Takashi Kawanabe

Control of morphology and crystallinity of chromium sputtered film

Abstract Chromium films prepared by the Facing Targets Sputtering (FTS) system have been characterized. The morphology and crystallinity of the films were controlled by deposition conditions such as argon gas pressure, substrate temperature and bias voltage. The morphology of chromium films is strongly dependent on argon gas pressure. A network-less surface morphology was found at a pressure as low as 0.2 mTorr and a clear column was found at a pressure as high as 10 mTorr. Crystallographically preferred orientation changed from Cr-b.c.c. (110) to Cr-b.c.c. (200) with an increase of substrate temperature from about 25 °C to 300 °C.

Magnetic and recording characteristics of Co-Cr-Ta/Cr thin film prepared on Si substrate

Co/sub 85/Cr/sub 15-x/Ta/sub x/ (x:0,2)/Cr films with microscopic flat surfaces were investigated for high-density recording media. These films were deposited on silicon disk substrates at the substrate temperature T/sub s/ of 350 degrees C at argon pressure as low as sub-mTorr by using facing targets sputtering (FTS) apparatus. The elevating of T/sub s/ promoted the in-plane c-axis orientation of Co crystallites. The media noise due to zigzag domain was found to be reduced by using a Cr underlayer as thick as 2500 AA at T/sub s/ of 350 degrees C. Media noise due to the non-uniform state of magnetization in the writing process can be reduced by using a smooth underlayer, suggesting that smooth film is preferable for high density recording. >

Recording characteristics of rigid disks with Co-based alloy films using durable silicon substrates

Co-based alloy films using silicon substrates were investigated for high-density magnetic recording disks. Silicon-disk substrates have several advantages, such as microscopically ultraflat surface roughness in the range of 1 nm or less, which results in a lower than ever flying height, lithographic fabrication of grooves for servo patterns, minimal outgassing from the substrates, higher substrate temperatures than for aluminum or glass substrates, and higher mechanical strength than for glass substrates. Recent Si substrates are mechanically durable because they have fewer microcracks than previous ones as a result of large improvements in machining processes such as chamfering and holing. In this study, Co85Cr13Ta2/Cr films were deposited by facing targets sputtering on 2.5 in. Si substrates at a substrate temperature of 100 °C and an argon gas pressure of 0.2 mTorr. A carbon protective layer and Z-DOL lubricant were applied on top of the magnetic layers. Their magnetic properties and recording characte...

Protective carbon films deposited by dc-bias facing targets sputtering with microscopic ultraflatness and strong sp3 coordination

Carbon thin films were deposited on hard disks as protective layers by facing targets sputtering (FTS), and their characteristics were evaluated to determine whether they would be suitable protective layers for thin-film magnetic recording media. The performance and lifetime of a hard disk drive (HDD) are intimately related to the head-disk interface. Increase in performance due to reduction of the flying height and magnetic spacing, and longer product lifetime are related to the properties of protective layers covering the surfaces of hard disks. Currently, such layers are generally sputtered amorphous carbon films, whose characteristics are strongly dependent on various sputtering conditions such as the argon gas pressure, substrate temperature, and dc and rf bias voltages. In this study, the dependence of the characteristics of carbon films on the dc bias voltage of the FTS was investigated, and the characteristics were also compared with those obtained without a dc bias voltage supply. The carbon film...

Deposition of high-durability protective layers with a composite structure of DLC and GLC by facing-targets sputtering

An amorphous carbon film is currently used for the protective layer for overcoating the surface of the recording layer of a hard disk. In this study, the film was deposited by faring-targets sputtering (FTS), which can discharge at a lower argon gas pressure than other sputtering, such as dc magnetron sputtering, because the plasma is sufficiently confined by a magnetic field applied perpendicular to both of the target planes. As a result, the layers can be deposited without plasma damage. Thus, very smooth and uniform thin films can be obtained. The dependence of the structure and properties of carbon layers on various sputtering conditions such as the argon gas pressure, dc and rf bias voltages, and substrate temperature at room temperature, compared with the previous report, was investigated when layers with a thickness of 500 /spl Aring/ were deposited by FTS on glass and Al/Ni-P substrates. The surface appearances of the layers were observed by FE-SEM, and their structures were characterized by Raman spectroscopy. All the carbon films in this study revealed both diamondlike carbon (DLC: D) and graphitelike carbon (GLC: G) structures. The ratio of the integral intensity of the D peak to that of the G peak, I(D)/I(G), was measured by Raman spectroscopy. As a result, it was found that the ratio I(D)/I(G) was significantly dependent on the sputtering conditions and was well correlated with the surface appearance. The films with very low surface roughness had I(D)/I(G) ratios in the range of 196-1.99. This seems to indicate that the fine DLC grains are isolated and distributed with almost equal spacing in the homogeneous GLC matrix, occupying twice the area of the GLC structure. The films appear to have a composite structure of strong DLC and GLC.

Preparation of amorphous carbon films as protective layer by FTS system

Abstract AIN, ITO carbon films as a protective layer have been prepared by plasma-confining magnetron sputtering and Facing Targets Sputtering (FTS) methods. The nitride films reactively sputtered by magnetron sputtering, even if ionization was accelerated, proved to be insufficient in crystal orientation dispersion and the oxide films reactively sputtered even by plasma-free sputtering needed strict control in the reactive process. However, the FTS method can stably deposit single-element films with satisfactory properties. Carbon film deposited at argon gas pressure as low as 0.2 mTorr without plasma damage revealed a high tetrahedral coordination ratio and showed a textureless and flat surface.

TbFeCoCr magneto-optical media with high corrosion resistance

Abstract An attempt was made to obtain excellent corrosion resistant magneto-optical films with good magneto-optical properties by adding Cr to TbFeCo films at levels of more than 5 at%. Addition of Cr causes preferential decrease in sublattice magnetization of transition metals in rare-earth-transition metal amorphous alloys. As a result, Tb 19 Fe 45 Co 29 Cr 7 film was found to have high corrosion resistance with good Kerr rotation of 0.3° and also a high readout carrier to noise ratio (CNR) of 51 dB.

Micromagnetic properties of CoCrPtTa/CrV thin films for high density recording media

The magnetization reversal, the magnetostatic interactions and the thermal stability of CoCrPtTa thin films for high density recording media are investigated. The reversal is found to be remarkably incoherent, particularly in the thicker films. The magnetic stability is better in the thinnest film (10 nm), and the switching volume results larger than the grain size. The behavior is influenced by the grain segregation state of the films.