Contrary to textbook wisdom, the unusually long illuminating wavelength of 118 µm did not at all preclude researchers from the Max-Planck-Institute of Biochemistry (MPIB) to resolve details as small as 40 nm (= 0.04 µm).
This was made possible by the use of extreme THz field concentration at the sharp tip of a scanning atomic force microscope (AFM). The THz nanoscope thus breaks the diffraction barrier by a factor of 1500, and with its 40 nm resolving power matches the needs of modern nanoscience and technology. As a first application, the researchers demonstrate the mapping of free-carriers in state-of-the-art industrial transistors of the 65 nm-technology.
The MPIB team had pioneered near-field microscopy at both visible and infrared frequencies over the last decade, enabling nanoscale resolved chemical recognition of nanostructured materials. Only recently they realized, when imaging semiconducting nanostructures of state-of-the art processor chips, the importance of using far-infrared or THz radiation (the 118 µm wavelength radiation corresponds to 2.5 THz). THz illumination offers a 100-fold increased sensitivity to the conductivity of semiconducting materials when compared to infrared light. This extreme sensitivity is difficult to achieve by any other optical microscopy technique, rendering the described microscopy technique highly desirable for quality assurance and analysis of failure mechanisms in industrially produced semiconductor nanodevices.
An external theory collaborator (Javier Aizpurua, Donostia International Physics Center, Spain) joined the MPIB team to help predicting that indeed the long-wavelength THz radiation would develop a highly concentrated field right at the end of the scanning tip. With this assurance, the MPIB team set out to illuminate their home-built near-field microscope with 2.5 THz radiation from a gas laser. Doctoral student Andreas Huber succeeded to record the first THz images with 40 nm resolution. In collaboration with Infineon Technologies AG (Jesper Wittborn, München) he applied the new microscopy technique to characterize state-of-the-art transistors of the 65 nm-technology that before had been inspected with a transmission electron microscope (TEM). Comparing THz and TEM images of the transistors, the researchers could demonstrate that all major parts of the transistor (source, drain and gate) can be seen in the THz image. Strikingly, the THz images reveal mobile carrier concentrations around 1018cm-3 (that is one mobile carrier for each 100,000 Si atoms) which are essential for functional transistor devices. Mobile carriers are a central key for the practical transistor functionality but unfortunately they are not directly visible in TEM.
Hitherto, no powerful metrology tools are available allowing for simultaneous and quantitative mapping of both materials and carrier concentrations with nanoscale resolution. Therefore, the added values of seeing and even quantifying conducting carriers opens an enormous application potential for the THz near-field microscope. In fundamental physics research of conducting materials, the non-contact, non-invasive and quantitative mapping of mobile carriers with nanoscale resolution should trigger crucial insights into open scientific questions from the areas of superconductors, low-dimensional conductors, and correlated conductors. "After 40 years of THz research in three Max-Planck-Institutes I am now looking forward to THz nanoscopy solving basic conduction puzzles such as superconductivity" says Fritz Keilmann. THz nanosopy could be furthermore an interesting tool for chemical and structural analysis of compounds and biological systems, as THz radiation is also highly sensitive to vibrations of crystal lattices and molecules. "Future improvements of our technique could allow for THz characterization of even single nanocrystals, biomolecules or electrons" says Rainer Hillenbrand, leader of the Nano-Photonics Group at MPIB and the Nanooptics Laboratory at the newly established nanoGUNE research center (San Sebastian, Spain).
The demonstrated achievement is the direct outcome of a research plan subsidized since 2003 within a Nanofutur grant of the German Federal Ministry of Education and Research endowed to Rainer Hillenbrand. The plan had already anticipated a start-up company which indeed was founded in 2007 (Neaspec GmbH).
Eva-Maria Diehl | Max-Planck-Gesellschaft
Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory
SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences