Formation of microtubes from strained SiGe/Si heterostructures

Strain induced semiconductor nanotubes: from formation process to device applications

“…Due to the top-down fabrication aspect for strain induced SNTs, it is possible to achieve precise spatial placement of SNTs. Arrays of SiGe bilayer squares (30 × 30 µm 2 ) rolled up in the diagonal directions have been demonstrated [43], even though the formed microscrolls showed orientation variations that are 90 • apart due to the square geometry [42,43]. High aspect ratio tubes as long as 2 mm have been realized in arrays using a strained 4 nm Ga 0.3 In 0.7 P/4.4 nm Ga 0.7 In 0.3 P bilayer [22].…”

Magnetotransport in Nonplanar SiGe/Si Nanomembranes

“…The structure can be topped with another layer of n-type doped SiGe to aid in the electronic confinement [4]; such SiGe/Si modulation doped heterostructures have been shown to produce good electronic confinement both before and after selective etching of the sacrificial oxide layer. But unlike the strain-compensated structure of [4] that remained flat upon underetching, our structure releases the wings to curl up into a partial cylinder, similar to what happens in the inverted Si/SiGe structure described in [3] that curled downward. Curvature is measured in terms of a parameter , where is the width of the cavity, and is the radius of curvature.…”

Controlled Assembly and Dispersion of Strain-Induced InGaAs/GaAs Nanotubes

“…3. The tubes are well aligned to the lithographically defined rectangular mesa patterns, due to the crystal orientation dependence and geometry effect [5], [15]- [18]. The dimensions are 50 µm in length and ∼590 nm in diameter, with an aspect ratio of ∼85.…”

“…This is similar to a previous report [16] on Ga x In 1−x P bilayer tubes that were ∼2 mm long and 1 µm in average diameter. We attribute the diameter inhomogeneity to possible deviation of lithography patterns away from the crystal orientation that determines the rolling direction, as well as the variation in etch rate [15].…”