Photoemission band symmetries and dipole active modes of crystalline films of vinylidene fluoride (70%) with trifluoroethylene (30%) across the ferroelectric transition(s)
Photoemission band symmetries and dipole active modes of crystalline films of vinylidene fluoride (70%) with trifluoroethylene (30%) across the ferroelectric transition(s)
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DOI：
10.1088/0953-8984/12/22/306
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发表时间：
2000-06
期刊：
影响因子：
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通讯作者：
Jaewu Choi;S-J Tang;P. T. Sprunger;P. Dowben;V. Fridkin;A. V. Sorokin;S. Palto;N. Petukhova;S. Yudin
中科院分区：
文献类型：
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作者：
Jaewu Choi;S-J Tang;P. T. Sprunger;P. Dowben;V. Fridkin;A. V. Sorokin;S. Palto;N. Petukhova;S. Yudin
偏氟乙烯（70%）与三氟乙烯（30%）的结晶膜的电子占据带的对称性和振动偶极模式分别确定使用角分辨光电子能谱和高分辨率电子能量损失。占据的价带的对称性被保存在整个表面的“铁电”相变。电子结构的温度依赖性变化主要发生在导带中，并伴随着表面偶极重取向和表面布里渊区加倍跨越表面过渡，因此这些结果强烈支持一阶转变与单轴极化方向在这些结晶铁电聚合物薄膜。有令人信服的证据表明，这种表面相变是一个不适当的铁电过渡和不连续的。
The symmetry of the occupied electronic bands of crystalline films of vinylidene fluoride (70%) with trifluoroethylene (30%) and the vibrational dipole modes are identified using angle resolved photoemission and high resolution electron energy loss respectively. The symmetry of the occupied valence bands is preserved across the surface `ferroelectric' phase transition. The temperature dependent changes in the electronic structure occur primarily in the conduction band and are accompanied by a surface dipole reorientation and a surface Brillouin zone doubling across the surface transition, thus these results strongly support a first order transition with a uniaxial polarization direction in these crystalline ferroelectric polymer films. There is compelling evidence that this surface phase transition is an improper ferroelectric transition and discontinuous.