碳基阻变存储器导电通道调控及其机理研究

发布时间：2018-02-16 18:15

本文关键词： 阻变式存储器导电通道氧化还原限制电流非晶碳氧化石墨烯　出处：《东北师范大学》2016年博士论文　论文类型：学位论文

【摘要】：传统的浮栅型存储器受限于尺寸无法进一步缩小,为了更好满足未来信息存储需求,目前多种新型存储器件陆续被提出。其中,阻变式存储器(RRAM)以其结构简单、低功耗、读写速度快等优点,被认为非常有前景成为下一代信息存储器。RRAM一般是将固态电介质材料夹在两个电极之间,利用电介质中的导电通道形成和断裂来实现电阻转换。然而,目前RRAM的工作机理尚未十分明确,且器件性能仍需进一步提升。因此对导电通道进行深入研究,包括有效调控导电通道大小,探究导电通道尺寸效应以及控制阻变过程中导电通道通断位置等将有助于进一步理解RRAM并促进其发展。此外,在目前众多电介质材料中,碳基材料被公认为最有可能取代传统硅基材料应用在未来微电子领域中,因此碳基RRAM的研究对未来碳基电子学发展具有重要意义。本论文将在碳基阻变存储器导电通道调控和机理探究等方面开展工作,具体研究内容如下:导电通道尺寸调控:我们采用非晶碳(a-C)作为阻变层,Cu和Pt作为电极,构筑了Cu/a-C/Pt RRAM器件。通过调节限制电流调控了导电通道尺寸,并且观察到了非易失/易失性共存的特性和原子级别尺寸导电通道电导量子化现象。定量研究低阻态弛豫时间与通道尺寸以及温度关系表明:Cu/a-C/Pt RRAM器件易失性是由于小尺寸导电通道自身表面能过大导致的瑞利不稳定性所引起的。傅里叶热稳态方程计算发现随着导电通道尺寸增加其断裂所需焦耳热也增多。器件高阻态随着导电通道尺寸增加而降低可归因于温度导致的a-C亚稳态薄膜中sp2团簇增大。导电通道通断位置调控:针对RRAM导电通道随机形成与断裂导致器件阻变参数波动较大这一问题,这里我们采用恒电流作用方法提高Cu/a-C/Pt器件稳定性。恒电流作用能够有效增大a-C薄膜中sp2团簇尺寸,进而提高薄膜内局域电场,有效控制导电通道转变位置,实现均一的阻变特性;另一方面,我们利用多孔薄膜构筑了一种“forming-free”的RRAM器件。Ag电极蒸镀过程中能够在多纳米孔薄膜中预先形成Ag导电通道。进一步我们采用Ag导电通道作为纳米电极(尺寸与导电通道可比)来替代传统的微尺度电极提高碳基RRAM稳定性。实验表明,采用纳米尺度电极的器件相对于传统微尺度电极的存储器具有更为均一的阻变参数。导电通道机理探究:为了原位观察阻变过程中导电通道的动态过程,我们利用阻变过程中颜色(带隙)发生变化的半导体材料作为阻变层。本文采用光刻方法制备了平面微尺度的金/氧化石墨烯/金(Au/GO/Au)结构来替代传统的金属/绝缘体/金属堆叠结构。XPS和Raman表征证实了导电通道本质是还原氧化石墨(RGO)。利用光学显微镜我们观察到了RGO导电通道从负极向正极延伸生长。同时,研究发现环境湿度能够影响阻变过程:当环境湿度达到80%时,RGO导电通道能够部分被氧化为GO。并且RGO导电通道在关闭电压正极一侧发生氧化。结果表明水在GO的氧化还原过程中起到了至关重要的作用。
[Abstract]:Floating gate memory is limited to the size of the traditional cannot be further reduced, in order to better meet the future demand for information storage, at present many new memory devices have been proposed. Among them, resistive memory (RRAM) with its simple structure, low power consumption, read and write speed, is considered very promising to become the next memory information.RRAM is a general solid dielectric material sandwiched between two electrodes, using conductive channel in dielectric formation and fracture resistance to achieve conversion. However, the working mechanism of RRAM is not clear, and the performance of the device needs to be improved. So in-depth study of the conductive channel, including the effective regulation of conductive channel size, conductive explore the channel conducting channel size effect and control process of resistive on-off position will contribute to further understanding of RRAM and promote its development. In addition, the number of electric current Dielectric materials, carbon based materials have been recognized as the most likely to replace the application of traditional silicon-based materials in the future in the field of microelectronics, therefore the research of carbon based RRAM has important significance for the future development of carbon based electronics. This paper will change memory conductive channel regulation and mechanism research and other aspects of the work in carbon based resistance, specific research the contents are as follows: conductive channel size regulation: we use amorphous carbon (a-C) as a resistive layer, Cu and Pt as electrode, build a Cu/a-C/Pt RRAM device. By adjusting the current limit control of conductive channel size, and observed a nonvolatile / non-volatile coexistence properties and atomic level size conductive channel conductance quantum phenomenon. Quantitative research showed low resistance relaxation time and the channel size and temperature: Cu/a-C/Pt RRAM device is volatile due to the small size of the conductive channel due to the large Rayleigh surface can not The stability caused by the calculation. With the increase in size of the conductive channel required to fracture the Joule heat is also increased. The Fourier thermal steady state equations of devices with high resistance state with conductive channel size increases can be attributed to a-C metastable film on the temperature induced SP2 cluster increases. Conducting channel on-off position regulation: fluctuation of the problem the device parameters and fracture resistance change leads to the formation of random RRAM conductive channel, here we use methods of constant current Cu/a-C/Pt to improve device stability. Constant current effect can effectively increase a-C film SP2 clusters, and then increase the film within the local electric field, effectively control the conducting channel change position, realize uniform resistance characteristics; another.Ag, we use the porous film electrode of the RRAM device to build a "forming-free" in the process of evaporation in porous film in pre formed Ag Guide Electric channel. We use Ag as a further conductive channel (nano electrode size and conductive channel ratio) to replace the traditional micro electrode to improve the carbon RRAM stability. Experimental results show that the device using nano scale electrodes with respect to the memory of traditional micro electrodes with varying parameters is more uniform. The resistance conductive channel: in order to explore the mechanism of the dynamic process of conducting channels in situ observation of resistance change in the process, we use the color resistance change process (GAP) semiconductor material changes as resistive layer. The preparation of planar micro scale Au / graphene oxide / gold by photoetching method (Au/GO/Au) to replace the traditional metal / insulator / metal the stack structure of.XPS and Raman confirmed that the conductive channel is the essence of reduction of graphene oxide (RGO). We observed the growth of RGO conductive channel extending from the cathode to the cathode by optical microscope. When the study found that environmental humidity can influence the resistance change process: when the relative humidity reaches 80%, RGO conductive channels can be oxidized to GO. and RGO part of conductive channel in the closed side voltage cathode oxidation. The results show that the reduction of water in the GO oxidation process plays a very important role.

【学位授予单位】：东北师范大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP333

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