Improved ferroelectric properties of CMOS back-end-of-line compatible Hf_(0.5)Zr_(0.5)O_(2)thin films by introducing dielectric layers

Hf_(0.5)Zr_(0.5)O_(2)(HZO)ferroelectric thin films have gained significant attention for the development of next-generation ferroelectric memories by complementary-metal-oxide semiconductor(CMOS)back-end-of-line(BEOL)processing,due to their relatively low crystallization temperature.However,it remains challenging to achieve excellent ferroelectric properties with post deposition annealing(PDA)process at a BEOL compatible temperature.Along these lines,in this work,it is demonstrated that the ferroelec-tricity of 15 nm thick HZO thin film prepared by PDA process at 400℃can be improved to varying degrees,via depositing 2 nm thick dielectric layers of Al_(2)O_(3),HfO_(2),or ZrO_(2)at either the bottom or the top of the film.Notably,the HZO thin film with the top-Al_(2)O_(3)layer exhibits remarkable ferroelectric prop-erties,which are independent of the thickness of HZO.The 6 nm thick HZO thin film shows a total remanent polarization(2Pr)of 31 mC/cm^(2)under an operating voltage of 2.5 V.These results represent a significant advancement in the fabrication of high-performance,BEOL compatible ferroelectric mem-ories,as compared to previously reported state-of-the-art works.

Approaching 19%efficiency and stable binary polymer solar cells enabled by a solidification strategy of solvent additive

Additives play a crucial role in enhancing the photovoltaic performance of polymer solar cells(PSCs).However,the typical additives used to optimize blend morphology of PSCs are still high boiling-point solvents,while their trace residues may reduce device stability.Herein,an effective strategy of“solidification of solvent additive(SSA)”has been developed to convert additive from liquid to solid,by introducing a covalent bond into low-cost solvent diphenyl sulfide(DPS)to synthesize solid dibenzothiophene(DBT)in one-step,which achieves optimized morphology thus promoting efficiency and device stability.Owing to the fine planarity and volatilization of DBT,the DBT-processed films achieve ordered molecular crystallinity and suitable phase separation compared to the additive-free or DPS-treated ones.Importantly,the DBT-processed device also possesses improved light absorption,enhanced charge transport,and thus a champion efficiency of 17.9%is achieved in the PM6:Y6-based PSCs with an excellent additive component tolerance,reproducibility,and stability.Additionally,the DBT-processed PM6:L8-BO-based PSCs are further fabricated to study the universality of SSA strategy,offering an impressive efficiency approaching19%as one of the highest values in binary PSCs.In conclusion,this article developed a promising strategy named SSA to boost efficiency and improve stability of PSCs.