Difference between the cleaved surface and the polished surface on the Raman spectra of La₂₋ₓSrₓCuO₄

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The Raman spectra on the cleaved surface of La₂₋ₓSrₓCuO₄ is found to be different from those on the mechanically polished or chemically etched surface. On the cleaved surface, the step-like increase of the scattering intensity below 700 cm⁻¹ is washed away and the two-phonon peaks are preserved clearly even at the optimum doping. The difference is demonstrated on the optimally doped crystal at x=0.15 and the stripe phase crystal at x=0.115. The stripe phase is stabilized by defects induced by mechanical polishing.