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We investigate the surface structure and electronic properties of β-Sn islands deposited on a graphitized 6H-SiC (0001) substrate via low temperature scanning tunneling microscopy and spectroscopy. Owing to the confinement of the island geometry, quantum well states (QWSs) are formed, manifesting as equidistant peaks in the tunneling spectra. Furthermore, a distinct strip feature appears on the surfaces of odd-layer Sn islands, ranging from 15–19 layers, which is not present on the surfaces of even-layer Sn islands. The spatial distribution of strips can be modified by applying a bias pulse, using an STM tip. Furthermore, the strip-like structure shows significant impacts on the QWS. An energy splitting of the lowest unoccupied QWSs is observed in strip regions; this may be ascribed to caused the phase shift of the wave functions of the QWSs on the top surface, due to surface distortions created by the aforementioned strips. [ABSTRACT FROM AUTHOR]

We demonstrate the importance of interface modification on improving electron confinement by preparing Pb quantum islands on Si(111) substrates with two different surface reconstructions, i.e., Si(111)-7 x 7 and Si(111)-Root3 x Root3-Pb (hereafter, 7 x 7 and R3). Characterization with scanning tunneling microscopy/spectroscopy shows that growing Pb films directly on a 7 x 7 surface will generate many interface defects, which makes the lifetime of quantum well states (QWSs) strongly dependent on surface locations. On the other hand, QWSs in Pb films on an R3 surface are well defined with small variations in linewidth on different surface locations and are much sharper than those on the 7 x 7 surface. We show that the enhancement in quantum confinement is primarily due to the reduced electron-defect scattering at the interface. [ABSTRACT FROM AUTHOR]