Modification of cleaved surfaces of Bi2Sr2CaCu2O8 single crystals induced by ArF excimer laser irradiation

The variation of surface morphology and chemical composition of cleaved sur faces of (001) Bi2Sr2CaCu2O8 (BSCCO) crystals was investigated following ir radiation in vacuum with an ArF excimer laser. Results were obtained for la ser fluences in the range from 20 to 500 mJ/cm(2). Distinctive surface stru ctures of BSCCO have been observed having a strong correlation with the las er fluence and number of pulses delivered to the site. The development of a relatively smooth surface (delta similar to 20 nm) has been observed for i rradiation at 500 mJ/cm(2). The formation of a 'hexatic' micro-structure on the surface of ablated crystals suggests that a two-dimensional phase tran sition has occurred, At lower laser fluences, rough surfaces (0.05 mu m < d elta < 3 mu m) were developed with characteristic pyramids and/or cone-shap e islands. The results indicate that surface modification is due to differe nt mechanisms corresponding to the surface temperature being raised by dire ct laser irradiation and laser heated plasma. (C) 1999 Elsevier Science B.V . All rights reserved.