氧化镍外延薄膜的变温电阻开关特性和隧穿机制研究

发布时间：2018-01-25 16:20

本文关键词： 外延NiO_x薄膜变温电阻开关特性隧穿机制　出处：《西南大学》2017年硕士论文　论文类型：学位论文

【摘要】：氧化物薄膜电阻开关存储器(ReRAM)具有快速的读/写速度(~10 ns)、优异的耐受性(106次读/写次数)和超长的存储稳定性(~10年)等优点,而且结构简单,功耗低(~几十pJ),并兼容当前硅基半导体集成工艺,是现今最具应用潜力的新一代非易失性存储器之一。基于NiOx薄膜的ReRAM是迄今研究最深入的材料体系之一,然而,以往研究者多关注NiOx多晶薄膜的电阻开关特性,对Ni Ox外延薄膜,特别是金属基底上外延生长NiOx薄膜的研究相对甚少。此外,随着人类活动范围的延伸和现代科技的飞速发展,极端环境条件下ReRAM器件的稳定性研究也提上了日程。本文主要研究金属种子层上外延生长NiOx的薄膜电阻开关效应对温度的依赖性。首先利用射频磁控溅射方法沉积制备了富氧NiOx多晶(poly-NiOx)薄膜,研究了其电阻开关特性随测试温度的变化。Ag/poly-NiOx/Pt存储单元的电流-电压测试曲线呈现阈值型电阻开关特性:分别在2.1到2.4 V的正偏压范围和-2到-2.2 V的负偏压范围内观测到了高/低电阻态之间的稳定可逆跳变。随着测试温度的升高,负偏压范围的电阻开关现象在140℃基本消失,而正偏压范围内的电阻开关现象可维持到270℃。运用指数定律拟合室温下电流-电压曲线结果表明,薄膜隧穿电流属于缺陷主导的空间限制电流;运用Arrhenius作图法拟合的电流-温度曲线满足线性关系,表明薄膜隧穿电流随测试温度的变化符合肖特基热激发隧穿机制。在周期性电场作用下,从银电极扩散进入薄膜中的Ag离子在薄膜中的氧化还原反应导致存储单元呈现阈值型电阻开关特性。接下来,以MgO(100)基底上最优化制备条件下沉积制备的Pt(100)薄膜为外延种子层,沉积获得高取向的NiO(111)外延薄膜(epi-Ni Ox),三角锥形晶粒形成平整致密的膜面。Ag/epi-NiO(111)/Pt(100)存储单元的电流-电压曲线呈现出典型的双极性电阻开关特性:在160个稳定循环中,置/复位电压分别稳定在0.75和-0.9V;在-0.5V读取电压下,高/低电阻比大于5。指数定律拟合电压-电流曲线结果表明,薄膜隧穿电流机制符合缺陷主导的空间限制电流效应。随着测试温度的升高,其电阻开关现象可维持到80℃。运用Arrhenius作图法以及肖特基隧穿机制拟合高阻态电流-温度曲线满足线性关系,这表明高阻态漏电流随测试温度的变化符合肖特基热激发隧穿机制。在优化条件下,我们在Pt(100)种子层上沉积制备获得了膜面平整但嵌套纳米微孔的Ni O(100)外延薄膜。X射线Phi扫描和透射电镜测试结果证明epi-NiOx(100)与Pt(100)种子层满足“立方-立方”外延生长关系。Ag/epi-NiO(100)/Pt(100)存储单元呈现出优良的双极性电阻开关特性:在-0.4V读取电压下,高/低电阻比大于20,在连续测量的5000个稳定循环周期中置/复位电压一直稳定在0.6和-0.6V。其电阻开关特性在80℃测试温度下仍保持最优性能,可耐受130℃高温仍维持明显的电阻开关特性。低阻态电流-温度曲线的Arrhenius和肖特基隧穿机制拟合曲线符合线性拟合关系,这再次表明漏电流随测试温度的变化符合肖特基热激发隧穿机制。由于epi-NiOx薄膜为垂直上下电极的柱状晶粒结构,在周期性电场作用下,银上电极中的Ag离子沿着晶界扩散进入薄膜内部与薄膜中的电子发生氧化还原反应形成周期性导通/截断的导电桥通道,从而导致Ag/epi-NiOx/Pt存储单元呈现出比poly-NiOx薄膜更稳定,翻转电压大幅降低的双极性电阻开关特性,该存储单元有望应用于高温环境工作的新一代电阻开关存储器件。
[Abstract]:Oxide thin film resistive switching memory (ReRAM) with fast read / write speed (~10 NS), excellent tolerability (106 read / write cycles) and long storage stability (~10) etc., and has the advantages of simple structure, low power consumption (~ tens of pJ), and is compatible with current silicon based semiconductor integrated technology that is the most promising new generation of non-volatile memory. One of the NiOx film based on ReRAM is one of the most in-depth study materials so far however, researchers pay more attention to the resistance switching characteristics of NiOx polycrystalline thin films of Ni, Ox epitaxial thin film on metal substrate, especially the study on the growth of NiOx the thin film epitaxy is relatively little. In addition, with the rapid development of extending the range of human activities and the modern science and technology, under extreme environmental conditions on the stability of ReRAM devices is also on the agenda. This paper mainly studies the metal seed layer epitaxial growth of NiOx thin film resistor The temperature dependence of the switching effect. First using radio frequency magnetron sputtering deposition of enriched oxygen to prepare NiOx polycrystalline thin film (poly-NiOx), the current change of.Ag/poly-NiOx/Pt storage unit the resistance switching characteristics with the test temperature of the test curve of voltage threshold electric resistance switching characteristics show: at the negative bias range of positive bias range 2.1 2.4 V and -2 to -2.2 V observed in high / low resistance state between the stable reversible jump. With the increase of temperature, the resistance switching phenomenon of negative bias range disappeared at 140 degrees, while the resistance switching phenomenon of positive bias range can be maintained at 270 degrees. The voltage curve results the current law of exponential fitting at room temperature show that the film tunneling current limiting current defect belongs to the space leading; current temperature curves using Arrhenius mapping method fitting the linear relationship, show that the film tunnel The current change with the test temperature with Schottky Ge excitation tunneling mechanism. In the periodic electric field, from the silver electrode into the Ag ion diffusion oxidation in the films in the film reaction leads to storage unit threshold type resistive switching characteristics. Then, the MgO (100) substrate prepared by deposition of Pt optimization under the condition of (100) thin film epitaxial seed layer deposited high oriented NiO epitaxial thin film (111) (epi-Ni Ox), triangular conical grain forming dense membrane surface.Ag/epi-NiO (111) /Pt (100) current voltage curve storage unit showing bipolar resistive switching characteristics in 160 typical: a stable cycle, set / reset voltage were stable at 0.75 and -0.9V in -0.5V; read voltage, high / low resistance ratio more than 5. exponential law of voltage current curve fitting results show that the film tunneling current mechanism in line with the defects of leading space Among the current limiting effect. With the increase of temperature, the resistance switching phenomenon can be maintained at 80 degrees centigrade. By using Arrhenius mapping method and temperature curve fitting mechanism in Schottky tunneling high impedance current linear, suggesting that changes in the high impedance state leakage current with the test temperature with Schottky Ge excitation tunneling mechanism. Under the optimized conditions next, we in the Pt (100) seed layer deposited on the membrane surface were obtained but nested Ni O nano microporous (100) epitaxial.X X-ray Phi scanning and transmission electron microscopy results show that epi-NiOx (100) and Pt (100) seed layer to meet the "cubic cubic" epitaxial growth relationship between.Ag/epi-NiO (100 /Pt) (100) storage unit presents bipolar resistance switching characteristics: excellent in -0.4V read voltage, high / low resistance ratio is greater than 20, in the continuous measurement of 5000 stable cycle Center / reset voltage has been stable at 0.6 and -0.6 V. the resistance switching characteristics still maintain optimal performance at 80 DEG C test temperature, can withstand the high temperature of 130 DEG C and still maintain the resistance switching characteristics obviously. The temperature curve of low resistance current Arrhenius and Schottky tunneling mechanism in line with the linear fitting curve fitting relationship, it shows once again that the changes of leakage current with the test temperature with Schottky Ge excitation tunnel wear mechanism. Because the epi-NiOx film is a columnar grain structure under vertical electrode, the periodic electric field, silver electrode in the Ag ion diffusion into the internal electronic thin films along grain boundaries and in the film redox reaction to form Periodic conduction / truncation of the conductive bridge channel, resulting in Ag/epi-NiOx/Pt storage unit showing the film is more stable than poly-NiOx, bipolar resistance switching characteristics of switching voltage substantially reduced, the storage unit can be used in the high temperature environment of the new generation Resistor switch storage device.

【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O484;TM564;TP333

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