## 4 Conclusions  
The a-IGZO TFTs with printed Ag S/D electrodes from different types of silver sinks were studied in this work under optimized conditions. The performance of devices fabricated with silver salt ink was demonstrated much better characteristics than those fabricated with silver nanoparticle ink. Almost no carbon remained at the interface using the silver salt ink, which benefits from the easily removed solvent without adding any organic disperse stabilizer, thus a good contact between Ag electrodes and a-IGZO was formed. As a result, a reasonably well performing a-IGZO TFT was obtained with a mobility of 4.28 cm\({}^{2}\)/V\(\cdot\)s and a current on/off ratio over 10\({}^{6}\). This work provides a promising route for future printed electronic applications.  
**Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2076-3417/7/8/844/s1](http://www.mdpi.com/2076-3417/7/8/844/s1)]([http://www.mdpi.com/2076-3417/7/8/844/s1](http://www.mdpi.com/2076-3417/7/8/844/s1)). Figure S1. Images of the inkjet printing silver ink on (**a**) the glass and (**b**) the Al2O3; Figure S2. The thickness of the Ag electrodes by using two types of silver ink; Figure S3. Transfer characteristics curves (ID-VG) for devices by using (**a**) silver salt ink and (**b**) silver nanoparticle ink; Figure S4. Transfer characteristics curves (ID-VG) for devices by using silver nanoparticle ink under (**a**) thermal annealing and (**b**) UV-eriving; Figure S5. Schematic diagram of circuit for thin film transistor; Figure S6. The depth profile of the devices by using (**a**) silver nanoparticle ink; (**b**) EDS mapping; and (**c**) line scanning of the Ag/a-IGZO interface; Figure S7. The contact resistance of  
Figure 5: Comparision of Ag/a-IGZO interfaces for silver salt and nanoparticles inks. (**a**) TEM image of the silver/a-IGZO structure for silver salt ink; (**b,c**) Respectively show the amplified area and the EELS measurement of Ag, C, and O along marked scan line; (**d–f**) TEM images and the EELS measurement for the nanoparticles ink.  
devices with (**a**) silver salt ink and (**b**) silver nanoparticle ink; Figure S8. The variations of time-dependent transfer property under (**a**) positive gate-bias-stress (VG = 10 V) and (**b**) negative gate-bias stress (VG = \(-\)10 V); Figure S9. The mobility and the density of the a-IGZO by the Hall measurements; Figure S10. Inkjet printing silver nanoparticle ink film on (**a**) glass and (**b**) a-IGZO/AI2O3 with substrate temperature of RT, 40 \({}^{\circ}\)C and 60 \({}^{\circ}\)C, respectively; Inkjet printing silver salt ink film on (**c**) glass and (**d**) a-IGZO/AI2O3 with substrate temperature of RT, 40 \({}^{\circ}\)C and 60 \({}^{\circ}\)C, respectively; Figure S11. The output characteristic curves (ID-VD) and transfer characteristic curves (ID-VG) of the devices express through different greyscale.  
This work was supported by National Key R & D Program of China (No. 2016 YFB0401504), National Key Basic Research, NSFC (No. U1601651) and Development Program of China (973 program, Grant No. 2015 CB655004) founded by MOST, Guangdong Natural Science Foundation (2016A030313459), Science and Technology Project of Guangdong Province (2014B00915004, 2015A010101323, and 2016B090907001), the Fundamental Research Funds for the Central Universities (2015 ZP024 and 2015 ZZ063). The authors are grateful to SAE Magnetics (Dongguan, Guangdong) LTD for assistance in FIB-TEM characterization.  
[PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] designed the research; [PERSON] and [PERSON] performed the experiments; [PERSON], [PERSON] and [PERSON] analyzed the data; [PERSON], [PERSON], [PERSON] and [PERSON] provided valuable discussions and suggestions; [PERSON], [PERSON] and [PERSON] wrote the paper.  
The authors declare no conflict of interest.