Critical review of the current status of thickness measurements for ultrathin SiO2 on Si Part V: Results of a CCQM pilot study

Results are reported from a pilot study under the Consultative Committee for Amount of Substance (CCQM) to compare measurements of and resolve any relevant measurement issues in the amount of thermal oxide on (100) and (111) orientation silicon wafer substrates in the thickness range 1.5–8 nm. As a result of the invitation to participate in this activity, 45 sets of measurements have been made in different laboratories using 10 analytical methods: medium—energy ion scattering spectrometry (MEIS), nuclear reaction analysis (NRA), RBS, elastic backscattering spectrometry (EBS), XPS, SIMS, ellipsometry, grazing—incidence x‐ray reflectometry (GIXRR), neutron reflectometry and transmission electron microscopy (TEM). The measurements are made on separate sets of 10 carefully prepared samples, all of which have been characterized by a combination of ellipsometry and XPS using carefully established reference conditions and reference parameters. The results have been assessed against the National Physical Laboratory (NPL) data and all show excellent linearity. The data sets correlate with the NPL data with average root‐mean‐square scatters of 0.15 nm, half being better than 0.1 nm and a few at or better than 0.05 nm. Each set of data allows a relative scaling constant and a zero thickness offset to be determined. Each method has an inherent zero thickness offset between 0 nm and 1 nm and it is these offsets, measured here for the first time, that have caused many problems in the past. There are three basic classes of offset: water and carbonaceous contamination equivalent to ～ 1 nm as seen by ellipsometry; adsorbed oxygen mainly from water at an equivalent thickness of 0.5 nm as seen by MEIS, NRA, RBS and possibly GIXRR; and no offset as seen by XPS using the Si 2p peaks. Each technique has a different uncertainty for the scaling constant and consistent results have been achieved. X‐ray photoelectron spectroscopy has large uncertainties for the scaling constant but a high precision and critically, if used correctly, has zero offset. Thus, a combination of XPS and the other methods allows the XPS scaling constant to be determined with low uncertainty, traceable via the other methods. The XPS laboratories returning results early were invited to test a new reference procedure. All showed very significant improvements. The reference attenuation lengths thus need scaling by 0.986 ± 0.009 (at an expansion factor of 2), deduced from the data for the other methods. Several other methods have small offsets and, to the extent that these can be shown to be constant or measurable, these methods will also show low uncertainty. Recommendations are provided for parameters for XPS, MEIS, RBS and NRA to improve their accuracy. Copyright © 2004 John Wiley & Sons, Ltd.     

Spectroscopic ellipsometry investigations of porous SiO2 films prepared by glancing angle deposition

We present the optical and the structural properties of porous SiO₂ films fabricated by using a glancing angle deposition technique. The influence of the glancing angle on the pseudorefractive index of porous SiO₂ films was studied by spectroscopic ellipsometry in the UV–visible region. The relationships among the pseudorefractive index, the porosity, and the glancing angle are determined. The results show that the pseudorefractive index decreases and the porosity increases with the increase of glancing angle. The minimum pseudorefractive index is found to be 1.11 at 532 nm for the porous SiO₂ film deposited at a glancing angle of 87°. The structural and surface morphology of these samples was also investigated by using a scanning electron microscope. The results indicate that the as‐deposited SiO₂ thin films are porous with a tilted‐columnar structure and low pseudorefractive index. Copyright © 2013 John Wiley & Sons, Ltd.     

Considerations of the intermediate oxides via XPS elemental quantitative analysis for the thickness measurements of ultrathin SiO2 on Si

The thicknesses of intermediate oxides at the interface between ultrathin SiO₂ and Si substrates have been measured via XPS elemental quantitative analysis for some SiO₂/Si(100) and SiO₂/Si(111) samples with the silicon oxide thickness less than 2 nm. The measurements involve XPS determination of the Si relative atomic ratio, calculation of Si atomic densities for the intermediate oxide, etc. and then the intermediate oxide thicknesses and the number of monolayers are obtained by referencing the thickness data from two international comparisons for these samples. The results show that the thickness of the intermediate oxides is in the range 0.14–0.16 nm with an average value of 0.15 nm. The number of monolayers for the intermediate oxides at the interface is less than one monolayer with an average value of 0.60. In the present work, there are a series of approximations. By making these approximations many parameters, including L and R₀, used in the conventional calculation method are removed to give a simpler equation, which is valid when the thicknesses of SiO₂ overlayer and the intermediate oxides are very small. This, therefore, appears to be a simple and quick method to obtain approximate oxide thicknesses of modest accuracy. The present work does not in any way replace or improve on Eqns ( 2 –6) cited in the text. Copyright © 2010 John Wiley & Sons, Ltd.     

SiO2/蔗糖杂化溶胶制备SiC纤维前驱体

蔗糖;SiO2;杂化纤维;前驱体;SiC纤维;溶胶凝胶法     

Ultra‐thin SiO2 on Si IX: absolute measurements of the amount of silicon oxide as a thickness of SiO2 on Si

Results from a study conducted between National Metrology Institutes (NMIs) for the measurements of the absolute thicknesses of ultra‐thin layers of SiO₂ on Si are reported. These results are from a key comparison and associated pilot study under the auspices of the Consultative Committee for Amount of Substance. ‘Amount of substance’ may be expressed in many ways, and here the measurand is the thickness of the silicon oxide layers with nominal thicknesses in the range 1.5–8 nm on Si substrates, expressed as the thickness of SiO₂. Separate samples were provided to each institute in containers that limited the carbonaceous contamination to approximately < 0.3 nm. The SiO₂ samples were of ultra‐thin on (100) and (111) orientated wafers of Si. The measurements from the laboratories which participated in the study were conducted using ellipsometry, neutron reflectivity, X‐ray photoelectron spectroscopy or X‐ray reflectivity, guided by the protocol developed in an earlier pilot study. A very minor correction was made in the different samples that each laboratory received. Where appropriate, method offset values attributed to the effects of contaminations, from the earlier pilot study, were subtracted. Values for the key comparison reference values (agreed best values from a Consultative Committee study) and their associated uncertainties for these samples are then made from the weighted means and the expanded weighted standard deviations of the means of these data. These results show a dramatic improvement on previous comparisons, leading to 95% uncertainties in the range 0.09–0.27 nm, equivalent to 0.4–1.0 monolayers over the 1.5–8.0 nm nominal thickness range studied. If the sample‐to‐sample uncertainty is reduced from its maximum estimate to the most likely value, these uncertainties reduce to 0.05–0.25 nm or ～1.4% relative standard uncertainties. The best results achieve ～1% relative standard uncertainty. It is concluded that XPS has now been made fully traceable to the SI, for ultra‐thin thermal SiO₂ on Si layers, by calibration using wavelength methods in an approach that may be extended to other material systems. © Crown copyright 2009. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

Ultrathin SiO2 on Si IV. Intensity measurement in XPS and deduced thickness linearity

The procedures for measuring the intensities and for subsequent calculation of the thickness of thermal SiO₂ layers on Si in the range 0.3–8 nm have been evaluated to determine the best measurement protocols. This work is based on earlier work where the measurements for (100) and (111) Si surfaces indicate the need to work at a reference geometry. In the spectra, the Si 2p peaks may be separated clearly into the substrate Si and the overlayer SiO₂ but it is recommended here that, for accuracies better than 1%, the interface oxides are also analysed. The analysis here is for thermal oxides. Oxides grown by other routes may require a modification of this analysis. It is shown that, in evaluating the data to determine the layer thickness, the failure to remove x‐ray satellites or the use of a straight‐line background will both lead to unacceptable errors that may exceed 5%. On the other hand, if a Shirley background is used consistently for both the peak area analysis and for evaluation of the ratio of intensities for bulk SiO₂ and Si, R_o, the results should be linear over the above range to within ±0.025 nm. This excellent result includes the non‐linearities arising from elastic scattering effects and the data reduction method. Equations are provided, together with a value of R_o for Mg and Al x‐rays, to calculate the oxide thicknesses with the above linearity. In order to determine the oxide thickness accurately, the relevant inelastic mean free paths also must be known. Theoretical evaluations are only accurate to 17.4% and so better values need to be obtained by calibration. This paper provides the infrastructure to do this. Crown Copyright © 2003 Published by John Wiley & Sons, Ltd.     

Iron adsorption on SiO2/Si(111)

The adsorption of ferric and ferrous iron onto the native oxide of the SiO₂/Si(111) surface has been evaluated using X‐ray photoelectron spectroscopy (XPS). Through a series of immersion experiments, performed at room temperature and pH 1, it has been shown that the ferric species is strongly adsorbed onto the hydrophilic surface, while ferrous iron remains in solution. Dehydroxylation of the silica surface by etching with hydrofluoric acid reduces the concentration of receptive Si‐OH groups, thereby limiting iron adsorption. The experiments were reproduced in a combined ultrahigh vacuum‐electrochemical system (UHV‐EC), which allowed a carbon‐free surface to be prepared before contacting the iron solutions, and confirmed the strong affinity of ferric iron towards the SiO₂/Si(111) surface. Copyright © 2007 John Wiley & Sons, Ltd.     

SiO_2包覆超细CaCO_3的微晶分析和XPS研究

0引 言 超细碳酸钙在橡胶、塑料、造纸、涂料、油墨、医药、化妆品等工业中有广泛应用。碳酸钙粉末表面具有许多水羟基,表面是亲水疏油性的 ,易形成聚集体 ,分散性能差 ,直接应用效果不好。因此,根据其本身的性质及其应用目的,对其进行表面处理,以相应提高其应用性能。碳酸钙的表面处理是通过物理或化学方法将表面处理剂吸附或反应在碳酸钙的表面,形成表面改性层,使其表面活性化,以改善碳酸钙的表面性能。目前碳酸钙的表面改性大多为有机表面改性、偶连剂表面改性、高分子（聚合物）表面改性等 [1],而无机表面改性却很少有报道。我…     

SrS/α-SiO~2界面的XPS研究

TFEL器件中绝缘层与发光层之间的界面对电荷的输运特性、发光特性等有着十分重要的作用。本文通过XPS的测量,分析了新结构器件中SrS/α-SiO~2界面的各成分的芯电子能谱的变化和深度分布,发现Sr^2^+向SiO~2中扩散较深并以氧化物的形态存在,介质层以SiO~x(x=1.65～1.70)的形态存在。这些丰富的界面态有可能成为TFEL器件的初电子源而对SrS:Ce发光有贡献。     

Na-W-Mn/SiO_2催化剂中Na对甲烷氧化偶联制乙烯的作用(英文)

采用常规浸渍法制备了一系列Na（wt％）含量不同的Na－W－Mn／SiO_2催化剂,在流动态微型固定床常压反应装置上评价了这些催化剂的甲烷氧化偶联（OCM）制乙烯催化反应性能,并进行了XPS、XRD表征。实验结果表明,Na含量为0．39wt％－2．34Wt％的Na－W－Mn／SiO_2催化剂具有好的甲烷氧化偶联制乙烯性能,此时Mn以对反应有利的晶相存在,同时由于Na的表面富集,引起W、Mn向催化剂表面发生迁移。由此可见,在Na－W－Mn／SiO_2催化剂中,Na是甲烷转化和乙烯生成不可缺少的活性组分之一。     

PUT/SiO2复合材料的制备与表征

利用溶胶-凝胶法将硅烷染料、含硅氧烷的非线性聚氨酯与正硅酸乙酯(TEOS)共水解, 缩合制备了新型聚氨酯噻唑(PUT/SiO2)纳米复合材料, 并用IR、SEM、TEM、UV-Vis、DSC和TGA对其结构和性能进行了表征. 结果显示, 材料中聚氨酯与SiO2以共价键相连, 没有发生相分离, 且其中非线性较好的噻唑生色团含量和材料的玻璃化转变温度(Tg)、热分解温度(Td)都较纯非线性光学材料(NLO)聚氨酯(PU)有显著增加, 可以用来制备性能优良的二阶非线性光学器件.     

负载型ZnO/SiO2及ZnO-SiO2溶胶凝胶催化剂的表面结构研究

催化剂的表面结构不仅影响催化剂的催化活性, 而且还影响反应产物的选择性[1]. 制备催化剂的方法不同, 其表面结构及表面性质也不同[2~4]. 浸渍法简单实用, 有利于得到高分散、晶粒细小的高比表面催化剂, 而溶胶-凝胶法则由于其制备温度较低, 易于形成无定形的或介态的氧化物相[5]而可达到分子级的混合, 其活性组分能有效地嵌入网状结构中, 不易受外界的影响而聚集或长大, 因此对催化剂的稳定性更为有利[6,7].     

Band alignment and defect states in amorphous GaInZnO thin films grown on SiO2/Si substrates

The band alignment and defect states of GaInZnO thin films grown on SiO₂/Si via radio frequency (RF) magnetron sputtering were investigated by using X‐ray photoelectron spectroscopy, reflection electron energy loss spectroscopy, thermally stimulated exo‐electron emission and photo‐induced current transient spectroscopy.The band gap via reflection electron energy loss spectroscopy was 3.2 eV. The defect states via photo‐induced current transient spectroscopy and thermally stimulated exo‐electron emission were at 0.24, 0.53, 1.69 and 2.01 eV below the conduction band minimum of GIZO thin films, respectively. The defect states at 0.24 and 0.53 eV are related to the field‐effect mobility, and the defect stated at 1.69 and 2.01 eV is related to the oxygen vacancy defect. Copyright © 2016 John Wiley & Sons, Ltd.     

ZrO2助剂对Co/SiO2催化剂在Fischer-Tropsch合成反应中稳定性的影响

采用TPR、XRD、XPS和H2脉冲吸附等表征手段考察了ZrO2助剂对Co/SiO2催化剂在Fischer-Tropsch(F-T)合成中稳定性的影响。结果表明,ZrO2的引入促进了钴物种在催化剂上的分散并明显抑制了该催化剂的失活;在反应过程中ZrO2起到结构助剂的作用,明显抑制了Co/SiO2催化剂上硅酸钴或水合硅酸钴物种的生成。     

纳米Al_2O_3/SiO_2室温磷光复合材料的研究

通过溶胶-凝胶法制备出了纳米Al2O3/SiO2室温磷光材料,通过优化试验条件,确定铝硅摩尔比为0.20,煅烧温度为600℃,煅烧时间为2h条件下制备出的材料的发光性质最好,粒径为大约50 nm。该纳米Al2O3/SiO室温磷光材料的最大激发波长为406nm,最大发射波长为537nm,磷光寿命为0.53s。     

超临界CO2中模板法制备TiO2/SiO2复合多孔材料

在超临界CO2中以颗粒状活性炭为模板,正硅酸乙酯和钛酸四正丁酯为前驱体制备了TiO2/S iO2复合多孔材料。研究了超临界状态下不同涂层温度和涂层压力对涂层率的影响,当温度为40℃时,压力在22 MPa为该温度的最佳涂层压力;固定压力为22 MPa,涂层温度为70℃为最佳涂层条件。X射线衍射(XRD)的研究结果表明,产物由锐钛矿型TiO2、金红石型TiO2以及结晶的S iO2这3种物质构成。根据产物的N2气吸附-脱附等温线计算,产物的比表面积达到144.44 m2/g,平均孔径为7 nm左右。扫描电子显微镜的分析结果证明,产物在一定程度上实现了对模板的复制,同时透射电子显微镜显示,复合材料的纳米颗粒尺寸具有良好的分散性。     

PP/SiO2杂化复合材料的制备与性能研究

以正硅酸乙酯(TEOS),甲基丙烯酸甲酯(MMA)为主要原料,甲基丙烯酸一口一羟丙酯为活性单体,溶胶一凝胶法制备PMMA／SiO2杂化准凝胶,并以其为填充物对PP进行复合改性。采用FT-IR、XRD、SEM、PLM等对材料的结构进行分析,同时对其力学性能进行测试,研究了复合材料力学性能与组成、结构间的关系。研究发现,PMMA／SiO2杂化材料能诱导PP基体中口晶型的生成,并使PP球晶细化。PP／SiO2杂化复合材料(PSH)中siO2含量为2％(wt)时,缺口冲击强度较纯PP提高81％。     

壳聚糖表面修饰的SiO2负载Ni-B非晶态合金的制备及催化性能

以壳聚糖(CS)对SiO2进行表面修饰, 采用浸渍还原法制备了负载型Ni-B非晶态合金催化剂(Ni-B/CS/SiO2), 并采用XRD、FTIR、电感耦合等离子体发射光谱(ICP)、BET、XPS、TEM、SAED等表征方法研究了催化剂的非晶性质、原子组成、尺寸分布及粒径大小等. 考察了催化剂对糠醇加氢制四氢糠醇反应的催化性能, 并与没有壳聚糖修饰的Ni-B/SiO2催化剂及Raney Ni催化剂进行了对比. 结果表明, 加入壳聚糖制得的Ni-B/CS/SiO2催化剂的活性组分Ni-B团簇粒径更小, 表面活性组分浓度更高, 催化活性更高.     

NiB/SiO2非晶态合金催化剂用于糠醇加氢制四氢糠醇的研究

用化学镀方法制备了负载型NiB/SiO2非晶态合金催化剂,并采用ICP、BET、TEM、XRD等手段研究了NiB在SiO2表面的存在状态及非晶性质。研究了糠醇在该催化剂上加氢制备四氢糠醇的反应行为,考察了反应温度、压力、搅拌速度等因素对催化剂性能的影响。结果表明,在2.0MPa、120℃、550r/min时,糠醇的转化率在99％以上,四氢糠醇的选择性可达100％。在此条件下和骨架Ni的催化性能相当。     

新型PA6/EP/SiO2纳米复合材料的制备

PA6;SiO2;环氧树脂;原位聚合;纳米复合材料