Toyoaki Hirata

Crystal orientation in titanium thin films deposited by the sputtering method without plasma damage

Abstract Pure titanium thin films have been prepared by the Facing Targets Sputtering method under various sputtering conditions such as argon gas pressure P Ar , substrate temperature T S and bias voltage to substrate V B X-ray diffractometry showed that all the films were composed of more or less h.c.p. crystallites with (01 1 O), (0002) and (01 1 1) orientations parallel to film plane and some amount of amorphous-like fine grains. The high P Ar promoted the crystallinity and the development of (0002) orientation and produced the rough surface and columnar structure. Even at low P Ar , the deposition of initial layer with high (0002) intensity or the elevation of T S could lead to the development of (0002) orientation and the formation of smooth surface and columnless structure. The application of a moderate bias voltage to substrate caused the damage of crystallinity and the promotion of (01 1 0) and the promotion (01 1 1) orientations, but developed a very smooth surface and dense morphology. These results could be attributed to the behaviour of adatoms of the surface of substrate and growing film.

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 A/min. The saturation Kerr rotation at 830 nm, reflectance and coercive force of the specimen films 1000 A 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.

Kerr rotation and perpendicular magnetic anisotropy of CoCr films with Al ultrathin interlayers and single‐layer CoCr films

The Co81Cr19/Al multilayered films were prepared by using the plasma‐free sputtering apparatus. The specimen films with the thicknesses of Co81Cr19 and Al layers lCo‐Cr and lAl of 50–170 and 7–14 A, respectively, were investigated for the Kerr rotation angle θK and the reflectance R of the multilayered films with total thickness of 1500 A. Films with lCo‐Cr and lAl of 138 and 7 A, respectively, had a θK of 0.21° and R of 0.7 which is larger than Co81Cr19 single‐layer films prepared by conventional sputtering where θK and R are 0.036° and 0.4–0.5, respectively. These results indicate that the films were entirely homogeneous, that is, the surface and interior of the films may be almost the same for composition, microstructure and magnetic properties. Consequently, the Co81Cr19 thin films with Al ultrathin interlayers may be useful for microcrystalline magneto‐optical media with a high C/N ratio.

Co-Cr/Al multilayers for perpendicular magnetic/magneto-optical two-way recording media

Co-Cr/Al multilayers exhibit excellent magneto-optical characteristics due to the well-defined interfaces between Co-Cr and Al layers. Consequently, these multilayers may be useful in media for perpendicular magnetic/magneto-optical two-way magnetic recording systems.

Corrosion resistive Fe‐Si‐B films with low Hc and λs by reducing the high energy of γ electrons in tetrode sputtering

The thin films of the Fe‐Si‐B alloy have been prepared by using an rf tetrode sputtering system, which can deposit the amorphous films with smaller Si and B contents by reducing the high energy of γ electrons. The as‐deposited films with a composition of Fe80Si12B8 on the water‐cooled substrates at room temperature were amorphous and exhibited the saturation magnetization 4πMs of 11.5 kG, the coercivity Hc of 15 Oe, the relative permeability μr of 43, and the magnetostriction constant λs of 18×10−6. Some of them exhibited 4πMs as large as 15.0 kG, Hc as very low as 0.01 Oe, μr as high as 7,530, and λs as small as 1.5×10−7 after immersion in water for one day.

High permeability of Fe–Al–Si alloys films deposited on plasma‐free substrate by dc bias sputtering

Soft magnetic Fe75Al10Si15 (Sendust) films were deposited on substrates separated from the high‐energy plasma using the facing targets sputtering (FTS) apparatus. The Ar bias voltage VB was changed in the range of 0 to −150 V, and the substrate temperature Ts was adjusted in the range of 50∼400 °C. Films deposited at PAr of 1.0 mTorr and VB of −100 V possessed almost the same composition as that of the targets: Fe75Al10Si15. Films deposited at PAr=1.0 mTorr, VB=0 V and Ts=350 °C exhibited a saturation magnetization 4πMs=11.7 kG, a coercivity Hc=0.6 Oe, and a static relative permeability μrs=5000. On the other hand, films deposited at PAr=1.0 mTorr, VB=−100 V and Ts=50 °C exhibited 4πMS=12.0 kG, HC=0.4 Oe and μrs=8000. In addition, these films exhibited radio frequency relative permeability μrf of 2850 and 1050 at fM=10 and 50 MHz, respectively.

Effect of distribution of plasma density and floating potential on crystallite orientation of Co-Cr films in facing targets sputtering apparatus

For perpendicular magnetic recording media, Co-Cr films was prepared by using the facing targets sputtering (FTS) apparatus. The plasma density distribution was determined by single probe method. The understanding of close relationship between ion bombardment and film crystallinity seemed to be very important for preparing the ultra-high density recording media. Therefore, the dependence of crystallinity and c-axis orientation of hcp crystallites in the Co-Cr films on plasma exposure was investigated. In addition, the substrate position was optimized for depositing the excellent crystallinity and c-axis orientation Co-Cr films at high deposition rate.

Co-Cr/Al Multilayers for new perpendicular recording system

Co-Cr/Al multilayers exhibited excellent magneto-optical characteristics. This is due to the well-defined interfaces between Co -Cr and Al layers. The Kerr hysteresis loops for the film surface were almost tlie same in shape and magnitude as those measured for the whole films by using a vibrating sample magnetometer. Consequently, these multilayers may be useful in the media for a new perpendicular magnetic/magneto-oplical recording system.

Improvement in soft magnetism of Sendust sputtered films for high performance MIG head

Abstract Sendust thin films with relative permeability μ r up to 6000 were prepared by using the facing targets sputtering (FTS) system which is one of the plasma-free sputtering methods. The optimum values of the argon gas pressure P Ar , the substrate temperature T s and the bias voltage to the substrate V b were found.

Preparation of aluminum thin films by the facing targets sputtering system

Abstract The facing targets sputtering (FTS) system, typical of plasma-free sputtering systems, was used to deposit aluminum thin films composed of very fine grains with a smooth surface, large hardness and low resistivity. When the argon gas pressure P Ar was also low as 10 −1 Pa, the aluminum films deposited at a bias voltage to substrate V b of −40 V became smoother, more reflective and harder. The films deposited at a V b of −100 ∼−160 V revealed a definite (111) orientation of the aluminum crystallites parallel to the film plane. The resistivity ϱ of the films deposited at a P Ar below 10− Pa was almost equal to that of bulk aluminum.