Cu2O thin films were synthesized by sol-gel spin coating method. Cu (II) acetate hydrate (Cu(COOCH3)2xH2O) was used as the starting salt. A solution was prepared by dissolving Cu (II) acetate hydrate in monoethanolamine (MEA) and 2-methoxyethanol (2-ME). The precursor solution was spin coated on SiO2/Si substrates and coated film was dried at 150 oC for 20 min on a hot plate. Spin coating and drying process were repeated 2 times. And then, the films were annealed in N2 atmosphere at 400 oC for 30 min. After annealing in N2 atmosphere, the films were annealed in O2 atmosphere at 700 oC for 30 min under varying oxygen partial pressure of 0.04 Torr, 0.2 Torr and 0.9 Torr. The effects of oxygen partial pressure on structural and electrical properties of Cu2O thin films were studied. The morphology of copper oxide thin films were strongly affected by the annealing conditions and the structural properties were characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope. Effects of N2 annealing process prior to O2 annealing process and oxygen partial pressure on thin film quality were investigated. With N2 annealing process, continuous and dense Cu2O thin films was formed. The films annealed only in N2 atmos-phere, consist of Cu and Cu2O mixed phase. And followed by annealing with O2 atmosphere, the phase of the films is Cu2O under 0.04 Torr and 0.2 Torr oxygen partial pressure. The film annealed in 0.9 Torr oxygen partial pressure, CuO phase observed and roughness of the film was increased. Furthermore, copper oxide based thin film transistors were fabricated and characterized. Cu2O TFTs exhibited p-channel operation but field effect mobility and on/off current ratio were not satisfactory.
Cu2O 박막을 졸겔 스핀코팅 방법을 통해 합성하였다. Cu (II) acetate hydrate (Cu(COOCH3)2xH2O)를 전구체로 사용하였다. Cu (II) acetate hydrate를 monoethanolamine (MEA)와 2-methoxyethanol (2-ME)에 녹여 용액을 만들었다. 용액을 SiO2/Si 기판에 떨어뜨려 스핀코팅 한 후 핫 플레이트에서 150도, 20분 동안 dry 과정을 거쳤다. 스핀코팅과 dry 과정은 각각 2번 수행하였다. 그 후 N2 분위기에서 400도로 30분간 열처리한 후 산소 분압을 0.04 Torr, 0.2 Torr, 0.9 Torr로 변화시키며 700도에서 30분간 열처리하였다. 열처리 과정에서 산소 분압에 따른 Cu2O 박막의 구조적, 전기적 특성을 연구했다. XRD, SEM, TEM 분석을 통해 Cu2O 박막의 형태가 열처리 조건에 크게 영향을 받는 다는 것을 확인하였다. 또한 O2 분위기의 열처리 전에 N2 분위기의 열처리 과정이 박막에 미치는 영향을 조사하였다. N2 분위기의 열처리를 통해 continuous하고 dense한 Cu2O 박막이 얻을 수 있었다. N2 분위기에서만 열처리를 한 시료의 경우 Cu 상과 Cu2O 상의 혼합 상이 나타났고 이후 O2 분위기의 열처리를 통해 0.04 Torr, 0.02 Torr의 산소 분압에서는 Cu2O로 0.9 Torr에서는 CuO로 산화되었고 CuO 상이 나타나면서 박막의 roughness가 크게 증가하였다. 여기서 합성된 박막을 이용해 TFT를 제작하고 특성을 측정하였다. Cu2O 박막을 이용한 TFT 경우 p-channel 특성을 보였지만 낮은 field effect mobility와 on/off current ration 값을 나타내었다.
