Dresden 2026 – scientific programme

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FM: Fachverband Funktionsmaterialien

FM 19: Advanced Microscopy and Tomography for Functional Materials

FM 19.5: Talk

Thursday, March 12, 2026, 11:15–11:30, BEY/0E40

Tomographic Electron Holography reveals 3D-Potential Variations from Surface Segregation in p-n doped InGaAs Nanowires — •Kai-Luis Jakob¹, Laura Niermann¹, Tore Niermann¹, Frederik Otto¹, Rahel Specht¹, Daniel Wolf², Esmaielpour Hamidreza³, Gregor Koblmüller¹, and Michael Lehmann¹ — ¹TU Berlin — ²IFW Dresden — ³TU München

Mapping the three-dimensional electrostatic potential distribution at the nanoscale is crucial for tuning the electrical properties of semiconductor nanostructures, such as InGaAs nanowires utilized in optoelectronics. Off-axis electron holography enables measurement of the projected electrostatic potential with nanoscale spatial resolution; however, the 3D information typically remains inaccessible. In this work, we combine electron holography with tomography to reconstruct 3D potentials, thereby investigating subtle effects such as surface segregation, Fermi-level pinning, and damages induced by Focused Ion Beam preparation. Here, we focus on MBE-grown InGaAs nanowires featuring an axial p-n junction. A tilt series of holograms is acquired over a wide tilt range in a FEI Titan 80-300 TEM. Projected electrostatic potentials are reconstructed individually and aligned for tomographic reconstruction. This approach allows us to access the electrostatic potential and resolve both axial and radial changes from the wire core to its surface. We observed a largely constant potential step across the axial p-n junction of 0.5 V, however, near-surface regions exhibited deviations from it. At the surface of the n-doped segment, we found a thin p-type layer, likely attributable to known surface segregation.

Keywords: S/TEM; Tomography; Nanowires; p-n junction; Surface Segregation