Cobalt Films Research Articles

Influence of diffuse interfaces on the magnetoresistance in trilayer magnetic structures

The numerical Monte Carlo study of influence of diffuse interfaces on the magnetoresistance in trilayer magnetic structures Co/Cu(100)/Co and Pt/Co/Cu(100)/Co/Pt is carried out. The calculations of temperature dependence of the CPP magnetoresistance are realized for structures with thickness of cobalt films N=11 monolayers for cases with sharp and diffuse interfaces. Comparison of results shows that diffuse interfaces lead to appreciable influence on the magnetoresistance in these nanostructures.

Sunlight Control of Interfacial Magnetism for Solar Driven Spintronic Applications.

The inexorable trend of next generation spintronics is to develop smaller, lighter, faster, and more energy efficient devices. Ultimately, spintronics driven by free energy, for example, solar power, is imperative. Here, a prototype photovoltaic spintronic device with an optical‐magneto‐electric tricoupled photovoltaic/magnetic thin film heterojunction, where magnetism can be manipulated directly by sunlight via interfacial effect, is proposed. The magnetic anisotropy is reduced evidenced by the out‐of‐plane ferromagnetic resonance (FMR) field change of 640.26 Oe under 150 mW cm−2 illumination via in situ electron spin resonance (ESR) method. The transient absorption analysis and the first‐principles calculation reveal that the photovoltaic electrons doping in the cobalt film alter the band filling of this ferromagnetic film. The findings provide a new path of electron doping control magnetism and demonstrate an optical‐magnetic dual controllable logical switch with limited energy supply, which may further transform the landscape of spintronics research.

Growth of cobalt films at room temperature using sequential exposures of cobalt tricarbonyl nitrosyl and low energy electrons

Cobalt thin films were grown at room temperature using sequential exposures of cobalt tricarbonyl nitrosyl (CTN, Co(CO)3NO) and low energy (75–175 eV) electrons. During this cyclic growth process, the CTN molecules were first adsorbed on the substrate. The electrons then induced the desorption of the carbonyl and nitrosyl ligands from the adsorbed CTN. The removal of CO and NO ligands produced new adsorption sites. Subsequent CTN exposures allowed CTN to react with these new adsorption sites on the substrate. In situ ellipsometry was utilized to monitor the film thickness during the electron enhanced growth. Co growth rates as high as 1.3 Å/cycle were observed by in situ ellipsometry depending on the reaction conditions. The in situ ellipsometry also observed the CTN adsorption and the removal of the carbonyl and nitrosyl ligands. Quadrupole mass spectrometer measurements confirmed the desorption of CO and NO during electron exposures. X-ray photoelectron spectroscopy (XPS) measured N XPS signals from the Co films deposited using electron exposures at 200 eV. The N/Co XPS signal ratio was consistent with the dissociation of 13% of the nitrosyl ligands on the CTN precursors that lead to Co deposition. In contrast, the negligible C XPS signals from the Co films indicated that the CO ligands were desorbed completely from CTN by the electron exposures at 200 eV. Under identical reaction conditions at lower incident electron currents, the maximum growth rate was obtained at an electron energy of 125 eV. Because the Co growth depends on the electron flux, the Co films were deposited only on the surface area irradiated by the electron beam. The spatial profile of the Co film deposited using long electron exposure times was mapped by ex situ spectroscopic ellipsometry. This spatial profile displayed a pronounced flat top that was consistent with the electron flux desorbing nearly all the CO and NO surface coverage in the central area of the electron beam during each reaction cycle. The spatial profile was used to calculate an electron induced desorption cross section of σ = 2 × 10−17 cm2 at 200 eV. This cross section was in approximate agreement with the cross sections for the electron impact dissociation of CTN in the gas phase.

Evolution of magnetic anisotropy in cobalt film on nanopatterned silicon substrate studied in situ using MOKE

Evolution of magnetization behaviour of cobalt film on nano patterned silicon (1 0 0) substrate, with film thickness, has been studied. In situ magneto-optical Kerr effect measurements during film deposition allowed us to study genuine thickness dependence of magnetization behaviour, all other parameters like surface topography, deposition conditions remaining invariant. The nanopatterned substrate had a 8 nm thick amorphous silicon nitride surface layer. Thus, induced magnetic anisotropy in the Co film is expected to be of purely topographical origin, excluding any effect of the single crystalline Si (1 0 0) surface on magnetic anisotropy film due to possible epitaxy or surface step-induced anisoropy. In conformity with earlier results, the film induces a uniaxial magnetic anisotropy in the film, with its magnitude decreasing with increasing thickness. A magnetically dead layer of 2.6 nm forms at the interface with the substrate. Analysis of the magnetic layer thickness dependence of anisotropy shows that it has contributions from both, i) exchange energy which is volume dependent and, ii) stray dipolar fields at the surface/interface. This suggests that local magnetization follows only partially the topography of the rippled surface. As expected from energy considerations, for small film thickness, the local magnetization closely follows the surface contour of the ripples making the volume term as the dominant contribution. With increasing film thickness, the local magnetization gradually deviates from the local slope and approaches towards a uniform magnetization along the macroscopic film plane making the surface term as the dominant contribution. Significant deviation of the observed stray dipolar field contribution from the anisotropy energy calculated on the basis of Schlomann’s theory is observed, which can be attributed to several factors like, deviation of surface topography from an ideal sinusoidal wave, breaks of continuity along the ripple direction, topological defects like, pattern dislocations, and small film thicknesses compared to the correlation length of surface corrugations.

Electrochemical synthesis of CoOOH–Co(OH)2 composite electrode on graphite current collector for supercapacitor applications

CoOOH–Co(OH)2 film composed of hexagonal nanoflakes and flaky nanosheets were obtained on graphite current collectors for charge storage electrodes. Cobalt film was firstly electrodeposited cathodically on the graphite electrode in pyrophosphate media. The film was then transferred into KOH and CoOOH–Co(OH)2 composite electrode was produced by the application of a potential. The composite electrode cycled in KOH had CoOOH domination in the oxidized form and Co(OH)2 dominated the composite at the reduced potential. FTIR, XRD and SEM characterizations of the electrodes proves the compositional, structural and morphological behavior of the electrodes depending on their oxidation states, respectively. The binder-free cobalt-based composite electrode illustrates a specific capacity of 886 F g−1 at 5 mV s−1. The electrochemical performance of the as-synthesized nano-composite electrode displays cycle stability of 90.1% retention after 1000 cycles. The rate limiting step was the mass transfer between the resulting electrode and KOH electrolyte which was a mixture of diffusional and surface controlled mechanisms.

Thermal Annealing and Impurities Incorporation of Electrodeposited Cobalt Thin Film

Cobalt has recently attracted much attention as it is replacing copper in the ground rule metal level in advanced interconnects to minimize the resistivity increase in small features1. Defect-free filling of Co in small features has been demonstrated using various commercial additives2-4. Annealing has been used to further decrease and stabilize the resistivity of lines5. It is well known from copper studies that additives in electrolytes will not only be incorporated into the film as impurities but also affect the grain structures and resistivity of deposited film6, 7. Post deposition annealing has been used to further grow the grains and to influence the resistivity and reliability of lines and vias8. In this report, we use several different additives including dimethylglyoxime (DMG), sodium chloride (NaCl), and sodium 3-mercapto-1-propanesulfonate (MPS-Na) to study their individual and synergistic effects on impurity incorporation (C, N, Cl, S) in cobalt thin films. The film morphology, resistivity, crystallographic structure, and the impurity distribution were also investigated. Figures 1 (a) and (b) show the top-down SEM micrographs of two cobalt films deposited with different combinations of additives, one with 100 ppm DMG and 100 ppm MPS-Na, and the other with 100 ppm DMG and 100 ppm NaCl. A strong influence of additives on the morphology of Co films was observed. Figure 1 (c) shows the film sheet resistance change upon 300 C anneal in vacuum. The resistance decreases along the annealing time, but quickly settles within the first 2 hours except for the film deposited with a combination of the three additives (red line), 100 ppm DMG, 100 ppm NaCl, and 100 ppm MPS-Na. The later not only shows a much higher as deposited sheet resistance but also took a much longer 6 hours for the resistance to stabilize. Secondary ion mass spectroscopy (SIMS) was also used to quantify the impurities in the Co films. The resistivity change upon annealing will be discussed in detail in conjunction with the impurity and grain structure analysis. REFERENCES Gall, D., Electron mean free path in elemental metals. Journal of Applied Physics 2016, 119 (8), 085101.Rigsby, M. A.; Brogan, L. J.; Doubina, N. V.; Liu, Y.; Opocensky, E. C.; Spurlin, T. A.; Zhou, J.; Reid, J. D., Superconformal Cobalt Fill through the Use of Sacrificial Oxidants. ECS Transactions 2017, 80 (10), 767-776.Wafula, F.; Wu, J.; Branagan, S.; Suzuki, H.; Gracias, A.; van Eisden, J. In Electrolytic Cobalt Fill of Sub-5 nm Node Interconnect Features, 2018 IEEE International Interconnect Technology Conference (IITC), IEEE: 2018; pp 123-125.Kelly, J.; Chen, J.-C.; Huang, H.; Hu, C.; Liniger, E.; Patlolla, R.; Peethala, B.; Adusumilli, P.; Shobha, H.; Nogami, T. In Experimental study of nanoscale Co damascene BEOL interconnect structures, Interconnect Technology Conference/Advanced Metallization Conference (IITC/AMC), 2016 IEEE International, IEEE: 2016; pp 40-42.Kelly, J.; Kamineni, V.; Lin, X.; Pacquette, A.; Hopstaken, M.; Liang, Y.; Amanapu, H.; Peethala, B.; Jiang, L.; Demarest, J., Annealing and Impurity Effects in Co Thin Films for MOL Contact and BEOL Metallization. Journal of The Electrochemical Society 2019, 166 (1), D3100-D3109.Hau-Riege, S. P.; Thompson, C. V., In situ transmission electron microscope studies of the kinetics of abnormal grain growth in electroplated copper films. Applied Physics Letters 2000, 76 (3), 309-311.Zhang, W.; Brongersma, S.; Heylen, N.; Beyer, G.; Vandervorst, W.; Maex, K., Geometry effect on impurity incorporation and grain growth in narrow copper lines. Journal of The Electrochemical Society 2005, 152 (12), C832-C837.Ryu, C.; Kwon, K.-W.; Loke, A. L.; Lee, H.; Nogami, T.; Dubin, V. M.; Kavari, R. A.; Ray, G. W.; Wong, S. S., Microstructure and reliability of copper interconnects. IEEE transactions on electron devices 1999, 46 (6), 1113-1120. Figure 1

Electrodeposition of cobalt nanoparticles: An analysis of the mechanisms behind the deviation from three-dimensional diffusion-control

Electrochemical nucleation and growth of cobalt nanoparticles on aluminium was investigated by potentiostatic electrodeposition from cobalt sulphate solutions buffered with boric acid. At sufficiently low overpotential, the experimental current transients could be fairly reproduced by a mathematical model describing nucleation and growth under mixed kinetic-diffusion control, yielding an estimated number of particles per surface area in agreement with the SEM analysis of the deposits. However, the model gave estimates for the charge-transfer kinetic constant several orders of magnitude lower as compared to the Tafel analysis of cobalt electrodeposition on a previously electrodeposited cobalt film. This deviation can be explained by the inhibition of the direct attachment of metal ions, which can be induced by the adsorption of hydrogen onto cobalt particles and/or the formation of stable nanocluster aggregates. The implemented model failed to reproduce the current transients generated at larger overpotential values. A revision of the implemented mathematical model overcoming this limitation is proposed.

Structural, morphological, optical and magnetic properties of RF sputtered Co doped ZnO diluted magnetic semiconductor for spintronic applications

This article reports the fabrication and characterization of thin films of pure and cobalt doped ZnO (Co at 4% and 7%), a transparent diluted magnetic semiconductor (DMS) grown on ‘Si’ and glass substrates by RF magnetron sputtering technique. The crystalline structure and phase of the grown thin films were analyzed by using X-ray diffraction (XRD) method which confirmed the hexagonal wurtzite structure of the ZnO with slight lattice strain and change in orientation of the planes. The XRD also confirmed that, the films exhibit prominent peaks of (1 0 1) and (1 0 3) with polycrystalline nature. The morphology of the grown thin films was investigated by scanning electron microscopy (SEM) which confirmed the variation of micro-structure and size of the polycrystalline film’s surface. The energy dispersive X-ray spectra (EDS) from SEM have confirmed the presence of constituent elements in the films and concentration (in %) of each element. The crystalline properties and morphology of the film’s cross-section were studied by high resolution transmission electron microscopy (HR-TEM). The average thickness of the films was found to be about 600 nm from the cross-section electron microscopic images. The selected area electron diffraction (SAED) pattern from TEM was recorded for the Co (7%) doped ZnO film which has good polycrystalline quality. The optical transmittance of the films coated on corning glass substrates was investigated by UV–Visible spectrophotometer for pure, 4% and 7% Co doped ZnO films, which revealed the optical transparency of 85%, 75% and 65%, respectively. The room temperature ferromagnetism of the doped films was analysed by vibrating sample magnetometry and magneto optic Kerr effect. It was found that the ferromagnetic behaviour of films increases with ‘Co’ content and the results were discussed in detail.

The WC-Co/Fe–Ni interface: Effect of holding time on the microstructure, grain size and grain growth mechanism

The sinter-bonding of Fe-36 wt.% Ni powder to WC-Co, compacted under a vacuum, was performed at 1300 °C, for 2, 8 and 16 h. Three different holding times were studied during sample preparation. The results indicated that the compacted Fe-36 wt.% Ni/WC-Co sinter-bonded powders yielded a consolidated interface comprised primarily of hexagonal α-WC, cubic Fe0.64Ni0.36 and the presence of the Co3W3 complex, whose content increased as a function of holding time. Prolonged holding times promote bonding of the WC-Co/Fe–Ni component. However, excessive holding times result in significant contractions and failure by cracking. Furthermore, with increased holding time, grain sizes increased from the original size of 80 nm–390, 460, and 480 nm, when subjected to sintering temperatures of 1300 °C, for 2, 8 and 16 h, respectively. Grain growth occurs through the WC/Co/WC interfaces, not only in the liquid phase, but also in the solid state, at lower temperatures. Actual sintering temperatures are significantly lower than the melting point temperatures of cobalt or tungsten carbide because of the formation of intergranular films (complexion) at the WC/Co interface. Additionally, two abnormal grain-types were formed, exhibiting tungsten-rich characteristics that were complexed at the WC/Co interface, in addition to extreme abnormal grain growth (AGG), in the absence of cobalt films, located between the WC/WC grain boundaries. At the WC/Co interface, nanosized grains contribute to the AGG owing to the extremely large surface areas and short diffusion distances. The concentration gradient, together with extreme stress imbalance, at the WC-Co/Fe–Ni interface, results in particles to rotate, repack, and rearrange, which leads to the observed abnormal grains.

Epitaxial growth of cobalt doped TiO2 thin films on LaAlO3(100) substrate by molecular beam epitaxy and their opto-magnetic based applications

In this work, we report the growth process of pristine and cobalt (2%, 4%, 6% and 8%) doped TiO2 thin films on LaAlO3(100) substrate by molecular beam epitaxy (MBE) technique. The microstructural, magnetic, optical, photoconductivity and photocatalytic activity of the films were explored. Reflection high-energy electron diffraction (RHEED) confirms successful growth of single phase anatase TiO2 thin film and effects of cobalt (Co) doping on crystal phase depending on the growth conditions and correlating changes in their physical properties. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) establish highly pure crystalline nature and oxidation state of the elements. Magnetic measurements show room temperature ferromagnetism in all the thin films and suggest that growth conditions, oxygen vacancies and bound magnetic polaron (BMP) model account for the magnetic properties. The optical properties exhibit a red shift response associated with narrowing bandgap that influence photocatalytic activity. The 8% cobalt doped TiO2 film has shown 91% degradation with methylene blue and 88% degradation with Azo dye in 70 min under visible light irradiation exhibiting excellent photocatalytic performance. The photoconductivity measurements have confirmed photosensitive nature of TiO2 and 8% Co doped TiO2. Therefore, these opto-magnetic properties can be tuned for the applicability of future spintronic and optical devices.

Cobalt Intercalation of Graphene on Silicon Carbide

In this paper, we studied cobalt intercalation of single-layer graphene grown on the 4H-SiC(0001) polytype. The experiments were carried out in situ under ultrahigh vacuum conditions by high energy resolution photoelectron spectroscopy using synchrotron radiation and low energy electron diffraction. The nominal thicknesses of the deposited cobalt layers varied in the range of 0.2–5 nm, while the sample temperature was varied from room temperature to 800°C. Unlike Fe films, the annealing of Co films deposited on graphene at room temperature is shown to not intercalate graphene by cobalt. The formation of the graphene–cobalt–SiC intercalation system was detected upon deposition of Co atoms on samples heated to temperatures of above ~400°C. Cobalt films with a thickness up to 2 nm under graphene are formed using this method, and they are shown to be magnetized along the surface at thicknesses of greater than 1.3 nm. Graphene intercalation by cobalt was found to be accompanied by the chemical interaction of Co atoms with silicon carbide leading to the synthesis of cobalt silicides. At temperatures of above 500°C, the growth of cobalt films under graphene is limited by the diffusion of Co atoms into the bulk of silicon carbide.

Formation of Porous Nanostructure Cobalt Oxide Electrodeposits on Stainless Steel 304 Surface Used as Solar Absorber

Cobalt oxide layers was formed on a stainless steel type 304 surface after annealing heat treatment (400 oC / 10 hr) of the previously electrodeposited pure cobalt coating. The influence of heat treatment on surface morphology of pure cobalt films deposited has been studied. Crystallite structure transformation from hexagonal system to cubic system occurs. The coating layer morphology change from nano platelets to nano flecks was observed. SEM and EDAX are used for monitoring the gradually changes in the coated surface and nanostructure formation behavior. The degree of crystallitey and crystallite size changes, due to annealing at 400 oC/10 hrs, was measured by using XRD device. The optical properties were investigated by using UV-IR Spectrometry to study the effect of the formed surface coating at different electrodeposition conditions on the solar energy absorption behavior. The optimal solar absorptance was 98% at visible light wavelength range (400- 750 nm) for the films after annealing heat treatment.

Magnon dispersion in Ni/Co multilayers grown on Cu(100)

Motivated by recent studies on current-driven domain-wall motion we have explored the dispersion of spin waves (magnons) in ultrathin nickel/cobalt multilayers. The layers are grown epitaxially on Cu(100) surfaces and consist of $n$ nickel single-atom layers, each topped by a cobalt bilayer with $n=2$, 3, and $4\phantom{\rule{0.16em}{0ex}}(n\ifmmode\times\else\texttimes\fi{}\mathrm{N}{\mathrm{i}}_{1}\mathrm{C}{\mathrm{o}}_{2})$. Layers of the type $2\ifmmode\times\else\texttimes\fi{}{\mathrm{Ni}}_{2}{\mathrm{Co}}_{1}$ are also studied. While parallel to the film plane the magnon dispersion is nearly equal to that of pure cobalt films, magnons with wave vectors perpendicular to the film plane (standing waves) are considerably softened. The softening is attributed to a reduction of the effective interlayer exchange coupling between the two layers next to the interface with the Cu(100) substrate.

Magnetic phase transition and magnetic bistability in oxamato-based CoIICuII bimetallic MOF thin films

Thin films of an anionic oxamato-bridged cobalt(II)–copper(II) 3D MOF have been growth at 120 °C in DMSO through a one-pot reaction from Co(NO3)2·6H2O and (Me4N)2[Cu(2,6-Et2pa)2]·6H2O (2,6-Et2pa = N-2,6-diethylphenyloxamate) over Si(111) surfaces functionalized with carboxylic acid terminating groups. These heterobimetallic CoII2CuII3 MOF thin films (2) of about ten nanometers thickness show a ferrimagnetically ordered phase below ca. 10 K with a relatively large magnetic hysteresis similar to that of the bulk material of formula (Me4N)2[Co2Cu3(2,6-Et2pa)6]·5H2O (1).

Ammonia sensing performance of thin films of cobalt(II) phthalocyanine bearing fluorinated substituents

In this work, a new cobalt phthalocyanine derivative bearing 5-(trifluoromethyl)-2-mercaptopyridine substituents (CoPc) was synthesized and characterized. The redox properties of CoPc were studied by cyclic voltammetry (CV) and square wave voltammetry (SWV) methods. The sensing performance of CoPc thin films deposited by spin coating of its solution in ethylacetate was studied against low concentrations of ammonia (0.3 to 50 ppm) by measuring changes in the films’ conductivity at different humidity. It has been shown that the CoPc-based sensor displays an improved ammonia sensing performance in terms of sensitivity, response and recovery times. Ammonia can be detected in the presence of volatile organic vapors, and its detection limit was found to be 0.3 ppm. At the same time, low concentrations of CO2 comparable with the concentrations of ammonia do not influence on the sensitivity of CoPc film to ammonia, however the sensor response noticeably distorts in the presence of high CO2 concentrations in the gas mixture.

Influence of anisotropy on magnetoresistance in magnetic multilayer structures

Abstract The results of Monte Carlo study of influence of magnetic anisotropy on magnetoresistance in magnetic multilayer nanostructures are presented. Influence of anisotropy reorientation on magnetoresistance is considered on example of Co/Cu(100)/Co structure with anisotropy in plane of cobalt films, which is changed to anisotropy out plane in Pt/Co/Cu/Co/Pt structure with insertion of ultrathin films of platinum. It was shown that case of nanostructure with anisotropy out plane is characterized by important increase of magnetoresistance for structures with thicknesses of ferromagnetic films N ⩽ 11 monolayers.

Magnetoresistance Crossover in Cobalt/Poly(3-hexylthiophene,2,5-diyl) Hybrid Films Due to the Interface Effect

While organic electronic devices are multifunctional and offer high performance, they are nonetheless confronted with serious interface problems in their metal/organic-semiconductor contacts. In this work, a cobalt film is magnetron sputtered onto a P3HT film to simulate the Co/P3HT interface in a device. With decreasing Co thickness, the magnetoresistance is reversed from negative to positive, due to the increasing influence of the Co/P3HT interfacial layer. This result clearly shows the importance of the metal/organic interface in organic spin valves for spintronic applications.

Molecular mechanisms of atomic layer etching of cobalt with sequential exposure to molecular chlorine and diketones.

The mechanism of thermal dry etching of cobalt films is discussed for a thermal process utilizing sequential exposures to chlorine gas and a diketone [either 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hexafluoroacetylacetone, hfacH) or 2,4-pentanedione (acetylacetone, acacH)]. The process can be optimized experimentally to approach atomic layer etching (ALE); a sequential exposure to Cl2 and hfacH dry etchants at 140 °C is shown to proceed efficiently. The use of acacH as a diketone does not result in ALE with chlorine even at 180 °C, but the decrease of surface chlorine concentration and chemical reduction of cobalt is noted. However, thermal desorption analysis suggests that the reaction of chlorinated cobalt surface exposed to the ambient conditions (oxidized) with hfacH does produce volatile Co-containing products within the desired temperature range and the products contain Co3+. The effect of adsorption of ligands on the energy required to remove surface cobalt atoms is evaluated using the density functional theory.

Investigation of electroless deposition of cobalt films by EQCM in the presence of different amines

Electroless deposition (also called chemical deposition) is a commonly used chemical approach to prepare metallic layers on various substrates. Cobalt films were deposited on the copper electrode using dimethylamine borane (DMAB) as a reducing agent and different amines: diethylenetriamine (dien), triethylenetetraamine (trien), propylenediamine (prop), tetraethylenepentaamine (ttren), pentaethylenehexaamine (pnten). The deposition conditions of electroless deposition of cobalt films were investigated in more detail by means of electrochemical quartz crystal microgravimetry (EQCM). The effects of pH, temperature and concentration of the reactants on the deposition rate of cobalt films have been determined. It was found that the induction period of the deposition of cobalt films depends on solution composition, temperature, and the presence of different amines.

Improving Corrosion Resistance of Co Using Silane Coupling Treatment in Neutral Solution

Many products using a magnetic property, a mechanical property and chemical property of the thin metal film of the nm order are developing in the great many fields. The establishment of technology for corrosion prevention under nm level or the atom level is necessary to control corrosion without losing the characteristic of these products. In this study, surface treatments using BTSE, BTSPA, and BTSPS were evaluated from the viewpoint of improving the corrosion resistance of thin cobalt films. Corrosion behavior was evaluated corrosion current density using Tafel plots. Treated cobalt films were characterized by XPS and observed by SEM and AFM. A silane-coupling layer formed on the cobalt as a result of each of these treatments. However, the corrosion resistances offered by the different layers varied significantly. Immersion in BTSE with hydrogen peroxide for one hour did not yield an improvement, whereas immersion for 24 hours resulted in a large improvement. In contrast, immersion in BTSPA with hydrogen peroxide for 24 hours did not lead to a corrosion improvement, whereas immersion for one hour provided corrosion resistance. Immersion in BTSPS with hydrogen peroxide for either amount of time yielded no improvement, because of the poor coherency of the deposit on cobalt. These behaviors can be explained in terms of the hard and soft acid-base principle.