Observations on X‐ray enhanced sputter rates in argon cluster ion sputter depth profiling of polymers

Traditionally polymer depth profiling by X‐ray photoelectron spectroscopy (XPS) has been dominated by the damage introduced by the ion beam rather than the X‐rays. With the introduction of polyatomic and especially argon gas cluster ion‐beam (GCIB) sources for XPS instruments, this is no longer the case, and either source of damage may be important (or dominate) under particular conditions. Importantly, while ion‐beam damage is a near‐surface effect, X‐ray damage may extend micrometres into the bulk of the sample, so that the accumulation of X‐ray damage during long depth profiles may be very significant. We have observed craters of similar dimensions to the X‐ray spot well within the perimeter of sputter craters, indicating that X‐rays can assist GCIB sputtering very significantly. We have measured experimentally sputter craters in 13 different polymers. The results show that X‐ray exposure can introduce much more topography than might previously have been expected, through both thermal and direct X‐ray degradation. This can increase the depth of a crater by a remarkable factor, up to three in the case of poly‐L‐lactic acid and polychlorotrifluorothylene under reasonably normal XPS conditions. This may be a major source of the loss of depth resolution in sputter depth profiles of polymers. Copyright © 2012 John Wiley & Sons, Ltd.     

Influence of nitrogen partial pressure on the microstructure and morphological properties of sputtered RuN coatings

In this work, the production of RuN thin films using the reactive direct current magnetron sputtering technique is presented. Samples were grown with varying Ar/N₂ ratio with values of 60/40, 80/20, 85/15, 90/10, 95/5, and 100/0. X‐ray photoelectron spectroscopy was employed to determine the presence of RuN before and after a sputtering etching process. According to the high‐resolution of N1s spectra, 3 peaks were identified at 397.4 ± 0.3 eV, 398.3 ± 0.3 eV, and 398.8 ± 0.3 eV binding energies, corresponding to hybridizations of nitrogen with transition metals, oxynitrides, and oxycarbides. X‐ray diffraction analyses were performed, showing the coexistence of the RuN face‐centered cubic and Ru hexagonal compact packed phases. After the etching process, the samples grown at nitrogen flow rates greater than 15% continued to show the RuN face‐centered cubic phase. Atomic force microscope analyses showed that as the nitrogen concentration increased, the grain size and roughness also tended to increase.     

Inter‐diffusion effects in as‐deposited Al/Ni polycrystalline multi‐layers

Al/Ni multi‐layers, deposited by magnetron sputtering at room temperature have been studied by complementary techniques; XPS, sputter depth profiling, electron‐induced X‐ray emission spectroscopy (XES) and X‐ray diffraction (XRD). XPS depth profile technique evidenced an atomic diffusion dominated by Ni atoms. Moreover, the Ni diffusion results in the formation of an amorphous phase with a stoichiometry close to the Al₃Ni aluminide. Copyright © 2008 John Wiley & Sons, Ltd.     

New horizons in sputter depth profiling inorganics with giant gas cluster sources: Niobium oxide thin films

X‐ray photoelectron spectroscopy is used to study a wide variety of material systems as a function of depth (“depth profiling”). Historically, Ar⁺ has been the primary ion of choice, but even at low kinetic energies, Ar⁺ ion beams can damage materials by creating, for example, nonstoichiometric oxides. Here, we show that the depth profiles of inorganic oxides can be greatly improved using Ar giant gas cluster beams. For NbO_x thin films, we demonstrate that using Ar_x⁺ (x = 1000‐2500) gas cluster beams with kinetic energies per projectile atom from 5 to 20 eV, there is significantly less preferential oxygen sputtering than 500 eV Ar⁺ sputtering leading to improvements in the measured steady state O/Nb ratio. However, there is significant sputter‐induced sample roughness. Depending on the experimental conditions, the surface roughness is up to 20× that of the initial NbO_x surface. In general, higher kinetic energies per rojectile atom (E/n) lead to higher sputter yields (Y/n) and less sputter‐induced roughness and consequently better quality depth profiles. We demonstrate that the best‐quality depth profiles are obtained by increasing the sample temperature; the chemical damage and the crater rms roughness is reduced. The best experimental conditions for depth profiling were found to be using a 20 keV Ar₂₅₀₀⁺ primary ion beam at a sample temperature of 44°C. At this temperature, there is no, or very little, reduction of the niobium oxide layer and the crater rms roughness is close to that of the original surface.     

Effects of sputtering current on the bonding structure and mechanical properties of diamond‐like carbon films deposited by MFPUMST

Diamond‐like carbon (DLC) films on glass wafers were produced by middle frequency pulsed unbalanced magnetron sputtering technique (MFPUMST) at different sputtering current. The chemical bonding of carbon characterized by Raman spectroscopy and X‐ray photoelectron spectroscopy (XPS) show that the sp³ fraction in DLC films increases with increasing sputtering current from 100 to 300 mA, and then decreases above 300 mA. Mechanical properties like nano‐hardness and elastic recovery for these films under different sputtering currents analyzed by a nano‐indentation technique show the same tendency that nano‐hardness and elastic recovery increase with increasing sputtering current from 100 to 300 mA, and then decrease with increasing sputtering current from 300 to 400 mA. These results indicate that the sp³ fraction in the prepared DLC films is directly related to nano‐hardness and elastic recovery. The results shown above indicate that the parameter of the preparation—sputtering current has a strong influence on the bonding configuration of the deposited DLC films. The mechanism of sputtering current on the sp³ fraction is discussed in this paper. Copyright © 2009 John Wiley & Sons, Ltd.     

XPS study of impurities in Si‐doped AlN film

This paper reports an XPS study of impurities in a 100‐nm‐thick AlN film grown by metalorganic chemical vapor deposition (MOCVD) under low pressure on the n‐type 6H‐SiC substrate. The Si‐doped AlN film was characterized by the X‐ray photoelectron spectroscopy (XPS) in a high vacuum system, which reveals the content distribution and chemical states of impurities along depth. The XPS analysis of AlN film before and after argon‐ion etching indicates that there always exist Ga, O and C contaminations in AlN film. Especially, O contamination on the AlN film surface is mostly introduced during the growth of AlN layer by MOCVD. Meanwhile, most of O atoms bind with Al or Ga in Al―O and Ga―O chemical states. In particular, the Ga atoms in AlN film are always in two chemical states, i.e. Ga―Ga bond and Ga―O bond, which demonstrates that the aggregation of Ga is accompanying with AlN growth. Copyright © 2016 John Wiley & Sons, Ltd.     

Nondestructive in‐depth composition profile of oxy‐hydroxide nanolayers on iron surfaces from ARXPS measurement

In this work the maximum entropy method (MEM) is applied, for the first time, to angle‐resolved X‐ray photoelectron spectroscopy (ARXPS) data from oxy‐hydroxide films on iron surfaces. This nondestructively derives information on the in‐depth distribution of the composition and chemical state. An MEM algorithm was created and first tested on the simulated data. The reconstructed composition depth profiles agreed very well with the theoretical ones up to 5% Gaussian noise added to the data. The same algorithm was then applied to ARXPS data from iron samples to investigate the in‐depth variations in the composition and chemical state of the nanosized oxy‐hydroxide film naturally grown on the iron surface. The resulting surface film presents a complex multilayer structure with concentration gradients. The effect of air exposure on the structure was also investigated. Copyright © 2006 John Wiley & Sons, Ltd.     

Optimization of the depth resolution for profiling SiO2/SiC interfaces by dual-beam TOF-SIMS combined with etching

To examine precise depth profiles at the interface of SiO₂/SiC, a high resolution that can detect slight discrepancies in the distribution is needed. In this study, an experimental method to achieve a high resolution of less than 1 nm was developed by using dual-beam time-of-flight secondary ion mass spectrometry (TOF-SIMS). The analysis was preceded by the following three steps: (1) determination of the optimal analytical conditions of the analysis beam (Bi⁺) and sputtering beam (Cs⁺), (2) verification of the etching methods to thin the SiO₂ layer, and (3) confirmation of the benefits of the low-energy sputtering beam directed toward SiO₂/SiC samples. By using the secondary ion intensity peak-to-valley ratio of BN⁻ and BO⁻ of a sample with delta-doped boron multilayers, the appropriate Bi⁺/Cs⁺ condition for a high depth resolution was determined for each energy level of the sputtering beam. Upon verification of the etching methods to thin the SiO₂ layer, slight discrepancies were found between samples that were obtained with different etching methods. The difference in the roughness values of the etched surfaces was proactively utilized for the performance confirmation of the low-energy sputtering beam by means of precise observation of the profiles at the SiO₂/SiC interface. The use of a Cs beam with a low energy between 0.25 and 0.5 keV enabled the detection of slight discrepancies in the roughness of less than 1 nm between samples. The aforementioned method has the potential to accurately detect discrepancies in the intrinsic distribution at the SiO₂/SiC interface among samples.     

InGaAsP／InP异质结构材料组分,结构的准确测定与综合分析

采用Ｘ射线光电子能谱（ＸＰＳ）对ＩｎＧａＡｓＰ／ＩｎＰ异质结构金属有机化学蒸发沉积（ＭＯＣＶＤ）外延晶片作了表面元素组分定性、定量和深度分布分析。将其组分定量数据代入带隙经验公式，发现带隙的计算与用光压谱（ＰＶＳ）实验值十分吻合；但是代入晶体常数经验计算公式计算得到的失配率与由Ｘ射线双晶衍射（ＤＣＤ）测定的失配率却有明显差别。抽检的两个外延晶片的ＸＰＳ元素分析和元素的深度分布分析，以对比的方式展示两者元素的组成、化学状态在其表面和沿着深度方向的变化及其差异，由此得到的有关片子质量的正确判断，有力地证明了ＸＰＳ是研究ＭＯＣＶＤ外延膜材料的得力工具。     

Dye degradation studies of Mo‐doped TiO2 thin films developed by reactive sputtering

TiO₂ thin films with various Mo concentrations have been deposited on glass and n‐type silicon (100) substrates by this radio‐frequency (RF) reactive magnetron sputtering at 400°C substrate temperature. The crystal structure, surface morphology, composition, and elemental oxidation states of the films have been analyzed by using X‐ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and X‐ray photoelectron spectroscopy, respectively. Ultraviolet‐visible spectroscopy has been used to investigate the degradation, transmittance, and absorption properties of doped and undoped TiO₂ films. The photocatalytic degradation activity of the films was evaluated by using methylene blue under a light intensity of 100 mW cm⁻². The X‐ray diffraction patterns show the presence of anatase phase of TiO₂ in the developed films. X‐ray photoelectron spectroscopy studies have confirmed that Mo is present only as Mo⁶⁺ ions in all films. The Mo/TiO₂ band gap decreases from ~3.3 to 3.1 eV with increasing Mo dopant concentrations. Dye degradation of ~60% is observed in Mo/TiO₂ samples, which is much higher than that of pure TiO₂.     

Measurement of sputtering yields and damage in C60 SIMS depth profiling of model organic materials

Sputter‐depth profiles of model organic thin films on silicon using C₆₀ primary ions have been employed to measure sputtering yields and depth resolution parameters. We demonstrate that some materials (polylactide, Irganox 1010) have a constant and high sputtering yield, which varies linearly with the primary ion energy, whereas another material (Alq₃) has lower, fluence‐dependent sputtering yields. Analysis of multi‐layered organic thin films reveals that the depth resolution is a function of both primary ion energy and depth, and the sputtering yield depends on the history of sputtering. We also show that ～30% of repeat units are damaged in the steady‐state regime during polylactide sputtering. Crown Copyright © 2006. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

The effect of thermal annealing on the microstructure and mechanical properties of magnetron sputtered hydrogenated amorphous carbon films

Hydrogenated amorphous carbon films were deposited by magnetron sputtering of a carbon target in a methane/argon atmosphere. A postdeposition annealing at 300 °C was performed and the microstructure, bonding structure and mechanical properties of the as‐deposited and annealed films were analyzed and compared directly by high‐resolution transmission electron microscopy, micro‐Raman spectroscopy, XPS, and nanoindentation. The results showed that the carbon films are quite stable upon annealing, since there are only minor changes in microstructure and chemical bonding in the amorphous matrix. The hardness of the films remained unaffected, but the elastic properties were somewhat deteriorated. In comparison to the outcomes of our previous work on the growth of fullerene‐like hydrogenated carbon films, we can state that the formation of fullerene‐like carbon structures requires different sputtering process conditions, such as a higher ion energy and/or different sputtering target. Copyright © 2011 John Wiley & Sons, Ltd.     

Accurate measurement of sputtered depth for ion sputtering rates and yields: the mesh replica method

For the accurate measurements of crater depths, ion sputtering rates and ion sputtering yields in studies of sputter‐depth profiling using Auger electron spectroscopy (AES) or X‐ray photoelectron spectroscopy (XPS), a proposed mesh replica method has been evaluated. In this method, during ion sputtering, grids of between 50 and 400 mesh (per inch) are placed on the sample to retain unsputtered regions of the original surface to be used as reference. This enables a more accurate measurement of the depth to be made using a stylus profilometer close to the analytical region. The closer‐pitch meshes were thought to offer the prospect of measurements of higher accuracy. Calculations show that sputter deposits from the mesh sides may limit the mesh numbers used to 100 or those of a wider pitch for both stationary and rotated samples. A correlation with published data for stationary samples and new data for rotated samples confirms the calculations. In practice, it is difficult, without a special holder, to have intimate contact between the grid and sample. Such a holder is described. Further calculations concerning the shadowed profiles at the grid bar regions show that the grids may lift off the sample surface by 4–16 µm. This leads to non‐vertical crater walls in each mesh aperture. This effect, however, does not change the above conclusion on the mesh sizes to be used. In this range, the spurious appearance of Auger electrons emitted from the grid material is calculated to be less than 1%. This conclusion applies to the meshes evaluated here, which range in thickness from 13 to 29 µm. Thinner meshes may lead to the applicability of proportionately closer meshed grids in sputter‐profiling applications. Copyright © 2006 John Wiley & Sons, Ltd. The contribution of Martin P. Seah of the National Physical Laboratory is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.     

Preferential sputtering observed in Auger electron spectroscopy sputter depth profiling of AlAs/GaAs superlattice using low‐energy ions

Auger electron spectroscopy (AES) sputter depth profiling of an ISO reference material of the GaAs/AlAs superlattice was investigated using low‐energy Ar⁺ ions. Although a high depth resolution of ～1.0 nm was obtained at the GaAs/AlAs interface under 100 eV Ar⁺ ion irradiation, deterioration of the depth resolution was observed at the AlAs/GaAs interface. The Auger peak profile revealed that the enrichment of Al due to preferential sputtering occurred during sputter etching of the AlAs layer only under 100 eV Ar⁺ ion irradiation. In addition, a significant difference in the etching rates between the AlAs and GaAs layers was observed for low‐energy ion irradiation. Deterioration of the depth resolution under 100 eV Ar⁺ ion irradiation is attributed to the preferential sputtering and the difference in the etching rate. The present results suggest that the effects induced by the preferential sputtering and the significant difference in the etching rate should be taken into account to optimize ion etching conditions using the GaAs/AlAs reference material under low‐energy ion irradiation. Copyright © 2005 John Wiley & Sons, Ltd.     

Incident angle and energy dependences of low‐energy Ar+ ion sputtering of GaAs/AlAs multilayered system

Dependences of the depth resolution in Auger electron spectroscopy sputter‐depth profiling of a GaAs/AlAs superlattice reference material on the incident angle and energy of primary Ar⁺ ions were investigated. The results revealed that the depth resolution is improved for the lower primary energy as a square root of the primary energy of ions at both the incident angles of 50° and 70° , except for 100 eV at 50° , where the significant deterioration of the depth resolution is induced by the preferential sputtering of As in AlAs, and the difference in the etching rate between GaAs and AlAs. The deterioration of the depth resolution, i.e. the difference in the etching rate and the preferential sputtering, observed for 100 eV at 50° was suppressed by changing the incident angle of ions from 50° to 70° , resulting in the high‐depth resolution of ～1.3 nm. The present results revealed that the glancing incidence of primary ions is effective to not only reducing the atomic mixing but also suppressing the difference in the etching rates between GaAs and AlAs and the preferential sputtering in the GaAs/AlAs multilayered system. The results also suggest that careful attention is required for the optimization of conditions of sputter‐depth profiling using GaAs/AlAs superlattice materials under low‐energy ion irradiation. Copyright © 2009 John Wiley & Sons, Ltd.     

The effect of nonmetallic element P in electroless Ni‐P coating on the passivation process during chemical conversion treatment

Pure Ni and electroless Ni‐P coating (ENPC) were passivated by a chemical conversion treatment. The passive films formed on pure Ni and ENPCs (with content of P 2.9, 7.2 and 11.7 at.% respectively) were analyzed by X‐ray photoelectron spectroscopy (XPS). High‐resolution XPS was also used to analyze the chemical states of the elements detected in the passive films. The results indicated that the detected Ni and P were in elemental states, and no compound with Ni and P element was detected in passive film, meaning that Ni and P did not participate in the formation of the passive film. The content of film‐forming reaction product in passive film increases with the content of element P in Ni‐P coating, suggesting that the nonmetallic P in Ni‐P coating played an important role in the formation of the passive film. The XPS results were used to analyze the formation mechanism of the passive film. Copyright © 2014 John Wiley & Sons, Ltd.     

氮化铝薄膜的组成分析

Al N是一种无机非铁性压电材料 ,具有宽的带隙、高的电阻率、高的抗击穿电压、高的声传播速率和低的传输损耗 ,在微电子器件中有着广泛的应用前景 [1] .由于 Al N薄膜的声速在整个无机非铁性材料中最高 ,因而成为 GHz级声表面波器件的首选材料 [2 ] .要实现 Al N薄膜的表面声波器件应用 ,不但结构重要 [1] ,组成也很重要 [3] ,因为薄膜的组成对其性质影响很大 .Al N压电薄膜要求整个膜层的 Al/N比一致 .富 Al会使薄膜介电性能变差 ,富 N会使薄膜结构致密度变差 .因而对其组成研究是非常重要的 .Penza等 [3] 采用X射线光电子能谱 ( X…     

In situ ion beam sputter deposition and X‐ray photoelectron spectroscopy (XPS) of multiple thin layers under computer control for combinatorial materials synthesis

Deposition of ultra‐thin layers under computer control is a frequent requirement in studies of novel sensors, materials screening, heterogeneous catalysis, the probing of band offsets near semiconductor junctions and many other applications. Often large‐area samples are produced by magnetron sputtering from multiple targets or by atomic layer deposition (ALD). Samples can then be transferred to an analytical chamber for checking by X‐ray photoelectron spectroscopy (XPS) or other surface‐sensitive spectroscopies. The ‘wafer‐scale’ nature of these tools is often greater than is required in combinatorial studies, where a few square centimetres or even millimetres of sample is sufficient for each composition to be tested. The large size leads to increased capital cost, problems of registration as samples are transferred between deposition and analysis, and often makes the use of precious metals as sputter targets prohibitively expensive. Instead we have modified a commercial sample block designed to perform angle‐resolved XPS in a commercial XPS instrument. This now allows ion‐beam sputter deposition from up to six different targets under complete computer control. Ion beam deposition is an attractive technology for depositing ultra‐thin layers of great purity under ultra‐high vacuum conditions, but is generally a very expensive technology. Our new sample block allows ion beam sputtering using the ion gun normally used for sputter depth‐profiling of samples, greatly reducing the cost and allowing deposition to be done (and checked by XPS) in situ in a single instrument. Precious metals are deposited cheaply and efficiently by ion‐beam sputtering from thin metal foils. Samples can then be removed, studied and exposed to reactants or surface treatments before being returned to the XPS to examine and quantify the effects. Copyright © 2016 The Authors Surface and Interface Analysis Published by John Wiley & Sons Ltd.     

Growth and characterization of ultrathin carbon films on electrodeposited Cu and Ni

Ultrathin carbon films were grown on different types of metallic substrates. Free‐standing foils of Cu and Ni were prepared by electroforming, and a pure Ni film was obtained by galvanic displacement on a Si wafer. Commercial foil of Ni 99.95% was used as a reference substrate. Carbon films were grown on these substrates by chemical vapour deposition in a CH₄‐H₂ atmosphere. Obtained films were characterized by Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, and ultraviolet photoemission spectroscopy. The XPS at grazing collection angle was used to determine the thickness of carbon films. Depending on the deposition parameters, the films of graphene or graphite were obtained on the different substrates. The uniformity of graphene and its distribution over the sample area were investigated from Raman data, optical images, and XPS chemical maps. The presence of graphene or graphite in the films was determined from the Raman spectra and Auger peak of C KVV. For this purpose, the D parameter, which is a fingerprint of carbon allotropes, was determined from C KVV spectra acquired by using X‐rays and electron beam. A formation of an intermediate layer of metal hydroxide was revealed in the samples with graphene overlayer.     

VAMAS interlaboratory study on organic depth profiling

We present the results of a VAMAS (Versailles project on Advanced Materials and Standards) interlaboratory study on organic depth profiling, in which twenty laboratories submitted data from a multilayer organic reference material. Individual layers were identified using a range of different sputtering species (C₆₀ⁿ⁺, Cs⁺, SF₅⁺ and Xe⁺), but in this study only the C₆₀ⁿ⁺ ions were able to provide truly ‘molecular’ depth profiles from the reference samples. The repeatability of profiles carried out on three separate days by participants was shown to be excellent, with a number of laboratories obtaining better than 5% RSD (relative standard deviation) in depth resolution and sputtering yield, and better than 10% RSD in relative secondary ion intensities. Comparability between laboratories was also good in terms of depth resolution and sputtering yield, allowing useful relationships to be found between ion energy, sputtering yield and depth resolution. The study has shown that organic depth profiling results can, with care, be compared on a day‐to‐day basis and between laboratories. The study has also validated three approaches that significantly improve the quality of organic depth profiling: sample cooling, sample rotation and grazing angles of ion incidence. © Crown copyright 2010.