Contrast and resolution enhancement of a near-field optical microscope by using a modulation technique

A new design of a tunneling near-field optical microscope (TNOM) combined with an atomic force microscope (AFM) is presented. This design can be used to generate three different images of the sampleʹs surface: a non-contact (tapping mode) AFM image, a conventional TNOM and an image of a modulation signal of the conventional TNOM, which we call AC-TNOM. The images are obtained simultaneously, using a single light source. It is shown that the AC-TNOM has better resolution (∼200 Å) and contrast compared to conventional TNOM (∼400 Å).