Facing Targets Sputtering Method Research Articles

Optical and electrical transport properties of facing-target sputtered Al doped ZnO transparent film

Al doped zinc oxide thin film was prepared by dc facing-target sputtering method and its structural, optical, and electrical transport properties have been investigated. The average transmittance of the films is greater than 90% in the wavelength region of 450–700nm while the resistivity is as high as 3×10−3Ωcm. The band gap energy derived from the transmission data is 3.76eV, which is higher than that of pure ZnO thin film. This band gap growth phenomenon cannot be explained in terms of the Burstein-Moss effect. The resistivity and Hall effect measurements suggest that the interaction between the charge carriers and phonons plays a key role in the electrical transport properties of the film between 60 and 300K. The film exhibits negative magnetoresistance at low temperatures, which can be well described by a semiempirical expression that takes into account the third order s-d exchange Hamiltonians describing a negative part and a two-band model for positive contribution.

Particle size reduction and enhanced diffusion of Fe and Pt atoms in FePt–C granular films by N addition

N-doped FePt–C nanocomposite films were fabricated using facing-target sputtering method under different N2 partial pressures (PN) at room temperature. Annealing at 650°C turns the amorphous films into ordered structures. Nitrogen doping not only make the ordering of FePt particles easier than the ordering in FePt–C films, due to the enhanced diffusivity of Fe and Pt atoms, but also effectively limits the growth of the FePt particles during the thermal induced ordering, especially for the annealed films fabricated at PN=40%, where the average size of well-isolated FePt particles is only ∼8nm. The particle size reduction and the enhanced diffusion of Fe and Pt atoms can be ascribed to the desorption of doped N atoms and dissociation of FeN bonds during annealing. The room-temperature coercivity of the samples decreases with the PN due to the particle size reduction and thus the enhancement of the thermal agitation for small particles during the magnetizing procedure.

Fabrication of Fe–Co–C thin films using facing targets sputtering method

We report the fabrication of carbon-doped (0–9 at.%) Fe–Co thin films deposited using facing targets sputtering method. Adding carbon of 2.5 at.% has an effect on decreasing coercivity in the case that the internal stress is approximately zero. Further addition of carbon does not influence the soft magnetic properties, whereas the saturation flux density decreases down to 2 T. The lowest coercivity of 12 Oe in hard axis is obtained with the saturation flux density of 2.4 T and clear uniaxial anisotropy (anisotropy field: 200 Oe) in the (Fe 65Co 35) 97.5C 2.5 film. The Fe–Co–C film exhibits better frequency characteristics than Fe–C films due to higher anisotropy field and saturation flux density.

L 1 phase transformation and magnetic behaviors of (Fe, FePt, FePtCu)–C nanocomposite films

As-deposited (Fe, FePt, FePtCu)–C nanocomposite films with fixed C atomic fraction xc=47 fabricated using facing-target sputtering method at room temperature are composed of ∼2–3-nm amorphous metal granules buried in a-C matrix. Annealing at high temperatures turns the amorphous granules into α-Fe, α-Fe- and L10-structured FePt, and L10-ordered FePtCu for Fe–C, FePt–C, and FePtCu–C films, respectively, and makes a-C preferential graphitization. As-deposited granules are superparamagnetic at 300K, and ferromagnetic at 5K. The zero-field-cooled (ZFC) and field-cooled (FC) curves reveal that there exist strong intergranular interactions at temperatures below 300K, and the size distribution of granules becomes broad by Pt and Cu addition. The M-H loop of annealed Fe31Pt22C47 films exhibits a two-step saturation behavior because of the coexistence of soft and hard ferromagnetic phases. As the Cu atomic fraction is 14%, the coercivity of annealed Fe23Pt16Cu14C47 films reaches a large value of ∼11.2kOe at 5K and decreases to ∼7.2kOe at 300K.

Thin Ferromagnetic Films Deposition by Facing Target Sputtering Method

Facing targets sputtering system, constructed specially for ferromagnetic cathode sputtering, was investigated in this study. The currentvoltage (I-V ) characteristics, deposition rate dependence on the discharge power, dependence on the distance between the center axis of targets and substrate, and on distance between the targets were investigated. Magnetic field distribution between two targets was measured. FTS system has been used successfully to prepare Fe films on glass substrate in various temperatures. The highest deposition rate for this film was 2.2 nm/s when distance between targets was 70 mm and the distance between substrate and a distance from the center axis of targets was 60 mm. X-ray diffraction (XRD) and Atomic Force Microscope (AFM) were used to analyze the surface structure of Fe thin films. It was found that films crystallite sizes depend on deposition temperature.

Reduction of iron diffusion in silicon during the epitaxial growth of β-FeSi2 films by use of thin template buffer layers

We fabricated continuous highly (110)/(101)-oriented β-FeSi2 films on Si (111) substrates by the facing-target sputtering method. An epitaxial thin β-FeSi2 template buffer layer preformed on the silicon substrate was found to be essential in the epitaxial growth of thick β-FeSi2 films. It was proved that the template reduced the iron diffusion into the silicon substrate during thick β-FeSi2 film fabrication. Even though the annealing was performed at high temperature (880 °C) for a long duration (10 h), iron diffusion was effectively hindered by the template. By introducing this template buffer layer, an abrupt interface without appreciable defects between the β-FeSi2 film and the silicon substrate formed. The mechanism for the reduction of iron diffusion by the template buffer layer is discussed.

Magnetic properties and fine structure of FePt–(C4F8)n granular thin films

Abstract FePt–(C4F8)n granular films have been prepared by facing targets sputtering method with plasma polymerizing reaction. The FePt alloy was deposited on fused quartz substrate as same as the (C4F8)n matrix was polymerized. Then, they were annealed at 600°C in reduced air. Their magnetic properties and fine structures were investigated. The films prepared at C4F8 partial pressures of 0.10 and 0.20 mTorr, which consisted of fine FePt particles with a size of 5–10 nm, had high coercivities of 4–8 kOe caused by the stress between FePt particles and fluorocarbon matrix.

ＣｏＰｔ‐（Ｃ４Ｆ８）ｎグラニュラー薄膜の磁気特性

We studied CoPt-(C4F8)n granular thin films for use in high-density magnetic recording media. The (C4F8)n matrix in granular film is very hard and flat, and these properties are advantageous for recording media. CoPt-(C4F8)n granular films were fabricated by the facing targets sputtering method with plasma polymerizing reaction. The CoPt alloy was deposited on substrate and the (C4F8)n matrix was polymerized at the same time. After annealing at 300°C, the CoPt-(C4F8)n thin film had a high coercivity of 4.1 kOe. AFM images of the CoPt-(C4F8)n granular thin films indicated that the grain size was decreased by addition of (C4F8)n matrix. It is considered that the CoPt-(C4F8)n granular films has the potential to be used in high-density recording media.

Thin film properties by facing targets sputtering system

In this study, film thickness distribution and c-axis crystalline orientation of deposited thin films were studied after preparing Co–Cr thin films, a promising ultra-high density perpendicular magnetic recording media, with a facing targets sputtering (FTS) apparatus. Electrical discharge characteristics needed for the optimum operation of sputter device was also studied in order to prepare thin films of superior c-axis crystalline orientation with FTS method (apparatus) in which thin film of fine quality can be formed because temperature increase of substrate due to the bombardment of high-energy particles can be restrained. As a result of the study, it is confirmed that the FTS method can give stable working under broad magnetic field and range of gas pressure and stable electrical discharge under low Ar gas pressure. Film thickness of prepared thin film shows fairy regular distribution and could obtain good thin films whose dispersion angle of c-axis crystalline orientation is about 3.5°.

Structure and GMR in Ni-Fe/Cu Multilayers Fabricated by an Ultra-clean Sputtering Process

The relation between the dry-etching time of the substrate and the magnetoresistance (MR) is discussed for Ni-Fe/Cu multilayers fabricated by a facing-targets sputtering method. The role of the underlying, Ta, Fe, Ni-Fe, or Ni-Fe fabricated in an N2 mixed sputtering atmosphere (Ni-Fe (N2)), is also discussed from the viewpoint of the relation between the microstructure and the GMR properties. Dry etching of the substrate surface with RF plasma before film deposition results in a remarkable increase in the MR ratio. An underlying 30-Å-thick Ta layer increased the MR ratio, while a 5-Å-thick Ni-Fe (N2) underlayer decreased it From an analysis of the structure and magnetic properties of the multilayers, it is concluded that enlargement of the grain diameter in the multilayers led to an enhancement of the interlayer magnetic coupling, and resulted in the remarkable increase in the MR ratio

Microstructure of antiferromagnetic layer affecting on magnetic exchange coupling in trilayered NiFe/25 at% NiMn/NiFe films

The correlation between the microstructure of antiferromagnetic (AF) NiMn layer and exchange coupling performed at the ferromagnetic (F)/AF layer interface was discussed in the trilayered Si(1 0 0)/NiFe/25 at% NiMn/NiFe films with various thickness combinations fabricated by a facing-targets sputtering method. Unidirectional anisotropy constant, J k performed at the lower F/AF interface became large with increasing underlaid F layer thickness d AF up to 200 Å and showed constant value about 0.06 – 0.07 erg/cm 2 beyond it when the AF layer thickness ( d AF) > 200 A ̊ . On the other hand, J k at the upper interface rose to peak with increasing d AF at 100–200 Å and then fell down to zero at 1000 Å in contrast to the J k at the lower interface. Following the field cooling study of trilayered films in a wide temperature range (10–473 K), it was concluded that the blocking temperature of γ-NiMn grains at the lower interface were distributed more widely down to the cryogenic temperature when d F = 50 A ̊ in comparison with d F = 200 A ̊ . This difference was supposed to be caused by the difference of the in-plane diameter of γ-NiMn grains epitaxially grown on the underlaid NiFe grains growing with increasing d F. The cross-sectional TEM observation for the trilayer with d AF = 1000 A ̊ made it clear that the crystal structure of NiMn layer had separated from γ-NiMn phase into α-Mn + θ-NiMn phase with increasing d AF, and resulted in the vanishing of J k at the upper interface.

Effect of Substrate Surface Cleaning on GMR in Co/Cu Multilayers

The correlation between the cleanness of the substrate and the magnetoresistance (MR) is discussed for Co/Cu multilayers fabricated by a facing-targets sputtering method. Dry-etching of the substrate surface with RF plasma before film deposition results in a remarkable increase in the MR ratio, especially in multilayers whose Cu space layer thickness (dcu) is from 9Å to 11Å. From an analysis of the structure and magnetic properties of multilayers, it was concluded that an enlargement of the grain diameter in the multilayers led to an enhancement of the interlayer magnetic coupling, and resulted in the remarkable increase in the MR ratio. An exposing study of dry-etched substrates under various atmospheres, confirmed that dry-etching desorbed H2O and/or O2 gases from the surface and enhanced the mobility of sputtered adatoms on it.

Effect of Gas Adsorption onto the Interface on the Exchange-Coupling Field of Ni-Fe/25 at%Ni-Mn Film

The effect of gas adsorption onto the interface on the exchange-coupling field of Ni-Fe/25 at%Ni-Mn film was investigated. Ni-Fe/25 at%Ni-Mn/Ni-Fe trilayer films were prepared on an Si(100) substrate by a facing-targets sputtering method. The lower interface of trilayer films was exposed for 1 hour in various atmospheres controlled by introducing air or N2 through a variable leak valve. The strength of the exchange coupling, Jk, decreased rapidly when the air pressure during exposure exceeded 1×10-7 Torr. From the temperature dependence of Jk and cross-sectional TEM observation, it was found that γ-Ni-Mn became easy to separate into α-Mn+θ-NiMn with increasing air pressure, leading to the decrease in Jk at R.T. This structural change in Ni-Mn layer was considered to be caused by the H2O/O2 gas adsorption or partial oxidation on the lower Ni-Fe surface, preventing epitaxial growth of γ-Ni-Mn grain on it.

Effect of the Surface Cleaning of the Substrate on the Exchange-Coupling Field of an Ni-Fe/25at%Ni-Mn Film

The effect of gas adsorption onto the substrate on the exchange-coupling field of an Ni-Fe/25 at%Ni-Mn/Ni-Fe film was investigated. Trilayer films were prepared on an Si(100) substrate by the facing-targets sputtering method. The strength of the exchange coupling, Jk, at R.T. increased rapidly when the substrate surface was etched with RF plasma. From analysis of the structure of films, and in view of the temperature dependence of Jk, it was concluded that the increase in Jk was caused by enlargement of the in-plane diameter of γ-Ni-Mn grains epitaxially grown on underlaid Ni-Fe grains. From an exposing study of dry-etched substrate in various atmospheres, dry- etching was considered to desorb H2O and/or O2 gasses from the surface and to enhance the mobility of sputtered adatoms, thus causing enlargement of the underlaid NiFe grain size.

Effects of discharge pressure on the properties of Ag/Ni superlattices prepared by facing-target sputtering

Giant magnetoresistance (GMR) effect in magnetic multilayered thin films is strongly affected by interface roughness. We prepared [Ag/Ni]60 superlattices on Corning’s 7059 glass substrates using a novel facing-target sputtering method and observed that the interface roughness can be controlled by varying the discharge pressure (PAr). The samples prepared at PAr≊10 mTorr exhibit sharpest interfaces, good (111) texture, and largest GMR effects (Δρ/ρs=9% at room temperature). Lower PAr promotes interface mixing while higher PAr results in much rougher interfaces and emergence of structural defects. Both cases weaken the antiferromagnetic coupling strength and thus reduce the MR effect. When PAr≥30 mTorr, we observed a further degradation of the multilayered structure. The GMR effects in these samples disappeared. Low-temperature annealing can improve the flatness of the interfaces and film structure, while higher-temperature annealing (≳300 °C) decomposes the multilayer structures.

Ｎｉ‐Ｆｅ／２５ａｔ％Ｎｉ‐Ｍｎ積層膜の交換磁気異方性

Ni-Fe/25 at%Ni-Mn/Ni-Fe trilayer films were prepared on Si(100) substrate by the facing-targets sputtering method. Unidirectional magnetic anisotropy, induced by exchange coupling at the interface between the Ni-Fe and Ni-Mn layers, was observed in the Ni-Fe layer. The strength of the exchange coupling, Jk, was about 0.07 erg/ cm2 at R. T. and fell to 0 when the film was heated above 170°C (blocking temperature, TB). As a result of field cooling in the direction opposite to the easy direction initially induced, the sign of Jk changed from positive to negative, even at temperatures less than TB. This change in Jk suggests that the Neel temperatures of grains at the interface were broadly distributed.

Ba ferrite thin films with large saturation magnetization deposited by sputtering in mixture of Xe, Ar and O/sub 2/

BaM ferrite films 5000 /spl Aring/ thick were deposited on a ZnO underlayer at a substrate temperature of 600/spl deg/C by the facing targets sputtering method in a mixture of Xe and Ar of 0.19 Pa in addition to O/sub 2/ of 0.01 Pa. The Xe partial pressure P/sub Xe/ was varied from 0.0 to 0.19 Pa and then the P/sub Ar/ was varied from 0.19 to 0.0 Pa. The films deposited at P/sub Xe/ of 0.19 Pa had almost the stoichiometric composition of BaM ferrite and the crystallite size <D xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">, the full width at half maximum of the rocking curve /spl Delta//spl theta//sub 50/, saturation magnetization 4/spl pi/M/sub s/, squareness S, perpendicular coercivity H/sub c/spl perp// were 300 /spl Aring/, 3.7/spl deg/, 5.1 kG, 0.51 and 2.3 kOe, respectively. It should be noted that it had larger 4/spl pi/M/sub s/ than that of bulk BaM ferrite, for which 4/spl pi/M/sub s/ is 4.8 kG.&lt;<ETX>&gt;</ETX></D>

Synthesis of Fe16N2 Compound Films by Reactive Sputtering

Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films (of thickness 3000Å) were fabricated on MgO (001) substrates by the conventional dc facing target sputtering method using a controlled reactive plasma, at an electron temperature of T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> =0.3 eV, an electron density of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> =1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> , a deposition rate of 200Å/min and an N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> flow ratio ranging from 10% to 20%. In the as-deposited state, single α' phases with various nitrogen contents were formed. After annealing at 150°C for two hours, an α" phase (≅11 at% N) and an α' phase (11.1 at% N and 1 to 2 at% N) were formed. The M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> value was nearly the same as for α-Fe (2.2 T), despite the existence of the α" phase. The lattice constant c of the α" phase in these films agreed well with the value reported by Jack, but lattice constant a values were about 1 to 3% smaller than Jack's value. The unit cell volumes of the α" phase in these films were between 192.5 and 202.6Å <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , from 1.4 to 6.3% less than Jack's value of 205.5Å <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Modification of magnetic properties of Fe/Mn multilayers with modulation of layer thickness (abstract)

It seemed to be possible to distort the Fe crystal lattice in Fe/Mn multilayers, because the atomic radii of α-Fe and α-Mn with cubic crystal lattice are 1.26 and 1.29 Å, respectively. It is very interesting to investigate how crystallographic and magnetic characteristics of the Fe/Mn multilayers were changed by modulating the thickness of Fe and Mn layers. In this study, 2000-Å-thick Fe/Mn multilayers with sharp periodicity were deposited on plasma-free substrate Si wafer by the facing target sputtering method. The Ar gas pressure pAr was set at 2 mTorr. Deposition rates of Fe and Mn layers were 5 and 2 Å/s, respectively. The thicknesses of Fe and Mn, δFe and δMn, were in the range of 20–200 Å and 5–100 Å, respectively. The crystallites in Fe and Mn layers revealed the distinct orientation of α-Fe(110) and α-Mn(411) planes, respectively. The Fe(110) interplanar distance dFe increases from value close to Mn(411) interplanar distance dMn to that close to dFe with increase of the Fe layer thickness δFe in the range of 10–100 Å. The distortion of Fe crystal lattice increased with decrease of δFe and increase of interface number. The difference between the saturation magnetization 4πMs measured for the specimen multilayers and that calculated for the single layer films of simply diluted alloy increased with increase of δFe. However, 4πMs of the Fe layers in Fe/Mn multilayers did not changed with δMn except for the films with δFe as extremely small as 20 Å. And 4πMs took the value of nearly zero at δFe of 10 Å. In the range of δMn of 20–50 Å, the Fe lattice distortion was most remarkable and the coercivity Hc increased highly due to the large in-plane uniaxial anisotropy. Hc took its maximum value of about 70 Oe at δFe and δMn of 50 Å. This result may imply that the distortion of both layers are most remarkable. Consequently, it was confirmed that dFe and the crystallite size in Fe layers were changed and Hc was modified by modulating both δFe and δMn.

The control of magnetic characteristics of BaM ferrite thin films by bias sputtering (abstract)

The thin films of a magnetoplumbite type of barium (BaM) ferrite have been deposited on SiO2/Si substrates at a rate of 100 Å/min in a gas mixture of 10% O2–90% Ar at a pressure of 2 mTorr by using the facing targets sputtering (FTS) apparatus. They possessed excellent chemical stability and high corrosion resistivity as well as perpendicular anisotropy as large as applicable for perpendicular magnetic recording media. They also seem to be applicable for millimeter wave isolator and circulator. In this study, the saturation magnetization Ms, the coercive force Hc, and the anisotropy field Hk of BaM ferrite films have been controlled by adjusting the rf-bias voltages to substrate Vb during sputtering, where Vb was always negative. The dependencies of Ms and Hc on Vb were shown in Fig. 1. Ms took the maximum value as large as 345 emu/cc at Vb of −30 V and decreased as Vb decreased in the range below −50 V. On the other hand, the perpendicular Hc decreased as Vb increased in the range above −100 V and took the minimum value as low as 910 Oe at Vb of −95 V. Hk and the magnetic anisotropy constant Ku also greatly depended on Vb. Such an apparent Vb dependence of these magnetic characteristics of BaM ferrite films seem to be attributed to the definite change in c-axis orientation of hexagonal crystallite and the different distribution of Fe3+ ions among several occupation sites. These results indicated that the c-axis orientation of BaM ferrite crystallites were promoted by applying proper Vb. Consequently, the bias sputtering technique with FTS method may be useful for preparing the BaM ferrite films composed of the multilayers with different magnetic characteristics, even if only one pair of targets are used without adjusting the other sputtering conditions.