Abstract
The development of p-type metal oxide thin-film transistors (TFTs) is far behind the n-type counterparts. Here, p-type CuAlO2 thin films were deposited by spin coating and annealed in nitrogen atmosphere at different temperature. The effect of post-annealing temperature on the microstructure, chemical compositions, morphology, and optical properties of the thin films was investigated systematically. The phase conversion from a mixture of CuAl2O4 and CuO to nanocrystalline CuAlO2 was achieved when annealing temperature was higher than 900 °C, as well as the transmittance, optical energy band gap, grain size, and surface roughness of the films increase with the increase of annealing temperature. Next, bottom-gate p-type TFTs with CuAlO2 channel layer were fabricated on SiO2/Si substrate. It was found that the TFT performance was strongly dependent on the physical properties and the chemical composition of channel layer. The optimized nanocrystalline CuAlO2 TFT exhibits a threshold voltage of − 1.3 V, a mobility of ~ 0.1 cm2 V−1 s−1, and a current on/off ratio of ~ 103. This report on solution-processed p-type CuAlO2 TFTs represents a significant progress towards low-cost complementary metal oxide semiconductor logic circuits.
Highlights
Over the past decades, metal oxide thin-film transistors (TFTs) have been extensively investigated for the next-generation active-matrix liquid crystal displays, organic light-emitting diode displays, and other emerging electronic circuits applications due to their excellent electrical properties and outstanding optical transparency [1, 2]
We present a solution route to prepare CuAlO2 thin films
The enhancement of the crystallinity may be attributed to the fact that more energy absorption accelerated the growth of crystallites at higher annealing temperature
Summary
Metal oxide thin-film transistors (TFTs) have been extensively investigated for the next-generation active-matrix liquid crystal displays, organic light-emitting diode displays, and other emerging electronic circuits applications due to their excellent electrical properties and outstanding optical transparency [1, 2]. Bottom-gate TFTs using the obtained nanocrystalline CuAlO2 thin films as channel layers were fabricated and they exhibit a mobility of ~ 0.1 cm2V−1 s−1, a threshold voltage of − 1.3 V, and a current on/off ratio of ~ 10 [3]. For the film annealed at 700 °C, only weak CuO phase diffraction peaks at 35.8° and 38.9° were observed, indicating that 700 °C is not enough for the formation of CuAlO2 phase [11].
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