Formation and morphological change of voids induced by electromigration in polycrystalline Cu interconnects on TiN have been investigated at various current density conditions at elevated temperatures. At first voids were formed at grain boundaries, then they grew further to elongate in the electric field direction. Void elongation parameter (a ratio of void diameters in longitudinal to lateral directions to the electric field) was 2.53 when the current density was 9×106A/cm2, while it was 1.31 when the current density was 3×106A/cm2at 400°C, 50h. Occurrence of void elongation is enhanced with increase in current density, and its relationship to grain boundaries are discussed by FIB-SIM image analysis.

A microstructure of the massively transformed γ-TiAl (γm) phase in a Ti-48at.%Al alloy, which was heat treated in the high-temperature α-Ti (disordered hep) single phase field (1683K), followed by ice water quenching, has been examined using high-resolution electron microscopy. The characteristic features of the microstructure originated from the α→γ massive transformation have been clarified in detail, which are as follows. (1) Extremely thin hep plates (about 0.8–2nm in thickness), which are considered to be a retained α phase, are found to exist in the γ m phase. (2) Twin boundaries are found to be not flat interfaces, that is, twin interfaces are not on the exact (111) mirror plane. This situation is attributed to the existence of a number of partial dislocations at the twin boundaries. (3) Antiphase relationship between the regions either side of the thin rotated domain wall [1] is confirmed. The validity of this situation is explained by assuming that the thin rotated domain wall has been grown from a simple antiphase domain boundary. On the basis of these facts, mechanism of the α→γ massive transformation has been discussed.

Evaluation of the shape memory characteristics under thermal and stress cycles is indispensable to ensure the reliability of shape memory alloys used in nuclear power reactors. Then the effect of γ↔E cyclic transformation on the shape memory characteristics was investigated in Fe-14Mn-6Si-9Cr-5Ni (wt%) alloy. ε martensites were stress-induced by pulling specimens at room temperature, and they were reverse transformed by heating under various stresses. The change of surface relief during reverse transformation was observed by a hightemperature optical microscope equipped with a tensile machine. The recovery stress was measured by this apparatus after the “yclic transformation” was repeated various times. The reverse-transformed microstructures were observed by transmission electron microscopy. As a result, the amount of residual ε martensite increased with increasing stress applied during reverse transformation. As the “cyclic transformation” was repeated, the recovery stress remarkably increased at first, and then gradually decreased. This rapid increase of recovery stress is attributed to not only the increase of elongation when specimen is deformed but also the increase of stacking faults which act as nucleation sites of martensite. The decrease of recovery stress is attributed to the decrease of elongation.

The developments of the laser diagnostics at Kyushu University for studies of high temperature plasmas and plasma-surface interactions are reviewed, followed by the recent results and future plans.

This paper reports heterojunction photodiode properties and its application to a compact scanner. The photodiode has ITO / p-a-SiC:H / a-Si:H / metal structure. This diode has high photo to dark current ratio and small photocurrent saturation voltage, because of the excellent blocking characteristics for a heterojunction with large built in potential. Moreover, a-Si:H / metal contact has been investigated. A contact linear image sensor has been fabricated using the heterojunction photodiode array and compact optical system. Performance tests showed excellent results. Good reproduced images have been obtained.