Challenges during Flash Lamp Annealing of Aerosol‐Deposited Barium Titanate Films

Aerosol‐deposited films display a reduced electromechanical response due to a grain size below 100 nm, deposition‐induced residual stresses, and conductivity due to local defects. Although heat treatment can facilitate grain growth, residual stress relaxation, and defect recombination, it limits the possible applications of aerosol deposition, especially for temperature‐sensitive substrates. Flash lamp annealing is utilized to selectively heat treat aerosol‐deposited barium titanate films with different thicknesses from 2 to 16 μm. Simulations and X‐ray diffraction indicate increasing temperature difference between the film surface and the substrate‐film interface up to 170 °C for the 16 μm‐thick film. While the relative permittivity can be improved by flash lamp annealing from 90 to 150 at 1 kHz and a 6 μm thickness, it still lags behind samples conventionally annealed at 500 °C, as the introduced thermal gradient can lead to surface cracks due to thermal stresses. Preannealing is proposed to reduce surface crack opening displacement compared to flash lamp annealed films. This supports the impact of remanent shrinkage during the first annealing cycle. While apparent challenges associated with the selective annealing of aerosol‐deposited films are discussed, flash lamp annealing remains a promising method for reducing annealing time and utilizing temperature‐sensitive substrates.