This paper presents, for the first time, the design concepts of an isolation type 12OOV reverse blocking IGBT(RB-IGBT) for matrix converter. The device features thin wafer technology and deep boron diffusion technique. From experimental results, it has been found that the 12OOV RBIGBT attains about 20% reduction in total generated loss when it compared to the Combination of the IGBT and the diode while keeping improved blocking capability with both polarities. The high efficiency matrix converter can be achieved by using the RB-IGBTs and has a great possibility to replace the conventional DC-linked-type circuits.

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SmCo 5 has the highest uniaxial magnetocrystalline anisotropy (Ku) of all the materials yet known. The recording performance of longitudinal Sm-Co thin films have been demonstrated [1]. It is only until recently that the films have been successfully prepared with c-axis perpendicular to the film plane orientation [2][3][4], make it possible for application in perpendicular magnetic recording medium. However, almost all the papers in the literature Cu layer with the thickness of about 200 nm has been used to achieve perpendicular magnetic anisotropy. Such thick underlayer is not suitable for perpendicular magnetic recording considering the writing head performance, when the medium with soft magnetic under layer (SUL). Furthermore, the Sm-Co film thickness in the previous study is about 40 nm. The films thickness has to be reduced from the practical recording application point of view. In this paper, the magnetic properties of thin SmCo 5 film has been studied. A thin sandwich structure, Ru/Cu/Ru, is proposed as a new structure of the underlayer for SmCo 5 films with perpendicular magnetic anisotropy. The first Ru layer is deposited to improve the Cu(111) orientation, and the second Ru layer is to restrict the interlayer diffusion between Cu and SmCo 5 . The Sm-Co films as thin as 10 nm with excellent perpendicular anisotropy have been obtained with the total sandwich underlayer as thin as 15 nm. The Sm-Co (x nm)/Ru (5nm)/Cu (y nm)/Ru (5nm) films were prepared by sputtering. The thickness of Sm-Co film was ranging from 10 to 40 nm, while thickness of Cu underlayer was ranging from 5 to 20 nm. Both Ru and Cu were prepared without substrate heating. The Sm-Co layer was prepared at the substrate temperature of 350 o C. The Sm concentration in each film was about 17 at.%, which is almost the same as the stoichiometric composition of SmCo 5 . The films are characterized by a vibrating sample magnetometer (VSM) with maximum applied field of 24 kOe and an X-ray diffractometer (XRD). Results and discussion Fig. 1 (a) shows XRD patterns of 20 nm thick Sm-Co layer deposited onto sandwich underlayer of Ru (5nm)/Cu (y nm)/Ru (5nm). Fig. 1 (b) shows XRD patterns of x nm Sm-Co film deposited onto underlayer of Ru (5nm)/Cu (5nm)/Ru (5nm). It is of interest to note that peaks diffracted from Ru could not be observed in the XRD patterns. It may be due to the relatively thin Ru layer thickness and very small grain size. The Cu (111) peak is observed in all the XRD diagrams. The dispersion angle of those Cu (111) plane are all below 6 degree. This indicates all those Cu layer have good (111) orientation. As shown in Fig.1 (a), the intensity of SmCo 5 (002) increases with the increase of the intensity of Cu (111). This indicates the (002) plane for SmCo 5 has the epitaxial relation with Cu (111). Both SmCo5 (001) and SmCo 5 (002) peaks can be observed in all the XRD patterns. The above results indicate all the films have c-axis orientation perpendicular to the film plane. Hysteresis loops of the films have been measured by VSM. The in...