Flexible
semiconductor materials, where structural fluctuations
and transformation are tolerable and have low impact on electronic
properties, focus interest for future applications. Two-dimensional
thin layer lead halide perovskites are hailed for their unconventional
optoelectronic features. We report structural deformations via thin
layer buckling in colloidal CsPbBr
3
nanobelts adsorbed
on carbon substrates. The microstructure of buckled nanobelts is determined
using transmission electron microscopy and atomic force microscopy.
We measured significant decrease in emission from the buckled nanobelt
using cathodoluminescence, marking the influence of such mechanical
deformations on electronic properties. By employing plate buckling
theory, we approximate adhesion forces between the buckled nanobelt
and the substrate to be
F
adhesion
∼
0.12 μN, marking a limit to sustain such deformation. This work
highlights detrimental effects of mechanical buckling on electronic
properties in halide perovskite nanostructures and points toward the
capillary action that should be minimized in fabrication of future
devices and heterostructures based on nanoperovskites.
We observe that different growth conditions and resulting morphologies of CsPbBr3 nanocrystals yield opposite stokes shift size-dependent trends. This emphasizes the different photo-physics for quantum-confined nanoplate and nanocube morphologies.
This work analyzes the viscous flow and elastic deformation created by the forced axial motion of a rigid cylinder within an elastic liquid-filled tube. The examined configuration is relevant to various minimally invasive medical procedures in which slender devices are inserted into fluid-filled biological vessels, such as percutaneous revascularization, interventional radiology, endoscopies and catheterization. By applying the lubrication approximation, thin shell elastic model, as well as scaling analysis and regular and singular asymptotic schemes, the problem is examined for small and large deformation limits (relative to the gap between the cylinder and the tube). At the limit of large deformations, forced insertion of the cylinder is shown to involve three distinct regimes and time-scales: (i) initial shear dominant regime, (ii) intermediate regime of dominant fluidic pressure and a propagating viscous-peeling front, (iii) late-time quasi-steady flow regime of the fully peeled tube. A uniform solution for all regimes is presented for a suddenly applied constant force, showing initial deceleration and then acceleration of the inserted cylinder. For the case of forced extraction of the cylinder from the tube, the negative gauge pressure reduces the gap between the cylinder and the tube, increasing viscous resistance or creating friction due to contact of the tube and cylinder. Matched asymptotic schemes are used to calculate the dynamics of the near-contact and contact limits. We find that the cylinder exits the tube in a finite time for sufficiently small or large forces. However, for an intermediate range of forces the radial contact creates a steady locking of the cylinder inside the tube.
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