Micro‐Raman study of exfoliated Bi 2 Sr 2 CaCu 2 O 8+ δ single crystals with different thicknesses

Exfoliated Bi 2 Sr 2 CaCu 2 O 8+ δ (Bi‐2212) single crystals were prepared by micromechanical cleavage of bulk Bi‐2212 single crystals on SiO 2 /Si substrates. Room temperature micro‐Raman spectra were collected using a 532‐nm laser source. The evolutions of the spectra of A 1g (Bi), A 1g (Sr), and A 1g (O Bi ) Raman modes with different thicknesses of the samples were studied. The refractive index of Bi‐2212 single crystal was obtained by studying the intensity evolutions based on the interference effect. The observed wavenumber shifts of the A 1g (Bi), A 1g (Sr), and A 1g (O Bi ) modes were analyzed. Copyright © 2011 John Wiley & Sons, Ltd.