Sensitive mapping of liquid dielectric topography and thickness variation A technique that induces and maps tiny topographical changes in thin liquid dielectric films could have applications in interfacial science and industry. Shimon Rubin, Brandon Hong and Yeshaiahu Fainman of the University of California, San Diego used a heating laser to induce thermocapillary flows in thin liquid dielectric films. These films are used, among various things, for UV photolithography of semiconductors and microelectronics applications. The team mapped the changes caused by the flows using surface plasmon resonance microscopy, a non-contact imaging method that measures changes of the collective oscillations of surface electromagnetic waves and electrons in the metal substrate. The technique successfully identified subnanometer-scale topographical changes caused by the thermocapillary flow. It overcomes problems in currently used techniques, such as white light interferometry, which is not sensitive enough to detect small, local thickness variations. The technique has many potential applications, including the study of light-induced thickness changes in photosensitive materials.