Spectromicroscopy and chemical imaging applied to the study of photocathode materials and devices

We applied different and complementary techniques to study the surface and interface local properties of materials (such as cesium iodide) and devices that are used for photodetection. These techniques, based on the photoexcitation of electrons, allowed us to correlate the local chemical and morphological properties of materials with their quantum efficiency: a crucial step for the optimization of large area photodetectors. We also present some experimental results achieved by a novel spectroscopic technique: local phototransport measurements by Scanning Near-Field Optical Microscopy (SNOM). This technique is able to overcome the diffraction limit for the lateral resolution and to supply information on the local photoconductivity as well as on the local properties of buried interfaces with a spatial resolution better than 50 nm. Both types of information are important for the study of devices used for a spatially resolved photodetection.