Reflection-mode near-field optical microscope with a metallic probe tip for observing fine structures in semiconductor materials

We have developed a near-field scanning optical microscope with a metallic probe tip without an aperture that can be operated in the reflection mode. This near-field microscope can also be easily operated simultaneously as a scanning tunneling microscope. To prevent the unwanted contribution of specular reflection from contaminating the observed signal, dark-field illumination of the sample surface is employed. The microscope is suitable for characterizing opaque samples such as metals and semiconductor materials. We evaluated its imaging performance by obtaining both the near-field optical and scanning tunneling images of a semiconductor grating with a pitch period finer than the light wavelength.