be employed as transparent TFTs. [13][14][15] Recently, rapid advance in transparent electronic devices for transparent TV, mobile, wearable, and even VR devices require the development of transparent TFTs and their high-performance channel layers. Moreover, AOS-based TFTs could meet the requirement of the next-generation organic light emitting diode TV, such as ultra-high frame rate, larger size, and higher resolution, due to their high mobility. [16,17] Among various metal oxide semiconductor channel materials, multicomponent metal oxide semiconductors based on the In and Zn cations matrix are considered as promising candidates for channel materials for transparent TFTs, since they have inherent merits, such as high mobility, large area uniformity from their amorphous structure, and compatibility with various processing methods. [18][19][20][21][22][23] For the realization of highperformance and highly stable oxide semiconductor-based TFTs, the control of atomic ratio in the metal oxide semiconductor channel is a key factor. For this purpose, there have been a lot of research efforts on the compositional control or doping process of the oxide semiconductor channel layer. [24][25][26][27][28][29][30][31] Olziersky et al. have reported on the role of composition of InGaZnO channel on the performance of TFT devices. [31] They referred that the InGaZnO TFTs showed improved performance and worse stability characteristics, when the In/Ga ratio is higher according to the electrical resistivity of channel films. The In cations generally play a role as a mobility enhancer, due to the spheric s orbital of the indium oxide. The TFTs with indium oxide matrix showed high mobility of 10-30 cm 2 V −1 s −1 and large current at on-state, becasue the largely overlapped s orbital of In 2 O 3 enhanced the conductivity of the electrons. [32][33][34] However, the poor stability issue of TFTs with large indium contents-channel induced by the oxygen vacancies still remain a critical drawback. [35] Several elements with high bonding strength with oxygen, such as, gallium (Ga), zirconium (Zr), hafnium (Hf), and yttrium (Y), are adopted in the indium oxide channel material as an oxygen binder and a stabilizer of the channel layer. [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] Although several elements have been employed as stabilizer in oxide semiconductor channel-based TFTs, investigation of the stabilizing element in oxide semiconductor is still lacking. In particular, The Hf-doped indium zinc tin oxide (Hf:InZnSnO) channel for high performance and stable transparent thin film transistors (TFTs) is developed by using a simultaneous cosputtering of InZnSnO and HfO 2 targets. The effects of In and Hf composition in Hf:InZnSnO channel on the performance and stability under bias stress for the Hf:InZnSnO channel-based TFTs are investigated. Herein, the In cations enhance the electrical properties, while the Hf cations reduce the oxygen vacancies in the Hf:InZnSnO channel layer. Adjusting the atomic ratio of In of the...
We fabricated transparent and flexible silicon oxycarbide (SiOC) hard coating (HC) films on a colorless polyimide substrate to use as cover window films for flexible and foldable displays using a reactive roll-to-roll (R2R) sputtering system at room temperature. At a SiOC thickness of 100 nm, the R2R-sputtered SiOC film showed a high optical transmittance of 87.43% at a visible range of 400 to 800 nm. The R2R-sputtered SiOC films also demonstrated outstanding flexibility, which is a key requirement of foldable and flexible displays. There were no cracks or surface defects on the SiOC films, even after bending (static folding), folding (dynamic folding), twisting, and rolling tests. Furthermore, the R2R-sputtered SiOC film showed good scratch resistance in a pencil hardness test (550 g) and steel wool test under a load of 250 g. To test the impact protection ability, we compared the performance of thin-film heaters (TFHs) and oxide-semiconductor-based thin-film transistors (TFTs) with and without SiOC cover films. The similar performance of the TFHs and TFTs with the SiOC cover window films demonstrate that the R2R-sputtered SiOC films offer promising cover window films for the next generation of flexible or foldable displays.
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