Metal Sheet of Atomic Thickness Embedded in Silicon.

The controlled confinement of the metallic delta-layer to a single atomic plane has so far remained an unsolved problem. In the present study, the delta-type structure with atomic sheet of NiSi2 silicide embedded into a crystalline Si matrix has been fabricated using room-temperature overgrowth of a Si film onto the Tl/NiSi2/Si(111) atomic sandwich in ultrahigh vacuum. Tl atoms segregate at the growing Si film surface, and the 1.5-3.0 nm thick epitaxially crystalline Si layer forms atop the NiSi2 sheet. Confinement of the NiSi2 layer to a single atomic plane has been directly confirmed by transmission electron microscopy. The NiSi2 delta-layer demonstrates a p-type conductivity associated with the electronic transport through the two hole-like and one electron-like interface-state bands. The basic structural and electronic properties of the NiSi2 delta-layer remain after keeping the sample in air for one year.

The manipulation of C60 in molecular arrays with an STM tip in regimes below the decomposition threshold.

The ability of scanning tunneling microscopy to manipulate selected C(60) molecules within close packed C(60) arrays on a (Au,In)/Si(111) surface has been examined for mild conditions below the decomposition threshold. It has been found that knockout of the chosen C(60) molecule (i.e., vacancy formation) and shifting of the C(60) molecule to the neighboring vacant site (if available) can be conducted for wide ranges of bias voltages (from -1.5 to +0.5 V), characteristic manipulation currents (from 0.02 to 100 nA) and powers (from 2 × 10(-8) to 0.1 µW). This result implies that the manipulation is not associated with the electrical effects but rather has a purely mechanical origin. The main requirement for successful C(60) knockout has been found to be to ensure a proper 'impact parameter' (deviation from central impact on the C(60) sphere by the tip apex), which should be less than ~1.5 Å. A certain difference has been detected for the manipulation of C(60) in extended molecular arrays and molecular islands of a limited size. While it is possible to manipulate a single C(60) molecule in an array, in the case of a C(60) island it appears difficult to manipulate a given fullerene without affecting the other ones constituting the island.