Ni Film Thickness Research Articles

Finite-temperature magnetism of thin Ni films in sandwiches of Cu

The finite-temperature magnetism of thin Ni films sandwiched in Cu(001) layers, is discussed with the use of the itinerant-electron theory including the effect of spin fluctuations by means of the functional-integral method within the static and single-site approximations. The spatial- and temperature-dependent magnetization and the Curie temperature are computed by varying the Ni-film thickness from one to ten layers. The calculated results are discussed with reference to the recent experiments on Cu/Ni/Cu and Au/Ni/Au sandwiches and on compositionally modulated Ni-Cu superlattices.

Epitaxial growth of body-centered-cubic nickel on iron

Studies by low-energy electron diffraction (LEED) and Auger electron spectroscopy of nickel films grown in ultra-high vacuum onto a clean Fe{001} surface show that the films have the body-centered cubic structure with the same lattice constant and the same multilayer relaxation as the clean substrate, as long as they are thinner than about 6 layers. LEED intensity analyses show that the multilayer relaxation of both clean Fe{001} and 3-layer thick Ni films involves 5% contraction of the first and 5% expansion of the second interlayer spacing. These new values of the multilayer relaxation of clean Fe{001} represent an improvement over previous determinations. Thicker Ni films, up to 100 layers, have a complicated structure that is neither b.c.c. nor f.c.c. Short anneals at temperatures between 200 and 650°C cause rapid diffusion of Ni into the Fe substrate with little evidence for formation of the stable f.c.c. phase of Ni.

Mixing of nickel and silicon by incoherent-light-pulse annealing

Mixed layers of Ni and Si were formed by pulsed incoherent-light annealing of Ni thin films evaporated on Si substrates. Incoherent light pulse of 36 μs produced in an arc-discharge plasma system was used as the energy source for annealings. A thin layer (300 Å) of amorphous silicon ( a-Si) deposited on 800–1000 Å thick Ni films was found to increase light absorption significantly. The light energy needed to form uniform mixing was measured to be about 23 J/cm 2. Rutherford backscattering and Auger electron spectroscopy techniques were used for qualitative analysis of a-Si/Ni/Si samples. Optimum operating conditions of the light source was determined.

Effect of crystal texture on the magnetic properties of thin HCP Co-Ni films

In order to study the effect of crystal texture on the coercivity and squareness ratio of ferromagnetic thin films, Co-20 wt. % Ni films of various thicknesses (500Å <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim1.0\mu</tex> m) were sputter deposited on glass, single and polycrystalline substrates using a R.F. diode. The crystal texture and preferred orientation of sputtered Co-Ni films were determined by x-ray diffraction technique. The chemical composition and distribution of non-metallic elements of sputtered films were studied by energy dispersive analysis of x-ray and scanning Auger microprobe respectively. Scanning and transmission electron microscopes were used to study the structure and morphology of the films. The sputtered Co-Ni films were found to have a simultaneous presence of [0002] and [ <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10\bar{1}0</tex> ] orientations with a stable HCP structure. The change of preferred orientation of Co-Ni films with thickness (500Å to 1μm) resulted in dramatic changes in coercivity, squareness ratio and the shape of the M-H hysteresis loops of the films. It appeared that the magnetic behavior of these films was predominantly controlled by the texture of the films and was less sensitive towards the thickness.

Retardation and suppression of nickel silicide formation by N + implantation

The effects of implanted N on Ni 2Si formation have been studied using 4He + backscattering spectrometry and the 14N(d,α) 12C nuclear reaction. Ni films 1.5–4 kÅ thick were evaporated onto Si 〈100〉 and 〈111〉 substrates; were implanted with N + into the Ni film and through the Ni film into the substrate; and were thermally annealed under vacuum at 290 and 350°C. The two cases behave differently. For the N initially in the Ni film on Si 〈100〉, the reaction is greatly suppressed if the N is above a threshold dose φ th of about 1 × 10 16 N/cm 2, independent of the Ni film thickness. Changing the substrate orientation to 〈111〉 raises the threshold φ th . The nitrogen profile changes its distribution from an as-implanted approximate gaussian located in the Ni films to a peak positioned at the NiSi interface without loss of N. For the case when the N is initially in the Si substrate, the growth rate of Ni 2Si is retarded, but not suppressed. These results are explained in terms of a model based on the chemical affinity of N to Si and Ni and on the fact that Ni is the moving species in Ni 2Si growth.

Generation and attenuation of phonons at ferromagnetic resonance in thick Ni films

The generation and attenuation of phonons at ferromagnetic resonance has been studied both theoretically and experimentally. We have observed for the first time the effect of resonant reabsorption of phonons propagating through thick Ni films. The predictions of the theory are in very good agreement with experiment.

(111) Monocrystalline Nickel Films

(111) oriented thin monocrystalline Ni films have been prepared by vacuum evaporation and examined by transmission electron microscopy and electron diffraction. In high vacuum, at room temperature, a layer of NaCl was first evaporated onto a freshly air-cleaved muscovite substrate clamped to a copper block with attached heater and thermocouple. Then, at various substrate temperatures, with other parameters held within a narrow range, Ni was evaporated from a tungsten filament. It had been shown previously that similar procedures would yield monocrystalline films of CU, Ag, and Au.For the films examined with respect to temperature dependent effects, typical deposition parameters were: Ni film thickness, 500-800 A; Ni deposition rate, 10 A/sec.; residual pressure, 10-6 torr; NaCl film thickness, 250 A; and NaCl deposition rate, 10 A/sec. Some additional evaporations involved higher deposition rates and lower film thicknesses.Monocrystalline films were obtained with substrate temperatures above 500° C. Below 450° C, the films were polycrystalline with a strong (111) preferred orientation.

Magnetic Anisotropy in F.C.C. Single Crystal Cobalt—Nickel Electrodeposited Films. I. Magnetocrystalline Anisotropy Constants from (110) and (001) Deposits

AbstractA study of the magnetocrystalline anisotropy of electrodeposited (001) and (110) single crystal f.c.c. Co—Ni films of thicknesses between 100 and 1000 Åhas been carried out, at 20 °C, by torque magnetometry. The composition dependence of K1 from the thicker films is found to agree with previous results from bulk alloys of the Ni‐rich compositions, but, apart from the work of Andrä and Spinarke (1969), differs from previous results from thinfilms. The constants K2 and K3 have been measured and have both been found to be negative over the whole composition range.

Thermoelectric Power of Vacuum-Evaporated Au–Ni Thin-Film Thermocouples

Continued investigations of the thermoelectric properties of Au–Ni thin-film thermocouples have been made. The thickness dependence of the Seebeck coefficient for Ni films of variable thickness on bulk Au was determined and found to be sensitive to the thermal history of the thin film thermocouples. By developing suitable preparation techniques for these thermocouples, involving several periods of annealing, time-invariant calibration curves were obtained. The thickness dependence of the Seebeck coefficient was found to follow closely the predictions of the size-effect theory of Mayer.