Stable Aqueous Dispersion of ZnO Nanocrystals for Printing Thin Film Transistors
A.S.G. Khalil, D. Roy Chowdhury, M. Ali, C. Busch, R. Schmechel, M. Winterer
Nanoparticle Process Technology (NPPT), DE
Keywords: zinc oxide nanoparticle, ink-jet printing, transistor
Abstract:Zinc oxide (ZnO) nanomaterials have attracted great interest due to their unique properties and applications in electronics, optics and photonics [1,2]. Different preparation methods have been reported to synthesize ZnO nanoparticles (ZnO NP). Here, the ZnO NP have been synthesized by chemical vapor synthesis (CVS) , which is a modified chemical vapor deposition (CVD) process. By using this method, highly crystalline, less aggregated and narrow-sized distribution ZnO NP can be obtained. The prepared particles have been characterized by XRD, TEM, and some other techniques. As-prepared particles have a primary size of about 20 nm as measured by XRD (Fig. 1). For the fabrication of printable devices based on nanoparticles, stable colloidal dispersions of these materials are highly desirable . In this work, aqueous and non-aqueous dispersions of ZnO NP have been prepared successfully after the addition of new stabilizers. The prepared dispersions are stable for several weeks without observable sedimentation. The Zeta potential and the size of the ZnO NP in these dispersions have been monitored for several weeks and showed quite invariable values. In addition, it has been found that the optimization of the ultrasonic treatment of the dispersion is very important, leading to less-aggregated particles with sizes close to the size of the primary particles. The realization of these stable dispersions has given the opportunity to form ZnO NP films (Fig. 2) for different applications on glass and silicon substrates by ink-jet printing and spin coating techniques. Furthermore, thin film transistors based on ZnO NP have been fabricated with the help of spin coating in the bottom gate configuration. The transistor output characteristics clearly manifest the n-type behavior of the ZnO NP (Fig. 3). The curves display saturation at higher drain voltages. The fabrication of devices based on these ZnO NP using ink-jet printing is currently under investigation. References  Z. L. Wang, J. Phys.: Condens. Matter., 16, R829, 2004.  Ü. Özgür,Ya. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S.-J. Cho, H. Morkoç J. Appl. Phys., 98, 041301, 2005.  J. Brehm, M. Winterer, H. Hahn, J. Appl. Phys., 100, 064311, 2006.  B. T. Nguyen, J. E. Gautrot, M. T. Nguyenb and X. X. Zhu, J. Mater. Chem., 17, 1725, 2007.