X-ray Studies of Pb Quantum Size Effect Islands on Si(111)
Abstract
Recent work has shown that below ∼10nm a material's electronic properties and its structure are correlated because of the relationship between electron quantization and geometry known as Quantum Size Effects (QSE). An example is Pb islands grown on Si(111). In this system the Pb islands grow in bi-layer increments: a strong indication of QSE because bi-layer heights add three nodes to the electron wave-function at the Fermi energy. Important information, however, is still missing. In particular the wetting layer thickness between the Si and the Pb islands is unknown even though this parameter determines the well height that confines the electrons and selects stable island heights. We present surface x-ray diffraction results that show that the wetting layer thickness is in fact 1ML thick. Diffuse scattering measurements for growth at 225K show that the first monolayer of Pb grows in a completely disordered structure (possible small Pb clusters). As the coverage is increased to 1.2ML, Pb islands 7-layers high (on top of the wetting layer) begin to form. Island formation continues up to ∼2.5ML. Above this coverage island size increases until the islands coalesce to form a closed film near 6-8ML. *Supported by DOE No W-7405-ENG-82
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARD32007C