两种信息存储材料的外场响应研究

发布时间：2018-04-09 13:46

本文选题：LiNbO_3　切入点：Ge_2Sb_2Te_5　出处：《南京大学》2013年硕士论文

【摘要】：随着闪存在读取速度、尺寸大小和功耗上局限性的逐渐突显,寻找一种闪存替代技术成为了各大电子行业巨头研究的重要方向。目前最主要的四种闪存替代技术分别是铁电随机存储器、磁阻随机存储器、相变随机存储器和阻变随机存储器。本论文主要研究了两种信息存储材料,一种是铌酸锂(LiNbO3)单晶,它是典型的铁电材料,可以用于光电调制、倍频、光参量振荡、以及全息记录等。另一种是锗锑碲(Ge2Sb2Te5)合金薄膜,它是相变存储材料,可以用于非易失性存储器。本论文研究主要针对关系到这两种材料的实际应用的核心基础问题展开,即铌酸锂中铁电畴的生长和弛豫问题,以及锗锑碲中的非晶-晶态相变问题,分别研究了它们对外电场和外应力场的响应情况。主要创新成果如下： 1.利用扫描探针显微镜研究了外电场下近化学计量比铌酸锂单晶中铁电畴的生长和弛豫特性。对于扫描极化方式制备的条形畴,我们发现,畴区生长的平均初始宽度随着极化电压的增加而线性增加,随着扫描速率的增加而指数衰减；畴区的弛豫随初始宽度的减小呈现稳定无弛豫、长度缩减、及完全消失这三种状态,临界稳定初始宽度随晶片厚度指数增长；为保持相邻条形畴区独立不相融合的状态,其间距应大于条形畴的宽度；沿铌酸锂不同晶向极化的条形畴在生长形态、宽度和粗糙度方面有差异。对于定点脉冲极化的畴区,我们发现,根据畴区中心出现的与外电场反向的异常翻转区大小的不同,对应有两类不同的相邻畴区间相互作用。对于中心异常翻转区较小的准实心畴区,邻近区域的再次极化会使先极化畴区的中心异常翻转区消失,畴区沿外场方向进一步生长；而对于中心异常翻转区较大的非完整环形畴区,邻近区域的再次极化则会加速先极化畴区的弛豫消失过程。这两种不同的影响可能源于畴构型的差异。 2.利用脉冲激光沉积系统制备了非晶态的Ge2Sb2Te5薄膜,并研究了外加机械应力对其升温晶化行为的影响。发现,张应力使得晶化温度降低,而压应力使得晶化温度升高。随应力从压应力变化到张应力(张、压应力分别以正、负应力值表示),晶化温度近似线性下降。实验中,我们还观察到由应力大小不均匀导致的晶化温度的展宽现象。
[Abstract]:This paper mainly studies two kinds of information storage materials , such as ferroelectric random access memory , magnetoresistive random access memory , phase change random access memory and random access random access memory . The main four kinds of flash memory replacement technologies are ferroelectric random access memory , magnetoresistive random access memory , phase change random access memory and random access random access memory . The paper mainly studies two kinds of information storage materials , one is lithium niobate ( LiNbO 3 ) single crystal , it is a typical ferroelectric material , it can be used for photoelectric modulation , frequency doubling , optical parametric oscillation , and holographic recording . The other is Ge2Sb2Te5 alloy thin film , it is phase change storage material , can be used in non - volatile memory .

This paper mainly focuses on the core basic problem of the practical application of the two materials , namely , the growth and relaxation of the ferroelectric domains of lithium niobate and the amorphous - crystalline phase transition in the germanium - antimony tellurium , and the responses of their external electric field and external stress field are studied respectively . The main innovations are as follows :

1 . The growth and relaxation properties of the ferroelectric domains in the lithium niobate single crystal under the external electric field were investigated by using a scanning probe microscope .

For the stripe domains prepared by scanning polarization , we find that the average initial width of the domain grows linearly with the increase of the polarization voltage , and decreases exponentially with the increase of the scanning rate ;
The relaxation of the domain region decreases with the decrease of the initial width . The critical stable initial width increases with the thickness of the wafer .
in ord to maintain that state of independent non - phase fusion of adjacent strip domain regions , the spacing should be greater than the width of the stripe domain ;
The stripe domains of different crystal orientations of lithium niobate differ in growth morphology , width and roughness .

For the domain region of fixed - point pulse polarization , we found that there are two different kinds of adjacent domain - interval interactions , depending on the size of the abnormal inversion region opposite to the external electric field in the domain center .
For a large non - complete circular domain region of the central abnormal inversion region , the re - polarization of the adjacent region accelerates the relaxation disappearance process of the first polarized domain region .

2 . The amorphous Ge2Sb2Te5 thin film was prepared by pulsed laser deposition system . The influence of applied mechanical stress on the crystallization behavior was studied . It was found that tensile stress caused the crystallization temperature to decrease . The compressive stress caused the crystallization temperature to increase . As the stress changed from the compressive stress to the tensile stress , the crystallization temperature was approximately linearly decreased . In the experiment , we also observed the broadening of crystallization temperature caused by the nonuniform stress magnitude .

【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TP333;O484.4

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