Observation and control of Si surface and interface processes for nanostructure formation by scanning reflection electron microscopy

Abstract

We observe the oxidation process on clean Si surfaces using high-resolution scanning reflection electron microscopy and form nanostructures on them using focused electron-beam- (EB-) induced surface reactions. Si thermal oxidation occurs layer by layer, and the interface between the oxide film (<1 nm thickness) and Si substrate becomes atomically abrupt. When the sample is heated to 700-800 °C after being irradiated by the focused EB on the surface at room temperature, SiO2 film is selectively decomposed from the EB-irradiated area, resulting in the exposure of a clean Si substrate. The typical width of the clean Si `open windows' is about 10 nm. Using selective reactions during heating after the deposition of Si and Ge films on the patterned samples, Si nanowires and Ge nanoislands with 10 nm size are formed on Si surfaces. Ga-adsorbed Si nanoareas and Ga nanodots are also formed by selective adsorption of Ga on the Si window areas.

Investigation of the effect of high-temperature annealing on stability of ultrathin Al2O3 films on Si(001)

“…Figure 1͑b͒ shows that the 2ϫ1 RHEED spots disappeared and only a 1ϫ1 diffraction pattern could be observed after the growth of an amorphous 0.6-nm-thick Al 2 O 3 film on the Si͑001͒-2ϫ1 surface. Because amorphous film does not contribute to the specular spot intensity, 15 the SREM image of Fig. 1͑b͒ is not a surface image but an interface image between the Al 2 O 3 film and Si͑001͒.…”

Pattern level assembly of Ge quantum dots on Si with focused ion beam templating

“…With the exception of forming only one island on top of a sufficiently small mesa, 5 the above examples do not provide the means for controlling the individual placement of each island on a specified site. In order to achieve such control and obtain patterns of arbitrary complexity, local surface modification techniques are more appropriate, such as electron beam lithography to open windows in a surface oxide, 16 scanning tunneling microscope nanopatterning, 17 or a focused ion beam ͑FIB͒ templating of Si ͑Refs. 18-20͒ and GaAs ͑Ref.…”

In-Situ Focused Ion Beam Micropatterning of Ge Islands

“…Beyond the random nature of self-assembly being able to choose the island nucleation site will open future device applications such as quantum cellular automata [1]. The growth on Mesa structures or windows in an ultra thin oxide are successful methods to control nucleation sites [2,3], but with major disadvantages like not being able to incorporate the islands in an epitaxial silicon film. The ability to laterally pattern substrates without changing surface topography is therefore a key to novel device technologies.…”