Study On Functional Oxide Ink For Printed Electronics And Its Application

In the field of microelectronics manufacturing,modern printing technologies such as drop-on-demand printing which is based on digital control technology have advantages such as non-contact,directly graphing,custom graphing,etc.,which show great potential in large-area and low-cost electronics manufacturing,so it is widely concerned by academia and industry.Oxide materials are widely used in all kinds of electronic devices because of their good electrical and optical properties,so the development of oxide inks for drop-on-demand printing is of great significance to the future printed electronics.In this paper,the design and application of functional oxide ink are systematically studied,which are based on the main problems of printed electronics.An ink for high quality oxide film printing was designed,and the mechanism of the component interaction was studied.At the same time,the deficiencies of the film-forming properties of the ink were studied and improved,and the practicability of the ink was successfully verified through the device preparation and characterization.In general,the application of this ink can effectively improve the deposition uniformity,low the sintering temperature and avoid the crack of printed oxide film,so as to reduce additional equipment investment.The main results are as follows:(1)Aiming at the problem that ink deposition morphology is greatly affected by evaporation environment,an ink containing high boiling point solvent(glycol)and polymer gelling-assistant(polyacrylamide,PAM)was designed and prepared,which has the characteristic of thermal-induced-gelling.It can limit the spatial distribution of solute before most of the solvent evaporates,thus breaking the strong correlation between the evaporation of solvent and the deposition morphology and making the printing morphology more stable and controllable.The zirconia thin films and their arrays were successfully printed by using this ink.The films were highly uniform,and their homogeneity index H was only 1.7%.Compared with the zirconia thin films which was unoptimized,the improvement rate can reach 97%.(2)In the aspect of low-temperature sintering,considering the contradiction between reducing the external heat input and limiting the internal heat release intensity,it is proposed that the external heat input for the polymerization of oxide precursor can be reduced by the mild local exothermic effect inside the ink,so as to reduce the sintering temperature of printed films.In the study,the precursor enrichment effect and in-situ thermal gain effect of gel network in the process of thermal-induced gelation were applied,and zirconia thin film with good electrical properties was printed with a sintering temperature of 250°C.The dielectric constant of the film reached 10,and the leakage current density was 5.4×10^-6 A/cm² at 1 MV/cm.(3)Considering the problem of film cracking,which is originated from the failed resistance of gel structure to stress damage,it is proposed to adopt binary-solvent system to modulate the self-assembly behavior of ink components so that a network structure with higher cross-linking degree can be formed during the gelation process,which can reduce the nucleation ability of the crack,thus obtaining printed zirconia film with high quality.The results show that when the volume ratio of water in the solvent reaches 12.5%,the zirconia film has good cracking resistance as well as good uniformity.(4)Based on the above research results,printed zirconia thin film was applied to gate insulator layer of thin film transistor(TFT)devices,and the TFT devices obtained good electrical properties.The mobility of In-Ga-Zn oxide TFT(IGZO-TFT)based on printed zirconia film is 10.8 cm²/V·s,and the on/off ratio is 10⁷,which proves the practicability of printed zirconia dielectric layer.(5)Printed indium oxide thin film was applied to the active layer of TFT devices,and the TFT devices obtained good electrical properties.The mobility of TFT based on printed indium oxide film is 5.0 cm²/V·s,and the on/off ratio is 10⁶.At the same time,the result shows that the PAM additive has a positive modulation on the threshold voltage of printed indium oxide TFT devices,which is conductive to obtain enhancement mode devices.The threshold voltage of printed indium oxide TFT device was 0.7 V,which achieved a positive shift of 3 V compared with that of printed indium oxide TFT device without PAM additive.