Atomic Structure Evaluation of Solution-Processed a-IZO Films and Electrical Behavior of a-IZO TFTs

Abstract

Understanding the chemical reaction pathway of the metal–salt precursor is essential for modifying the properties of solution-processed metal-oxide thin films and further improving their electrical performance. In this study, we focused on the structural growth of solution-processed amorphous indium-zinc-oxide (a-IZO) films and the electrical behavior of a-IZO thin-film transistors (TFT). To this end, solution-processed a-IZO films were prepared with respect to the Zn molar ratio, and their structural characteristics were analyzed. For the structural characteristic analysis of the a-IZO film, the cross-section, morphology, crystallinity, and atomic composition characteristics were used as the measurement results. Furthermore, the chemical reaction pathway of the nitrate precursor-based IZO solution was evaluated for the growth process of the a-IZO film structure. These interpretations of the growth process and chemical reaction pathway of the a-IZO film were assumed to be due to the thermal decomposition of the IZO solution and the structural rearrangement after annealing. Finally, based on the structural/chemical results, the electrical performance of the fabricated a-IZO TFT depending on the Zn concentration was evaluated, and the electrical behavior was discussed in relation to the structural characteristics.

Investigation on Atomic Bonding Structure of Solution-Processed Indium-Zinc-Oxide Semiconductors According to Doped Indium Content and Its Effects on the Transistor Performance

“…Finally, the IZO film was fabricated via a condensation reaction by annealing up to 550 °C. A detailed description of the chemical reaction pathway can be found in our previous study [ 31 ]. A noteworthy point in the TGA thermal reaction result of the IZO solution with respect to the In concentration is that the weight of the reaction by-product increases, as shown in Figure 7 c. The TGA measurements started at almost the same weight as the IZO solution (30 ± 0.5 mg), but the weight of the by-products after the thermal reaction increased linearly with the In concentration.…”

“…Note that the 0.25 M of Zn molarity was determined by considering the thickness of the IZO film, and the TFT characteristics with respect to the Zn molar ratio were confirmed in our previous experiments. (refer to [ 31 ] for further details).…”

Analyzing Acceptor-like State Distribution of Solution-Processed Indium-Zinc-Oxide Semiconductor Depending on the In Concentration

“…In case of solution-processed IZO semiconductors, the amorphous random network structure is determined by Zn-O bonding, and depending on the In concentration In atoms replace Zn atoms. The enhanced electrical conductivity of IZO semiconductors has been empirically confirmed [26,27]. By replacing the ionic bonding of Zn 2+ with the ionic bonding of In 3+ , the In-O bonding structure can act as donor, and free electrons are generated through the reaction of the dangling bond D InO − → D InO 0 + e − .…”

“…The source/drain electrodes were fabricated through thermal deposition, and the finger-type structure had a W/L ratio of 2000 µm/80 µm. The detailed fabrication process for the electrical characteristics of solution-processed IZO TFTs can be found in previous studies [26,27].…”

“…The source/drain electrodes were fabricated through thermal deposition, and the finger-type structure had a W/L ratio of 2000 μm/80 μm. The detailed fabrication process for the electrical characteristics of solution-processed IZO TFTs can be found in previous studies [26,27]. The electrical characteristics of the TFTs with respect to temperature were efficiently controlled and measured using a vacuum chamber probe station (M56VC) (MS Tech., Kyoungki, Republic of Korea).…”