ABSTRACT:p-Phenylselenomethylstyrene (1) as a new selenium-containing vinyl monomer was prepared. It was readily polymerized free radically in the presence of 2,2'-azobis(isobutyronitrile) (AIBN) as initiator at 60°C to afford corresponding homopolymers having number-average molecular weights of about 8600. From the copolymerization of 1 with styrene, Q and e of 1 were 1.40 and -1.06, respectively. Photoirradiation of the copolymer of styrene and 1 in the presence of methyl methacrylate effectively afforded a graft copolymer composed of a polystyrene backbone and poly(methyl methacrylate) branches.

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Since the report by Nomura et al. [1] thin film transistors (TFTs) based on amorphous oxide semiconductors (AOSs) have emerged as a promising technology, particularly for active-matrix TFT-based backplanes, due to their superior electrical performance when compared with conventional amorphous silicon and polycrystalline silicon TFTs. Among the various AOSs, amorphous indiumgallium-zinc-oxide (a-IGZO) TFTs have high field-effect mobilities exceeding that of a-Si by a factor of 10 2 , a small subthreshold swing, good uniformity attributed to the amorphous structure, a low off current, good stability under electrical stress, and can be processed at low temperatures. Several research groups have already presented a-IGZO based working devices with remarkable electrical and optical properties. We have recently demonstrated high performance a-IGZO TFTs which exhibited a field effect mobility µ FE of 19.4 cm 2 /Vs, a subthreshold swing S of 0.5 V/decade, and a ratio of on and off current I ON /I OFF of 10 8 , respectively [2].Despite recent successes, some outstanding issues related to the a-IGZO TFT electrical performance still remain to be resolved, such as obtaining good electrical contact between source/drain (S/D) electrodes. A previous report [3] on contact resistance of candidate metal electrodes and a-IGZO showed the trend that the contact resistance decreases with the work function of the metallic electrode. High work function electrodes showed Schottky contacts, while reactive electrodes did ohmic contact. However, using reactive metals for an electrical contact require a high reproducibility of the process.We focus here on an investigation of Cu electrodes to obtain good ohmic characteristics in a-IGZO based TFTs. Specifically, we discuss the S/D series resistances and their effects on the TFT performance. The TFT S/D series resistance, the intrinsic field effect mobility µ FE-i , transfer length L T , and effective contact resistance R C-eff were extracted by the well-known transmission line method (TLM) using a series of TFTs with different channel lengths.The bottom gate type a-IGZO TFTs with staggered structure were prepared on heavily doped n-type silicon substrates having a LPCVD SiN x layer of 100 nm. Thin films of a-IGZO (80 nm thick) were deposited using DC magnetron sputtering with sintered InGaZnO 4 (99.999% purity) as the target material. Sputtering was performed at room temperature in an argon atmosphere with an oxygen partial pressure of 4%. A 4 inch diameter ceramic target, This paper focuses on the viability of low-resistivity electrode material (Cu) for source/drain electrodes in thin film transistors (TFTs). The effective resistances between Cu source/drain electrodes and amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors were examined. Intrinsic TFT parameters were extracted by the transmission line method (TLM) using a series of TFTs with different channel lengths measured at a low source/drain voltage. The TFTs fabricated with Cu source/drain electrodes showed good transfe...

ABSTRACT:The photopolymerization of styrene with benzyl phenyl selenide proceeded smoothly to give polystyrene having benzyl and phenylsclcno groups at a-and w-chain ends, respectively, and the degree of functionality was 0.95. In a limited range of conversion, both the polymer yields and number average of molecular weights (M.) increased with the reaction time and the M. linearly increased with yield. The addition of styrene to the polystyrene with irradiation increased the molecular weight of the polymer. In the photopolymerization of methyl methacrylate, similar polymerization behavior was observed. The tacticity of the poly(methyl methacrylatc) was in good agreement with that prepared by radical mechanism. Photoirradiation of polystyrene having phenylseleno group at the w-end in the presence of methyl methacrylate effectively afforded a block copolymer of styrene and methyl methacrylate.KEY WORDS Radical Polymerization / Benzyl Phenyl Selenide / p-Methoxybenzyl p-Trimethylsilylphenyl Selenide / Photoiniferter / Polymeric Photoiniferter / Block Copolymer / End functional polymers are useful precursors for novel block, graft and star polymers. The synthesis of end functional polymers are conventionally prepared by anionic, cationic, and radical polymerization. 1 -11 Preparation by radical polymerization with iniferter method is quite convenient and hence widely used. 12 -16 Otsu and coworkers 1 7 -19 proposed iniferter for the design of the polymer chain end structure. An iniferter is an initiator which also functions as chain transfer agent and/or primary radical terminator. It is attractive for preparing simple block copolymers and more complex polymer architectures using various monomers which do not polymerize by an ionic mechanism. 20 -23 Iniferters mainly use organic sulfur compounds such as tetraalkylthiuram disulfides, dithiocarbamates, and tetramethylene disulfide.We recently reported that photopolymerization of styrene in the presence of di phenyl diselenide, 24 similar to the case of tetraalkylthiuram disulfides 25 to afford polystyrene carrying phenylseleno groups at both chain ends (P-A) (eq I). By the irradiation of light to the polymers with selenide moieties (P-A) in styrene, polystyrene with higher molecular weight (P-B) was obtainOse-Se-Q + n P-A + m CH2=3

p-Methylselenostyrene (1) and p-phenylselenostyrene (2) as selenium-containing vinyl monomers were prepared. Both monomers are readily polymerized free radically to afford the corresponding polymers having molecular weight of about 20000 -150000.These homopolymers are stable below 300 "C. From the copolymerization with styrene, Q values of 1 and 2 were calculated to be 1,18 and 1,03, respectively. On the other hand, e values of these monomers are 4 , 2 4 and -0,04, respectively, indicating the electron withdrawing character of the seleno groups.