Susumu Sobue

Solid-Phase Reactions in Al Alloy/TiN/Ti/Si Systems Observed by In Situ Cross-Sectional TEM

The mechanism of solid-phase reactions for multilayers of Al-1%Si-0.5%Cu/TiN/Ti/n+-Si substrates has been investigated by means of in situ and high-resolution/analytical cross-sectional transmission electron microscopy (X-TEM). We have succeeded for the first time in real-time observation of the instant of barrier breakdown of the TiN layer. An intermediate Al-Ti-Si(-N) layer ( ~4 nm thickness) composed mainly of microcrystallites was formed at the Al alloy/TiN interface at ~450° C, and the microcrystalline phase grew along the TiN grain boundaries. At over ~500° C, the Al diffused downward very rapidly through the TiN layer, forming an Al region under the TiN layer. It is concluded that the rapid redistribution of the Al may be caused by movement along the TiN grain boundaries in the microcrystalline state.

Electrochemical deposition of iron sulfide thin films and heterojunction diodes with zinc oxide

Iron sulfide thin films were fabricated by the electrochemical deposition method from an aqueous solution containing FeSO4 and Na2S2O3. The composition ratio obtained was Fe:S:O = 36:56:8. In the photoelectrochemical measurement, a weak negative photo-current was observed for the iron sulfide films, which indicates that its conduction type is p-type. No peaks were observed in X-ray diffraction pattern, and thus the deposited films were considered to be amorphous. For a heterojunction with ZnO, rectification properties were confirmed in the current-voltage characteristics. Moreover, the current was clearly enhanced under AM1.5 illumination.

Preparation of highly luminescent hybrid gel incorporating NAC-capped CdTe quantum dots through sol–gel processing

Highly photoluminescent gel was prepared by embedding water soluble quantum dots (QDs) in an inorganic–organic hybrid gel matrix using a conventional sol–gel process. Aminopropyltrimethoxysilane and citric acid (CA) were found to be the best combination for the gel preparation. 13C-NMR and FT-IR studies indicated hydrogen bond formation between the amine group of APS and the carboxyl group of CA. IR-light radiation curing was comparable to thermal curing and reduced the gelation time to a considerable extent (71 %). The resulting composite formed a hybrid gel phosphor with excellent transparency by embedding CdTe QDs into the matrix and emitted light of various colors with high photoluminescence efficiency (40 %). The gel phosphor retained the PL properties after storage in air for one year. In addition, the strength of the hybrid phosphor was demonstrated by a coin-flipping test.

Dependence of diffusion barrier properties in microstructure of reactively sputtered TiN films in Al alloy/TiN/Ti/Si system

Abstract We have been investigated the diffusion barrier properties of the reactively sputtered titanium nitride (TiN) in Al1wt%Si0.5wt%Cu/TiN/Ti/Si system. The lower dense but N-rich TiN film was easy to react with the Al, showing the poor diffusion barrier properties. By means of plan-view TEM, lots of disorder regions and vacancies in the TiN film could be observed. We conclude that the rearrangement in the lower dense films is easier to occur by thermal treatment, giving rise to diffusion of Ti atoms, even if the TiN is N-rich film. This conclusion indeed implies the dense degree of the TiN film in atomic level has a significant effect on the reaction between the TiN and the Al, or the diffusion barrier properties.