Current-sensing scanning near-field optical microscopy using a metal probe for nanometre-scale observation of electrochromic films.

A novel technique for scanning near-field optical microscopy capable of point-contact current-sensing was developed in order to investigate the nanometre-scale optical and electrical properties of electrochromic materials. An apertureless bent-metal probe was fabricated in order to detect optical and current signals at a local point on the electrochromic films. The near-field optical properties could be observed using the local field enhancement effect generated at the edge of the metal probe under p-polarized laser illumination. With regard to electrical properties, current signal could be detected with the metal probe connected to a high-sensitive current amplifier. Using the current-sensing scanning near-field optical microscopy, the surface topography, optical and current images of coloured WO3 thin films were observed simultaneously. Furthermore, nanometre-scale electrochromic modification of local bleaching could be performed using the current-sensing scanning near-field optical microscopy. The current-sensing scanning near-field optical microscopy has potential use in various fields of nanometre-scale optoelectronics.