Optical Second Harmonic Generation from Periodic Steps on Rutile TiO_2(110)

概要

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We have succeeded in observing optical second harmonic generation (SHG) from steps on the TiO_2 surfacesadsorbed with HCOOH. The samples were single crystals of rutile TiO_2 with (110), (15 15 4), (13 9 0), and (671)faces. These samples underwent annealing in O_2 gas, HF etching, and immersion into HCOOH aqueous solution toadsorb HCOOH molecules on their surfaces. Their surfaces were characterized by reflection high energy electrondiffraction (RHEED) and atomic force microscopy (AFM), and were confirmed to have regularly aligned stepscreated by the miscut of the samples. SH intensity as a function of the sample rotation angle was measured inair with the incident angle of 2° at the SH photon energy of 2ω = 4.66 eV. The SH intensity from the surfaceswith steps were 2 to 3 orders of magnitude stronger than that from the (110) surface. The SH intensity patternsfrom these stepped surfaces were anisotropic. The result indicates that the contribution of the surface steps wasobserved selectively.
2010-02-27