is effectively suppressed even at 800 degrees C. Details of the composition profiling, film crystallinity and remnant polarization are discussed in view of the nanobarrier thickness.     

Ti/Al2O3 Functionally Gradient Material Prepared by the Explosive Compaction/SHS Process

1.IntroductionDistinctinterfacesoccurincompositesorasare-sultofthefabricationprocessasincoatingandbond-ing.Thepresenceofadistinctillterfacecanleadtoproblemsduringfabricationorserviceuse.Forexam-ple,delaminationorcrackingalongabondinglayerformetal-ceramiccompositemayoccurasaresultofmechanicalstressesorthermalstressesthataredevelopedfromthedifferenceinthermalexpansionbetweenmaterialsifthebondinglayerissubjectedtotemperaturevariation[1].Therecentdevelopmentintheprocessingoffunctionallygradientmat…     

Resistance Random Access Memory Based on a Thin Film of CdS Nanocrystals Prepared via Colloidal Synthesis

We demonstrate that resistance random access memory (RRAM) can be fabricated based on CdS-nanocrystal thin films. A simple drop-drying of the CdS-nanocrystal solution leads to the formation of uniform thin films with controlled thickness. RRAMs with a Ag/Al(2) O(3) /CdS/Pt structure show bipolar switching behavior, with average values of the set voltage (V(Set) ) and reset voltage (V(Reset) ) of 0.15 V and -0.19 V, respectively. The RRAM characteristics are critically influenced by the thickness of the Al(2) O(3) barrier layer, which prevents significant migration of Ag into the CdS layer as revealed by Auger electron spectroscopy (AES). Interestingly, RRAM without an Al(2) O(3) layer (i.e., Ag/CdS/Pt structure) also shows bipolar switching behavior, but the polarity is opposite to that of RRAM with the Al(2) O(3) layer (i.e., Ag/Al(2) O(3) /CdS/Pt structure). The operation of both kinds of devices can be explained by the conventional conductive bridging mechanism. Additionally, we fabricated RRAM devices on Kapton film for potential applications in flexible electronics, and the performance of this RRAM device was comparable to that of RRAMs fabricated on hard silicon substrates. Our results show a new possibility of using chalcogenide nanocrystals for RRAM applications.     

Magnetic Sector ICPMS with Desolvating Micronebulization: Interference-Free Subpicogram Determination of Rare Earth Elements in Natural Samples

A new method has been developed combining desolvating micronebulization with magnetic sector inductively coupled plasma mass spectrometry (ICPMS) for the analysis of all 14 stable rare earth elements (REEs) in small samples of marine particulate matter. Application is demonstrated for REEs in suspended particles from a deep ocean hydrothermal vent plume and a geological reference material. A 100-fold reduction in oxide formation, relative to standard nebulizer-spray chamber sample introduction, makes oxide interference correction negligible, even for samples that are very enriched in Ba and light REEs. Enriched isotopes for one light and one heavy REE ((145)Nd and (171)Yb) are used as both isotope dilution and internal standards, providing determination of all the REEs in one analysis. This standardization scheme eliminates the need for multimass drift correction used previously to achieve acceptable accuracy with external standardization techniques. Instead, the method exploits capabilities for accurate and precise determination of isotope ratios, a principal strength of ICPMS, and the mass-independent sensitivity of electric field scans on our double-focusing instrument. We demonstrate overall precision of ≤2% (1σ) and accuracy better than 6% for all the REEs (except Er = 8.7%), based on comparison to recommended values for USGS certified reference material BHVO-1 (basalt). This performance is similar to that obtained by full isotope dilution mass spectrometric techniques, but the new method is far simpler, requires 5 min sample(-)(1), and avoids interferences introduced by complex mixtures of enriched isotopes. Sensitivity of (1.2-1.4) × 10(6) counts s(-)(1) ppb(-)(1) and background intensities of 2-60 counts s(-)(1) provide excellent detection limits of 1-40 ppq, a 100-fold improvement on established ICPMS methods. The low sample introduction rate (100 μL min(-)(1)) allows unprecedented absolute detection limits of 1-20 fg.     

Atomic layer deposition of Al(2)O(3) and ZnO at atmospheric pressure in a flow tube reactor

Improving nanoscale thin film deposition techniques such as atomic layer deposition (ALD) to permit operation at ambient pressure is important for high-throughput roll-to-roll processing of emerging flexible substrates, including polymer sheets and textiles. We present and investigate a novel reactor design for inorganic materials growth by ALD at atmospheric pressure. The reactor uses a custom "pressure boost" approach for delivery of low vapor pressure ALD precursors that controls precursor dose independent of reactor pressure. Analysis of continuum gas flow in the reactor shows key relations among reactor pressure, inert gas flow rate, and species diffusion that define conditions needed to efficiently remove product and adsorbed reactive species from the substrate surface during the inert gas purge cycle. Experimental results, including in situ quartz crystal microbalance (QCM) characterization and film thickness measurements for deposition of ZnO and Al(2)O(3) are presented and analyzed as a function of pressure and gas flow rates at 100 °C. At atmospheric pressure and high gas flow, ZnO deposition can proceed at the same mass uptake and growth rate as observed during more typical low pressure ALD. However, under the same high pressure and flow conditions the mass uptake and growth rate for Al(2)O(3) is a factor of ～1.5-2 larger than at low pressure. Under these conditions, Al(2)O(3) growth at atmospheric pressure in a "flow-through" geometry on complex high surface area textile materials is sufficiently uniform to yield functional uniform coatings.     

Electrochemical fabrication of nanodimensional multilayer films

A novel method of fabricating nanodimensional multilayer films using electrochemistry is described. A thin layer of tantalum (Ta) is sputtered on a smooth insulating substrate. Ta is partially electrochemically oxidized (anodized) forming a Ta(2)O(5) layer. The rate of Ta consumption, the rate of Ta(2)O(5) expansion, and the dependence of Ta(2)O(5) thickness on anodization conditions have been carefully characterized to enable accurate predictions of the resulting thicknesses of both layers. Due to strong planarization action of the anodization process, the resulting interfaces Ta/Ta(2)O(5) and Ta(2)O(5)/electrolyte are remarkably smooth. The next layer of Ta is deposited on top of Ta(2)O(5), and the process is repeated as many times as needed. The Ta(2)O(5) layers are amorphous and pinhole free. We report fabrication of 10-layer structures with pitches ranging from 200 nm down to 12 nm and with excellent uniformity between the layers. The smallest achieved thickness of Ta layers is only 2.8 +/- 0.1 nm. The edges of such films, after proper polishing and etching, could serve as templates in nanoimprint lithography and in other applications.     

高温含水气氛对Pt改性NiCoCrAlY合金氧化行为的影响

为了研究Pt改性NiCoCrAlY合金在高温含水气氛中的高温抗氧化行为,进一步理解高温含水气氛对Pt改性涂层表面形貌以及产物的影响,采用电镀方式在NiCoCrAlY合金表层制备了一层1.5μm厚的Pt层,然后对涂层进行热处理。对Pt改性NiCoCrAlY涂层在1 050℃的空气和含水气氛下的高温氧化行为进行对比研究。采用扫描电镜(SEM)观察表面形貌,采用X射线衍射仪(XRD)、能谱(EDS)分析了涂层的相结构及成分。结果表明:在含水气氛下,Pt改性合金表面生成针状Al_2O_3,基体不同相β-NiAl与γ'-Ni_3Al在含水气氛中表现出不同的Al_2O_3生长速率,从而导致氧化层中生长应力的堆积,导致氧化层的剥落。     

The use of nanoscaled Al mid-layer for enhancing the electrical conductivity of ZnO

A nanoscaled Al thin film was placed between two ZnO thin films to form a ZnO/Al/ZnO multilayer thin film structure. Individual Al and ZnO thin films with difference thicknesses were first prepared and characterized for the optical and electrical properties. The multilayer structure was then obtained by depositing individual layers with desired thicknesses in sequence. We show that by appropriate selections of layer thickness, the use of a nanoscaled Al mid-layer in ZnO enhances the electrical conductivity of the ZnO without scarifying its optical transmittance.     

Biocompatible Nb2O5 thin films prepared by means of the sol–gel process

Thin biocompatible oxide films with an optimised composition and structure on the surface of titanium and its alloys can improve the implant integration. The preparation of these thin oxide layers with the intended improvement of the surface properties can be realised by means of the sol-gel process. Nb2O5 is a promising coating material for this application because of its extremely high corrosion resistance and thermodynamic stability. In this study, thin Nb2O5 layers ( < 200 nm) were prepared by spin coating of polished discs of cp-titanium with a sol consisting of a mixture of niobium ethoxide, butanol and acetylacetone. The thickness, phase composition, corrosion resistance and the wettability of the oxide layers were determined after an optimisation of the processing parameters for deposition of oxide without any organic impurities. The purity of the oxide layer is an important aspect in order to avoid a negative response to the cell adhesion. The biocompatibility of the oxide layers which was investigated by in vitro tests (morphology, proliferation rate, WST-1, cell spreading) is improved as compared to uncoated and TiO2 sol-gel coated cp-titanium concerning the spreading of cells, collagen I synthesis and wettability.     

溅射Ni11Co26Cr6Al0.5Y涂层对镍基合金在1000 ℃氧化行为的影响

通过对有/无Ni11Co26Cr6Al0.5Y涂层镍基合金在1000℃进行氧化动力学曲线测定,及组织结构观察,研究了Ni11Co26Cr6Al0.5Y涂层对镍基合金高温氧化行为的影响。结果表明:高温氧化期间,合金发生外氧化和内氧化,外氧化层由NiO、NiCrO_4、CoWO_4构成,中间氧化物由TiO_2、Al_2O_3、NiWO_4构成,中间层氧化物层抑制了基体中Al元素向外扩散,形成平直连续的Al_2O_3内氧化物层;合金氧化动力学曲线呈现起伏波动的特征。镍基合金经溅射Ni11Co26Cr6Al0.5Y涂层,可有效改善合金的抗氧化性能;涂层的氧化动力学曲线仅在氧化初期有轻微增重而后趋于平稳,遵循抛物线规律,其形成的Al_2O_3氧化膜未发生明显剥落,仅在涂层内及近涂层/基体界面区域存在少量Al_2O_3内氧化物。     

Ion beam synthesis of aluminium nitride: characterisation of thin AIN layers formed in microelectronics aluminium

Abstract

Buried AlN thin layers have been formed by high dose N⁺ ion implantation into microelectronics grade Al films (containing 1 at.-%Si), which were deposited on Si wafers. The structures obtained have been characterised by spreading resistance measurements, transmission electron microscopy, secondary ion mass spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. The results show the formation of buried dielectric precipitates of crystalline AlN at implantation doses below the threshold and a continuous polycrystalline AlN layer at doses above the threshold. The AlN grains have the wurtzite structure, sizes of about 10–15 nm, and a preferred orientation in relation to the Al matrix, namely, <110>_AIN parallel to <110>_Al. The data also show that, under certain conditions, the main impurities (Si and O) are gettered in the buried layer. Moreover, for thin Al films, the formation of a Si rich surface layer is observed. This surface layer is formed by Si diffusion from the substrate, probably due to the penetration of N⁺ ions into the Si substrate. The distribution and evolution of these impurities and the different phases formed are studied as a function of the thickness and grain size of the Al film, as well as of the annealing processes.

MST/3304     

In situ transmission electron microscopy observation of pulverization of aluminum nanowires and evolution of the thin surface Al2O3 layers during lithiation-delithiation cycles

Lithiation-delithiation cycles of individual aluminum nanowires (NWs) with naturally oxidized Al(2)O(3) surface layers (thickness 4-5 nm) were conducted in situ in a transmission electron microscope. Surprisingly, the lithiation was always initiated from the surface Al(2)O(3) layer, forming a stable Li-Al-O glass tube with a thickness of about 6-10 nm wrapping around the NW core. After lithiation of the surface Al(2)O(3) layer, lithiation of the inner Al core took place, which converted the single crystal Al to a polycrystalline LiAl alloy, with a volume expansion of about 100%. The Li-Al-O glass tube survived the 100% volume expansion, by enlarging through elastic and plastic deformation, acting as a solid electrolyte with exceptional mechanical robustness and ion conduction. Voids were formed in the Al NWs during the initial delithiation step and grew continuously with each subsequent delithiation, leading to pulverization of the Al NWs to isolated nanoparticles confined inside the Li-Al-O tube. There was a corresponding loss of capacity with each delithiation step when arrays of NWs were galvonostatically cycled. The results provide important insight into the degradation mechanism of lithium-alloy electrodes and into recent reports about the performance improvement of lithium ion batteries by atomic layer deposition of Al(2)O(3) onto the active materials or electrodes.     

Optimization of ALD-(Zn,Mg)O buffer layers and (Zn,Mg)O/Cu(In,Ga)Se2 interfaces for thin film solar cells

(Zn,Mg)O films, fabricated by atomic layer deposition, ALD, are investigated as buffer layers in Cu(In,Ga)Se₂-based thin film solar cells. Optimization of the buffer layer is performed in terms of thickness, deposition temperature and composition. High efficiency devices are obtained for deposition at 105-135 °C, whereas losses in open circuit voltage are observed at higher deposition temperatures. The optimal compositional region for (Zn,Mg)O buffer layers in this study is for Mg/(Zn + Mg) contents of about 0.1-0.2, giving band gap values of 3.5-3.7 eV. These devices appear insensitive to thickness variations between 80 and 600 nm. Efficiencies of up to 16.2% are obtained for completely Cd- and S-free devices with (Zn,Mg)O buffer layers deposited with 1000 cycles at 120 °C and having a band gap of 3.6 eV.