Nanoscale Force Measurement Technique for Advanced Scanning Tunneling Microscopy (STM)

TO-114 • PT 1.2455 • As of 10/2023
Peter Grünberg Institute
Quantum Nanoscience (PGI-3)

Technology

Our technology presents an advanced method for measuring the force interaction caused by a sample, particularly for scanning tunneling microscopes (STM), as well as a scanning tunneling microscope itself. The method involves applying a bias voltage to a tip and bringing it into close proximity to the sample, resulting in a measurable current flowing between the tip and the sample. During the process, a sensor and signal converter is formed in the region of the force interaction. This sensor and signal converter modifies the current flowing through the tip-sample contact based on the strength of the force interaction. The method is executed in close proximity to the sample or tip, and both should preferably be electrically conductive or at least semiconductive.

Problem addressed

The scanning tunneling microscope (STM) and its functioning are generally known and understood. The STM achieves lateral spatial resolutions of up to 0.1 Å due to its unique design features, allowing for the visualisation of nanostructures through topography and/or local electronic density of states in the valence electrons range. The atomic force microscope (AFM) utilises the force interaction between a tip and a sample to image the sample surface. Unlike the STM, the AFM has various fundamentally different designs and operating modes, differing in the method of force detection. These variations reflect attempts to improve AFM resolution into the atomic range, which has proven to be exceptionally challenging.

Solution

This new technology combines the advantages of atomic force microscopy (AFM) and scanning tunneling microscopy (STM) in a novel way.

By reducing the sensor and signal converter to nanoscale dimensions and placing it at the tip-sample contact, it overcomes the limitations of macroscopic sensors used in AFM, allowing for atomic resolution. Additionally, the current detection in scanning tunneling microscopy enables superior lateral resolution, making it advantageous for force microscopy. The technology provides images with unprecedented resolution, depicting the atomic-geometric and chemical structure of the sample, including intermolecular bonds. It offers high-resolution microscopy with minimal equipment requirements.

Benefits and Potential Use

This technology allows for the identification of nanoscale objects based on their chemical and atomic-geometric structure. It offers a new variant of force microscopy that can provide quantifiable forces. The dependence of current on bias voltage can be measured, similar to how the elastic properties of a cantilever in AFM can be varied. The technology is applicable in various fields, including materials science, nanotechnology, and biological research. It enables the visualisation and analysis of intermolecular interactions, making it valuable for studying molecular structures and dynamics.

The technology can be implemented in scanning tunneling microscopes, as well as in systems such as fracture contacts, where a defined interaction centre is formed between a tip and a sample. By adsorbing, condensing, or resublimating the sensor and signal converter at the tip-sample contact, it allows for in-situ sensor formation and imaging of the sample's atomic-geometric and chemical contrast. This new paradigm for STM experiments opens up possibilities for advanced research and analysis.

Development Status and Next Steps

Forschungszentrum Jülich has extensive expertise in this field and holds several patents. The technology described above has already been initially verified through prototypes and is continuously being developed further. The Peter Grünberg Institute (PGI-3) – Quantum Nanoscience – already cooperates with numerous national and international companies and scientific partners.

Forschungszentrum Jülich focuses on energy and cost-efficient devices, suitable for various emerging technologies. We are continuously seeking for cooperation partners and/or licensees in this and adjacent areas of research and applications.

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