AES Depth Profiling Research Articles

Experimental and theoretical study on the production of carbide-rich composite nano-coatings

Carbides are known for high hardness and corrosion resistance and therefore applicable as protective coatings. C/Si and C/W multilayers (the individual layer thicknesses were between 10 and 20 nm) have been irradiated at room temperature by argon and xenon ions. The energies varied between 40 and 120 keV while the fluences were in the range of 0.07 - 6 × 1016 ions/cm2. The SRIM simulation was applied to have the proper ion energy. The irradiation induced intermixing and carbide (SiC and WC) formation at the interfaces already for the lowest irradiation fluence. The component in-depth distribution has been determined by AES depth profiling which showed that it varied greatly as a function of the irradiation conditions and layer structure. In both material pair the thickness of the produced carbide increased with square root of fluence but the mixing mechanism were different: local spike for C/W and ballistic for C/Si. The mixing efficiency was lower for the C/Si than for the C/W.

Novel method for the production of SiC micro and nanopatterns

In this paper we report on a novel, large area method to produce SiC nano- and micro patterns at room temperature where the compound and pattern formation happens in one step. We have previously demonstrated that SiC can be produced by noble gas irradiation of a Si/C multilayer system utilizing the ion beam mixing (IBM) taking place at the interfaces. Here we show that by applying IBM in samples masked in any desired way patterned SiC surfaces, micro and nanostructures, result. Two different masking layers were applied to demonstrate the capabilities of the method; a Langmuir-Blodgett (LB) film of 590 nm silica nanoparticles and a lithographic grid, of 2 μm periodicity, mounted to the surface of a Si/C multilayer system. The systems were irradiated by Xe+ ions of 120 keV. The samples before and after IBM have been analyzed by AFM, SEM and AES depth profiling, proving that patterning occurred: the non-covered areas became SiC rich regions, while the covered areas remained untouched. As a possible application for the patterned samples, the gold-coated LB patterned nanostructure was used for surface enhanced Raman spectroscopic detection of an organic dye molecule (R6G) demonstrating the efficiency of IBM for producing SERS substrates consisting of a very stable compound like SiC.

Preferential sputtering effects in depth profiling of multilayers with SIMS, XPS and AES

Multilayer profiles are studied using the MRI model with extension to preferential sputtering. The results show a clear distinction with respect to the main contributions to the depth resolution, namely surface and interface roughness, and atomic mixing. For dominating roughness, the effect of preferential sputtering is more pronounced for the residual surface composition profile (detected by XPS and AES), but it is zero for the sputtered matter composition profile (detected by SIMS). Dominating mixing results in a strong effect of preferential sputtering on the shape of the profile. While in that case its effect on the XPS or AES depth profile is relatively moderate, its effect on the SIMS depth profile is surprisingly strong and appears to be in contradiction to textbook statements. Interface width, location and layer thickness are always affected by preferential sputtering in XPS and AES depth profiles, but SIMS depth profiles are only affected if the contribution of atomic mixing to depth resolution cannot be ignored. In conclusion, a new definition of multilayer resolution is proposed which is based on the normalized amplitude of the wave-like profiles. The successful application of MRI model extended for preferential sputtering is given for fitting an experimental AES depth profile of an Ag/Ni multilayer.

Preferential sputtering and mass conservation in AES and SIMS depth profiling

The preferential sputtering and the mass conservation upon AES and SIMS depth profiling have been evaluated quantitatively based on the Mixing-Roughness-Information (MRI) model. The simulation results demonstrated that (a) the preferential sputtering plays an important role in the reconstruction of the true concentration-depth profile; (b) the mass conservation is a nature consequence in SIMS depth profiling but it is not fulfilled in AES depth profiling; (c) the layer thickness can be determined by applying the mass conservation law in AES depth profiling if the atoms preferentially sputtered out from the mixing zone are taken into account.

Evaluation of sputtering induced surface roughness development of Ni/Cu multilayers thin films by Time-of-Flight Secondary Ion Mass Spectrometry depth profiling with different energies O2+ ion bombardment

As a follow up on a previous paper on the quantitative evaluation of sputtering induced surface roughness and its influence on Auger electron spectroscopy depth profiling of polycrystalline Ni/Cu multilayers thin films, the ion sputtering induced surface roughness of these multilayered Ni/Cu polycrystalline thin films under low energy (0.5, 1.0 and 2.0 keV) O2+ ion bombardment and 1.0 keV Cs+ ion sputtering were investigated with Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Atomic Force Microscopy (AFM). The lowest energy (0.5 keV) O2+ ion sputtering gave the best depth resolution for the different energy ion sputtering. Furthermore the 1.0 keV Cs+ ion sputtering led to a better resolution than the O2+ ion sputtering. The ToF-SIMS depth resolution was also better than the AES depth profiling with a 2.0 keV Ar+ ion sputtering. The Mixing-Roughness-Information depth (MRI) model used for fitting of the ToF-SIMS depth profiles accounts for the broadening upon experimental depth profiling owing to the effects of atomic mixing, surface roughness and information depth. The MRI fitted roughness parameters obtained from the ToF-SIMS depth profiling are in good agreement with the root-mean-square roughness obtained from the AFM topography scans of the crater bottom. Ion sputtering induced roughness and depth resolution during ToF-SIMS depth profiling of Ni/Cu multilayers were quantitatively evaluated according to the MRI fitting parameters.

Microstructural and electrical properties of heat treated resistive Ti/Pt thin layers

Study of DC sputtered Ti/Pt thin film layers on SiO2/n-Si substrate with the emphasis on post deposition heat treatment is presented. Microstructural and morphological properties of Ti/Pt thin films annealed in the range 300–700°C in air are investigated and correlated with measured electrical properties. AES depth profile and composition of the sample annealed at 400°C and 700°C showed significant diffusion of Ti throughout the Pt layer toward surface, accompanied with enhanced oxygen incorporation, while keeping rather constant TiOx composition throughout the structure. AFM and SEM analyses of Ti/Pt film morphology showed that Pt grain size was almost temperature independent up to 400°C, while above 500°C, grain growth was enhanced. XPS analyses confirmed that most of Ti incorporated in the film was in oxide state (Ti4+) after annealing at 700°C. EBSD analyses confirmed strong (111) texture of Pt polycrystalline grains annealed above 500°C.Resistance of meandered Ti/Pt resistors was found to decrease significantly above 500°C and complies well with the microstructural rearrangements determined by AFM and AES analyses. It was further determined that by increasing the annealing temperature from 300°C to 700°C, a monotonic increase of temperature coefficient of resistance from 1400ppm/°C to 2400ppm/°C, respectively, was obtained. This represents a considerable improvement in sensitivity of Ti/Pt layers used as a temperature sensing devices. Resistance exhibited linear temperature dependency with nonlinearity better than 0.84%.

Zirconium-based conversion film formation on zinc, aluminium and magnesium oxides and their interactions with functionalized molecules

Zirconium-based conversion treatment of zinc, aluminium and magnesium oxides have been studied in-situ using ATR-FTIR in a Kretschmann geometry. This set-up was coupled to an electrochemical cell, which allowed to obtain chemical and electrochemical information simultaneously as a function of conversion time. This elucidated the strong relation between physico-chemical surface properties and zirconium-based conversion kinetics. Whereas the surface hydroxyl density of zinc and aluminium increased during conversion, magnesium (hydr)oxide was shown to dissolve in the acid solution. Due to this dissolution, strong surface alkalization can be expected, explaining the rapid conversion kinetics. AES depth profiling was used to determine the final oxide thickness and elemental composition. This confirmed that magnesium is most active and forms a zirconium oxide layer approximately 10 times thicker than zinc. On the other hand, the presence of zirconium oxide on aluminium is very low and can be considered as not fully covering the metal oxide. Additionally, the converted oxide chemistry was related to the bonding mechanisms of amide functionalized molecules using ATR-FTIR and XPS. It was shown that inclusion of zirconium altered the acid-base properties, increasing the substrate proton donating capabilities in case of magnesium oxide and increasing hydrogen bonding and Bronsted interactions due to increased surface hydroxide fractions on zinc and aluminium substrates.

Multi-phase structured hydrogenated amorphous silicon carbon nitride thin films grown by plasma enhanced chemical vapour deposition

In this work, hydrogenated amorphous silicon carbon nitride (a-SiCN:H) films were grown by plasma-enhanced chemical vapour deposition (PECVD) process using SiH4, CH4 and N2 gas discharge. The effects of N2 flow-rate on the structure, optical as well as photoluminescence properties were investigated. AES depth profile and FTIR spectroscopy analysis were used to probe the distribution of elemental composition and the bonding configuration within the film structure respectively. As a complement, Raman analysis were done to investigate the presence and properties of the amorphous carbon phases within the films. The films grown on both c-Si and glass substrates were multiphase in structure with dominant component of a-SiCN:H, a-SiC:H and a-CN:H phases. Optical spectrophotometer measurements indicated that the band gap energy was dependent on the dominant phase present in the film structure and the overlapping of the tail states within the band gap, contributed to the low ETauc values of the films. The origin of the most dominant PL emission from the films was shown to be contributed by radiative transition and recombination within the band tails of the sp2-C clusters within the film structure.

High Temperature Reliability Assessment and Degradation Analysis for Diamond Semiconductor Devices

The long-term reliability of Schottky pn diodes (SPNDs) on diamond having widely used Ti/Pt/Au electrodes was investigated at 500°C in order to identify degradation phenomena at higher temperatures. A vital degradation event was observed after the passage of about 100 hours in that both forward and reverse currents were progressively reduced. AES depth profiling and X-STEM-EELS analyses revealed that this occurred because the Ti contact material changed to insulating (or semiconductive) TiO2, causing large series resistance.

On characterizing microscopically the adhesion interphase for the adhesion between metal and rubber compound Part III. Effect of brass-plating amount for brass-plated steel cord

Three kinds of brass-plated steel cords with different brass-plating amounts from 2.62 to 5.01 g/kg were prepared and their adhesion properties to rubber compounds were studied. Adhesion properties decreased with the increase in the brass-plating amount from 2.62 to 3.88 g/kg. Furthermore as the increase of brass-plating amount over 3.88%, adhesion property increased. The strong adhesion of brass-plated steel cord with low brass-plating amount to the rubber was shown not only after curing but also after hostile aging treatments. The good adhesion stability against humidity aging of adhesion property for brass-plated steel cord with low brass-plating amount to rubber compound was discussed in terms of the formation and growth of adhesion interphase determined by AES depth profile. The good adhesion stability of brass-plated cord with low brass-plating amount can be resulted from the suppression of the excessive growth of copper sulfide and the inhibition of dezincification due to the low brass-plating amount.

Analysis of 16 QFN Device I/O Pads for Solderability Failures

In-process failures were experienced during printed circuit board (PCB) SMT assembly of a 16 Quad Flat No Leads (QFN) device. The failures appeared to be solderability related with QFN unit I/O pads not soldering robustly and sometimes leading to QFN detachment following board mounting. When assembly did take place on affected QFN units, the resulting solder joint was observed to be weak. This paper reports on very systematic analyses of the QFN device I/O pads using optical inspections, AES surface, AES depth profiling, SEM/EDX, SIMS, FIB and TEM cross-sectional measurements to determine the root cause of the failure and the failure mechanism. The detached QFN units, suspect and good unsoldered units, passing and failing units obtained from customers were examined. The industry standard surface mount solderability testing was performed on good and suspect parts, and all were observed to pass as evidenced by >95% coverage of the I/O pads. Optical inspections and a wide variety of physical analysis of the pads on fresh parts showed no anomalies with only the expected Au over Pd over Ni found. AES analysis was performed including depth profiling to look for any issues in the NiPdAu over base Cu plating layers that could be contributing the solderability failures. The AES depth profiling indicated AuPd film on the Ni under layer for the I/O pads as expected. No unexpected elements or oxide layers were observed at any layer. Then, one failing and one passing units were compared by doing FIB cross-section, FIB planar section and TEM cross-section analysis. The cross-sectional analysis showed rough Ni surface for the failing units, while the Ni surface was relatively smooth for the passing unit. Further, finer Cu grains and Ni grains were observed on the passing units. Additionally, the lead frame fabrication process mapping showed rough Cu, Ni “texturing” and use of low electro chemical polishing (ECP) current on the bad units compared to that of the good units. All affected bad units were confirmed coming from a second source Cu supplier with the rough Cu. The weak and irregular NiSn IMC formation on the bad units caused IMC separation and possible spalling during board solder reflow primarily due to the rough base Cu and irregular grain sizes and resulting lower ECP lead frame plating current. A possible final factor was marginally low Pd thickness. In conclusion, the 16 QFN device solderability failure root cause summary and the lessons learned from a wide variety of analysis techniques will be discussed.

The Influence of Water Radiolysis on Corrosion By Supercritical Water

Development of is attractive because of the high thermal efficiency afforded by operating at supercritical temperatures. The nuclear core materials to be used in supercritical water reactors (SCWR) will be exposed to the aqueous coolant at supercritical temperatures and under high radiation fields. Understanding the response of the structural alloys to the aggressive chemical conditions generated by supercritical water radiolysis is important to ensure the integrity and enhance the usable life of SCWRs. This paper reports on the corrosion behavior of Alloy 625, Incoloy® 800H, and Type-310 stainless steel, the candidate materials proposed for use in a Canadian pressure-tube SCWR heat transport system. These materials were exposed to simulated reducing and oxidizing conditions in a Hastelloy® autoclave containing subcritical (saturated steam at 285°C) and supercritical water (at 400°C and 250 bar) in the absence of radiation, and while being subjected to gamma radiation at 285°C under saturated conditions, thereby simulating the in situ generation of water radiolysis products. After exposure, the alloy specimens were retrieved and characterized by SEM-EDX, Raman spectroscopy, XPS, and AES depth profiling. On all of these materials, the oxide films formed in the presence of radiation were thinner than those on unirradiated surfaces, and those formed in the presence of oxygen were thinner than those grown in the absence of oxygen. The kinetics of oxide growth were found to be slower at the lower temperature. The nature of the corrosion products formed and the role of various alloying elements in influencing the protection offered by the corrosion product oxide are discussed in detail.

The chemical resistance of nano-sized SiC rich composite coating

30keVGa+ implantation was applied to a nominally C(20nm)/Si(20nm)/C(20nm)/Si(20nm)/C(20nm)/Si substrate multilayer system. Due to the irradiation intermixing occurred and a layer containing C, Si, Ga and (amorphous) SiC was obtained. The thickness (7–30nm) and composition of the layer depended on the fluence of irradiation. The chemical resistance of the layer was tested by applying microwave oxidation and various polysilicon etchants and was found to be excellent if the SiC concentration was above 20%. Using an etchant with an etching rate of about 100nm/s for poly-Si during 10s had not affected the integrity of the intermixed region with a thickness of 10nm; only some defects appeared. With a further increase of the etching time the size of defects increased resulting in inhomogeneous layer removal. The in-depth composition of non-defective region that remained on the surface was determined by AES depth profiling, which revealed that the intermixed layer did not change during the harsh etching except the removal of its thin surface layer containing less than 20% SiC. The etching rate of the intermixed layer is orders of magnitude lower than that for poly-Si.

XPS and AES sputter‐depth profiling at surfaces of biocompatible passivated Ti‐based alloys: concentration quantification considering chemical effects

Ti‐based materials are frequently used worldwide for orthopedic implants. New β‐type or glassy alloys with nontoxic alloying elements are investigated with expected improved biofunctionality. The surface regions and surface layers formed at the materials are decisive for the integration of the implant in the body. Thus, the investigation of the surfaces with analytical methods such as XPS and AES is an essential task. We investigated such materials with different alloying elements after electrochemical passivation by both XPS and AES depth profiling. We discuss chemical changes due to the ion sputtering and motivate the use of non‐differentiated spectra for AES quantification. The behavior of the alloy elements in the investigated depth profiles is discussed. Copyright © 2014 John Wiley & Sons, Ltd.

Quantification of AES depth profiling data of polycrystalline Al films with Gaussian and non-Gaussian surface height distributions

Sputtering-induced roughness is the main distortional factor on the depth resolution of measured depth profiles, in particular, for sputtering of polycrystalline metals. Frequently, the surface height distribution of the sputtering-induced roughness exhibits an asymmetrical feature. In such a case, a non-Gaussian height distribution function (HDF) has to be applied for the quantification of a measured depth profile. By replacing the usually applied Gaussian HDF with that of an asymmetrical triangle in the Mixing-Roughness-Information depth model, measured Auger electron spectroscopy depth profiling data of the interface of polycrystalline Al films on Si are perfectly fitted. The asymmetric triangle height distributions obtained from the best fit are a reasonable approximation of the height distributions measured by atomic force microscopy. Copyright © 2013 John Wiley & Sons, Ltd.

Quantification of N<sub>2</sub><sup>+</sup> Implanted AES Depth Profiling Data in Al

The nitrogen implanted profile in aluminum generated by 60keV N2+ bombardment is simulated numerically by the Stopping and Range of Ions in Matter (SRIM) program and is fitted analytically by the Schulz-Wittmaack expression. Taking the SRIM simulated profile as true concentration-depth profile of implanted nitrogen in aluminum matrix, the corresponding measured AES depth profiling data of implanted nitrogen are well fitted by the Mixing-Roughness-Information (MRI) model.

Quantification of the N<sub>2</sub><sup>+</sup> Implanted AES Depth Profiles in Cobalt Films

The nitrogen implanted profiles in cobalt films that are generated by N2+bombardment with three energies of 0.5, 2.0 and 5.0 keV are simulated by the analytical Schulz-Wittmaack expression and the SRIM program, respectively. Taking the both simulated profiles as concentration-depth profiles, the corresponding measured AES depth profiling data of implanted nitrogen are perfectly fitted by the Mixing-Roughness-Information depth (MRI) model.

Microstructure and Compositional Distribution of Selenized Cu(In,Ga)Se_2 Thin Film Utilizing Cu_2In_3, CuGa and Cu_2Se

A high-quality CIGS film with a selenization process needs to be developed for low-cost and large-scale production. In this study, we used <TEX>$Cu_2In_3$</TEX>, CuGa and <TEX>$Cu_2Se$</TEX> sputter targets for the deposition of a precursor. The precursor deposited by sputtering was selenized in Se vapor. The precursor layer deposited by the co-sputtering of <TEX>$Cu_2In_3$</TEX>, CuGa and <TEX>$Cu_2Se$</TEX> showed a uniform distribution of Cu, In, Ga, and Se throughout the layer with Cu, In, CuIn, CuGa and <TEX>$Cu_2Se$</TEX> phases. After selenization at <TEX>$550^{\circ}C$</TEX> for 30 min, the CIGS film showed a double-layer microstructure with a large-grained top layer and a small-grained bottom layer. In the AES depth profile, In was found to have accumulated near the surface while Cu had accumulated in the middle of the CIGS film. By adding a Cu-In-Ga interlayer between the co-sputtered precursor layer and the Mo film and adding a thin <TEX>$Cu_2Se$</TEX> layer onto the co-sputtered precursor layer, large CIGS grains throughout the film were produced. However, the Cu accumulated in the middle of CIGS film in this case as well. By supplying In, Ga and Se to the CIGS film, a uniform distribution of Cu, In, Ga and Se was achieved in the middle of the CIGS film.

Effect of CaO Addition on the Ignition Resistance of Mg-Al Alloys

The ignition resistance was investigated for CaO added Mg-Al alloys. The ignition resistance was examined by DTA for quantitative data, furnace chip ignition test for the safety of machined chips and torch ignition test for safety of products. The ignition resistances under all conditions greatly increased by CaO addition. AES depth profile was performed to evaluate the ignition resistance in terms of surface oxide stability. In the case of Mg-Al alloy without CaO, there was the thick and porous MgO oxide layer on the surface. The depth profile for CaO added Mg-Al Mg alloys indicated that the surface consisted of the thin and dense oxide layer mixed with MgO and CaO. [doi:10.2320/matertrans.M2010397]

Properties of Transparent Conducting ATO Films Deposited by RF Magnetron Sputtering

We have discussed the effects of substrate temperature and Sb2O3 composition on properties of ATO thin films by RF magnetron sputtering. Above 250°C of substrate temperature, the films exhibited good crystallographic and electrical properties. At fixed substrate temperature of 250°C, the electrical properties of ATO film were enhanced with increasing Sb concentration. From the AES depth profile and XRD pattern for the film with 92:8 of SnO2:Sb2O3 composition, we found that Sb was uniform and there was no secondary phase or phase separation in ATO film. The rms roughness of the films was minimum value, 1.54 nm, at the composition of 92:8 wt%. For the ATO thin film with 92:8 composition exhibited good chemical endurance and thermal stability, which seems to be good for touch panel applications.