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Abstract
The effect of illumination on the hydrofluoric acid etching of AlAs sacrificial layers with systematically varied thicknesses in order to release and roll up InGaAs/GaAs bilayers was studied. For thicknesses of AlAs below 10 nm, there were two etching regimes for the area under illumination: one at low illumination intensities, in which the etching and releasing proceeds as expected and one at higher intensities in which the etching and any releasing are completely suppressed. The “etch suppression” area is well defined by the illumination spot, a feature that can be used to create heterogeneously etched regions with a high degree of control, shown here on patterned samples. Together with the studied self-limitation effect, the technique offers a way to determine the position of rolled-up micro- and nanotubes independently from the predefined lithographic pattern.
Highlights
Introduction and BackgroundRolled-up nanotech [1, 2] has become a powerful technology with applications in a broad range of research fields, including optofluidics [3], micromachinery [4,5,6], magnetofluidics [4, 7], biophysics [4, 8], nanomechanics [9], and waveguiding for different spectral ranges and applications [10,11,12]
Large arrays of periodically ordered microtubes can be fabricated by a combination of lithography and deliberate self-rolling of strained layers upon selective underetching [1, 13,14,15]
Numerous existing studies offer highly sophisticated methods for precise lateral positioning of rolled-up semiconductor nanostructures by controlling the starting edges [13,14,15, 28, 29], but difficulties arise for thin layers due to the extensive, successive lithography steps involved, and ways to control the stopping point of rolling remain largely lacking without modifying the structure
Summary
Introduction and BackgroundRolled-up nanotech [1, 2] has become a powerful technology with applications in a broad range of research fields, including optofluidics [3], micromachinery [4,5,6], magnetofluidics [4, 7], biophysics [4, 8], nanomechanics [9], and waveguiding for different spectral ranges and applications [10,11,12]. Numerous existing studies offer highly sophisticated methods for precise lateral positioning of rolled-up semiconductor nanostructures by controlling the starting edges [13,14,15, 28, 29], but difficulties arise for thin layers due to the extensive, successive lithography steps involved, and ways to control the stopping point of rolling remain largely lacking without modifying the structure. Intense light exposure of a certain substrate area leads to a complete suppression of the underetching effect, and as a result, the formation of rolled-up InGaAs/GaAs tubes can be controlled spatially. This method allows for control over the roll-up stopping point and is suitable for very thin sacrificial layers
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