All-Solution-Processed InGaO3(ZnO)m Thin Films with Layered Structure

We fabricated the crystallized InGaZnO thin films by sol-gel process and high-temperature annealing at 900°C. Prior to the deposition of the InGaZnO, ZnO buffer layers were also coated by sol-gel process, which was followed by thermal annealing. After the synthesis and annealing of the InGaZnO, the InGaZnO thin film on the ZnO buffer layer with preferred orientation showed periodic diffraction patterns in the X-ray diffraction, resulting in a superlattice structure. This film consisted of nanosized grains with two phases of InGaO3(ZnO)1 and InGaO3(ZnO)2 in InGaZnO polycrystal. On the other hand, the use of no ZnO buffer layer and randomly oriented ZnO buffer induced the absence of the InGaZnO crystal related patterns. This indicated that the ZnO buffer with high c-axis preferred orientation reduced the critical temperature for the crystallization of the layered InGaZnO. The InGaZnO thin films formed with nanosized grains of two-phase InGaO3(ZnO)m superlattice showed considerably low thermal conductivity (1.14 Wm−1 K−1 at 325 K) due to the phonon scattering from grain boundaries as well as interfaces in the superlattice grain.