Lateral control of self-assembled island nucleation by focused-ion-beam micropatterning

Abstract

We demonstrate that the nucleation sites of nanoscale, self-assembled Ge islands on Si(001) can be controlled by patterning the Si surface in situ with a focused ion beam. At low doses of 6000 Ga+ ions per <100 nm spot, the selective growth is achieved without modifying the initial surface topography. At larger doses, topographic effects produced by sputtering and redeposition control the selective nucleation sites. Islands grown on irradiated spots are smaller with higher aspect ratio than islands grown on clean Si(001), suggesting a strong surfactant effect of Ga.

Beyond the heteroepitaxial quantum dot: Self-assembling complex nanostructures controlled by strain and growth kinetics

“…Features such as dots and QDMs can be located precisely using substrate prepatterning, e.g., with a focused ion beam. 25,26 Length scale reduction can be accomplished by growing with higher Ge content ͑see Fig. 8͒.…”

Focused Ion Beam Nanopatterning for Optoelectronic Device Fabrication

“…Furthermore, locally modifying the GaAs surface using FIB bombardment can be applied to the selective growth of InGaAs/InP on GaAs substrate by hydride vapor phase epitaxy technique [23], [24]. Similarly, controlling the nucleation sites of Ge islands on an Si substrate using FIB patterning for quantum structure growth has been recently demonstrated [25].…”

Towards Directed Self-Assembly of Quantum Dot Mesocrystals of Ge/Si Using Focused Ion Beam Patterning

“…Similar ideas apply at the regions of high curvature in the corners halfway up the stripes. They can be explained with a 3D version of our model, which will be discussed in detail elsewhere [22].…”

“…monolayers/s (ML/s) at a substrate temperature T s between 620 and 840 C. The samples were cooled to RT before characterization. In order to study buried footprints, some specimens were etched with a mixture of HF:1 H 2 O 2 : 2 CH 3 COOH: 3 (BPA solution), which is known to etch selectively SiGe alloys over pure Si [22]. Qualitative information on the island composition profiles are obtained by using a different etchant, namely NH 4 OH: H 2 O 2 [23].…”

“…Modification of the surface has been achieved by means of lithography, [18][19][20] nano-indentation [21] and ion-beam processing. [22][23][24][25] The various techniques and experiments cover a large range of surface features to direct the growth including pits, [18,19,22] stripes, [26][27][28] mesas, [29,30] and oxide windows, [31] as well as a wide range of QD areal density, growth temperatures, composition and deposition thickness. We have investigated the use of a Ga+ focused ion beam (FIB) to direct write patterns on Si (001) surfaces to direct precise positioning of Ge QDs at sub-100 nm lengthscales.…”