Kang Hyo Min, Baek Seung-Hyub, Song Jong Han, Cho Yong Soo, Choi Ji-Won
Electronic Materials Research Center, Korea Institute of Science and Technology , Seoul, 136-791, Republic of Korea.
ACS Comb Sci. 2014 Sep 8;16(9):478-84. doi: 10.1021/co500057u. Epub 2014 Jul 23.
Perovskite CaCu3Ti4O12 has drawn a great deal of attention for various electronic applications due to its giant dielectric property as well as a strong stability in a wide range of temperature. In this paper, we use an off-axis continuous composition-spread (CCS) sputtering method to investigate the full range dielectric characteristics of calcium copper titanate thin films. The film compositions are continuously distributed by deposition from two targets of CaTiO3 and CuTiO3. A slightly Ca-deficient, Cu- and Ti-rich film, which has a 0.9:3.2:4.3 ratio for Ca:Cu:Ti, demonstrated the best performance by showing a dielectric constant of 781 at 100 kHz. On the other hand, all other films far away from the CaCu3Ti4O12 composition showed suppressed dielectric properties. Analyses by X-ray photon spectroscopy, micro-Raman microscopy, transmission electron microscopy, and Rutherford backscattering spectroscopy reveal that there are three possible origins for such superior performance at off stoichiometric thin films: (1) bulk doping by excessive Cu and Ti ions, (2) chemically modified grain boundary, and (3) the lowered electrode-sample interface resistance. Our result will provide a new insight into engineering the dielectric properties using off-stoichiometric synthesis.
钙钛矿型CaCu3Ti4O12因其巨大的介电性能以及在很宽温度范围内的强稳定性，在各种电子应用中引起了广泛关注。在本文中，我们使用离轴连续成分扩展（CCS）溅射方法来研究钛酸钙铜薄膜的全范围介电特性。薄膜成分通过从CaTiO3和CuTiO3两个靶材沉积而连续分布。一种钙略微不足、富含铜和钛的薄膜，其Ca:Cu:Ti比例为0.9:3.2:4.3，在100 kHz时介电常数为781，表现出最佳性能。另一方面，所有远离CaCu3Ti4O12成分的其他薄膜的介电性能都受到抑制。通过X射线光子能谱、显微拉曼显微镜、透射电子显微镜和卢瑟福背散射能谱分析表明，非化学计量比薄膜具有如此优异性能可能有三个原因：（1）过量的铜和钛离子进行体掺杂；（2）化学改性的晶界；（3）降低的电极 - 样品界面电阻。我们的结果将为利用非化学计量比合成来调控介电性能提供新的见解。
