ESCA Techniques Research Articles

Esca and reels characterization of electrically conductive polyimide obtained by ion bombardment in the keV range

AbstractPolymide films were bombarded with Ar+ at 150 keV at various doses from 5 × 1012 to 2 × 1017 ions cm−2. Ion bombardment was found to produce a drastic decrease of the electrical resistivity of the polymide from about 1016 to 3 × 10−3 Ω cm, the effect being dependent on the ion dose. The chemical structure of the conductive films obtained was characterized by means of ESCA and REELS techniques. The modification of the original polymer seems to proceed at low ion doses (up to 5 × 1014 ions cm−2) by means of the progressive elimination of the carbonyl groups and the related destruction of the imidic rings, while at high doses (from 5 × 1015 ions cm−2) the carbonization of the polyimide occurs with the production of an amorphous carbon still containing significant amount of residual N and O atoms.

On the passivation of nickel in aqueous solutions - I. The identification of insoluble corrosion products on nickel electrodes using optical and ESCA techniques: by R.E. Hummel, R.J. Smith and E.D. Verink Jr. (pp.803–813, Vol. 27, No. 8)

On the passivation of nickel in aqueous solutions - I. The identification of insoluble corrosion products on nickel electrodes using optical and ESCA techniques: by R.E. Hummel, R.J. Smith and E.D. Verink Jr. (pp.803–813, Vol. 27, No. 8)

Characterization of TiN Films Prepared by ion Beam Assisted Deposition

AbstractOne of the advantages of the ion beam assisted deposition process is its controllability of the processing parameters such as: ion-to-atom arrival ratio and the ion energy. In this study, the effects of the nitrogen ion energy (from 1 KV to 30KV) on the TiN film morphology and microstructures were systematically investigated as a function of ion-to-atom arrival ratios, using TEM, XTEM, SEM, ESCA and other analytical techniques.

Characterization of TiN Films Prepared by Ion Beam Assisted Deposition

ABSTRACTOne of the advantages of the ion beam assisted deposition process is its controllability of the processing parameters such as: ion-to-atom arrival ratio and the ion energy. In this study, the effects of the nitrogen ion energy (from 1 KV to 30KV) on the TiN film morphology and microstructures were systematically investigated as a function of ion-to-atom arrival ratios, using TEM, XTEM, SEM, ESCA and other analytical techniques.

Observation of anomalous high resistance to implanted areas caused by reactive ion etching (RIE)

Oxide etching for contact hole definition and sidewall spacer formation is normally performed using fluorocarbon gas mixtures in a plasma reactor. A significant amount of over-etching must be allowed to compensate for uneven oxide thickness and poor process uniformity. During this time underlying silicon material is subjected to energetic particle bombardment which under severe circumstances can induce polymer deposition and radiation damage. Recent results indicate that contacts made to n + and/or p + areas, defined by reactive ion etching, suffer from high resistance which can lower circuit yield. In view of the foregoing, experiments were performed to investigate this phenomena as well as to find a solution whereby the problem of high contact resistance could be circumvented. Reactive ion etching (RIE) was performed in an hexode etcher using CHF 3, O 2 gas mixture at 50 mtorr. Plasma etching was performed in a single wafer etcher using a gas mixture of CHF 3, C 2F 6 and He at 1.5 torr. The as-etched samples were analysed using spreading resistance profiling (SRP), RBS-channeling measurements, ESCA and 4-point probe techniques. These measurements were used to investigate both the presence and the electrical activity of the implanted dopants. The nuclear reaction 1H( 15N, αγ) 12C at 6.38 MeV was employed to profile the hydrogen depth distribution. Cross sectional TEM was performed in order to characterize the extent of the damage. Contact chains defined by dry processing were used for electrical evaluation. It is shown that the silicon surface can be restored after RIE via an in situ low power etch with NF 3. The effectiveness of such a procedure was verified by contact resistance and thermal wave measurements.

CEMS study of irradiation effects on the chemical bonding of SnO 2

For a comparative study of ion irradiation effects on the chemical bonding of metal oxides, SnO 2 thin films were irradiated by 180 keV 120Sn ions and 80 keV N + ions, and analyzed by conversion electron Mössbauer spectroscopy (CEMS) and ESCA techniques. The results show that only 120Sn ion irradiation causes appreciable rupture of the SnO bonds. This phenomenon is interpreted by a proposed thermal spike model. Theoretical estimates are consistent with the experimental results.

Wire Aging of Hydrocarbon Gases with TMAE Additions

We report on experimental results describing wire aging properties of the CRID/RICH detectors in the TMAE gas environment. This test used 7, μm and 33 μm diameter carbon fibers, and 20 μm diameter gold-plated tungsten wires as sense wires, and operated in gas mixtures of either CH4 or C2H6 at 1 atm, together wth 0.6 Torr of the photoionizing vapor TMAE (tetrakis dimethylamino ethylene), which serves as a photocathode in the CRID detectors. The wires were damaged by the Fe55 X-rays. This paper is based on irradiation of 20 wires, each being a separate test. The gas purity was consistent with requirements of CRID detectors (< 1 ppm of oxygen, < 1 ppm of water). The test explored the aging as a function of wire diameter, wire material, gas flow, gas temperature, rate of radiation and gas type. Several chemical analyses of the deposit samples were performed (FTIR, ESCA and GC-MS techniques).

The passivation of nickel in aqueous solutions—I. The identification of insoluble corrosion products on nickel electrodes using optical and ESCA techniques

In situ differential reflectometry in conjunction with ESCA techniques are used to identify various surface films which form electrochemically on nickel. The film observed on pure Ni in a 0.15 N Na 2SO 4 electrolyte has been identified to be primarily Ni(OH) 2. At different values of pH and potential, NiO has been found to form simultaneously with Ni(OH) 2. At solutions with pH > 8, the Ni(OH) 2 film partially transforms into a third oxide, presumably NiOOH, which can only be observed in situ.

Catalysis by amorphous metal alloys. Part 3.—Catalytic activity of raney copper catalysts prepared from amorphous Cu62Zr38 powder

Raney-type copper catalysts were prepared by treating the pulverized amorphous and crystalline Cu62Zr38 alloys with dilute HF. The catalytic activity for the hydrogenation of olefins was much greater with the catalyst from the amorphous alloy. The great enhancement of the activity of this catalyst was ascribed to its porous structure, the high surface concentration of copper, the high frequency of the distribution of active sites and the electronic state of the surface site, which were clarified by studies of the surface states using ESCA, XRD, SEM and carbon monoxide chemisorption techniques.

Corrosion of a stainless steel with low nickel content under static conditions

The pattern of selective release of chromium, iron and molybdenum from a non-prepassivated ferritic stainless steel, with the designation SS 2326 and a nickel content of 0.3%, has been measured in artificial saliva under static conditions using nuclear tracer and ESCA techniques. The ICP-method was used to detect nickel which was found only in one case. The release rate of chromium, iron and molybdenum showed a strong time-dependent decrease as a consequence of chromium enrichment in the surface. This was shown by ESCA-measurements. This kinetics is characteristic for a passivating alloy i.e. self passivation. In view of the low nickel content of the SS 2326 steel compared to conventional stainless steel, the material may possess potential for use as a dental or orthopaedic biomaterial.

Wavelength dependence of the surface photo-oxidation of Bisphenol A polycarbonate

ESCA and difference uv techniques have been used to monitor the changes which take place in the surface and bulk chemistry, during photo-oxidation of Bisphenol A polycarbonate, as a function of irradiation wavelength over the range 280–330 nm. Whereas for the surface, the maximum change is observed at 280 nm, in the bulk this occurs at 290 nm. Irradiation at 310 nm, which gives bulk changes similar to natural weathering, does not involve the carbonate group in the surface so that the initial photo-instability of polycarbonate cannot be attributed to a photo-Fries rearrangement of this moiety. The surface photo-reactions are consistent with photo-oxidation.

The mechanism of oxidation of Fe-Ni-Co alloys; The role of Ti and Mo

Specimens of pure Ti and Mo, as well as 250 grade maraging steel, were heat treated in superheated steam at 485°C for 3 h. The composition profiles and binding energies were studied, using AES and ESCA techniques. It has been shown that the mechanism of oxide formation is that of cation migration.

Electron and Ion Spectroscopic Studies of the Passive Film on Iron‐ Chromium Alloys

Binary iron‐base alloys containing chromium additions of 3, 9, 12, and 18% were passivated in borate buffer (pH 8.4). The passive films formed on these alloys were investigated by Auger, ESCA, and SIMS techniques. For the Fe‐3Cr alloy passivated in the potential range 0.65–1.45V vs. RHE, the Auger spectra showed negligible Cr in the passivation layer. For the Fe‐9Cr, Fe‐12Cr, and Fe‐18Cr alloys, the Cr content was lower at the surface of the passive film and passed through an apparent maximum within the film. ESCA measurements indicate that the passive film of Fe‐18Cr alloy has a higher content of bound water in the form of OH− than Fe‐3Cr alloy. The SIMS results for the Fe‐Cr alloys generally confirm the relative measurements of Cr in the passive film found from Auger measurements.

Sulfur chemistry in a copper smelter plume

Sulfur transformation chemistry was studied in the plume of the Utah smelter of Kennecott Copper Corporation from April to October 1977. Samples were taken at up to four locations from 4 to 60 km from the stacks. Data collected at each station included: SO 2 concentration, low-volume collected total paniculate matter, high-volume collected size fractionated paniculate matter, wind velocity and direction, temperature, and relative humidity. Paniculate samples were analyzed for S(IV). sulfate, strong acid, anions, cations, and elemental concentrations using calorimetric, ion Chromatographie, FIXE, ESCA, ion microprobe, and SEM-ion microprobe techniques. The concentration of As in the paniculate matter was used as a conservative plume tracer. The ratios Mo/As, Pb/As, and Zn/As were constant in particulate matter collected at all sampling sites for any particle size. Strong mineral acid was neutralized by background metal oxide and/or carbonate particulates within 40km of the smelter. This neutralization process is limited only by the rate of incorporation of basic material into the plume. Two distinct metal-S(IV) species similar to those observed in laboratory aerosol experiments were found in the plume. The formation of paniculate S(IV) species occurs by interaction of SO 2 (g) with both ambient and plume derived aerosol and is equilibrium controlled. The extent of formation of S(IV) complexes in the aerosol is directly proportional to the SO 2(g) and paniculate (Cu + Fe) concentration and inversely proportional to the paniculate acidity. S(IV) species were stable in collected paniculate matter only in the neutralized material, but with proper sampling techniques could be demonstrated to also be present in very acidic particles at high ambient SO 2(g) concentrations. Reduction of arsenate to arsenite by the aerosol S(IV) complexes during plume transport is suggested. The SO 2(g)-sulfate conversion process in the plume is described by a mechanism which is first order in SO 2(g). Equations are derived describing sulfur chemistry when both S(IV) and sulfate formation occur in a plume. The formation of sulfate results primarily in the formation of < 0.5 μm particulates. The formation process is not correlated with plume expansion, paniculate acidity, metal content, or S(IV) species. Due to meteorological restrictions on sampling, data were collected only during periods of maximum insolation. The formation of sulfate from SO 2(g) in the plume during periods of high insolation is temperature dependent with an apparent activation energy of 16.6 ± 1.4 kcal mol −1 and a k 1, value of 0.039h −1 at 25°C.

ESCA and SIMS analysis of the composition of passive films formed on E-brite stainless steel

Anodic oxide films were formed on E-brite 26% Cr-1% Mo stainless steel in 1.0M NaCl+H 2SO 4 solution (pH 3.3). ESCA and SIMS techniques have been used to determine the composition of the passive film. It was found by both techniques that molybdenum was present on the outermost part of the film, however, it was not detected by Auger electron spectroscopy as reported by other workers. The SIMS results showed that there was a chromium enrichment in the passive film.

Electron spectroscopy of ion beam and hydrocarbon plasma generated diamondlike carbon films

Mechanically hard, electrically insulating (diamondlike) carbon thin films have been produced by low energy carbon ion beam deposition and by decomposition of butane gas. Deposition parameters are presented for these two methods. The ion beam films can be produced with or without a secondary discharge in the ion source and the parameters are given for these two modes of operation. ESCA and electron energy loss (EELS) techniques have been used to examine the electronic character of these films. ESCA carbon (1s) spectra show that the films are composed mostly of C–C bonds and that a negative bias is important to eliminate C–H bonds from the butane generated films. EELS data show that the films are more diamondlike in that the strong graphitic feature at 6.5 eV is not evident in these films. Among the other measured properties of these films, the refractive index (2.3 at 5 μm) and hardness (1850 knoop) are in keeping with the diamondlike character of these films.

The corrosion of unprotected steel in an inert-gas atmosphere containing water vapour, oxygen, nitrogen and different amounts of sulphur dioxide and carbon dioxide

The atmospheric corrosion of a commercial steel has been studied in a nominal inert gas. This gas exists inside the cargo tanks of some crude-oil tankers. The gas contained 3.0–21%O 2, 0–12%CO 2, 0–300 ppm SO 2; the balance was N 2. Relative humidity was 90% at 295 K (22.0°C). In contrast to the behaviour at moderate concentrations of SO 2 at high concentrations protective films were formed on the surface of the steel. A mechanism for the process is given. Corrosion products were studied using X-ray, i.r. and ESCA techniques. The following phases were identified: FeS, α-FeSO 3·3H 2O, γ-FeSO 2·3H 2O, FeSO 3·2H 2O and FeSO 4·7H 2O. Crystallographic data of the previously unknown phases γ-FeSO 3·3H 2O and FeSO 3·2H 2O are given.

The effects of heat treatment and implantation of aluminium on the oxidation resistance of FeCrAlY alloys

The oxidation resistance of FeCrAlY alloys is known to be due to the rapid formation of a protective film containing α-Al 2O 3. The near-surface concentration of Al has been increased by ion implantation, and for a dose of 10 17 Al + ions cm −2 (equivalent to 4.5 μ cm −3 the parabolic oxidation rate constant has been reduced by a factor of 140 in tests at 1100°C. Heat treatment prior to oxidation also proved beneficial for reasons which are discussed. These relate to the diffusivity of Cr and other spinel-forming elements within the metal. Analysis of Al +-implanted steels after oxidation, using ESCA and EDS techniques, confirmed the high concentration of Al 2O 3 within the oxide, and SEM examination showed that the scale is much more compact than in the unimplanted case. Suggestions are made for enhancing still further the efficacy of Al + implantation as a means of improving oxidation resistance and for optimizing the synergistic effect of yttrium and aluminium.

Oxidation state and surface segregation of Mo ions in titania catalysts evidenced by ESR, UV and ESCA techniques

Incorporation of Mo ions into a TiO 2 matrix has been studied as a function of preparation procedure and heat treatment conditions, using ESCA, UV and ESR spectroscopies. Oxidation state, coordination geometry and incorporation of Mo ions into the TiO 2 particles have been considered. For anastase samples, UV and ESCA techniques show that surface and bulk concentrations of Mo are about identical, with the majority of Mo being in the form of Mo 6+ and a significant quantity existing as Mo 5+ in distorted octahedral symmetries. ESR spectroscopy only detects substitutional ions designated Mo s 5+ in very small amounts (∼1% of the 0.5% Mo introduced). For rutile, heated at 800°C in air, ESCA technique shows that the surface concentration is enriched in Mo in the +6 oxidation state by a factor 10 compared to the bulk, whereas UV spectroscopy shows that Mo is mainly incorporated in the bulk in the form of Mo 5+ presenting two different environments of the distorted octahedral type. ESR techniques detect substitutional Mos in very small amounts (∼1% of the 0.5% Mo introduced). For rutile samples, directly prepared by the flame method, the surface concentration of Mo is about twice that of the bulk, Mo ions being mainly in a +6 oxidation state at the surface and +5 in the bulk. Strong surface enrichment (× 10–20) occurs after heating anastase or rutile at 800°C in air. Rutile samples turn out to be composed of MoO 3 islands at the surface of TiO 2 doped with Mo(V) ions in Mo ensembles or clusters occluded in the TiO 2.

Analysis of the oxide/semiconductor interface using Auger and ESCA as applied to InP and GaAs

This paper compares the Auger and ESCA techniques used to characterize the interfaces of thermally grown and anodic oxides of InP and GaAs. In the anodic oxide of GaAs, the Ga–O bonding extends deeper into the GaAs than the As–O bonding. In the anodic oxide of InP, both the P–O and In–O bonding penetrate to the same depth. The anodic oxide–GaAs interface changes with electrolyte. There is elemental P at the interface of the thermal oxide on InP, but it was not possible to prove or disprove the existence of elemental As at the anodic oxide/GaAs interface. It was found that the ESCA technique provided much needed bonding information which greatly facilitates characterizing the interface. It appears essential that both composition and bonding be determined.