Surface bismuth removal after Bi nanoline encapsulation in silicon

Abstract

Recently, several kinds of atomic-scale wires have been reported for nano-scale device and interconnect applications. The Bi nanoline is one of the most promising candidates because of its structural perfection and the capability to be buried in an epitaxial Si layer. A surfactant layer of Bi is necessary for the encapsulation process, and this remains on the sample surface after the burial, but it needs to be removed so that the buried Bi line may be properly characterized by I– V measurements, X-ray diffraction, etc. without perturbations from the surface layer. It is shown by RHEED observation that the thermal desorption is not suitable for this purpose, because the one-dimensional structure of the buried Bi line is disrupted over the same time scale as for removal of the surfactant Bi. Chemical wet etching of the surface layer was found to be a better solution to the removal of the surfactant Bi atoms without destroying the buried Bi lines.