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SUMMARY:Quantitative Reconstruction of Low Aspect Ratio MoS₂ Bubbles via
  Specular Contrast - Chenyang Zhao\, Cavendish Laboratory
DTSTART:20251209T140000Z
DTEND:20251209T150000Z
UID:TALK241732@talks.cam.ac.uk
CONTACT:Boyao Liu
DESCRIPTION:Bubbles formed in van der Waals (vdW) materials play a crucial
  role in modulating strain\, electronic structure\, and optical response\,
  yet their geometries are challenging to quantify using conventional micro
 scopy. Techniques such as AFM\, SEM\, and PL mapping suffer from issues in
 cluding surface damage\, limited imaging areas\, and indirect strain infer
 ence. In this seminar\, I will present a new quantitative approach for cha
 racterising MoS₂ bubble structures using specular contrast in scanning h
 elium microscopy (SHeM). By performing multi-angle imaging and tracking th
 e angular-dependent intensity maxima associated with the local specular sc
 attering condition\, we achieve contact-free 3D reconstruction with height
  precision better than 100 nm\, surpassing the nominal 30 μm beam spot si
 ze by nearly 300×. I will introduce the physical basis of helium specular
  scattering\, the speculometric-stereo reconstruction scheme\, and support
 ing ray-tracing simulations. The method provides accurate bubble curvature
  radii (~10 mm) and apex heights (~1 μm)\, revealing its capability to re
 solve extremely low-aspect-ratio deformations. Beyond MoS₂\, this work h
 ighlights specular-contrast SHeM as a powerful metrology tool for non-inva
 sive\, slope-sensitive topography mapping in a broad class of soft\, insul
 ating\, or delicate 2D materials.
LOCATION:B2.009\, Ray Dolby Centre\, Cavendish Laboratory
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