He+ backscattering and Auger electron spectroscopy study of the ion-induced modification of copper films deposited on single-crystal silicon

The sputtering yields of copper due to argon ion milling were measured by mega-electronvolt He⁺ Rutherford backscattering and Auger electron spectroscopy for thin copper films deposited on 〈111〉-oriented silicon substrates. We found that recrystallization occurs in the copper films during the argon ion bombardment. The copper profile broadens at the Si-Cu interface and the spread increases with the beam energy during ion milling.     

Auger study of interfacial reaction between sputter-deposited NiTi films and a glass substrate containing titanium oxide

The interfacial reaction between magnetron sputter-deposited NiTi films and various glass substrates, namely silica glass, borosilicate glass and borosilicate glass containing titanium oxide, were studied. It was found that the glass substrate containing titanium oxide showed a broad transition region (20–30 nm) in which the titanium-to-nickel and silicon-to-oxygen ratios varied markedly with depth. In accordance with the existence of a broad transition region, the shapes of O KLL Auger lines showed a continuous change in the oxide species through the transition region. In contrast, the interface between NiTi films and borosilicate and silica glasses showed only a narrow transition region indicating that no interfacial interaction occured during or after the sputter deposition. These facts suggest that titanium oxide dissolved in borosilicate glass plays an important role. The results are discussed on the basis of the thermodynamics for oxide formation. It is shown that the existence of various oxidation state for titanium and a single oxidation state for silicon and boron are responsible for the difference in the widths of the transition regions observed in the three different substrates.     

Formation of crystalline aluminum silicate hydroxide layer during deposition of amorphous alumina coatings by electron beam evaporation

Aluminum oxide films were deposited on fused silica and borosilicate glass substrates by electron beam evaporation, without any substrate heating. Grazing incidence X-ray diffraction measurements found that a layer of crystalline aluminum silicate hydroxide was formed at the interface of the substrate and the amorphous alumina film, the latter transformed to γ-alumina phase on heat treatment at 800 °C. The aluminum silicate hydroxide layer was produced by the chemical reaction between condensing Al and Al–O species, OH⁻ from the residual water vapors in the chamber and Si atoms from the underlying silica and borosilicate glass substrates.     

Auger electron spectroscopy study of the sputtering effect on platinum silicide surfaces

Modifications of platinum silicides in the composition range between Pt₃Si and PtSi induced by argon ion beams were studied by angle-integrated Auger electron spectroscopy (AES). A platinum surface enrichment, which was stronger at low sputtering energies and in silicon-rich silicides, was found in the 1–5 keV ion energy range. In all silicides sputtering yield ratios Y_Si/Y_Pt of about 2.9 and 2.1 were estimated for the 1 keV and 5 keV steady state regimes respectively. Simultaneous analysis of low and high energy platinum and silicon Auger lines indicated that the platinum enrichment extended over a range of a few tens of ångströms and was slightly higher at the surface than in the subsurface region. The platinum enrichment, its energy dependence and the in-depth graded composition of the altered layer are discussed in terms of silicon preferential sputtering, recoil implantation and surface segregation. Dynamic surface composition changes were also studied, and a model which accounts for the various “shapes” of the transient regimes and their dependence on the height of the steps in the sputtering energy is shown schematically. Shape analysis of the core-valence-valence Auger lines suggests that changes in the chemical bonding in platinum silicides are induced by ion bombardment so that enrichment with platinum results in the formation of compounds which are richer in platinum.     

Refractory metal silicide formation by ion implantation

A systematic study of interface mixing of transition metal-Si structures by ion implantation was carried out. High resolution Auger analyses at the mixed region of the implanted samples showed an energy shift of the Auger Si LVV transition and a change in the spectrum relative to that of elemental silicon. The elemental depth distribution obtained using Auger electron spectroscopy combined with ion sputtering illustrated a composition plateau for the ion-implanted structures. The X-ray diffraction data show the presence of silicides. These results illustrated metal silicide formation and a reduction in the thermal reaction barrier for forming refractory metal silicides by ion implantation.     

Adhesion failures on hard coatings induced by interface anomalies

In this work, the lack of adhesion occurred during the up-scaling of the deposition of tribological coatings in a semi-industrial apparatus is interpreted. The adhesion problems were detected for both hard and self-lubricant coatings from W-Ti-N and W:C systems, respectively, when they were deposited in a 4 cathodes TEER^® chamber by reactive unbalanced magnetron sputtering. In spite of cleaning the substrates surface by ion bombardment prior to deposition, by establishing a discharge close to the substrate, insufficient adhesion critical load values were measured by scratch-testing.A powerful set of complementary techniques was used to the detailed analysis of the interfaces in order to understand and overcome the adhesion problems: RBS gave some insights on the nature of the problem by detecting composition anomalies in the substrate/coating interface; Auger spectroscopy was used for identifying the underneath chemical composition close to the interface; cross section TEM gave the final evidence of the presence of a contamination layer attributed to malfunctioning of the ion cleaning process, which was the cause of the lack of adhesion.     

动态离子束混合制备的钛氧化物薄膜的AES和XPS研究

分别采用O 和Ar 离子束轰击的动态离子束混合技术,在不锈钢基体上制备钛的氧化物薄膜。经X射线光电子能谱(XPS)和俄歇电子能谱(AES)分析,研究这两种工艺制备薄膜的化学组成和价键状态。结果表明,采用动态离子束混合技术制备的薄膜,可形成与基体有组分梯度的界面过渡层,减小了薄膜内应力,同时薄膜与基体具有较好的热学相容性,从而提高了薄膜的附着性能。Ar 束轰击的动态离子束混合沉积钛的氧化物薄膜中,Ti主要以 4价存在,而O 束轰击的动态离子束混合沉积形成的钛氧化物薄膜中含有次价态的钛氧化物。     

Barium borosilicate glass as a matrix for the uptake of dyes

Barium borosilicate (BBS) and sodium borosilicate (SBS) glass samples, prepared by the conventional melt-quench method, were used for the uptake of Rhodamine 6G dye from aqueous solution. The experimental conditions were optimized to get maximum uptake and was found to be 0.4 mg of dye per gram of BBS glass sample. For the same network former to modifier ratio, barium borosilicate glasses are found to have improved extent of uptake for the dye molecules from aqueous solutions compared to sodium borosilicate glasses. Based on ²⁹Si MAS NMR studies on these glasses, it is inferred that significantly higher number of non-bridging oxygen atoms present in barium borosilicate glasses compared to sodium borosilicate glasses is responsible for its improved uptake of Rhodamine 6G dye. ¹¹B MAS NMR studies have confirmed the simultaneous existence of boron in BO₃ and BO₄ configurations in both barium borosilicate and sodium borosilicate glasses. The luminescence studies have established that the dye molecule is incorporated into the glass matrix through ion exchange mechanism by replacing the exchangeable ions like Na⁺/Ba²⁺ attached with the non-bridging oxygen atoms present in the glass.     

Effect of interfacial impurities on intermixing of bilayers

Mixing experiments were performed on Ni/Pt and René N4/Pt systems to understand the effect of interfacial impurities on the ion-beam mixing process. A layer of platinum 15 or 50 nm thick was deposited on metallographically polished sputter-cleaned nickel and René N4 substrates as well as on metallographically polished uncleaned René N4 by electron-beam deposition techniques. These targets were exposed to the bombardment of a Pt⁺ 1 MeV beam. A range of fluences, 2×10¹⁵ to 2×10¹⁶ Pt⁺/cm²⁺ was used to cause intermixing. The amount of mixing was evaluated by Rutherford backscattering spectroscopy and Auger sputter depth profiling. The mixing rates were the same for Ni/Pt and René N4/Pt with the clean interface. However, it was significantly less in René N4/Pt with an interfacial native oxide/impurity layer. The initial high volume fraction of precipitates in René N4 along the ion path became disordered under bombardment, and the alloying elements present significantly in the resultant solid solution did not influence the mixing process. Mixing in Ni/Pt and René N4/Pt with the clean interface appears to be dominated by thermochemical influences.     

An X-ray photoelectron spectroscopy study of the chemical changes in oxide and hydroxide surfaces induced by Ar+ ion bombardment

In the course of X-ray photoemission studies on the oxidation of metals and alloys and on bulk oxides, we found that in addition to physical sputtering Ar⁺ ion bombardment can in many cases reduce an oxide to a mixture of the original oxide, lower oxides and metal. The effect is even more pronounced in systems containing hydroxyl groups which are readily destroyed by the ion beam. Specific examples for oxidized cobalt, nickel and iron surfaces and their bulk oxides and hydroxides are given. The relative reduction rates of Co^II and Fe^III in CoFe₂O₄ are also examined. From these observations, it is clear that any depth compositional profiling using ion sputtering in conjunction with Auger or X-ray photoelectron spectroscopy should be treated with extreme caution. The mechanism for the chemical changes induced by ion bombardment is briefly discussed.     

The effect of substitution of Bi2O3 for alkali oxides on thermal properties, structure and wetting behavior of the borosilicate glass

The effect of substitution of Bi₂O₃ for alkali oxides in the borosilicate sealing glass on thermal properties, structure and wetting behavior of the borosilicate glass was studied. The thermal expansion coefficient (TEC) decreased with the substitution, however, the TEC varied little while the alkali oxides were completely consumed. The variation in glass transition temperature (T_g) and the FTIR results of the glasses indicated significant effect of Bi₂O₃ substitution on the glass structure, which caused a progressive conversion of BO₃ to BO₄ unit in the glass. The appropriate amount of Bi₂O₃ obviously improved the wetting performance of the borosilicate glass on Al₂O₃ substrate due to the high polarizability of Bi³⁺ ion.     

Interaction of water vapor with silicate glass surfaces: Mass-spectrometric investigations

The secondary ion mass-spectroscopy technique was used to study the results of hydration of borosilicate, aluminosilicate, and soda-lime silicate glasses in ¹H₂ ¹⁸O water vapor containing 97% of the isotope ¹⁸O. It is shown that hydration of the surface of the soda-lime silicate glass occurs as a result of the ion-exchange reaction with alkali metals. In the case of borosilicate and aluminosilicate glasses, water molecules decompose on the glass surface, with the observed formation of hydrogenated layer in the glass being the result of a solid-state chemical reaction—presumably, with the formation of hydroxides from aluminum and boron oxides.     

Metallization of polytetrafluoroethylene substrates by ion plating

The paper deals with the adhesion of copper films deposited using the ion plating technique onto polytetrafluoroethylene (PTFE) substrates. The substrates were biased by an r.f. voltage; copper was evaporated by electron bombardment. The results showed that careful sputter cleaning in an argon-oxygen (or helium- oxygen) mixture is essential to achieve good adhesion.Diagnostics by IR spectroscopy indicated that sputter cleaning in pure argon induced some damage at the substrate surface and that PTFE chains were broken. Microscopic inspection gave evidence that sputter cleaning in an argon-oxygen mixture increased the roughness of the substrate surface. Results of adhesion strength measurements for silver films on PTFE substrates after reactive sputter cleaning are presented and discussed. The formation of CuOCbonds at the interface is assumed to play an essential role.     

Interfacial reactions between titanium film and single crystal α-Al2O3

Titanium is commonly used to join metals and ceramics by active metal brazing methods. In this work, titanium was sputter deposited on to single-crystal -Al₂O₃ substrates and the interfacial reactions between the titanium film and the Al₂O₃ substrate were studied. Al₂O₃ was reduced by titanium when samples were annealed at 973 and 1173 K for 300 s in an argon gas flow. Metallic aluminium was produced at the interface, and this diffused from the interface into the titanium film. At 1173 K, the intermetallic compound Ti₃Al and the intermediate titanium oxides, such as Ti₂O and TiO, were formed. The Al⁰ diffusion is important in stimulating interfacial reactions.     

Residual compressive stress in sputter-deposited TiC films on steel substrates

Polycrystalline TiC films with thickness between 0.1 and 2.8 microm were deposited by r.f. sputtering onto 1010 steel and borosilicate glass substrates at 200°C. All films were found to be in a state of compression. For a film grown under a given set of deposition conditions, the incremental compressive stress, i.e. the average stress in the uppermost deposited layer, was generally found to be largest near the film-substrate interface and to become constant with film thickness t_f for t_f ? 0.3 microm. However, for a given t_f the incremental stress increased with a decrease in the argon sputtering pressure P_Ar. Experimental results showed that the incremental compressive stress in bulk films could be directly related to the trapped argon concentration. Argon incorporation is due to the burial of energetic species incident on the growing film surface from two primary sources: energetic neutrals produced by Ar⁺ ions scattered off the target in binary collisions and Ar⁺ ions accelerated to the substrate owing to its induced negative potential with respect to the positive space charge region in the r.f. discharge. The trapped argon concentration from both contributions increased with decreasing P_Ar. All films grown on steel substrates exhibited good adhesion as indicated by indentation and diamond stylus scratch tests. The residual compressive stress in the films was found to be beneficial for wear-related applications in which the film was subjected to a large tensile stress.     

Auger electron spectroscopy depth profiling studies on stationary and rotated samples of a new model metal/semiconductor multilayer structure

Multilayer structures for application in microelectronics are becoming increasingly complex. A sputter deposited multilayer structure composed of chromium, nickel and silicon layers with a total thickness of 310 nm on a smooth silicon substrate was characterized by transmission electron microscopy (TEM) and by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) depth profiling. AES depth profiles of the Ni/Cr/Si multilayers were obtained with Ar⁺ ion bombardment at various angles of incidence using stationary and rotated samples. In some cases a strong influence of semiconductor structure on the experimentally obtained metal-metal and metal-semiconductor interface widths was observed. Owing to ion beam induced Si(LVV) Auger electrons in the crater wall of the Ni/Cr/Si sample, a distortional influence on depth resolution during simultaneous AES analysis and ion sputtering was found. Silicide formation during sputtering at the silicon-metal interfaces was confirmed by XPS. The measured compositional depth profiles are explained with respect to the influence of polycrystalline metallic and amorphous semiconductor structures; the effects of ion beam induced topography, atomic mixing and silicide formation are discussed.     

Ion-induced phase formation in metal-silicon systems

By using megaelectronvolt ⁴He ion backscattering techniques and transmission electron microscopy, we have investigated the interactions of ion beams with thin film structures in a number of silicide-forming systems. The mixed layer was found to be an equilibrium compound for near-noble metals and an amorphous phase for refractory metals. Differences in behavior have also been observed in near- noble metal systems. For palladium, the Pd₂Si phase grew with ion dose and remained crystalline up to high dose. For nickel, the compound Ni₂Si was formed initially and became amorphous on prolonged irradiation. All the results indicate the significance of atomic mobility at target temperatures in determining the phase formation and in explaining the sensitivity of the silicides to ion bombardment.     

Titanium deposition onto ion-bombarded and plasma-treated polydimethylsiloxane: Surface modification,interface and adhesion

Titanium films were deposited by electron beam evaporation onto polydimethylsiloxane (PDMS) substrates. Ar⁺ bombardment as well as O₂ plasma pretreatments were found to enhance the adhesion of the titanium films markedly. X-ray photoelectron spectroscopy and scanning electron microscopy were used to study the influence of the pretreatments on the PDMS surface morphology. Both pretreatments resulted in cross-linking and thereby an increased strength of the substrate surface. X-ray photoelectron spectroscopy was also used, together with in situ electron beam evaporation, to study the initial titanium film growth on as-prepared and Ar⁺-bombarded samples. The C 1s and O 1s peak shifts showed an enhanced film-substrate interaction attributed to formation of Ti-C and Ti-O bonds respectively. The film-substrate interaction was also observed as a change in the titanium film growth mode. If the samples were ion bombarded prior to deposition the film growth changed from a pronounced three-dimensional growth towards a more two-dimensional growth mode.     

Preparation and characterization of carbon and titanium carbide coatings

Carbon and titanium carbide coatings were deposited onto 304 and 316 stainless steel, Monel 400, molybdenum and copper substrates by the d.c. diode sputtering method. The former were prepared using a graphite target in an argon atmosphere whereas the latter were deposited using a titanium target in an argon-methane gas mixture. The coatings were characterized using Auger electron spectroscopy, X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, scanning electron microscopy and X-ray diffraction techniques. The adhesion of the coatings to the substrates and the effect of annealing on their crystallinity were studied.     

Friction and wear behaviour of ion beam modified ceramics

In the present stud, the sliding friction coefficients and wear rates of carbide, oxide, and nitride materials for potential use as sliding seals (ring/liner) Were measured under temperature, environmental, velocity, and loading conditions representative of a diesel engine. In addition, silicon nitride and partially stabilized zirconia discs were modified by ion mixing with TiNi, nickel, cobalt and chromium, and subsequently run against-carbide pins, with the objective of producing reduced friction via solid lubrication at elevated temperature, Unmodified ceramic sliding couples were characterized at al temperatures by friction coefficients of 0.24 and above. However, the coefficient at 800° C in an oxidizing environment was reduced to below 0.1, for certain material combinations, by the ion implantation of TiNi or cobalt. This beneficial effect was found to derive from lubricious titanium, nickel, and cobalt oxides.