【作者】 董清臣；

【导师】 张伟风；

【作者基本信息】 河南大学 ， 凝聚态物理， 2011， 硕士

【摘要】 2000年,美国休斯顿大学的科学家S. Q. Liu等人发现电脉冲触发可逆电阻转变效应,他们并提出RRAM(resistance random access memory)概念,同时发现RRAM还具有高响应速度、尺寸伸缩性强、多位存储、结构简单等优点。从此, RRAM的研究已成为材料学物理学、电子器件的领域研究热点。人们在机理研究、材料探索、以及器件研制等方面都取得了长足进展。RRAM可能成为通用存储器,但是性能指标有待进一步优化。由于RRAM是一种全新的存储技术,目前,电阻开关效应真正的机制存在争议,由于机制的不明确束缚了阻变存储器的在应用中的步伐。电阻转变过程中元素的变化、部位的确认以及电阻转变的重复性问题,是当前RRAM研究所面临的紧要问题;同时,寻找性能、制备都满足要求的材料仍是RRAM发展的关键。作为候选电阻式随机存取存储器的材料主要有:具有简单结构的二元氧化物、具有复杂成分的钙钛矿型的多元氧化物、有机化合物。其中最具潜力的当属二元过渡金属氧化物半导体材料,研究的热点主要有:二氧化钛、氧化锌、氧化镍、二氧化锆、氧化铜、氧化铈等。它的存储单元具有简单的类似电容的三明治结构,由两边的金属电极和中间的绝缘或半导体材料构成。这种电阻开关现象表现出了极为迅速的开关速度和巨大的开关比,具有重大的科学研究价值与意义和广阔的应用开发前景。氧化锌(ZnO)是直接带隙宽禁带化合物半导体材料,其禁带宽度为3. 37 eV,在室温下拥有60 meV的激子束缚能,具有高的热稳定性和卓越的光学性质。最近的研究发现,过渡金属掺杂的ZnO可减小本征载流子浓度并产生深能级,例如Mn掺杂ZnO,在室温下高阻态阻值变大,从而有助于增大RRAM器件的开关比。ZnO中进行Cu掺杂不仅可用于调控薄膜电阻,并使其呈现p型导电, ZnO:Cu还是典型的室温稀磁性半导体,作为多功能材料在应用方面很有前景。据我们所知,目前尚无ZnO:Cu阻变活性材料的报道。因此,本文选用ZnO:Cu薄膜作为阻变材料。1.本文采用纯度为99. 99%的ZnO、纯度为99. 9%的CuO和18. 2 MΩ的去离子水与聚乙烯醇配置的稀粘合剂溶剂作为原料制作ZnO:CuO陶瓷靶材。根据ZnO、CuO混合摩尔比分别为1 : 99, 5 : 95, 9 : 91,用天平称取一定量的ZnO、CuO粉末,经过多个步骤,这样我制备了ZnO、CuO摩尔比为1:99,5:97,9:91的ZnO: Cu陶瓷靶材。2.采用脉冲激光沉积(PLD)技术在Si、石英,铂金衬底上沉积ZnO及ZnO: Cu薄膜,并利用X射线衍射(XRD)、光致发光(PL)、拉曼谱、X射线光电子能谱(简称XPS)、原子力显微镜(AFM)等表征手段对制备出的样品进行表征。结果表明采用激光技术制备出ZnO:Cu薄膜结晶较好。为以后基于ZnO及ZnO:Cu的器件的制备和应用打下了基础。3.利用脉冲激光技术利用脉冲激光沉积(PLD)技术在FTO导电玻璃和铂金衬底上成功制备了ZnO: Cu薄膜,利用Keithley2400对Au/ ZnO: Cu/ FTO和Au/ ZnO: Cu/ Pt/Ti/SiO2/Si三明治结构的电学特性进行了研究,观测到明显的电阻开关效应的I-V特征曲线。讨论了可能的导电机制更多还原

【Abstract】 In 2000, scientists S. Q. Liu et al at the University of Houston found the reversible resistance switching effect induced by electrical impulses. They proposed the concept of RRAM (Resistance Random Access Memory). They also found RRAM with the high response speed, size strong scalability, a number of storage, simple structure. Since then, study of materials science and electronics device focus on RRAM field. People have made great progresses in the mechanism of the resistance switching, and the materal exporation and the development of resistance switching devices. RRAM devices may become a brand-new memory device, but performance indicators need be further optimized. RRAM possiblely become a new storage technology, but the real mechanism of resistance switching effect is controversial currently. Since the mechanism is not clear, the resistance-switching memory device is not put in use. The elements of chemical changes, the positions of the resistance change and the repeatability in the rensitance switching aren’t known ,this is the current critical issues of the RRAM device facing. Meanwhile, the performance of materals, the preparation of materals to meet the requirements is still the key to the development of RRAM devices.The candidate materials of the resistance random access memory are binary oxides with a simple structure, multiple perovskite oxides with complex composition, organic compounds. Undoubtedly the semiconductor materials of binary transition metal oxide are the most potential materals. The main researche topics focus on titanium dioxide, zinc oxide, nickel oxide, zirconia, copper oxide, cerim oxide and so on. The unit of storages is similar to the simple sandwich structure of capacitors that the metal electrode is in the both sides of the insulating or semiconduct material. This resistance switching phenomena exhibit very rapid switching speeds and huge off ratioes, this is of great scientific value and significance and broad prospects for the application development of the RRAM.Zinc oxide (ZnO) is semiconductor materials of wide band gap compound with a direct band gap, which is 3. 37 eV band gap . The exciton binding energy is 60 meV with the high thermal stability . ZnO have excellent optical properties at room temperature. Recent studies have found that ZnO doped by transition metals can reduce the intrinsic carrier concentration and produce deep level. For example, the resisstance of the high resistance state of Mn-doped ZnO become larger at room temperature than ZnO, thus helping to increase the ratio of the high resistance and low resistance. The Cu-doped ZnO can be used to control not only the thin film resistors, but also it showed p-type conductivity. Cu-doped ZnO materal is a classic diluted magnetic semiconductor at room temperature and a promising multi-functional material in applications. As far as we know, no paper of ZnO: Cu resistance switching has been reported recently . Therefore the ZnO: Cu film had been selected as the resistance switching materials in my study.1. 20 gram of ZnO and CuO powder was weighed with the balance according to molar ratios of 1 to 99, 5 to 95, and 9 to 91 respectively. After several steps, so I prepared three Cu-doped ZnO ceramic targets finally.2. By the pulsed laser deposition (PLD) ZnO and ZnO: Cu films were deposited on the Si, quartz, platinum substrate . by the X-ray diffraction(XRD), the photoluminescence(PL), the Raman spectroscopy(Raman), the X-ray photoelectron spectroscopy (XPS), the atomic force microscope (AFM), the samples prepared were characterized. The results show that the thin films crystallized perfectly by the pulsed laser deposition (PLD) technology.3. The ZnO: Cu films were successfully prepared by the pulsed laser deposition technique on FTO conducting glasses and Pt/SiO2/Si substrates. By the Keithley 2400, the electrical characteristics of the Au / ZnO: Cu / FTO sandwich structure were studied. Significant effects of the resistance switching characteristic were observed and possible conduction mechanisms were discussed.更多还原