Microwave absorption caused by free carriers was investigated. A 9.35 GHz microwave interferometer was constructed. The transmissivity of 525-mm-thick silicon substrates decreased from 60.4 to 3.8% as the resistivity decreased from 1000 to 4 cm. This characteristic was explained well by a numerical analysis using the free carriers absorption theory. Microwave free carrier photo absorption caused by lightinduced carriers was also investigated for p-type silicon samples coated with 100 nm thermally grown SiO 2 layers as well as SiO x layers deposited by the vacuum evaporation method. The effective minority carrier lifetime and recombination velocity were analyzed in the case of the photo induced carrier generation with 532 nm light illumination. The effective minority carrier lifetime was increased from 360 to 540 ms and the recombination velocity was decreased from 78 to 30 cm/s by 1:3 Â 10 6 Pa H 2 O vapor heat treatment at 260 C for 3 h for light illumination at 0.315 mW/cm 2 in the case of the thermally grown SiO 2 /Si because of the passivation of SiO 2 /Si interfaces. They were markedly increased from 30 to 380 ms and from 1300 to 60 cm/s, respectively, by the H 2 O vapor heat treatment in the case of the vacuumevaporated SiO x /Si. #

The dynamics of vibrational energy relaxation by collisions in molecular beams and free jet expansions are examined. Within the stochastic approach afforded by the use of the master equation, the incomplete relaxation process may be modelled by assuming a time-dependent transition rate matrix. In particular, we prove that for non-degenerate levels and weak interactions the state distribution is Boltzmannian if the transition rate matrix is of the Landau-Teller type. The ramifications of this result on the analysis of recent studies of vibrational relaxation in seeded beams is briefly discussed.

Thin-film transistors (TFTs) with transparent amorphous indium-tin-zinc-oxide (a-ITZO) channel were fabricated. The field effect mobility (μ) of the a-ITZO TFT was more than 15.0 cm 2 V −1 s −1 , which is higher than the generally reported value of amorphous indium-gallium-zinc-oxide (a-IGZO) TFT. However, μ deteriorated with a decreasing channel length of the a-ITZO TFT due to the annealing process after patterning of the ITZO. We studied the effects of the annealing process on the contact resistance between the a-ITZO film and the source/drain electrodes. A transmission line method (TLM) chart indicated that the parasitic resistances between the source/drain electrode and the back-channel region of the a-ITZO was 2 × 10 4 .Amorphous silicon thin-film transistors (a-Si:H TFTs) are widely used for active-matrix liquid crystal displays. However, a performance limit remains because the mobility of a-Si:H TFTs is at most 0.5 cm 2 V −1 s −1 , which is not enough to drive the next generation of flat panel displays. Therefore transparent amorphous oxide semiconductors (TAOS), whose mobility (μ) is over 10 times higher than the a-Si:H TFT, are considered prime candidates for practical use.In fact, several TAOS materials like zinc oxide, 1,2 indium-galliumzinc-oxide (a-IGZO), 3,4 zinc-tin oxide 5,6 and zinc-indium-oxide 7,8 have been studied for use in TFTs. In particular, a-IGZO is the most promising material and has been widely researched. Among the TAOS, we have also reported on amorphous indium-tin-zinc-oxide (a-ITZO) 9 as satisfying the demand for a higher μ TFT. This material is not only useful for high resolution displays, but also for driver circuits, memory devices and charge coupled devices. Since such applications require a shorter channel length to enhance their electrical properties, the contact resistivity between the back-channel of the a-ITZO and source/drain electrodes would be significant. 10 As for TFT fabrication, an annealing process is essential to stabilize the oxygen vacancies of the a-ITZO channel. However, the effect of the timing of the annealing process during the TFT fabrication on the contact resistivity is not yet clear. Due to the above reason, we fabricated two kinds of a-ITZO TFTs, with and without the annealing process, after patterning the ITZO channel, and compared their performance by measuring the contact resistance between the ITZO channel and source/drain electrodes. Experimental ProcedureTFT fabrication.-The 50-nm-thick a-ITZO films were deposited on a non-alkaline glass substrate by the RF magnetron sputtering of an ITZO ceramic target. Each concentration of In, Sn, Zn is under 50%. The deposition was performed at 150 • C in a mixed gas of Ar and O 2 at a deposition pressure of 1 Pa. The RF sputtering power was maintained at 100 W. The bottom-gate and etch-stopper type a-ITZO TFT was fabricated as follows. A 50-nm-thick Cr gate electrode was formed on a glass substrate. A 150-nm-thick SiOx film was deposited by plasma-enhanced chemical vapor deposition (PECVD) as a gate insulato...

Hysteresis of InGaZnO thin-film transistor (IGZO TFT) under negative-bias with illumination stress (NBIS) was investigated using double sweeping gate voltage (VGS) mode. We found that hysteresis of IGZO TFT was significantly enlarged by the NBIS with large negative gate voltage stress. On-current and S value in forward measurements started to show degradation under large-negative VGS stress due to acceptor-like defect creation; on the other hand, transfer curves in reverse measurements shifted to a positive VGS direction without S degradation. As a result of NBIS degradation, huge hysteresis can be observed. To explain the change in hysteresis under NBIS, degradation model consisting of acceptor-like bistable defects is proposed.

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