Yu. V. Nikulin

Magnetron sputtering of thin Cu(200) films on Ni(200)/SiO2/Si substrates

The possibility of oriented growth of thin copper films with a (200) texture on a SiO2/Si substrate by magnetron sputtering in medium vacuum is demonstrated for the case when a predeposited nickel layer with a (200) texture serves as an orienting sublayer.

The formation of the (200) and (110) textures in iron films prepared by magnetron sputtering

The effect of working-gas pressure on the texture of iron films on Si(100)/SiO2 substrates prepared by magnetron sputtering at room temperature is studied. It is shown that a change in working-gas pressure from 1.33 to 0.09 Pa leads to a change in the texture of the films from (110) to (200), which is accompanied by transition from a columnar to quasi-homogeneous microstructure of the films. It is found that the surface roughness of the film nonmonotonically depends on working-gas pressure and has a maximum in a pressure range corresponding to the coexistence of phases with the (110) and (200) textures in the film.

Effect of annealing temperature and rate of sputtering on the magnetic properties and microstructure of the polycrystalline nickel films with (200) texture

The dependences of the magnetic properties and morphology of polycrystalline nickel (Ni) films with the (200) texture that are fabricated using the dc magnetron sputtering on the SiO2/Si(100) substrates on sputtering rate annealing temperature T, and film thickness d are analyzed. It is demonstrated that an increase in the sputtering rate from 17 to 35 nm/min does not affect the saturation magnetization 4πM and ferromagnetic resonance line width ΔH but leads to a significant increase in the coercivity Hc for the films whose thickness d is greater than critical thickness dcr (d > dcr). It is also demonstrated that dcr depends on both sputtering rate and annealing temperature. The films with the thickness d > dcr exhibit the stripe domain structure whose period increases with increasing d and rate v. The annealing of the films with d ≥ 40 nm at T ≈ 200–400°C results in an increase in ΔH and Hc by a factor of 2–4, an increase in 4πM by 25%, an increase in grain size ξ by a factor of 20–30, and the formation of the stripe domain structure in the films that do not exhibit such structure prior to annealing and substantial strengthening of the (200) texture.

Effect of bias voltage polarity of a substrate on the texture, microstructure, and magnetic properties of Ni films prepared by magnetron sputtering

The influence of the bias voltage polarity Us on microstructure, crystallographic texture and magnetic properties has been investigated for Ni films with a thickness of ≈15–420 nm, which are obtained via magnetron sputtering at a working gas pressure P corresponding to the collision-deficient flight mode of atoms of the sputtered target between the target and the substrate. The Ni(111)-textured films have been shown to form at Us ≈–100 V, whose microstructure and magnetic parameters are almost unchanged with a thickness. In contrast, the Ni(200) films are formed at Us ≈ +100 V, whose magnetic properties and micro-structure depend significantly on the thickness d that manifests in a critical thickness d* ≈ 150 nm, when the structure of the film becomes inhomogeneous in the thickness, the remagnetization loops are changed from rectangular to supercritical with the formation of the band domain structure.

Surface roughness and magnetic properties of Co/SiO2/Si(100) polycrystalline films deposited via DC magnetron sputtering

For polycrystalline films of cobalt that have the thickness t ≈ 1.3–133 nm and that are deposited via DC magnetron sputtering on SiO2(0.1 μm)/Si(100) substrates, surface-roughness root-mean-square amplitude σ and surface correlation length ξ, which characterize the roughness of film surfaces, as well as saturation magnetization 4πM0, width of ferromagnetic-resonance line ΔH, coercitivity HC, and saturation fields HS, are studied as functions of film thickness t. It is shown that the behavior of dependences HC(t) and HS(t) coincides with the behavior of dependence σ(t)/t, whereas the behavior of 4πM0(t) depends on ratio t/σ(t). The dependence of the FMR line width on the film thickness, ΔH(t), is characterized by a minimum of ΔH ≈ 60 Oe present in the region of thicknesses of 30 to 60 nm. The behavior of dependence ΔH(t) is determined by ratio σ(t)/t at small thicknesses t ≤ 5 nm and by the behavior of σ(t) at t ≥ 5 nm.

Effect of Material of Metal Sublayer and Deposition Configuration on the Texture Formation in the Piezoactive ZnO Films

Effect of material of metal sublayer (aluminum, vanadium, chromium, iron, cobalt, nickel, and copper) and deposition configuration on the formation of the oblique and straight texture in the ZnO films is studied. The films that are synthesized in a dc magnetron sputtering system. It is shown that the piezoactive ZnO films with oblique texture that can generate shear waves are formed on the Cr and V metal sublayers in the shifted deposition configuration when the substrate is shifted relative to the magnetron axis toward the region of the target erosion. The piezoactive ZnO films with the straight structure that can generate longitudinal waves are formed on a chemically pure Al sublayer in the symmetric deposition configuration when the substrate is centered with respect to the target. Changes of the sublayer material in both deposition configurations or preliminary oxidation of the sublayer lead to the formation of the piezoactive ZnO films with mixed texture that excite shear and longitudinal waves. Chemical etching is used to show that the ZnO films with the oblique and straight textures exhibit piezoactive properties and can generate hypersound at thicknesses of no less than about 0.3 and about 0.9 μm, respectively.

Damping of longitudinal and shear acoustic waves in a structure with ZnO films with straight and inclined textures

We have reported on the results of an investigation of the damping of longitudinal and shear hyperacoustic waves in Al/ZnO/Al/ZnO/YAG structures (lutetium-doped yttrium–aluminum garnet) based on ZnO piezo-active films with straight and inclined textures, which are synthesized at substrate temperatures T ≈ 25–400°C in an unbalanced planar magnetron sputtering system. It has been shown that anomalously high values of damping up to 45 dB is observed for the passage of acoustic waves through ZnO films with straight textures, which are grown at a substrate temperature T ≈ 200–300°C; an increase in the deposition temperature to T ≈ 400°C leads to a decrease in the introduced acoustic losses by 30–40 dB.

Formation of textured Ni(200) and Ni(111) films by magnetron sputtering

The effect of the working gas pressure (P ≈ 1.33–0.09 Pa) and the substrate temperature (Ts ≈ 77–550 K) on the texture and the microstructure of nickel films deposited by magnetron sputtering onto SiO2/Si substrates is studied. Ni(200) films with a transition type of microstructure are shown to form at growth parameters P ≈ 0.13–0.09 Pa and Ts ≈ 300–550 K, which ensure a high migration ability of nickel adatoms on a substrate. This transition type is characterized by a change of the film structure from quasi-homogeneous to quasi-columnar when a film reaches a critical thickness. Ni(111) films with a columnar microstructure and high porosity form at a low migration ability, which takes place at P ≈ 1.33–0.3 Pa or upon cooling a substrate to Ts ≈ 77 K.

Deposition of NiFe(200) and NiFe(111) textured films onto Si/SiO2 substrates by DC magnetron sputtering

The effect of substrate temperature Tsub and bias voltage Ubias on the texture of NiFe films with thickness d ∼ 30–340 nm deposited by DC magnetron sputtering onto Si(111)/SiO2 substrates under working gas pressure ∼ 0.2 Pa has been investigated. It has been demonstrated that films grown at room substrate temperature have the (111) texture that is refined under a negative bias voltage. The deposition of films onto a grounded (Ubias ∼ 0) substrate heated to Tsub ∼ 440–640 K results in the formation of textured NiFe(200) films.

Effect of the Pressure of Working Gas on the Microcrystalline Structure and Magnetic Properties of the Co Film Deposited with the Aid of Magnetron Sputtering

Effect of argon pressure 0.09 ≤ P ≤ 1 Pa on the microcrystalline structure and magnetic properties of the cobalt films with a thickness of d ≈ 300 nm that are fabricated with the aid of magnetic sputtering on the SiO2/Si substrates is studied. It is demonstrated that the films obtained at a pressure of Р ≥ 0.2 Pa exhibit mixed crystal phase with close-packed hexagonal (CPH) and face-centered cubic (FCC) lattice with the CPH–Co(002)/FCC–Co(111) texture and column microstructure over thickness. The films deposited at a pressure of Р ≈ 0.09 Pa are characterized by the dominant FCC crystal phase with the FCC–Со(200) texture and inhomogeneous microstructure over thickness: at the interface with the substrate in a layer with a thickness of d1 ≈ 150 nm, the films exhibit quasi-homogeneous microstructure that is transformed into the granulated microstructure at d > d1. The films deposited at a pressure of Р ≈ 0.09 Pa have the saturation magnetization that is higher by 30% and the coercive force and linewidth of ferromagnetic resonance that are several times less than those of the film obtained at a pressure of Р ≈ 1 Pa.