Raman spectroscopy with UV excitation on untwinned single crystals of YBa2Cu3O7-d

S. BAHRS; S. REICH; A. ZWICK; A. R. GOÑI; W. BACSA; G. NIEVA; C. THOMSEN

PHYSICA STATUS SOLIDI B-BASIC RESEARCH

WILEY-V C H VERLAG GMBH

Año: 2004 vol. 241 p. 63 - 66

0370-1972

Recent reflectance anisotropy studies on the material showed a photobleaching effect in the in-plane components of the dielectric function around 2.2 and 4.1 eV [1]. We present Raman spectra of oxygen deficient YBa2Cu3O7?d detwinned single crystals taken with laser excitation of 3.7 eV, close to the UV feature in the dielectric function, in search for a signal from the defect-induced Raman modes. While two groups of defect-induced mode at 230 cm?1 and 600 cm?1 behave very similar at the 2.2 eV resonance, we find clear differences for UV excitation. A peak at 600 cm?1 is identified as a copper-oxygen-chain related, defect- induced modes by its Raman selection rules. While this mode is enhanced beyond the strength of the Raman-allowed modes, the group at 230 cm?1 is absent. Low temperature experiments showed no change of the peak height under illumination, though the peaks are known to photobleach in the visible. of the peak height under illumination, though the peaks are known to photobleach in the visible. induced modes by its Raman selection rules. While this mode is enhanced beyond the strength of the Raman-allowed modes, the group at 230 cm?1 is absent. Low temperature experiments showed no change of the peak height under illumination, though the peaks are known to photobleach in the visible. of the peak height under illumination, though the peaks are known to photobleach in the visible. clear differences for UV excitation. A peak at 600 cm?1 is identified as a copper-oxygen-chain related, defect- induced modes by its Raman selection rules. While this mode is enhanced beyond the strength of the Raman-allowed modes, the group at 230 cm?1 is absent. Low temperature experiments showed no change of the peak height under illumination, though the peaks are known to photobleach in the visible. of the peak height under illumination, though the peaks are known to photobleach in the visible. induced modes by its Raman selection rules. While this mode is enhanced beyond the strength of the Raman-allowed modes, the group at 230 cm?1 is absent. Low temperature experiments showed no change of the peak height under illumination, though the peaks are known to photobleach in the visible. of the peak height under illumination, though the peaks are known to photobleach in the visible. in the dielectric function, in search for a signal from the defect-induced Raman modes. While two groups of defect-induced mode at 230 cm?1 and 600 cm?1 behave very similar at the 2.2 eV resonance, we find clear differences for UV excitation. A peak at 600 cm?1 is identified as a copper-oxygen-chain related, defect- induced modes by its Raman selection rules. While this mode is enhanced beyond the strength of the Raman-allowed modes, the group at 230 cm?1 is absent. Low temperature experiments showed no change of the peak height under illumination, though the peaks are known to photobleach in the visible. of the peak height under illumination, though the peaks are known to photobleach in the visible. induced modes by its Raman selection rules. While this mode is enhanced beyond the strength of the Raman-allowed modes, the group at 230 cm?1 is absent. Low temperature experiments showed no change of the peak height under illumination, though the peaks are known to photobleach in the visible. of the peak height under illumination, though the peaks are known to photobleach in the visible. clear differences for UV excitation. A peak at 600 cm?1 is identified as a copper-oxygen-chain related, defect- induced modes by its Raman selection rules. While this mode is enhanced beyond the strength of the Raman-allowed modes, the group at 230 cm?1 is absent. Low temperature experiments showed no change of the peak height under illumination, though the peaks are known to photobleach in the visible. of the peak height under illumination, though the peaks are known to photobleach in the visible. induced modes by its Raman selection rules. While this mode is enhanced beyond the strength of the Raman-allowed modes, the group at 230 cm?1 is absent. Low temperature experiments showed no change of the peak height under illumination, though the peaks are known to photobleach in the visible. of the peak height under illumination, though the peaks are known to photobleach in the visible.