Ion beam sputtering of ZnS thin films

Ion beam sputtering was used to deposit adherent high quality ZnS films non-reactively. The optical properties of films thicker than 80.0 nm were found to be equivalent to those of bulk ZnS with a packing density of unity. Unlike that of evaporated films, the refractive index was insensitive to the substrate temperature but for thinner films was dependent on the substrate condition prior to deposition. The deposition of fully dense films is qualitatively explained using Muller's model of ion-assisted deposition. In the case of ion beam sputtering, the high energy species comprise energetic sputtered atoms and/or molecules, reflected beam ions and charge exchange neutrals.     

Ion beam sputter deposited Permalloy thin films

Ni₈₀Fe₂₀ thin films were deposited using a wide range of process parameters in a dual source ion beam sputter deposition system. The films were characterized structurally, chemically, and magnetically. Two modes of deposition were investigated; the first permitted concurrent second source bombardment during film deposition but was limited in net deposition rate to about 300 Å/m; the second provided deposition rates in excess of 1000 Å/m, but did not allow for concurrent ion bombardment from the second ion source. Depending on specific conditions film stress varied from slightly tensile to highly compressive in both deposition modes. This, combined with small variations in magnetostriction, resulted in films with vertical anisotropy and stripe domain patterns as well as conditions where well-formed closure domain patterns were observed in yoke shaped structures. For monolithic films, easy axis coercivities <0.7 Oe, anisotropy fields ≃5Oe and hard axis coercivities of <0.5 Oe were obtained     

Investigation of interface properties of Ti/Ni/Ag thin films on Si substrate

The interface structure and the adhesion of direct current (DC) sputtered Ti/Ni/Ag thin film metallization on n⁺Si substrate has been investigated. It is shown that beside the chemical preparation of the Si surface prior to sputtering also thermal annealing of sputtered metal structure has strong influence on the adhesion of sputtered layers to the silicon. Energy dispersive X-ray spectroscopy (EDS) analysis were performed on both, the delaminated layers and on the silicon surface to determine the exact delaminating interface, which was found to be between Si and Ti layer. Auger electron spectroscopy (AES) profile revealed no traces of contamination at Ti-Si interface. Measured high tensile residual stress, particularly in sputtered Ni layer (1.4-2 GPa) is found to reduce the metal stack adhesion.     

Reactions in Au/Nb bilayer thin films

The interdiffusion and intermetallic compound formation of Au/Nb bilayer thin films annealed at 200–400 °C have been investigated. The bilayer thin films were prepared by electron beam deposition. The Nb film was 50 nm thick and the Au film was 50–200 nm thick. The interdiffusion of annealed specimens was examined by measuring the electrical resistance and depth-composition profile and by transmission electron microscopy. Interdiffusion between the thin films was detected at temperatures above 325 °C in a vacuum of 10^-4 Pa. The intermetallic compound Au₂Nb₃ and other unknown phases form during annealing at over 400 °C. The apparent diffusion constants, determined from the penetration depth for annealing at 350 °C, are 3.5 × 10⁻¹⁵ m² s⁻¹ for Nb in Au and 8.6 × 110^7minus;15 m² s⁻¹ for Au in Nb. The Au surface of the bilayer films becomes uneven after annealing at over 400 °C due to the reaction.     

Reactions between zirconium/permalloy bilayer thin films

The interdiffusion and reactions of zirconium/permalloy bilayer thin films annealed at 150 to 350 °C were investigated. Nickel atoms preferentially diffuse from the permalloy layer into the zirconium layer. This preferential diffusion results in the growth of an amorphous phase between the zirconium and permalloy thin films. Consequently, the magnetic properties of the permalloy thin layer in the bilayer thin films change. The starting temperature of interdiffusion between zirconium and permalloy films is higher than that of a titanium/permalloy system reported previously.     

Ion beam induced interface mixing of Ni on PTFE bilayer system studied by quadrupole mass analysis and electron spectroscopy for chemical analysis

We have investigated interfacial chemistry in a 100 nm Ni on PTFE (polytetrafluoroethylene) bilayer system induced by 120 MeV Au ions with fluences varying from 1 × 10¹² to 5 × 10¹³ ions/cm². In-situ quadrupole mass analysis (QMA) shows emission of Fluorine (F) and different fluorocarbons (C_xF_y) such as CF, CF₃, C₂F₃ etc. during irradiation. Electron spectroscopy for chemical analysis (ESCA) studies show that Ni reacts with chemically reactive species such as F⁻/F and C_xF_y ions or radicals emitted during irradiation forming NiF₂ and metal-polymer complexes (-CFNi-). Rutherford backscattering spectrometry (RBS) was used to analyze the atomic transport at the interface and strong interface mixing is observed at the ion fluence 5 × 10¹³ ions/cm². Atomic force microscopy (AFM) studies before and after irradiation show that surface roughness is increased from 6.9 to 12.4 nm with increasing fluence. Observed results have been explained on the basis of the chemical reactions taking place within molten ion tracks in the polymer and hot zones around the ion paths created in the Ni film. The studies show that swift heavy ion irradiation introduces strong chemical alteration in the system and induces chemical reactions within the ion track, which enhance ion beam mixing in Ni-PTFE bilayer systems.     

Effects of temperature,thickness and atmosphere on mixing in Au-Ti bilayer thin films

The interdiffusion and intermetallic compound formation of Au-Ti bilayer thin films annealed at 125 to 350 °C have been investigated. The bilayer thin films were prepared through electron beam deposition at comparatively low temperature. The interdiffusion of annealed specimens was examined by measuring electrical resistance and the depth-composition profile, and by observation using a transmission electron microscope. Interdiffusion between the thin films was detected at temperature above 175°C in a vacuum of 10^–4 Pa. The starting temperature at which interdiffusion occurred decreases with lowering annealing vacuum. The intermetallic compounds AuTi, Au₄Ti, Au₂Ti and Ti₃Au form during annealing at over 250 °C. The activation energies of Au in Ti and Ti in Au obtained by the penetration depth are approximately 0.45 and 0.41 eV, respectively. These measurements indicate that the diffusion is controlled by a short-circuit mechanism. The diffusion of Ti species in Au depends on the annealing vacuum and Au thickness.     

Ion beam induced mixing at Co/Si interface

Ion beam mixing has emerged as a technique for understanding reactivity and chemistry at metal/Si interface and may find its applications in the field of microelectronics. We have investigated ion beam mixing at Co/Si interface induced by electronic excitation using 120 MeV Au⁺⁹ ion irradiation at different fluences, varying from 10¹² to 10¹⁴ ions/cm². Mixing was investigated by Rutherford Backscattering Spectroscopy (RBS) as a function of ion fluence and its mechanism across the interface is explained by the thermal spike model.     

Oxidation behavior of sputter-deposited Ti–Ni thin films at elevated temperatures

The isothermal oxidation kinetics of sputter-deposited equiatomic Ti–Ni thin films in pure oxygen from 823 to 923 K is studied using thermo-gravimetric analysis. The structure, composition-depth distribution and surface morphology of oxidized Ti–Ni thin films are investigated by X-ray diffraction (XRD), Auger electron spectroscopy (AES) and atomic force microscope (AFM), respectively. The results show that the oxidation kinetics of Ti–Ni thin films obeys a near-parabolic law. TiO₂, TiNi₃ and parent B2 phase are the compositions of oxidized Ti–Ni thin films. A double-layered scale including the outermost layer and the Ni-rich layer is formed outside the B2 matrix of oxidized Ti–Ni thin films. Moreover, thermal oxidation induces a surface smoothening of Ti–Ni thin films and surface roughness of oxidized Ti–Ni films decreases with the increasing oxidation temperature.     

Asymmetric switching behavior of Ni/Pb1.1(Zr0.3Ti0.7)O3/Pt thin films

An asymmetric behavior of P–E response was observed in Ni/Pb_1.1(Zr_0.3Ti_0.7)O₃/Pt multilayer thin films where Ni was used as top electrode. This interesting phenomenon was investigated by comparative analysis of the hysteresis loops and dynamic pyroelectric responses. The PZT thin films were prepared under the same conditions but different Ni and Pt top electrodes were used in the hysteresis loop measurement, and the Pt was used as the common bottom electrode. It is believed that this asymmetric behavior in hysteresis loop is originated from the strong domain pinning near the top Ni electrode. Dynamic pyroelectric response to 633 nm radiation of the Ni/Pb_1.1(Zr_0.3Ti_0.7)O₃/Pt thin films with polarization up and down was carried out. Higher dynamic pyroelectric response was observed in the positively poled film, in which the direction of the polarization was from the top to bottom electrode. It provides further evidence that the domain pinning near the top electrode dominates the asymmetric switching behavior.     

Low temperature interdiffusion in Cu/Ni thin films

Interdiffusion in Cu/Ni thin films was studied by means of Auger electron spectroscopy in conjunction with Ar⁺ ion sputter profiling. The experimental conditions used aimed at simulating those of typical chip-packaging fabrication processes. The Cu/Ni couple (from 10 μm to 60 nm thick) was produced by sequential vapor deposition on fused-silica substrates at 360, 280 and 25 °C in 10^-6 Torr vacuum. Diffusion anneals were performed between 280 and 405 °C for times up to 20 min. Such conditions define grain boundary diffusion in the regimes of B- and C-type kinetics. The data were analyzed according to the Whipple-Suzuoka model. Some deviations from the assumptions of this model, as occurred in the present study, are discussed but cannot fully account for the typical data scatter. The grain boundary diffusion coefficients were determined (for nickel through copper, Q_b = 33.7 kcal mol^-1 (1.46 eV), D_b⁰ = 4.2 × 10^-2 cm²s^-1; for copper through nickel, Q_b = 30.2 kcal mol^-1 (1.3 eV), D_b⁰ = 7.6 × 10^-5 cm²s^-1) allowing calculation of respective permeation distances.     

Ion beam sputter-deposition of LiCoO2 films

LiCoO₂ films, 200 nm in thickness, are produced by ion beam sputter-deposition. The structural, electrical and electrochemical properties of the films are studied by means of X-ray diffraction (XRD), electrical direct-current-measurements, and electron energy loss spectroscopy (EELS). The influence of preparation parameters like substrate temperature or oxygen partial pressure, are explored. While an oxygen deficiency was observed in films sputtered under pure argon atmosphere, the oxygen content of the thin films increases, significantly, in case of films sputtered under addition of O₂. At substrate temperatures below 300 °C, XRD measurements reveal a lattice structure similar to the low-temperature-phase, while the formation of the high-temperature-phase is clearly observed at temperatures above 500 °C and an Argon/Oxygen ratio of 3/2. Furthermore, the EELS technique is demonstrated to be a sensitive tool to characterize the lithiation state of the sputter-deposited thin films.     

Optical response and surface morphology of In/Ag bilayer thin films

In/Ag bilayer thin films were fabricated by maintaining the Ag layer thickness constant at 5 nm while varying the In layer thickness between 3 and 30 nm. It was observed that the grain size in the films increased with increase in thickness. In the case of the single layer In films the grain size increased from 60 to 350 nm as the thickness increased from 3 to 30 nm while the grain size increased from 80 to 280 nm in as the bilayer thickness increased from 8 to 35 nm. There is a red shift in the plasmon resonance from 372 to 522 nm in the case of the pure In layers whereas it was from 492 to 618 nm for the bilayer system. The Ag single layers exhibit a plasmon resonance at 540 nm. On coupling the In and Ag layers in the bilayers, additional resonances appear in the spectrum. The origin of the additional plasmon resonance peaks can be traced to the excitation of localized surface plasmons.     

MnSe/Ti薄膜电沉积制备及其表征

在钛电极表面上,采用电化学方法在0.1mol/L MnSO4和0.002mol/L SeO2的溶液中沉积硒化锰(MnSe)薄膜。循环伏安实验结果表明在-1.60～-1.70V电位范围易发生Mn和Se共沉积。然后采用XRD、SEM及EDS等研究沉积电位分别在-1.55、-1.60、-1.65和-1.70V时得到薄膜的特性,结果表明上述选定的电位不影响沉积层立方结构优先沿(200)晶面向;不同电位对沉积层形貌及化学计量数有显著影响。控制电位可以沉积得到不同特征的MnSe薄膜。     

Ion beam mixing of Co/Fe multilayers: Magnetic and structural properties

[Co(7 nm)/Fe(7 nm)]₆ multilayers were electron-beam evaporated onto Si(100) substrates in ultrahigh vacuum and irradiated at room temperature with 200-keV Xe ions, leading to ion beam mixing within the Co/Fe multilayer, but not with the Si substrate. Irradiation-induced changes in structural and magnetic properties were characterized by means of Rutherford backscattering spectroscopy, X-ray diffraction and in-plane magneto-optical Kerr effect. Irradiation with 1 × 10¹⁶ Xe ions/cm² induced Co/Fe intermixing to a 1 : 1 atomic concentration ratio (RBS) and the formation of the Fe₅₀Co₅₀ permendur phase in the intermixed zone (XRD). For lower ion fluences, the coercivity decreased strongly, but then increased slowly for higher fluences. The angular pattern of the relative remanence showed a perfect uniaxial anisotropy. The magnetic energy density was parametrized with the expression E_s / M_s ∝ (K_u1 / M_s) sin²(φ − φ₀) + (K_u2 / M_s) sin⁴(φ − φ₀), M_s being the saturation magnetization and φ₀ the symmetry angle. The second-order term K_u2 / M_s was found to decrease strongly with increasing Xe fluence.     

Study of annealing effects in Al-Sb bilayer thin films

In this paper, we present preparation and characterization of Al-Sb bilayer thin films. Thin films of thicknesses, 3000/1000 Å and 3000/1500 Å, were obtained by the thermal evaporation (resistive heating) method. Vacuum annealing and rapid thermal annealing methods were used to mix bilayer thin film structure. Results obtained from optical band gap data and Rutherford back scattering spectrometry showed mixing of Al-Sb bilayer system.