Challenges in probing space charge at sub-micrometer scale

An overview of current limitations and challenges with techniques, based either on acoustic or thermal perturbation, providing charge density profiles within insulations, is presented. Even though the resolution could be somewhat improved, technical limitations readily appear, related to the bandwidth of signals to be detected and to the sensitivity. Instead, our purpose here is to exploit near field techniques derived from AFM - Atomic Force Microscopy-. A booming of the availability and versatility of equipments is observed today. A spatial resolution of some tens of nanometers is accessible for charge detection which therefore let's the possibility to investigate selectively regions with specific properties. The measuring conditions and operating mode for both the sensitivity and spatial resolution of the techniques are addressed and examples of application of these techniques to charge detection in insulating materials are presented.