Comment on “Raman spectroscopy study of NaxCoO2 and superconducting NaxCoO2∙yH2O”

作     者：P. Lemmens P. Scheib Y. Krockenberger L. Alff F. C. Chou C. T. Lin H.-U. Habermeier B. Keimer 

作者机构：Institute for Physics of Condensed Matter TU Braunschweig D-38106 Braunschweig Germany Max-Planck-Institute for Solid State Research Heisenbergstrasse 1 70569 Stuttgart Germany Institute of Materials Science TU Darmstadt Petersenstrasse 23 D-64287 Darmstadt Germany Center for Materials Science and Engineering MIT Cambridge Massachusetts 02139 USA 

出 版 物：《Physical Review B》 (Phys. Rev. B Condens. Matter Mater. Phys.)

年 卷 期：2007年第75卷第10期

页      面：106501-106501页

核心收录：

学科分类：0808[工学-电气工程] 0809[工学-电子科学与技术（可授工学、理学学位）] 07[理学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学] 

摘      要：The effect of surface degradation of the thermolectric cobaltite on Raman spectra is discussed and compared to experimental results from Co3O4 single crystals. We conclude that on NaCl-flux grown NaxCoO2 crystals a surface layer of Co3O4 easily forms that leads to the observation of an intense phonon around 700cm−1 [Y. G. Shi et al., Phys. Rev. B 70, 052502 (2004)]. The Raman spectra on freshly cleaved crystals from optical floating zone ovens do not show such effects and have a high-frequency phonon cutoff at approximately 600cm−1 [P. Lemmens et al., Phys. Rev. Lett. 96, 167204 (2006)]. We discuss the relation of structural dimensionality, electronic correlations, and the high-frequency phonon cutoff of the thermolectric cobaltite.