Origins of emergent high-Tc ferroelectric ordering in heteroepitaxial ice film: Sum-frequency generation spectroscopy of H2O and D2O ice films on Pt(111)
Origins of emergent high-Tc ferroelectric ordering in heteroepitaxial ice film: Sum-frequency generation spectroscopy of H2O and D2O ice films on Pt(111)
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异质外延冰膜中出现的高温铁电有序的起源：Pt(111)上H2O和D2O冰膜的和频生成光谱
DOI：
10.1103/physrevb.97.075410
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
K. Watanabe & Y. Matsumoto
中科院分区：
文献类型：
--
作者：
N. Aiga;*T. Sugimoto;Y. Otsuki;K. Watanabe & Y. Matsumoto
用和频(SFG)谱研究了140K下在铂(111)衬底上生长的冰晶膜的铁电取向有序性。()冰膜氢键OH(OD)伸缩带的和频(SFG)谱显示了几个符号均为负的峰，表明()分子的净H-DOWN(Net-D-DOWN)铁电取向有序，其中质子优先指向铂衬底。根据分子间耦合产生的取向有序和OH(OD)振动激子分析了光谱特征。对SFG峰强度的定量分析表明，薄膜具有与层相关的强铁电取向有序性。SFG强度的温度依赖关系表明，在临界温度为167K时，铁电取向有序通过二级铁电-顺电转变而衰减，对于50双层厚度的冰膜和167K的双层厚度的冰膜，这两种冰膜的大小分别是铁电体冰的两倍多。高铁电性冰膜在铂(111)面上的同位素位移仅为4K左右，与典型的高氢键铁电体的大的同位素位移形成鲜明对比，约为几十个开尔文。冰/铂界面上的相互吸附和吸附-衬底相互作用以及冰膜氢键网络中的核量子效应是造成铁电取向有序及其同位素效应热稳定性的主要原因。
Using sum-frequency generation (SFG) spectroscopy, we have investigated ferroelectric orientational ordering ofandcrystalline-ice films grown on Pt(111) at 140 K. TheSFG spectrum of the hydrogen-bonded OH (OD) stretching band of() ice film shows a couple of peaks whose signs are all negative, indicating net-H-down (net-D-down) ferroelectric orientational ordering of() molecules with protons (deuterons) preferentially pointing toward the Pt substrate. The spectral features are analyzed in terms of the orientational ordering and OH (OD) vibrational excitons derived from intermolecular couplings. The quantitative analysis of the SFG peak intensity demonstrates the layer-dependent strong ferroelectric orientational ordering. Temperature dependence of the SFG intensity indicates that the ferroelectric orientational ordering decays via second-order type ferroelectric-paraelectric transition at critical temperatures ofand 167 K for(50 bilayers thickness) and(64 bilayers thickness) ice films, respectively, which are more than twice as large as that of ferroelectric bulk ice XI (forfor). The isotope shift offor the high-ferroelectric ice films on Pt(111) is only about 4 K, which is in stark contrast to a large isotope shift of, approximately several tens of Kelvin, of typical high-hydrogen-bonded ferroelectrics. The interadsorbate and adsorbate-substrate interactions at the ice/Pt interface and nuclear quantum effects in the hydrogen-bond network of ice film are responsible for the observed thermal stability of ferroelectric orientational ordering and its isotope effect.