Conventional Rf Diode Sputtering Research Articles

In situ ordered polycrystalline FePt L10 (001) nanostructured films and the effect of CrMn and Zn top layer diffusion

The nanostructure and magnetic properties of in situ ordered polycrystalline FePt thin films (9 nm) have been studied. Films were deposited with a MgO underlayer onto Si and glass substrates using conventional rf diode sputtering. Perpendicular anisotropy was obtained when the substrate temperature exceeded 490 °C. The maximum order parameter (S) was estimated to be ∼0.9. The coercivities (Hc) ranged from 5 to 12 kOe. Observed high values of the coercive squareness (S*) indicate the existence of exchange coupling. High resolution transmission electron microscopy indicates a defective region which might be associated with defect-related localized incoherent nucleation, thereby inducing low values of Hc. Zn and CrMn top layers at ambient temperature were deposited after the deposition of FePt films at elevated temperatures. Rapid thermal annealing of these samples at 180–450 °C for 1 min resulted in a decrease of S* from 0.8–0.85 to ∼0.5–0.6.

Preparation and properties of Pb(Zr, Ti)O 3 thin films deposited on Ir electrodes using a sputtering apparatus

Pb(Zr, Ti)O 3 films were prepared on Ir/SiO 2/Si substrates at the substrate temperatures from 450°C to 600°C by a conventional rf diode sputtering system using a ZrTi+ xPbO composite target. X-ray diffraction analysis showed that the crystallinity of films deposited with a ZrTi+24% PbO target was better than that of films deposited with a ZrTi+30% PbO target. The dielectric properties of the PZT films deposited on an Ir/SiO 2/Si substrate at 600°C with a ZrTi+24% PbO target with Au top electrodes were evaluated before and after the annealing at 400°C 10 min in an O 2 atmosphere. The value of remanent polarization obtained from the P– E hysteresis loop characteristics improved from 4.2 μC/cm 2 before annealing to 16.2 μC/cm 2 after annealing at an electric field of 180 kV/cm. The Ti buffer layer improved the crystallinity and/or microstructure of the PZT and Ir films, as evaluated by X-ray diffraction analyses, and reduced the leakage current of the PZT thin films.

La–Zn substituted hexagonal Sr ferrite thin films for high density magnetic recording

La–Zn substituted M type Sr-ferrite thin films were prepared by conventional rf diode sputtering. The crystallography, surface morphology, magnetic properties, and their temperature dependence were investigated by x-ray diffractometry, atomic force microscopy, and vibrating sample magnetometry. La–Zn substitution reduces the grain growth rate, so that it was possible to obtain fine grains with mean grain size about 12 nm×12 nm. Suitable amount of La–Zn substitution increases the saturation magnetization Ms of the films without changing the magnetocrystalline anisotropy of the material. As a result, the coercivity Hc increases with the increase of the La–Zn substitution. La–Zn substitution also reduces the values of dHc/dT of the films in the vicinity of room temperature.

LA-Zn DOPED SrM FERRITE FOR HIGH-DENSITY MAGNETIC RECORDING

La-Zn doped M type Sr-ferrite thin films with various doping concentration were prepared by conventional rf diode sputtering. La-Zn doping reduces the grain growth rate, so that fine grains with mean grain size about 12nm were prepared with superior magnetic properties. It is found that suitable amount of La-Zn substitution may increase the Ms of the films, and modify the tempareture coefficient of coercivity, while Hc increases with increasing concentration of La-Zn.

Ce-substituted yttrium iron garnet films prepared on Gd3Sc2Ga3O12 garnet substrates by sputter epitaxy

Ce-substituted yttrium iron garnet films are epitaxially grown in situ on (111)-oriented substrates of Gd3Sc2Ga3O12 garnet by conventional rf diode sputtering for application to magneto-optic waveguide devices in optical communication systems. The lattice constant of the substrates is larger than that of the previously used (Gd,Ca)3(Ga,Mg,Zr)5O12 garnet substrates whose lattice constant is smaller than that of the films. The lowest ever reported propagation losses of 9.7 dB/cm in the TE mode and 5.8 dB/cm in the TM mode are obtained for a film thickness of 0.5 μm at λ=1.55 μm.

Preparation of Ce-Substituted Yttrium Iron Garnet Films for Magneto-Optic Waveguide Devices

Ce-substituted yttrium iron garnet films are epitaxially grown in situ on (111)-oriented substrates of (Gd, Ca, Mg)3(Ga, Zr)5O12 garnet by conventional rf diode sputtering for application to magneto-optic waveguide devices in optical communication systems. Pure argon or argon containing a small amount of oxygen is used as the sputter gas. After sputtering, the films are annealed in a nitrogen atmosphere. By optimizing this process, film propagation loss can be reduced while maintaining a large Faraday rotation. A propagation loss of 13 dB/cm and a Faraday rotation of -3900°/ cm have been obtained at a wavelength of 1.55 µ m.

Barium ferrite thin-film recording media

Both longitudinal and perpendicular barium ferrite thin films are being pursued as overcoatless magnetic recording media. In this paper, prior research on thin-film Ba ferrite is reviewed and the most recent results are presented. Self-textured high-coercivity longitudinal Ba ferrite thin films have been achieved using conventional rf diode sputtering. Microstructural studies show that c-axis in-plane oriented grains have a characteristic acicular shape, while c-axis perpendicularly oriented grains have a platelet shape. Extended X-ray absorption fine structure (EXAFS) measurements indicate that the crystal orientations are predetermined by the structural anisotropy in the as-sputtered ‘amorphous’ state. Recording tests on 1500 Oe coercivity longitudinal Ba ferrite disks show performance comparable with that of a 1900 Oe Co alloy disk. To further improve the recording performance, both grain size and aspect ratio need to be reduced. Initial tribological tests indicate high hardness of Ba ferrite thin films. However, surface roughness needs to be reduced. For future ultrahigh-density contact recording, it is believed that perpendicular recording may be used. A thin Pt underlayer has been found to be capable of producing Ba ferrite thin films with excellent c-axis perpendicular orientation.

Magneto-optical properties of Al and In-substituted CeYIG epitaxial films grown by sputtering (abstract)

Cerium substitution to iron garnet strongly enhances magneto-optical (MO) effect in the visible region around hν=1.4 and 3.1 eV. We have previously proposed a Ce3+(4f)-Fe3+ (tet.) charge transfer model as an electronic transition inducing the strong MO effect. In this study, we have measured Faraday spectra of CeYIG films in which Fe ions were diluted with Al or In ions. These ions, respectively, are known to preferentially occupy tetrahedral and octrahedral iron sites in the garnet structure, giving us some information on the role of Fe3+ in the MO enhancement. The Y2Ce1Fe5−xMxO12 (M=Al, In; x=0–5) films were epitaxially grown in situ on (111)-oriented Gd3Ga5O12 (GGG) single crystal substrates by conventional rf diode sputtering. With the amounts of substitutions increasing, Faraday rotation and ellipticity of the films at hν=1.4 eV reduced at nearly the same rates for both ions of Al and In. We found from the analysis using molecular field theory that these reductions are in proportion to the magnetic moment of the tetrahedral iron sublattice. This indicates that the tetrahedral Fe3+ contributes to the electronic transition at 1.4 eV, supporting the proposed charge transfer model.

Magnetic easy axis randomly in-plane oriented barium hexaferrite thin film media

High coercivity, c-axis randomly in-plane oriented barium hexaferrite thin films have been successfully fabricated by using conventional rf diode sputtering and post-deposition annealing. Coercivities as high as 4100 Oe have been achieved. Ms, Sq, S*, SFD, and SFDr reach the values of about 270 emu/cc, 0.63, 0.90, 0.12, and 0.084, respectively. CoTi doping not only reduces the coercivity, but also reduces the grain size and improves the c-axis in-plane orientation. The composition of doped films can be controlled through different diffusion processes. In this way coercivities in a range between several hundred oersteds and 4000 Oe can be easily obtained.

Microstructure and MO enhancement in Ni-substituted Ba ferrite films prepared by sputtering (abstract)

Sputtered Ba ferrite films are promising media for magneto-optical (MO) recording because they have strong perpendicular magnetic anisotropy. However, MO activity of the Ba ferrites is low, which makes the feasibility as a practical medium poor. The MO activity is reported to be prominently enhanced by specific ions such as Bi3+, Co2+, and light rare earth ions in garnet ferrites, while, in Ba ferrites, the MO enhancement ions except Co2+ have not yet been known. We have recently found that Ni2+ substitution also enhances Faraday rotation in the visible region around hν=2.5 eV. In this paper we describe MO properties as well as microstructures of Ba1−xMxFe12−xNixO19 (M=La, Pr, x=0, 0.3, 0.6) films prepared by rf sputtering. The films were deposited on Gd3Ga5O12 (GGG) single crystal substrates at substrate temperature (Ts) of 400–600 °C by the conventional rf diode sputtering. When Ts≥550 °C for the incident rf power over 19 W/cm2, the films in situ crystallized in Ba–ferrite single phase. They had c-crystal axis well oriented normal to the film plane. The SEM and TEM observations revealed that the grain size in the films increases from several nm to ∼300 nm with increasing the incident power. The films with larger grains showed higher saturation magnetization and lower coercivity. Faraday rotation of the films was clearly enhanced in the visible around 2.5 eV with increasing Ni2+ substitution, though they showed rather complicated spectral structure inherent to the Ba ferrites. The enhancement factor of specific Faraday rotation at 2.5 eV was as large as 2×104 deg/x, independent of the kind of the rare earth ion substituted for Ba2+ for charge compensation. This implies that the substitution of the rare earth ion itself enhances no Faraday rotation in Ba ferrites. Thus, the MO enhancement around 2.5 eV may be attributed to the octahedrally coordinated Ni2+.

スパッタビーム法によるFe膜の結晶構造と磁気特性

Film deposition by means of a beam of sputtered particles was studied. The sputtered particles are ejected from a sputtering chamber and deposited on a substrate in another evacuated chamber. The method makes uses of the gettering effect of high-rate sputtering, together with a cold-wall effect that suppresses desorption of impure gases from chamber walls. The crystal structure and magnetic properties of Fe films thus deposited were studied. The films exhibit higher crystal growth, higher electrical conductivity, and lower coercivity than films deposited by a conventional RF diode sputtering system. These results suggest that, by further improvement of the system, the method may be applied to the production of various multi-element single-crystal films of high quality.

Low-temperature silicon homoepitaxy by rf sputtering

We have shown that silicon homoepitaxial growth can be achieved by conventional rf diode sputtering at a low growth temperature (Ts∼400 °C). Spectroscopic ellipsometry and the electron channeling pattern are presented to show that the film deposited on a HF-treated substrate is a single-crystalline film while the film deposited without HF treatment is a polycrystalline film. Ar-discharge cleaning of the substrate is also found to greatly improve the surface morphology of the deposited films.

Strong magneto-optical enhancement in highly Ce-substituted iron garnet films by sputtering (abstract)

Recently we succeeded in growing epitaxial films of Ce-substituted iron garnet (Y3−xCexFe5O12) with so much substitution as up to x=1.5, which strongly enhances magneto-optical (MO) effect in the near IR region around hν=1.4 eV.1 The enhancement per Ce ion surpasses that by Bi3+ ion in the IR region which has been the champion of the MO enhancement for 20 years. In this study we have measured the Faraday effect of the Ce-substituted garnet films in an extended photon energy range of hν=1–4 eV in order to elucidate the role of Ce3+ in the MO enhancement. The films (R3−xCexFe5O12: R=Y, Gd, Yb, x=0–3.0) were epitaxially grown in situ on Gd3Ga5O12 (GGG) and Nd3Ga5O12 (NGG) single-crystal substrates by conventional rf diode sputtering. For R=Y the Ce substitution was successfully extended to x=2.5 by sputtering under the reduced atmosphere of Ar+H2. The Ce substitution prominently enhanced Faraday effect not only in the IR region at hν=1.4 eV but also in the UV region at hν=3.1 eV, both having a paramagnetic dispersion relation with nearly equal magnitude though opposite in sign. We also found a new optical absorption due to Ce3+ at hν =2.0 eV which does not enhance the Faraday effect.

In-situ crystallization of YBaCuO films by the RF-diode sputtering method

A recently developed temple-bell-type substrate holder in the conventional RF-diode sputtering method was used to obtain high-quality YBa/sub 2/Cu/sub 3/O/sub 7-y/ films. Avoiding the rush of negative ions into the films by placing the substrate perpendicular to the target surface led to the formation of highly oriented films with smooth surfaces on the various kinds of oxide substrates. The as-grown films deposited on SrTiO/sub 3/ [100], SrTiO/sub 3/[110], and MgO [100] substrates showed a transition temperature of >80 K. The critical current densities were improved by post-oxygen annealing and reached values of more than 2*10/sup 5/ A/cm/sup 2/ at 77 K in the films on the MgO [100] and SrTiO/sub 3/ [100] substrates. However, AC susceptibility measurement showed that many weak links, presumably due to oxygen deficiencies, remained.

Preparation of amorphous Tb-Fe-Co thin films by plasma-free high-rate sputtering

The facing targets type of sputtering (FTS) apparatus [Naoe, Yamanaka, and Hoshi, IEEE Trans. Magn. MAG-16, 646 (1986)] can prepare amorphous Tb-Fe-Co thin films on plasma-free substrates at temperatures lower than 100 °C at a deposition rate as high as 5000 Å/min. The saturation Kerr rotation at 830 nm, reflectance and coercive force of the specimen films 1000 Å thick were 0.3, 48%, and 6 kOe, respectively, comparable to those obtained in films deposited at a one-hundredth lower rate by conventional rf diode and dc magnetron sputtering. Films with good uniformity of thickness, composition, and characteristics were deposited over the whole area of 12-in. disk substrates made of PMMA or glass, without deteriorating the pregrooves. At this stage, a C/N of about 46 dB has been attained.

Ba-ferrite thin film rigid disk for high density perpendicular magnetic recording

A magnetoplumbite type of hexagonal Ba-ferrite films, whose c-axis of crystallites is well oriented perpendicularly to the film plane, have been prepared by means of a conventional rf diode sputtering system. Morphological and crystallographic characteristics of sputtered Ba-ferrite films depend strongly on preparation conditions such as the distance between target and substrate d T-S and partial pressure of oxygen gas P O2 during the deposition. Ba-ferrite films with smooth surface are prepared at the extended d T-S in the region of low P O2 . Read/write characteristics of Ba-ferrite thin film deposited on thermally oxidized silicon wafer with radius of two inches were evaluated with ring type head. Recording density D 50 of Ba-ferrite thin film rigid disk depends strongly on Δθ 50 . In this work, D 50 of 110 and 190 kfrpi for Δθ 50 of 4.8 and 2.8°, respectively, have been attained.

Studies of MZS and MZOS Structures with Zinc Oxide Deposited by Conventional Rf Diode and Magnetron Sputtering Techniques

ABSTRACTHighly crystalline and c-axis oriented zinc oxide thin films were sputter deposited from a ceramic target using rf diode and magnetron sputtering techniques. A comparative evaluation of structure and electrical characteristics of ZnO films in the MZS and MZOS configurations is presented and the results are discussed. The physical and electrical properties were significantly influenced by highly energetic particles originating from the presence of oxygen neutrals in the plasma during the growth process and the behavior differed between the diode and magnetron sputtering processes.

New Microstructural Model for Sputtered Co-Cr Magnetic Thin Films

ABSTRACTRapidly solidified Co-Cr thin films with a perpedicular magnetic anisotropy have been extensively investigated as one of the most promising media for perpendicular magnetic recording system. Most of these films used to be prepared by conventional RF diode sputtering and vacuum evaporation methods. We have developed the Facing Targets Sputtering apparatus which is able to deposite the magnetic thin films without the bombardment by high energy particles to the substrate along with the capabilities to deposit films under wide range of argon gas pressure at high deposition rate. It has been found that the texture and crystallographic structure of the sputtered films are primarily dependent on the argon gas pressure and the films prepared by the Facing Targets Sputtering exhibit quite different properties from the films prepared by conventional methods. The films deposited in the argon gas at the low pressure on the plasma-free substrate using the Facing Targets Sputtering are composed of the fine polyhedral grains packed densely from the initial growth layer to the surface layer of the film. They show exellent c-axis orientation of hcp crystallites, smoother surface textures and the superior perpendicular magnetic anisotropy as compared with the films composed of so-called columnar grains deposited in the argon gas at the higher pressures using the conventional RF diode sputtering. These results imply that the sputtering apparatus which is capable to deposit Co-Cr films in the argon gas at relatively low pressure is indispensable for the preparation of superior perpendicular magnetic recording media. Therefore, the Facing Targets Sputtering apparatus seems to be quite suitable for this purpose. Further, we have proposed a new micro structural model with fine polyhedral grains obtained by our sputtering method, because this model will have the ideal structural characteristics for ultra high density perpendicular magnetic recording.

Differences between Sputtering Methods in The Formation of Amorphous Magnetic Alloy Films

ABSTRACTFe-Si, Co-Ta and Co-Zr amorphous films have been deposited by using various sputtering methods (conventional rf diode sputtering, rf triode sputtering, dc Targets Facing type sputtering (dc TF sputtering) and dual ion beam sputtering (DIB sputtering)). The lower limit of the Si and Ta content to form amorphous Fe-Si and Co-Ta films changes significantly with the sputtering method. These differences between the sputtering methods are mainly caused by the differences in the plasma potential which affects the amount of ion bombardment to the film surface during sputtering,and the minimum content of Si or Ta to obtain amorphous films decreases as the plasma potential increases. These results indicate that the ion bombardment suppresses the growth of crystallites and promotes the formation of the films with amorphous structures. This is confirmed by the deposition of Co-Ta and Co-Zr amorphous films under the condition of various amount of ion bombardment by using a DIB sputtering system.

Magnetron sputtering of permalloy for thin-film heads

Thick permalloy films, as needed für magnetic recording heads, lend themselves to sputtering with the high-rate magnetron method. Special magnetron cathodes, with a field strength about three times higher than usual, have been used. With a 6 mm thick target, more than 900 substrates (diameter 7.62 cm) can be deposited with one micron of permalloy. The sputtering rates were about 100 to 150 nm/min. DC bias of about 100 V and a magnetic field of ≥35 A/cm were needed for anisotropy and soft magnetic film properies. Argon-nitrogen mixtures were used as the sputtering gas, the nitrogen content being 0 to 2.8 %. Electrical resistivity and coercivity values are given for film thicknesses between 0.13 and 2 microns. Film composition was measured by X-ray fluorescence and AES methods. Though the nitrogen content in the film is smaller than 0.5 % (mole fraction), the coercivity shows a rapid decrease from 0.4 to 0.2 A/cm with increasing nitrogen in the sputtering gas. The same results have been found also for NiFe films, sputtered in a conventional RF-diode sputtering machine.