光电协同调控下HfO_(x)基阻变存储器的阻变特性

Resistive switching characteristics of HfO_(x)-based resistance random access memory under photoelectric synergistic regulation

利用磁控溅射法制备了Cu/HfO_(x)/Pt和Cu/HfO_(x)-ZnO/Pt器件.HfO_(x)器件和HfO_(x)-ZnO器件都表现出双极性阻变特性以及具有良好的保持性,但HfO_(x)-ZnO器件具有更加优异的阻变性能,例如均一性、耐受性和重复性.研究表明,通过增加ZnO富氧层有利于提高器件的阻变性能.另外,HfO_(x)薄膜的禁带宽度约为5.10 eV,对255 nm波长的光照没有响应.而HfO_(x)-ZnO薄膜的禁带宽度减小为4.31 eV,该器件在波长255 nm的光照作用下,不仅可以提高器件的阻变性能,还可以通过设置不同强度的光照使器件具有多级存储的能力.研究发现,器件在有无光照作用下的阻变行为都与薄膜中的氧空位有关,所以本文提出了氧空位导电细丝物理模型来解释器件的阻变行为.本文使用光电协同的方法为研制出低功耗、高存储密度的阻变存储器提供了新思路.

Cu/HfO_(x)/Pt and Cu/HfO_(x)-ZnO/Pt resistance random access memory(RRAM)devices are prepared by magnetron sputtering.The results show that the Cu/HfO_(x)/Pt device has the stable bipolar resistive switching characteristics,good retention(as long as 104 s),and a switching ratio greater than 103.The current conduction mechanism of HfO_(x)device is ohmic conduction at low resistance,while space charge limited current(SCLC)mechanism dominates at high resistance,and the conductive filament is composed of oxygen vacancies.Owing to the low content and random distribution of oxygen defects in the HfO_(x)film,the endurance and uniformity of the device are poor.Compared with HfO_(x)device,HfO_(x)-ZnO device exhibits lower operating voltage and better uniformity and stability.The main reason is that ZnO material has smaller formation energy of oxygen vacancy,which can produce more oxygen defects under electric field to participate in the resistive switching behavior of the device,thereby reducing the operating voltage and improving the uniformity of the device.In addition,owing to the existence of the interface between HfO_(x)and ZnO film,the random distribution of oxygen defects is inhibited,that is,the random fracture and formation of conductive filament are inhibited,which is beneficial to improving the uniformity of the device.In addition,the resistive switching behaviors of Cu/HfO_(x)/Pt and Cu/HfO_(x)-ZnO/Pt RRAM devices under different intensities of 255 nm ultraviolet illumination are studied.For Cu/HfO_(x)/Pt device,the light of 255 nm wavelength shows little effect on its resistive switching characteristics.For the Cu/HfO_(x)-ZnO/Pt RRAM device,the operating voltage and stability of the device can be improved by increasing the light intensity.Although the switching ratio of the device decreases with the increase of light intensity,the device can exhibit multiple resistance states by adjusting different light intensities to achieve multi-level storage.Finally,the analysis of the I-V curves of the devices indicates that the two types of devices show similar resistive switching mechanisms under the illumination of light or no light,which can be explained by the resistive switching mechanism of oxygen vacancy conductive filament.Therefore,a physical model based on the oxygen vacancy conductive filament is established to explain the resistive switching behavior of the device in this paper.