T. C. Banwell

Correlation between the cohesive energy and the onset of radiation-enhanced diffusion in ion mixing

A correlation between the cohesive energy of elemental solids and the characteristic temperature Tc for the onset of radiation-enhanced diffusion during ion mixing is established. This correlation enables one to predict the onset of radiation-enhanced diffusion for systems which have not yet been investigated. A theoretical argument based on the current models of cascade mixing and radiation-enhanced diffusion is provided as a basis for understanding this observation.

Chemical effects in ion mixing of a ternary system (metal‐SiO2)

The mixing of Ti, Cr, and Ni thin films with SiO_2 by low‐temperature (−196–25 °C) irradiation with 290 keV Xe has been investigated. Comparison of the morphology of the intermixed region and the dose dependences of net metal transport into SiO_2 reveals that long range motion and phase formation probably occur as separate and sequential processes. Kinetic limitations suppress chemical effects in these systems during the initial transport process. Chemical interactions influence the subsequent phase formation.

Effect of dose rate on ion beam mixing in Nb‐Si

The influence of dose rate, i.e., ion flux, on ion beam mixing in Nb‐Si bilayer samples was measured at room temperature and 325 °C. At the higher temperature, an increase in dose rate of a factor of 20 caused a decrease in the thickness of the mixed layer by a factor of 1.6 for equal total doses. At room temperature, the same change in flux had no effect on mixing. These results are consistent with radiation‐enhanced diffusion theory in the recombination‐limited regime.

Effects of ion irradiation on conductivity of CrSi2 thin films

Electrical resistivity measurements are used to study damage in CrSi_2 thin films induced by Ne, Ar, or Xe ion irradiation over a fluence range of 10^(10)–10^(15) ions cm^(−2). Irradiation produces a factor of 5–12 increase in film conductivity at the higher fluences. The influence of defect generation and recombination is evident. We speculate that formation of a compound defect is a dominant factor enhancing film conductivity. A temperature dependence at low fluences is reported and tentatively identified.

Thermal stability and electrical resistivity of 14N-implanted nickel contacts on n+-Si

Abstract We investigated the stability and electrical resistivity of evaporated nickel contacts on n + -Si after implantation with 14 N at a fluence of 2 x 10 16 cm -2 after sequential thermal annealing from 300 to 625°C. Unimplanted samples are used as a reference for comparison. The contact resistivity is determined from Kelvin measurements using a transmission line model interpretation. Interfacial reactions are studied using 2 MeV 4 He + backscattering spectrometry. We observe no silicide formation in 14 N-implanted samples until they have been annealed at above 550°C, whereas usual silicide formation is observed in unimplanted samples. The contact resistivity is sensitive to 14 N implantation and barrier formation, but not to the annealing temperature, and has a value of about 30 μω cm 2 . In addition to diffusion barrier formation, the implantation is also found to improve the adherence of nickel to silicon.

Influence Of Interfacial Oxide On Ion Mixing Of Al Bilayers: Measurement Of Interfacial Oxide

The elastic resonance scattering of 3.05 MeV 4He++by 160 is studied for the case where the oxygen is present as an interfacial impurity between a Si substrate and a metallic overlain film. A simple model is developed and experimentally tested to describe the effect of the overlayer on the excitation curve and on the incident beam energy required to obtain resonance. This analytical method is very useful to study the influence of interfacial oxygen on the reaction of metallic overlayers, as shown by specific results with Al.

Ion Beam Mixing of Sb Layers in Al

We have studied the atomic mixing of Sb layers in Al induced by irradiation with 110 keV Ar ions. Samples with 10 and 230 A Sb layers sandwiched in Al were made by sequential vacuum deposition and analyzed by backscattering spectrometry. The mixing was characterized by finding the increase, σ 2 , in the variance of the Sb signal in the backscattering spectra. For 10 A layers irradiated at 90 and 270 K, the profiles are Gaussian and σ 2 increases linearly with dose of implanted Ar ions. The mixing is essentially independent of temperature up to ∼ 290 K, where it increases sharply. For 230 A layers irradiated at 90 and 270 K, the profiles are approximately Gaussian but develop a flat top as the Al:Sb ratio approaches 1:1. At 90 K σ 2 increases monotonically with dose up to 3.6 × 10 16 Ar/cm 2 , but at 270 K it develops a plateau at a dose of ∼ 2.2 × 1016 Ar/cm 2 , which corresponds to Al:Sb = 1:1. No such plateau is observed at 90 K. Again, the mixing showed very little variation with temperature between 90 and 270 K, but rose abruptly above 300 K.

Xenon Irradiation-Induced Changes In CrSi 2 Thin Films

Measurements of electrical resistivity are used to monitor changes in CrSi2 thin films induced by Xe irradiation over a fluence range of ≈ 1010 - 1014 cm-2. Behavior associated with defect generation and recombination are evident at high fluences. A temperature dependence at low fluences is reported and tentatively identified.

Ion-Induced Mixing in Ni-Sio 2 Bilayers

We report on our studies of Ni transport induced by 300 keV Xe irradiation of 25 nm Ni films evaporated on thermally grown SiO 2 at Xe fluences of 10 13 -10 16 cm -2 and at temperatures of 300-750 K during irradiation. Cross-sectional TEM, and selective etching combined with 2 MeV He backscattering spectrometry and ESCA were used to profile the Xe and Ni within the SiO 2 . At 300 K, backscattering shows cascade mixing dominates, although only ~ 1/35 that predicted by cascade theory, with most of the Ni in the SiO 2 contained in a resolution limited peak adjacent to the SiO 2 interface. TEM shows that this Ni is contained in a 5 nm band, 5 nm below the interface as Ni oxide clusters. Examination of the satellite structure of the Ni 2p line by XPS also shows this band is predominantly Ni 2+ . At 750 K, the near-surface peak vanishes and only recoil implantation is evident. Ni0 is evident by XPS in samples irradiated at 300 K, though not at higher temperatures. We explain our results in terms of phase separation during cooling of the collision cascade.