Scanning near-field optical microscopy investigations on local optical switching of self-organized photochromic nanostructures

UHV-deposited ultrathin films of photochromic fulgides are prepared which exhibit intrinsic nanostructures of controllable size and are stable at room temperature. Interconversion between the two fulgide forms, the colorless E-isomer and the colored C-isomer, can be achieved optically by irradiation with UV or visible light, respectively. Local absorption detection of the isomeric states is realized via scanning near-field optical microscopy (SNOM). The optical image-contrast measured in SNOM corresponds to the nanostructure topography observed in atomic force microscopy and scales with the material volume. Such nanostructured photochromic films are candidates for application in rewritable optical recording, promising high storage capacity.