Hitoshi Komoriya

Patterned media fabricated by lithography and argon-ion milling

Using continuous film prepared by lower gas sputtering, a dot array with a more stable single domain was achieved. The requirements for magnetic properties of patterned media were different from that of perpendicular continuous-film media. The switching field distribution in dot arrays depends on fluctuation in dot size. The smallest size of dot arrays, fabricated by most simple method as lithography and ion-milling, is 50 nm.

Magnetic duplication for precise servo writing on magnetic disks

A servo pattern of a 20 Gbit/in/sup 2/ level was directly duplicated on hard disks by using a magnetic duplication method, and the accuracy of the signal and the following performance on the duplicated servo pattern were evaluated. The phase servo pattern was composed of straight lines and was lithographically formed on a mastering disk. The period accuracy of the readback signal was very high. The repeatable position error for adjacent tracks in a prototype drive was measured, and the difference between two adjacent RPE trajectories was sufficiently small. The magnetic duplication method showed the possibility of precise servo-track writing for high-density hard disk drives.

Nanopattern transfer from high-density self-assembled nanosphere arrays on prepatterned substrates

We have fabricated nanoimprint moulds with high-density well-defined nanopatterns by pattern transfer from self-assembled nanosphere arrays on prepatterned substrates. Silica nanospheres of 100 and 25 nm diameter were regularly arranged over large areas in a self-assembling manner by capillary force via a dip-coating technique on topographically patterned substrates having 220 nm pitch line/space patterns. The nanosphere arrays were used as etching masks, and nanodot arrays with the same arrangements were created on the silica substrate surfaces by reactive ion etching (RIE). By developing a combined pattern transfer process using Ru and SiO(x) mask layers and CF4 and O2 RIE, the aspect ratio between the height and diameter of the nanodots made from the 25 nm nanospheres is improved to about two. It is demonstrated that the nanopatterns of the moulds can be inversely transferred into polymer surfaces reproducibly by UV nanoimprint process.

Over 100 Gbits/in/sup 2/ longitudinal magnetic recording

Summary form only given. A recording density of 106 Gbits/in/sup 2/ has been achieved using a high-sensitivity spin-valve head and a thermally stable synthetic ferrimagnetic medium (SFM). The use of a highly stable medium allowed the demonstration to be made with a bit aspect ratio of 5.3 which is higher than the projected value. Some selected parameters are given for the demonstration.

Automated optical passive alignment technique for PLC modules

We have developed an automated optical passive alignment technique for planar lightwave circuit (PLC) modules. Our technique is based on aligning a laser diode (LD) on a PLC module, and can be used to create an optical network unit. The PLC module we propose consists of a LD and a photodiode, which are mounted on the surface of the PLC platform without a lens. Because these elements send light directly to the waveguide on the PLC platform and receive light from the waveguide, a precise alignment technique is required. We therefore developed the mirror image alignment method in order to automatically align the LD on the PLC with extreme accuracy. The method is effective regardless of the position of the LD and the thickness of the solder. The mirror image method uses the markers on the PLC and their images, which are reflected on the front wall of the LD. The achieved accuracy for positioning was within 1 micron in the lateral direction and within 0.5 degrees in the rotational direction. These systems are now being used at a Fujitsu factory.