Beyond polar dead-layers and leakage in BST-based varactors for NFC and 5G telecommunications – BePolar

Emerging communication technologies like 5G or Near Field Communication call for voltage tunable ferroelectric (FE) film capacitors to work at higher frequencies or lower voltage, thus requiring the reduction of the FE thickness. Unfortunately, two interface-related phenomena, the FE “dead layer” and leakage current, impede this evolution. Recent encouraging ab initio calculations showed the importance of the chemical bonding, polar discontinuity and distortion mismatch at electrode/FE perovskite interfaces for polarization stabilization and Schottky barrier height (SBH) adjustment. A systematic interface engineering using Combinatorial Pulsed Laser Deposition will chemically modulate electrode/(Ba,Sr)TiO3 interfaces of industrial capacitors. Advanced spectroscopy and microscopy methods coupled with first-principles calculations will help to understand the chemical, structural and electronic mechanisms controlling the SBH and FE polarization at the interface. TRL 6 industrial prototype varactors with the optimized interfaces will be tested against 5G and NFC specifications.