Nano Cuprous Oxides Film Prepared by Magnetron Sputtering
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S3.14.1
Nano Cuprous Oxides Film Prepared by Magnetron Sputtering Yang-Ming Lu，Jun-Yuan Chen，Tzuu-Shaang Wey Department of Electronics Engineering& Nano Research and Development Center, Kun Shan University of Technology, Taiwan, ROC Abstract Cuprous oxide (Cu2O) is a direct-gap semiconductor with band-gap energy of 2.0 eV and has been extensively investigated as a candidate for a photovoltaic material. However, practical applications have not been achieved to date due to the difficulty in controlling its physical properties. We have investigated the controllability of the formation of pure Cu2O thin films deposited by the reactive DC sputtering method and analysis by XPS and Raman spectrometer to identify the Cu+1 in the cuprous oxide. The formation of pure Cu2O films is not only dependent on the substrate temperature but also strongly effected by the oxygen and argon flow rate ratio. When the substrate temperature was kept constant at 100℃ and varied the oxygen and argon flow rate ratio from 3ml/min to 10ml/min，it is found a mixture of Cu2O and CuO phases is formed. At the flow rate of oxygen to 5ml/min, the pure and single phase of Cu2O is formed. Further increasing the oxygen flow rate, the phase is changed to be the CuO phase. The crystallity is improved as increasing the substrate temperature. The electrical resistivity of Cu2O obtained in this study is about 316 ohm-cm at 100℃ substrate temperature and 2.66Pa condition. The dependence of cupper oxides resistivity is not only on the substrate temperature and reactive gases but also on the sputter pressure. Because the characteristic resistivity values change with sputter pressure variation due to different phase compositions forming in the films. The lowest resistivity of Cu2O film is obtained when the Cu2O single phase exists in the films.
S3.14.2
Introduction Cu2O has itself been considered a promising candidate for possible application in photovoltaic devices. It is a reddish, non-stoichiometric p-type semiconductor of nature both ionic and covalent native with a direct forbidden band gap of 2.17eV,an acceptor level 0.4 eV above the valence band, and doner levels 1.1 eV and 1.3 eV below the conduction band[1].There are many attractive advantages have been point out for cuprous oxide[2]: (1) The starting material (Cu) is relatively cheap, nontoxic and aboundly available on the earth. (2) The manufacture cost of preparing cuprous oxide is relative low. (3) The Hall mobility of cuprous oxide is usually larger than 10 cm2/V.s in spite of the low formation temperature[3]. (4) To produce large area devices with cuprous oxide is possible. (5) The Cu2O has a high absorption coefficient in visible regions Cu2O is a non-stoichiometric p-type semiconductor with an estimated theoretical efficiency of solar energy conversion approaching 12% for a top cell in a two-(or three) solar cell stack[4]. Several techniques have been used to prepare thin films of Cu2O Such as: electrodeposition [5], spraying [6] ,Chemical vapor deposition [7], thermal oxidation [8],molecular b
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