WO3外延薄膜制备与阻变特性研究

RESEARCH ON FABRICATION AND RESISTIVE SWITCHING BEHAVIORS OF WO3 EPITAXIAL THIN FILMS

郭沫含

11849399

硕士

物理学

陈朗

2020-05-28

2020-07-08

哈尔滨工业大学

深圳

随着信息化社会的不断发展，各界对于非易失性存储器有了更高的需求。在非易失存储器中，铁电存储器、相变存储器和磁阻存储器因其结构与应用上的问题限制了其发展。其中，阻变存储器因读写速度快、存储密度高等优势成为非易失性存储器领域翘楚之一。而阻变材料则为阻变存储器工作的基础。作为一种具有A位缺失型钙钛矿结构的二元过渡金属氧化物，WO3被视为一种具有良好应用潜力的阻变材料。因此，优化WO3薄膜制备流程、挖掘WO3器件阻变特性，对于丰富和完善阻变材料体系具有重要意义。本文从WO3制备出发，生长出具有外延结构的WO3薄膜，并对其阻变特性进行测试。利用脉冲激光沉积技术，在LAO基底上生长WO3薄膜，通过调节生长参数，研究温度与氧压对WO3结构与形貌的影响。通过原子力显微镜检测，其表面生长质量随温度和氧压的升高均呈倒V型变化，600 ℃和13 Pa分别为其温度和氧压拐点，此条件下均方根粗糙度仅为357.68 pm，并有较为明显的台阶。经X射线衍射技术表征，其(100)、(200)特征峰位明显，且衍射曲线有明显震荡，结晶性良好。选择与WO3晶格常数接近的Ca0.96Ce0.04MnO3(CCMO)作为底电极，Pt金属作为顶电极，设计具有三明治结构的LAO/CCMO/WO3/Pt阻变器件。通过分析倒易空间图谱，WO3与CCMO、LAO的Qx值高度重合，外延性优异。利用半导体测试仪，对LAO/CCMO/WO3/Pt器件施加循环电压以模拟擦写过程，研究WO3的厚度与氧压对其阻变特性的影响。随着WO3厚度增大，开关比呈上升趋势，在WO3为125 nm时达峰值25。抗疲劳性随厚度增加呈倒V型变化趋势，在WO3为100 nm状态下抗疲劳性能最佳。随着生长氧压升高，其I-V曲线向上移动趋势显著，电阻值明显降低。同时，开关特性增强，抗疲劳性先增强后减弱。然而，厚度和氧压的改变对WO3外延器件的保持特性几乎无影响。在10000 s的检测时间内，各组器件阻值均无明显波动。对WO3外延器件的I-V曲线取对数后进行拟合分析，在0 V - 20 V、2 V - 0 V的扫描过程中欧姆效应为主要导电机制，而在20 V - 2 V扫描过程中空间电荷限制电流效应(SCLC)占据主导作用。

With the development of information-based society, people have much higher demands of non-volatile memory. Because of the shortcomings of structure, ferroelectric random access memory, phase change random access memory and magnetoresistive random access memory were limited in practical use. However, the resistive random access memory has become the most potential memory in the field of non-volatile memory due to its advantages of fast read-write speed and high storage density. As one kind of binary transition metal oxide, WO3 has great application potential in the field of resistive switching materials due to its unique A-site deletion perovskite structure. Therefore, it is of great significance to optimize WO3 thin film fabrication process and explore the resistive switching behaviors of WO3 devices to enrich and improve the resistive switching materials system. In this paper, we will research the fabrication and the resistive switching behaviors of the epitaxial WO3 thin films.We fabricated WO3 thin films on LAO wafer using pulsed laser deposition, and researched the influence of temperature and oxygen pressure to WO3 thin films’ structure and morphology by adjusting the growth parameters. After detected by atomic force microscope, we found that the surface quality shown a V shape with the increase of temperature and oxygen pressure. The inflection point of temperature and oxygen were 600 ℃ and 13 Pa respectively. And in this situation, the root mean square roughness of WO3 was just 357.68 pm, and the step could be clearly observed on its surface. After defected by X ray diffraction, (100) and (200) characteristic peaks were evident, we could analysis WO3 has good crystallinity due to the oscillation on X ray diffraction curve. We selected Ca0.96Ce0.04MnO3(CCMO) as bottom electrode, and Pt as top electrode, to form the sandwich structure LAO/CCMO/WO3/Pt devices. After analyzing the reciprocal space atlas, the Qx of WO3 was coincident with CCMO and LAO, therefore the epitaxial of WO3 was distinguished.We applied circulating voltage on LAO/CCMO/WO3/Pt devices using semiconductor tester, in order that investigating the influence of thickness and oxygen pressure to the resistive switching behaviors of WO3. The On/Off rate had an upward trend with the increase of WO3 thin films’ thickness. When the thickness was 125 nm, WO3 got highest On/Off rate of 25. The anti-fatigue performance had an Invert-V trend with the increase of thickness, and got best performance when the thickness of WO3 was 100 nm. With the increase of oxygen pressure, the I-V curve had an obvious trend to move upward, therefore the resistance decreased. Meanwhile the On/Off rate increased, the anti-fatigue performance strengthened then weakened. However, thickness and oxygen pressure had little influence to the retention performance of WO3. During the 10000 seconds periods, the resistance of devices had no obvious fluctuations. After fitting analyzed of I-V curves of devices, we could found that during the 0 V - 20 V and 2 V - 0 V process, Ohm effect was the major conducting mechanism. And during 20 V - 2 V process, the space charge limited was the major conducting mechanism.

WO3 外延薄膜 脉冲激光沉积 阻变特性 空间电荷限阈效应

WO3 epitaxial thin films PLD resistive switching behaviors SCLC

中文

联合培养

南方科技大学

郭沫含. WO3外延薄膜制备与阻变特性研究[D]. 深圳. 哈尔滨工业大学,2020.