A scanning apertureless near-field optical microscope as an instrument for characterizing the optical properties of a surface with nanometer spatial resolution
The operating principles of an apertureless scanning near-field optical microscope (ASNOM) are described. The metalized needle of an atomic force microscope is a probe in the device, and the optical interaction with objects on the surface is localized near its tip, which is a few nanometers in size. The needle’s body is several microns long, ensuring high efficiency of its electromagnetic interaction with the light waves incident on it from the outside and emitted by it into space. The nano-antenna formed by the needle thus raises the efficiency of the optical interaction between nano-objects and the electromagnetic ether by 4–5 orders of magnitude. Results from scanning semiconductor and polymer structures are presented that demonstrate the ability of ASNOM to produce high-contrast images of objects’ optical properties (absorption, reflection, and thermal expansion) with resolutions of 10–50 nm, regardless of wavelength.