Stellenticket Humboldt-Universität zu Berlin

There is an increasing interest in coupling the dynamic strain of surface acoustic waves (SAWs)
to electrical excitations in semiconductor heterostructures containing 2D materials to acoustically
manipulate their optoelectronic properties. While optical phenomena in 2D nanostructures can be
conveniently mapped by photoluminescence, local probing of mechanical properties remains
challenging. This task can, nevertheless, be assisted by high-frequency (GHz) SAWs, which are
particularly suitable for probing very thin objects due to their micron-size wavelengths and their
confinement near the surface.

Objective:
The goal of this project is to spatially probe the SAW profile in semiconductor heterostructures
containing 2D materials using atomic-force microscopy (AFM). The key objectives are:

1. Characterization of the efficiency of SAW transfer onto stamped 2D flakes such as BN
   and transition-metal dichalcogenides.
2. Exploration of the interaction between SAWs and 2D materials either stamped of epitaxial.

Methodology:
The project will involve a combination of clean-room, RF characterization and AFM scanning
probe techniques. The key tasks include:

1. Sample fabrication: Sputtering of piezoelectric films such as ZnO or AlN, and patterning
   of interdigital transducers (IDTs) for the excitation and detection of SAWs. Transfer of 2D flakes.
2. RF characterization of SAW resonators: Measurement of the reflection and transmission
   coefficients of the IDTs.
3. SAW imaging using AFM: spatial mapping of the SAW profile in the substrates and 2D materials.

Expected Outcomes:
The expected main results of the project are

• Fabrication of the integrated system.
• Detailed study of SAW transfer efficiency in 2D materials, mapped with AFM.
• Detection of acoustoelectric or acoustooptical effects.

Skills and Requirements

• Background in solid state physics, materials science, or related fields.
• Experience or interest in clean-room technology, electrical measurement or optical
  spectroscopy techniques.
• High motivation, excellent interpersonal and project management skills.

Opportunities and Benefits

• Modern labs with a wide range of experimental techniques.
• Supportive environment with experts for various scientific sub-fields.
• International and culturally diverse community.
• Location in the heart of Berlin with excellent public transport connections.
• Subsidized travel ticket.

Dr. Mingyun Yuan
+49 30 20377-503
yuan@pdi-berlin.de