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We study triplet migration properties in NPB (N,N -diphenyl-N,N -bis(1-naphthyl)-1,1 -biphenyl-4,4 -diamine) films using time resolved gated spectroscopy and dispersive migration theory as our main tools of analysis. We show that in NPB, a well-known hole transporter in organic light emitting diodes, at high excitation densities triplet migration follows two regimes-a dispersive non-equilibrium regime (distinguished by exciton energetical relaxation within the distribution of hopping sites and as a consequence the hopping frequency being time dependent) that evolves into a second, non-dispersive equilibrium regime. Further, we observe a third region, which we term acceleration. From the turning over time between dispersive and non-dispersive dynamics, we deduce the width of the triplet density of states (DOS). We observe how the DOS variance changes when one decreases the thickness of the NPB film and note how surface effects are becoming important. Furthermore, the DOS variance of NPB changes when another organic layer is evaporated on top, namely Ir(piq)3 (tris(1-phenylisoquinoline)iridium(III)). We believe that these changes are due to the different polarizable media in contact with the NPB film, either vacuum or Ir(piq)3. We also show in this paper that the triplet level when time approaches zero is much higher in energy than the relaxed triplet levels, as quoted in most published papers; these values are thus incorrect for NPB. Lastly, it is possible that even at room temperature, the dispersive regime might be important for triplet migration at high initial triplet concentrations and might affect the diffusion length of triplets to a certain extent. However, more experimentation needs to be performed in order to address this question. Overall, we have characterized the triplet migration dynamics of NPB fully and shown that it agrees with previously published observations for other organic semiconductors and theoretical considerations.

To develop a thermally stable barrier metal for interconnections in LSI, films deposited by sputtering a Ti-rich TIN,., target were investigated (in what follows, the film deposited in this manner will be referred to as TiN,,J. Both film quality and the electrical property of the Al-alloy/Si contact with thin barrier metal were evaluated. It was found that the TiN layer formed by this method was twice as thick as the TiN layer formed by the conventional method, the TiN/TiSi, layer formed was smooth and the silicide layer was five times thinner than when the conventional method was used. The TiN layer formed by nitridation of TiNo.* (50 nm)/Si had a grain structure with a grain size of approximately 10 MI and was strongly oriented to TiN (200). In the silicide layer, the grain size was approximately 50 MI and a semistable phase was formed. It was also found that contact resistance to N'Si was similar to that formed by using the conventional Ti nitridation method while the contact resistance to P' Si was slightly lower than when the conventional method was used. In addition, it was found that the contact resistance became lowest when the rapid thermal nitridation (RTN) temperature was approximately 700°C and the formed film was stable when it was thermally treated. When a Ti layer was used, the N' IP junction showed a leakage problem after it was annealed at temperatures higher than 450°C. However, when TiNo.4 was used, no leakage problem was observed even when the junction was annealed at 525 "C. These superior junction characteristics were due to the thermally stable and thick TiN layer.