In2Se3 나노와이어의 합성 및 이를 이용한 단일 나노와이어 소자의 특성 분석

Abstract

Synthesis of In2Se3 nanowires using the vapor-liquid-solid (VLS) mechanism and fabrication of the single In2Se3 nanowire devices for phase change random access memory applications have been demonstrated. In the VLS mechanism, nanoscale gold particles forming Au-In-Se alloy above the eutectic temperature were used as catalyst. To decide appropriate synthesis conditions, the effects of different experiment conditions such as growth temperature, duration of reaction and reactor pressure have been investigated. The structure and composition of as-grown In2Se3 nanowires were analyzed using the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It turns out that as-grown In2Se3 nanowires have a length of 5 to 30 μm and a diameter of 50 to 500 nm thick with Au nanoparticle at the tip. To fabricate single In2Se3 nanowire devices, the synthesized In2Se3 nanowires removed from the substrate by physical scratch and sonicated in IPA solution for 30 ~ 60 seconds. Then this solution was dropped onto a Si/SiO2 substrate with a pre-patterned pad array prepared using optical lithography and lift-off process. For interconnection between nanowires and probing pads, Pt was deposited using focused-ion beam (FIB) technique. By applying electrical pulse, the phase of fabricated devices has changed from crystalline to amorphous. The required reset voltage for c-α transition is 8V with a pulse width of 50 ns, and the required set voltage for α-c transition is 5.5V with a pulse width of 100 μs. The resistivity switching ratio (RSR) of 10^3 has been achieved. Low-frequency noise characteristic was also investigated in order to evaluate the material quality. The normalized current noise spectral density of amorphous phase is nearly 3 orders higher than that of crystalline phase. This difference implies that more crystal defects are existed in amorphous phase compared with crystalline state. The Hooge parameter is calculated as low as 10^-4 for crystalline phase, indicating high crystal quality of the as-grown In2Se3 nanowires.