Dr. Benedikt Haas
Profil
Zusammenfassung
Dr. Benedikt Haas entwickelt Methoden zur atomaren Charakterisierung von Materialien mittels Elektronenmikroskopie, insbesondere zur Messung und Modellierung von Gitterschwingungen und elektrischen Feldern auf atomarer Skala. Seine Expertise liegt in der strukturellen Analyse von Halbleitern, zweidimensionalen Materialien und ferroelektrischen Schichten, um deren Eigenschaften für elektronische und optoelektronische Anwendungen zu verstehen und zu optimieren.
Skills
Stammdaten
Identität, Organisation und Kontakt aus HU-FIS.
Forschungsthemen3
Pumpen, Messen und Modellieren atomarer Vibrationen im Elektronenmikroskop
Quelle ↗Förderer: DFG Sachbeihilfe Internationale Kooperation Zeitraum: 06/2024 - 06/2027 Projektleitung: Dr. Benedikt Haas
SFB 1772/1: Struktur und kollektive Anregungen in mol2Dmat-Heterostrukturen durch schnelle Elektronen (TP A05)
Quelle ↗Förderer: DFG Sonderforschungsbereich Zeitraum: 10/2025 - 06/2029 Projektleitung: Prof. Christoph T. Koch, PhD, Dr. Benedikt Haas
Pumpen, Messen und Modellieren atomarer Vibrationen im Elektronenmikroskop
Quelle ↗Förderer: DFG Sachbeihilfe Internationale Kooperation Zeitraum: 06/2024 - 06/2027 Projektleitung: Dr. Benedikt Haas
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Publikationen25
Top 25 nach Zitationen — Quelle: OpenAlex (BAAI/bge-m3 embedded für Matching).
ACS Nano · 158 Zitationen · DOI
Controlled substitutional doping of two-dimensional transition-metal dichalcogenides (TMDs) is of fundamental importance for their applications in electronics and optoelectronics. However, achieving p-type conductivity in MoS2 and WS2 is challenging because of their natural tendency to form n-type vacancy defects. Here, we report versatile growth of p-type monolayer WS2 by liquid-phase mixing of a host tungsten source and niobium dopant. We show that crystallites of WS2 with different concentrations of substitutionally doped Nb up to 1014 cm–2 can be grown by reacting solution-deposited precursor film with sulfur vapor at 850 °C, reflecting the good miscibility of the precursors in the liquid phase. Atomic-resolution characterization with aberration-corrected scanning transmission electron microscopy reveals that the Nb concentration along the outer edge region of the flakes increases consistently with the molar concentration of Nb in the precursor solution. We further demonstrate that ambipolar field-effect transistors can be fabricated based on Nb-doped monolayer WS2.
Journal of Applied Physics · 105 Zitationen · DOI
This work presents the first atomic scale evidence for ferroelectric polarization inversion on the unit cell level in a wurtzite-type material based on epitaxial Al0.75Sc0.25N thin films. The electric field induced formation of Al-polar inversion domains in the originally N-polar film is unambiguously determined by atomic resolution imaging using aberration-corrected scanning transmission electron microscopy (STEM). Anisotropic etching supports STEM results confirming a complete and homogenous polarization inversion at the film surface for the switched regions and the virtual absence of previous inversion domains in as-deposited regions. Local evidence of residual N-polar domains at the bottom electrode interface is observed and can be explained by both stress gradients and electric field deflection. The epitaxial relationship of the sapphire/AlN/Mo/AlScN multilayer stack is discussed in detail. Selected-area electron diffraction experiments and XRD pole figures reveal a Pitsch–Schrader type orientation relation between the Mo electrode and the AlScN film.
Advanced Functional Materials · 81 Zitationen · DOI
Abstract The recent emergence of wurtzite‐type nitride ferroelectrics such as Al 1‐ x Sc x N has paved the way for the introduction of all‐epitaxial, all‐wurtzite‐type ferroelectric III‐N semiconductor heterostructures. This paper presents the first in‐depth structural and electrical characterization of such an epitaxial heterostructure by investigating sputter deposited Al 1‐ x Sc x N solid solutions with x between 0.19 and 0.28 grown over doped n‐GaN. The results of detailed structural investigations on the strain state and the initial unit‐cell polarity with the peculiarities observed in the ferroelectric response are correlated. Among these, a Sc‐content dependent splitting of the ferroelectric displacement current into separate peaks, which can be correlated with the presence of multiple strain states in the Al 1‐ x Sc x N films is discussed. Unlike in previously reported studies on ferroelectric Al 1‐ x Sc x N, all films thicker than 30 nm grown on the metal (M)‐polar GaN template feature an initial multidomain state. The results support that regions with opposed polarities in as‐grown films do not result as a direct consequence of the in‐plane strain distribution, but are rather mediated by the competition between M‐polar epitaxial growth on an M‐polar template and a deposition process that favors nitrogen (N)‐polar growth.
Kooperationen4
Bestätigte Forscher↔Partner-Paare aus HU-FIS — Gold-Standard-Positive für das Matching.
Pumpen, Messen und Modellieren atomarer Vibrationen im Elektronenmikroskop
other
SFB 1772/1: Struktur und kollektive Anregungen in mol2Dmat-Heterostrukturen durch schnelle Elektronen (TP A05)
university
Pumpen, Messen und Modellieren atomarer Vibrationen im Elektronenmikroskop
university