High-resolution space charge distribution in micro-scale dielectric films

Space charge, as an intrusive microscopic parameter of dielectric, dictates the energy storage performance and its insulation deterioration in a wide range of servicing environments. However, the distribution of space charge within micron-scale dielectric films and the underlying interface problem are obscured by the limited resolution of existing measurement methods. Picosecond laser induced pressure-wave propagation (LIPP) technology is employed to measure the space charge of dielectric films (down to 3.8 μm) with spatial resolution of 200 nm. By decreasing the metal-dielectric potential barrier and increasing the metal coverage, the symmetric charge distribution in 5.8 μm biaxially oriented polypropylene (BOPP) promotes the electric field uniformity, moving the peak electric field from vicinity of metal-dielectric interface to the middle of film. The injection of space charge is in excellent accordance with the band gap measured by ultraviolet spectrum and energy level splitting simulated by density functional theory. Bridging the metal-dielectric interface and space charge distribution, this work provides fundamental understanding of universal interface problem and guides exploration of robust dielectrics for universal environment service. Space charge influences significantly the energy storage and insulation of dielectric materials, yet its distribution in micron-scale films remains poorly understood due to measurement limitations. Here, the authors utilize picosecond laser induced pressure-wave propagation technology to achieve high-resolution mapping, revealing insights into charge distribution and guiding the development of robust dielectrics for diverse applications.