Insitu Observation of the Formation Dynamics of Nanohelices

Abstract

Strained InGaAs/GaAs bridges were released by a focused ion beam in order to observe the relaxation dynamics of the structure. Releasing the bridges resulted in the formation of chiral nanotubes with diameter of 920 nm and length 8.5 microns. The total time required for nanoscroll formation took > 20 minutes. From observing the scrolling action through time, it was found that the strain relief process differed from traditional wet etched nanoscrolls due to the simultaneous relief of strain from the released structures.

Strain induced semiconductor nanotubes: from formation process to device applications

“…The next step is to expose the sacrificial layer to the etchant so that the bilayer can be released from the substrate. This can be done by simply making a scratch on the wafer [34,39], selectively growing on the sidewall [40], or by a more controllable, systematic and manufacturable way such as lithographical patterning [25,26,29,[41][42][43]. For arsenide based structures, high composition Al x Ga 1−x As is commonly used as sacrificial layers.…”

“…On the other hand, rolling velocity was not affected by tube diameter in the range 20-500 nm. In another report, the formation dynamics of In 0.2 Ga 0.8 As/GaAs helical structures was demonstrated by releasing a strained bridge by a focused ion beam to form nanoscrolls [29].…”

“…For hybride nanotubes, selfassembled monolayers (SAMs) have been deposited on a In x Ga 1−x As/GaAs bilayer to form radial superlattices [23]; tubular structures of SiGe/SiO x /Ti [24] and In 0.3 Ga 0.7 As/Cr [25] have been reported; and SiGe/Si/SiN/Cr nanoshells have been demonstrated [26,27]. The strain induced formation mechanism has also been generalized to form various other kinds of 3D architectures [28][29][30]. In addition, the rolled up tubes can be embedded by epitaxially overgrown films to form hollow micro-or nanochannels in semiconductor materials [15,18].…”