Investigation of few-atoms-thick films by time-resolved high resolution optical microscopy

Thin films science and technology plays an important role in the high-tech industry. The quest for development of smaller and smaller devices requires advanced materials and new processing techniques. Thus, determination of the nature, functions and new properties of thin films can be used to develop new technologies for future applications. The aim of this project is to use high resolution optical imaging techniques to provide a new probe to characterize and measure the physical and optical properties of few-atoms-thick films. Recently, imaging capabilities beyond the diffraction limit has been demonstrated using the light focusing properties of transparent microspheres, providing sub-100-nm-resolution with visible light illumination. The microsphere-assisted optical imaging enhances the spatial resolution of traditional optical systems, allowing to image sub-wavelength structures. Since lateral super-resolution exploit the evanescent waves present on the sample-microsphere interface, a high sensitivity to thickness inhomogeneity is also expected, i.e. a high longitudinal resolution. A microsphere-assisted microscope will be merged with a time-resolved reflectivity/transmissivity apparatus, implemented through the ASynchronous OPtical Sampling (ASOPS) technique. ASOPS allows high-speed pump-probe scanning over a nanosecond time window without a delay line. This set-up will generate transient reflectivity/transmissivity maps with high longitudinal resolution. The degree of adhesion of the thin films to the substrate, their thermomechanics and spatial uniformity will be investigated and characterized. Novel dynamic Atomic Force Microscopy (AFM) techniques will complement the nanoscale investigation of the thin films. Finally, it will be important to develop models for the data interpretation, also in view of the great deal of spectroscopic information that is potentially available in each pixel of an image. In this respect, automated analysis techniques will be considered.