Research On The Preparation Of Al-Doped HfO₂ Ferroelectric Films And Its Resistive Properties

Among the new generation of memory devices,ferroelectric heterostructures memristor has received wide attention owing to their fast operation,simple device structure,low power consumption,and nondestructive readout.As the functional layer of memristor,the electrical properties of ferroelectric thin film materials are directly related to their suitability for the preparation of related devices.Among many ferroelectric materials,HfO₂ is favored by researchers for its compatibility with complementary metal oxide semiconductor processes,harmless chemical composition,simple lattice structure,and excellent ferroelectricity down to 10 nm thickness.The optimization of process parameters to prepare ferroelectric layers suitable for ferroelectric memristor can strongly promote the development of memory-resistive devices.In this paper,the Al-doped HfO₂ ferroelectric films are adpoted to investigate the effects of oxygen vacancies,doping concentration,annealing temperature and other factors on their ferroelectric properties,which is further combined with MoS₂ layer to form a heterojunction,thus improving the device resistive switching performance.The main contents are as follows:（1）The mechanism of oxygen vacancy-induced structural transformation to ferroelectric phase and the promotion of oxygen vacancy formation by Al doping were investigated by density flooding theory calculations.The Al-doped HfO₂ ferroelectric thin films were prepared by atomic layer deposition technique to study the variation in electrical properties under conditions of different doping concentration,annealing temperature,annealing time and thickness.It was found that the films had the maximum remanent polarization value 2Pr = 32.35 μC/cm2 for the preparation process of 1:19 doping concentration,950 ℃ annealing temperature and60 s annealing time,and there was a linear relationship between the doping concentration and the optimum annealing temperature.In addition,the results show that decreasing the annealing time to 30 s can appropriately increase the leakage current and reduce the polarization reversal voltage from 7 V to about 4 V,which is more suitable for the preparation of resistive memory devices.（2）Based on the results of the study on the effect of the preparation process of Al-doped HfO₂ ferroelectric thin films on their electrical properties,the ferroelectric functional layers were prepared.The formation of MoS₂/Al:HfO₂ heterojunction by magnetron sputtering improves the resistive transformation window of the whole structure from about 10 to more than 1000,which is more than 100 times higher.Moreover,by adjusting the positive or negative polarization voltage,multi-stage adjustment of the resistive state is realized,and the switching ratio can be varied in the range of 6 to above 1000,which demonstrates the potential of this heterojunction for resistive memory applications.