Performance modification in solution-processed SnZnO thin film transistor
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1247-C11-19
Performance modification in solution-processed SnZnO thin film transistor Dong Lim Kim1, Doo Na Kim, You Seung Rim, Si Joon Kim, and Hyun Jae Kim1,a) 1 School of Electrical and Electronic Engineering, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul, 120-749, Republic of Korea ABSTRACT Tin zinc oxide (SnZnO) thin film transistors (TFTs) with different component fraction fabricated by solution process were reported. Sn chloride and Zn acetate were used as precursor and the maximum annealing temperature was 500 ℃. The electrical characteristics of TFTs were acutely affected by the molar ratio between Sn and Zn in the lattice, and showed the highest mobility and on-to-off ratio of about 17 cm2/Vs and 2×106, respectively. The origins of the high performance were traced through both structural and electrical aspects. Sn was generally considered to offer carrier path by superposition of s orbital, but it was found that the increase of Sn fraction only below specific value in lattice contributed to increase mobility, which could be explained by the structural distortion and the defect generation. Zn atoms introduced in the lattice were necessary to control both mobility and carrier concentration. From these results, the solution-processed SnZnO TFT with high performance was suggested. INTRODUCTION Since the concept of transparent amorphous oxide semiconductor (TAOS) had been proposed, plenty of researches on this field has been performed owing to its outstanding application upon large area electronics such as flat panel display and solar cell panel [1,2]. The major workhorse in TAOS application has long been indium gallium zinc oxide (InGaZnO) [3-5], which showed high performance with some variations in the metal components of material [6,7] and in the deposition methods [3,8]. The high performance of InGaZnO lattice was attributed by In which offers a carrier path because its spherical-shaped s orbital spanned largely enough to overlap with neighbors [9]. Despite its performance-improving role, usage of In became weak point due to its limited resource. Accordingly, researches on new materials as a suitable alternative of In have been attempted over the heavy transition metal species like tin. The oxidized form of tin, SnO2, itself could be a channel of thin film transistors (TFTs) with excellent mobility [10,11], however the conductivity should be modified as it is highly conductive suffering the oxygen deficient state. Using vacuum process the modification of the conductivity could be done by changing the ambient during deposition. Still it remained difficult in solution process due to its lack of ambient-controllability. The incorporation of another metal into SnO2 lattice in the manners of doping or alloying could be an effective way to control the performance of the lattice in solution process as well as vacuum process. And Zn incorporation into SnO2, forming SnxZnyO2x+y or simply SnZnO, have been studied most broadly in the purpose of realizing active layer for TFT with high mobility and efficient
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