Amorphous InGaZnO Thin Film Transistor Fabricated with Printed Silver Salt Ink Source/Drain Electrodes
Recently, amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs) with inkjet printing silver source/drain electrodes have attracted great attention, especially for large area and flexible electronics applications. The silver ink could be divided into two types: one is based on silver nanoparticles, and the other is silver salt ink. Organic materials are essential in the formulation of nanoparticle ink as a strong disperse stabilizer to prevent agglomeration of silver particles,
... f silver particles, but will introduce contact problems between the silver electrodes and the a-IGZO active layer after annealing, which is difficult to eliminate and leads to poor device properties. Our experiment is aimed to reduce this effect by using a silver salt ink without stabilizer component. With optimized inkjet printing conditions, the high performance of a-IGZO TFT was obtained with a mobility of 4.28 cm 2 /V·s and an on/off current ratio over 10 6 . The results have demonstrated a significant improvement for a-IGZO TFTs with directly printed silver electrodes. This work presents a promising platform for future printed electronic applications. Amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs) with inkjet printed silver source/drain (S/D) electrodes have been proposed in many reports     . The experimental conclusions show a contact problem between the silver S/D electrodes and the a-IGZO active layer when using silver nanoparticles ink. The organic carbon residues are difficult to remove after the annealing process, which results in poor device performance that cannot meet the requirements of driving large-sized flat panel displays  . Therefore, the development of electronics fabricated with silver salt ink are of great potential in display application. In this work, a-IGZO TFTs with printed S/D electrodes are fabricated using a silver salt ink and silver nanoparticle ink respectively. It was found that the organic carbon could be effectively reduced at the interface by using silver salt ink, which indicates the solving of the contact problem to some extent by this manner, accordingly well-performing a-IGZO TFTs were obtained successfully and reasonably. Experimental The schematic structure of the bottom-gate, top-contact a-IGZO TFT with inkjet print Ag S/D electrodes is shown in Figure 1a . To prepare the device, a 300-nm-thick layer of Al:Nd alloy (3 wt % of Nd) was firstly sputtered on glass as gate electrode at room temperature. Then, the film was anodized in the electrolyte consisting of ammonium tartrate solution and ethylene glycol, accordingly forming a 200-nm-thick Al 2 O 3 :Nd gate dielectric layer on the surface of Al gate. Next, a 25-nm-thick a-IGZO active layer was deposited on Al 2 O 3 by radio frequency (RF) magnetron sputtering in an Ar/O 2 gas mixture with a power of 80 W, and subsequently the sample was annealed at 400 • C for 1 h on a hotplate. Finally, the Ag S/D electrodes were directly printed onto the a-IGZO active layer.