Ihlefeld Jon F, Tian Wei, Liu Zi-Kui, Doolittle W Alan, Bernhagen Margitta, Reiche Peter, Uecker Reinhard, Ramesh Ramamoorthy, Schlom Darrell G
Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2009 Aug;56(8):1528-33. doi: 10.1109/TUFFC.2009.1216.
BiFeO3 thin films have been deposited on (001) SrTiO3, (101) DyScO3, (011) DyScO3, (0001) AlGaN/GaN, and (0001) 6H-SiC single crystal substrates by reactive molecular beam epitaxy in an adsorption-controlled growth regime. This is achieved by supplying a bismuth over-pressure and utilizing the differential vapor pressures between bismuth oxides and BiFeO3 to control stoichiometry in accordance with thermodynamic calculations. Four-circle x-ray diffraction and transmission electron microscopy reveal phase-pure, epitaxial films with rocking curve full width at half maximum values as narrow as 7.2 arc seconds (0.002 degrees). Epitaxial growth of (0001)-oriented BiFeO3 thin films on (0001) GaN, including AlGaN HEMT structures, and (0001) SiC has been realized using intervening epitaxial (111) SrTiO3 / (100) TiO2 buffer layers. The epitaxial BiFeO3 thin films have 2 in-plane orientations: [1120] BiFeO3 || [1120] GaN (SiC) plus a twin variant related by a 180 degrees in-plane rotation. This epitaxial integration of the ferroelectric with the highest known polarization, BiFeO3, with high bandgap semiconductors is an important step toward novel field-effect devices.
通过反应分子束外延在吸附控制生长模式下，已将BiFeO₃薄膜沉积在（001）SrTiO₃、（101）DyScO₃、（011）DyScO₃、（0001）AlGaN/GaN和（0001）6H-SiC单晶衬底上。这是通过提供铋过压并利用铋氧化物与BiFeO₃之间的蒸气压差，根据热力学计算来控制化学计量比实现的。四圆X射线衍射和透射电子显微镜显示出相纯的外延薄膜，其摇摆曲线半高宽窄至7.2弧秒（0.002度）。利用中间的外延（111）SrTiO₃ /（100）TiO₂缓冲层，已实现了（0001）取向的BiFeO₃薄膜在（0001）GaN（包括AlGaN HEMT结构）和（0001）SiC上的外延生长。外延BiFeO₃薄膜具有2个面内取向：[1120] BiFeO₃ || [1120] GaN（SiC）加上通过180度面内旋转相关的孪晶变体。这种具有最高已知极化率的铁电体BiFeO₃与高带隙半导体的外延集成是朝着新型场效应器件迈出的重要一步。
