Oxide Films on 1:1 Nickel-Tin Alloy

INDIUM PHOSPHIDE FILMS 1069growth time. The resistivity parallel to the surface did not depend on deposition conditions and was one order of magnitude larger than that measured vertically to the film surface. For sulfur-doped films, the carrier concentration increased and the resistivity decreased with increasing deposition temperature. Especially, noteworthy was the fact that resistivity increased two orders of magnitude at the H2S partial pressure of 10 -6 atm in the feed gas. These results are considered to be caused by the grain boundary. Electron mobility increased with the partial pressure of H2S gas up to 200 cm2/V 9 sec at an electron concentration of about 101~ cm -~.A model in which grain boundaries act as free carrier traps was utilized to elucidate the electronic transport behavior. The barrier heights for undoped films were 0.2-0.3 eV and decreased inversely with the increase in electron concentration. The density of trapping states was determined as 3 X 10 TM cm-~. ABSTRACTThe corrosion resistance of electrodeposited tin-nickel alloy is due to a thin passive film, believed to be mainly tin oxide with some tin and nickel hydroxides. Thin electrodeposited gold on tin-nickel also is corrosion resistant and is of interest as an electric contact material. Presumably, a similar protective film forms on the tin-nickel layer exposed at pores in the gold. These observations have been made with deposits of both single phase (SnNi) and multiphase mixtures of SnNi, NisSn4, and NisSn2. The protective film can be removed by mechanical wear but will spontaneously reform, taking approximately 150'0 hr in air at room temperature to reach a limiting thickness. However, the resistance of tin-nickel to many corrodents is restored in less time, after only a few days of aging. Similar observations of the development of passivity were made with freshly plated tin-nickel deposits on copper, with aged deposits on copper that were chemically etched immediately before exposure, and with newly fractured edges of tin-nickel electroforms. If the substrate is exposed by wear-through or by brittle fracture of tin-nickel the corrosion resistance of the material is determined by the substrate, and may not be restored by aging.Electrodeposited tin-nickel alloy has considerable technological importance because of its corrosion resistance. This material is equiatomic, having the weight percent (w/o) composition, 65 Sn-35 Ni. It does not appear (1) in the equilibrium diagram for the binary tin-nickel system, which suggests that it is thermo-Present address: Centronics. Hudson. New Hamushire 03051. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 61.129.42.15 Downloaded on 2015-05-16 to IP

mentioning

confidence: 95%

mentioning

confidence: 98%

The Corrosion Resistance of Worn Tin‐Nickel and Gold‐Coated Tin‐Nickel Alloy Electrodeposits

Antler

Drozdowicz

Hornig

1977

“…Looking at the figures one sees that the bulk ratios of Sn to Ni are different. However, the ratio differences are much greater than the precision of +--2% per component from RBS, ISS, and AES measurements (7,8,14). (Sn/Ni) Cu is 2/1 and (Sn/Ni)SS is N6/1.…”

Section: Discussionmentioning

confidence: 94%

Analysis of SnNi Electroplate by Secondary Ion Mass Spectrometry, Ion Scattering Spectrometry, and Rutherford Backscattering

Schubert¹

1978

Two batches of SnNi electroplate, expected to be composed of equal atomic amounts of Sn and Ni, have been examined by secondary ion mass spectrometry, ion scattering spectrometry, and Rutherford backscattering. Tin oxides and hydroxides were found in the surface region, which is Sn-rich; no Ni oxides or hydroxides were seen. The Sn/Ni ratio for the two batches was 45/55 and 52/48 a/o. After Ar+-sputter cleaning, films of the type which occur during and immediately after electroplating could not be reproduced in 10 .8 Torr O3. The regenerated films contained substantial amounts of nickel oxides and hydroxides.Electroplated metastable SnNi is of technological interest for a broad range of metallic coating applications. It is suitable as a decorative coating and as a protective corrosion barrier (1). Usage as one of the electroplated components of electrical components has also been proposed (2). Its main attractive feature is that surface films on electroplated SnNi form rapidly in air or most aqueous solutions and exhibit a high degree of passivity to further corrosion (3-5). In order to understand the nature of these films, a detailed analysis is important.With reasonable care during electroplating, the deposit is expected to have equiatomic composition (3), although a broad range of compositions can be plated (6). Current knowledge of the surface film composition has been obtained through Auger electron spectroscopy (AES), electron spectroscopy for chemical analysis (ESCA), and passivation potential curves. AES studies show the surface to be a tin-rich oxide (7) or a nickel polystannate (8). These two results are not in conflict since AES does not detect hydrogen nor chemical bonding in general. The ESCA study has reached a similar conclusion (9). Passivation-potential techniques indicate that the surface is nickel stannate (3, 4), however, with films that are only tens of angstroms thick (7,9), electrochemical techniques are not sufficient to give an unambiguous analysis. This paper describes the surface analysis of SnNi electroplate by three techniques; Rutherford backscattering (RBS), ion-scattering spectrometry (ISS), and secondary ion mass spectrometry (SIMS). ExperimentalThe SIMS experiments were carried out in a stainless steel ion pumped UHV system. These included molecular composition depth profiles and film regeneration with 02 exposure. A 2 keV focused Ar + ion source with variable current density has been de-

“…It was early argued [see Fig. (5b)] that the underlayer must be nonstoichiometric everywhere except at one interior plane: rich in O = near the CdO/ electrolyte interface, rich in Cd + + near the Cd/CdO interface; thin and glassy, nonstoichiometric, continuous; of the variable composition so elegantly demonstrated directly by Hoar quite recently on iron-tin using Auger techniques (16). (5b)] that the underlayer must be nonstoichiometric everywhere except at one interior plane: rich in O = near the CdO/ electrolyte interface, rich in Cd + + near the Cd/CdO interface; thin and glassy, nonstoichiometric, continuous; of the variable composition so elegantly demonstrated directly by Hoar quite recently on iron-tin using Auger techniques (16).…”

Section: On Mechanismsmentioning

confidence: 98%

Anodic Passivation by “ CdO ” Studied by ESR

Casey¹,

Gardner²

1975

The appearance of superoxide 02-and ozonide O8-ions in strong KOH electrolyte at temperatures 25 ~ to -40~ during the anodic oxidation of cadmium and oxygen evolution has been investigated using the electron spin resonance technique. The fact that 02-forms at the higher temperatures and Ospredominates at --40~ correlates with the appearance of fl-Cd(OH)2 at higher and ~-Cd(OH)2 at lower temperatures, but it is argued that this correlation is coincidental and that it is the character of the surface states of the elusive and dynamic "CdO" underlayer beneath the Cd(OH)~ that determines which paramagnetic species is produced. These new facts and the interpretation are discussed within the framework of the solid state/solution-precipitation mechanism. * Electrochem2cal Society Active Member.