[6p-S44-1~21] 9.2 Nanowires and Nanoparticles

▼ [6p-S44-18] Effect of Au thickness on the Bimetal-catalyzed Growth of InGaZnO Nanowires
from Amorphous Thin Film

〇(M1)JenichiClairvaux Escubio Felizco¹, Mutsunori Uenuma¹, Daiki Senaha¹, Yasuaki Ishikawa¹, Yukiharu Uraoka¹ (1.NAIST)

Keywords:bi-metal, IGZO, nanowire

Although considerable research has been devoted to InGaZnO in amorphous phase, rather less attention has been given to its crystalline state, especially in nanostructured form. In particular, a few literatures have reported the fabrication of InGaZnO nanowires. Moreover, these studies employed extremely high temperature processing techniques (>1400°C) or contamination-prone solution processes [1-2]. Our study reports the growth of InGaZnO nanowires directly from amorphous InGaZnO thin film at 700°C using Mo and Au as bimetal catalyst. The effect of the thickness of Au thin film catalyst on the morphology of the nanowires is also investigated. Amorphous InGaZnO thin films (200 nm) were deposited at room temperature on pre-cleaned Si substrates (1cm x 1cm) via RF magnetron sputtering using sintered (In:Ga:Zn ~2:2:1) targets. Subsequently, Mo (100 nm) and Au (1, 2, 5 nm) thin films were deposited using Electron Beam Evaporation. Annealing was then performed at 700°C for 2h under N₂ atmosphere. Shown in Fig. 1a is the IGZO 100 nm Mo/1 nm Au sample annealed at 700°C. Very few and small nanowires were formed, which appeared to be only at the onset of growth. When a thicker Au thin film of 2 nm was used, nanowires of 150-250 nm diameters and 1-5µm lengths grew. However, when a 5 nm Au thin film was deposited, only few nanowires with about the same lengths but with 250-500 nm diameters were formed. This is possibly due to the formation of large nanoparticle catalysts when a thick film is used. Similar to what has been reported in ZnO nanowires, given the same annealing conditions, a higher amount of In, Ga, Zn and O atoms are needed for larger Au particles to reach the supersaturation at the nanoparticle vicinity, which would lead to nanowire growth [3]. The larger diameter formed also suggests that the nanoparticle diameter greatly affects the nanowire diameter. EDX analyses confirmed the composition of the nanowires to be InGaZnO while TEM analysis verified their single crystallinity.