The study of nanophotonics helps develop and advance tools such as optical tweezers and nanoscale photocatalysts that can ultimately lead to new discoveries and achievements in nanotechnology. The extremely precise measurements needed to understand how optical forces interact with nanoscopic particles can be difficult to attain, making increasingly sensitive tools and techniques especially important in this field of study. A team led by scientists from Osaka University, Osaka Prefecture University and Nagoya University have optimized the method of photoinduced force microscopy (PiFM) to create a 3D force field map of nanoparticles in unprecedented subnanometer resolution.
PiFM uses an atomic force microscopy (AFM) cantilever and a tunable laser is used to irradiate the sample. The optical gradient force between the probe tip and the sample is measured to create a 3D map of the optical near-field. The researchers in this study used heterodyne frequency modulation (heterodyne-FM) under ultra-high vacuum (UHV) conditions to improve the thermal stability of the measurements, and the result was a 3D force field visualization with a spatial resolution of about 0.7 nm. The study was published in Nature Communications.
“We reduced the photothermal effect with this unique technology and achieved a resolution of less than one nanometer for the first time ever,” said Yasuhiro Sugawara, senior author of the study.
The research demonstrates the value of using heterodyne-FM techniques and UHV conditions with PiFM and could be applied by scientists designing and evaluating nanomaterials or working with photocatalysts and optical functional devices.
Photo: (a) A schematic image of photoinduced force microscopy. (b) Photoinduced force microscopy image of a quantum dot. Credit: Osaka University