Oxide thin-film transistors (TFTs) were fabricated using a polycrystalline In-Ga-O (IGO) thin film as the n-channel active layer by direct current magnetron sputtering. The 50-nm-thick IGO TFT showed a field-effect mobility of 39.1 cm 2 V À1 s À1 , a threshold voltage of 1.4 V, and a subthreshold gate voltage swing of 0.12 V/decade. The polycrystalline IGO thin film showed the cubic bixbyite structure of In 2 O 3 without an obvious preferred orientation. The average grain size of polycrystalline IGO was approximately 10 m. The high mobility of IGO TFT is related to the In 2 O 3 crystalline phase and large grain size of the IGO film. #

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The authors developed an ambipolar field-effect transistor (FET) based on an organic-inorganic hybrid structure that consisted of an indium zinc oxide and pentacene double layer fabricated on a SiO2∕n++-Si substrate. Although the FETs based on an indium zinc oxide or pentacene single layer only showed unipolar FET characteristics, the hybrid FET showed definite ambipolar FET characteristics. The authors obtained a highly saturated field-effect hole and electron mobilities of 0.14 and 13.8cm2∕Vs. Furthermore, the authors demonstrated electroluminescence from hybrid FETs using tetracene as an emitting layer. The authors’ success shows that the hybridization of organic and inorganic materials opens up a new field in electronics.

Amorphous indium–gallium–zinc oxide (a-IGZO) films were deposited by DC magnetron sputtering and post-annealed in air at 300–1000 °C for 1 h to investigate the crystallization behavior in detail. X-ray diffraction, electron beam diffraction, and high-resolution electron microscopy revealed that the IGZO films showed an amorphous structure after post-annealing at 300 °C. At 600 °C, the films started to crystallize from the surface with c-axis preferred orientation. At 700–1000 °C, the films totally crystallized into polycrystalline structures, wherein the grains showed c-axis preferred orientation close to the surface and random orientation inside the films. The current–gate voltage (I d–V g) characteristics of the IGZO thin-film transistor (TFT) showed that the threshold voltage (V th) and subthreshold swing decreased markedly after the post-annealing at 300 °C. The TFT using the totally crystallized films also showed the decrease in V th, whereas the field-effect mobility decreased considerably.