Scanning magneto-optical lens for surface analysis

We demonstrate the essential principles for performing a novel form of metastable-atom microscopy, namely focusing and scanning of a He 2(3)S beam. A magneto-optical lens, in conjunction with time-varying magnetic field components, has been used to scan a beam of He 2(3)S atoms across a sample surface in a manner analogous to other scanning probe techniques. The instrument developed is the first to apply methods in the laser manipulation of atoms specifically to the study of surfaces. With the lens in its current arrangement, a beam of He 2(3)S atoms with an intensity of similar to 6 x 10(12) atoms s(-1) cm(-2) may be directed anywhere within a sample area of similar to 64 mm(2) at a focal distance of 1.4 m and with a focal spot full-width at half-maximum of < 2 mm. Such control over the intensity and position of the He 2(3)S beam greatly benefits the surface analysis technique of metastable de-excitation spectroscopy, as demonstrated with example spectra from a clean Si( 1 1 1) 7 x 7 surface.