多鐵性自旋過(guò)濾隧道結(jié)的制備與多態(tài)存儲(chǔ)研究
發(fā)布時(shí)間：2018-11-22 17:53
【摘要】：傳統(tǒng)鐵電隨機(jī)存取存儲(chǔ)器的基本單元是一個(gè)鐵電電容,需要一定的電容面積獲得足夠的電荷量來(lái)存儲(chǔ)信息,難以實(shí)現(xiàn)高密度存儲(chǔ)。其讀出方式是破壞性的,在讀出后需要重寫信息,限制了讀出時(shí)間。近年來(lái)出現(xiàn)的鐵電隧穿存儲(chǔ)以鐵電隧道結(jié)為基本單元,是一種鐵電極化調(diào)控的阻性存儲(chǔ)方案,有望實(shí)現(xiàn)高密度、低功耗非易失性存儲(chǔ)。在這樣的背景之下,結(jié)合自旋閥磁隧道結(jié),本文設(shè)計(jì)制備了一種多鐵性自旋過(guò)濾閥隧道結(jié),可在一個(gè)存儲(chǔ)單元內(nèi)同時(shí)實(shí)現(xiàn)鐵電隧道結(jié)和磁隧道結(jié)的功能,獲得四態(tài)非易失性存儲(chǔ),同時(shí)還研究了超薄鐵電薄膜的極化弛豫行為。論文主要研究?jī)?nèi)容與結(jié)果如下:(1)在(001)取向的SrTiO3單晶襯底上制備了一系列不同相對(duì)厚度的Pr0.8Ca0.2MnO3/BaTiO3異質(zhì)結(jié),磁滯回線測(cè)量表明厚度為9個(gè)晶胞高度(u.c.)的Pr0.8Ca0.2MnO3薄膜在10K以下處于鐵磁相,壓電力顯微鏡表征表明5u.c.厚的BaTiO3仍有鐵電性,確定優(yōu)化的復(fù)合勢(shì)壘為Pr0.8Ca0.2MnO3(9 u.c.)/BaTiO3(5 u.c.)。(2)制備了 LaNiO3/Pr0.8Ca0.2MnO3/BaTiO3/La0.7Sr0.3MnO3 外延異質(zhì)結(jié)構(gòu),通過(guò)紫外光刻、離子束刻蝕等微加工手段獲得多鐵性隧道結(jié)原型器件。測(cè)試結(jié)果表明,器件具有區(qū)別明顯的四種非易失性阻值狀態(tài),隧穿電致電阻約為100%,隧穿磁致電阻約為24%,并且發(fā)現(xiàn)鐵電勢(shì)壘的極化方向可調(diào)制Pr0.8Ca0.2Mn03的自旋極化率,進(jìn)而影響器件的隧穿磁致電阻值。(3)不同厚度的BaTiO3薄膜鐵電疇弛豫現(xiàn)象不同,7 u.c.的超薄BaTiO3膜中,鐵電疇的面積變化緩慢,而極化強(qiáng)度逐漸變小;40nm厚的BaTiO3薄膜中,弛豫通過(guò)鐵電疇面積不斷變小完成。溫度對(duì)Pb(Zr0.1Ti0.9)O3薄膜的鐵電疇保持性有很大影響,溫度越高,疇保持性越差。鐵電疇形狀影響弛豫時(shí)間,形狀越接近圓的鐵電疇弛豫越慢,保持性越好。
[Abstract]:The basic unit of traditional ferroelectric random access memory (FRAM) is a ferroelectric capacitance. It is difficult to realize high density storage because it needs a certain capacitance area to obtain enough charge quantity to store information. The readout method is destructive and needs to be rewritten after reading, which limits the readout time. In recent years ferroelectric tunneling storage, which is based on ferroelectric tunneling, is a kind of resistive storage scheme regulated by iron electrode, which is expected to achieve high density, low power consumption and non-volatile storage. In this context, combined with the spin valve magnetic tunnel junction, a multi-iron spin filter valve tunnel junction is designed and fabricated, which can realize the functions of ferroelectric tunnel junction and magnetic tunnel junction simultaneously in a memory cell. The four-state nonvolatile storage is obtained, and the polarization relaxation behavior of ultrathin ferroelectric thin films is also studied. The main contents and results are as follows: (1) A series of Pr0.8Ca0.2MnO3/BaTiO3 heterojunctions with different relative thickness have been prepared on (001) oriented SrTiO3 single crystal substrates. The hysteresis loop measurements show that the thickness is 9 unit cell height (u. C.) The Pr0.8Ca0.2MnO3 films are in ferromagnetic phase below 10K, and the results of PPM show that 5u. C. Thick BaTiO3 still has ferroelectric properties. It is determined that the optimized composite barrier is Pr0.8Ca0.2MnO3 (9 u. C.) / BaTiO3 (5 u. C.). (2) to prepare LaNiO3/Pr0.8Ca0.2MnO3/BaTiO3/La0.7Sr0.3MnO3 epitaxial heterostructure. The prototype devices of multi-iron tunneling junctions were obtained by ion beam etching and other micromachining methods. The test results show that the device has four distinct non-volatile resistance states, the tunneling resistance is about 100 and the tunneling magnetoresistance is about 24. It is also found that the polarization direction of the ferroelectric barrier can modulate the spin polarizability of Pr0.8Ca0.2Mn03. Furthermore, the tunneling magnetoresistance of the device is affected. (3) the ferroelectric domain relaxation phenomenon of BaTiO3 thin films with different thickness is different, 7 u. C. In ultrathin BaTiO3 films, the area of ferroelectric domains changes slowly, but the polarization intensity becomes smaller, while in BaTiO3 thin films with 40nm thickness, the relaxation is achieved by decreasing the area of ferroelectric domains. The temperature has a great influence on the ferroelectric domain retention of Pb (Zr0.1Ti0.9) O 3 thin films, and the higher the temperature, the worse the domain retention. The shape of ferroelectric domain affects the relaxation time, and the closer the ferroelectric domain is to the circle, the slower the relaxation is, and the better the retention is.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TP333;O484.4
，
本文編號(hào)：2350125
[Abstract]:The basic unit of traditional ferroelectric random access memory (FRAM) is a ferroelectric capacitance. It is difficult to realize high density storage because it needs a certain capacitance area to obtain enough charge quantity to store information. The readout method is destructive and needs to be rewritten after reading, which limits the readout time. In recent years ferroelectric tunneling storage, which is based on ferroelectric tunneling, is a kind of resistive storage scheme regulated by iron electrode, which is expected to achieve high density, low power consumption and non-volatile storage. In this context, combined with the spin valve magnetic tunnel junction, a multi-iron spin filter valve tunnel junction is designed and fabricated, which can realize the functions of ferroelectric tunnel junction and magnetic tunnel junction simultaneously in a memory cell. The four-state nonvolatile storage is obtained, and the polarization relaxation behavior of ultrathin ferroelectric thin films is also studied. The main contents and results are as follows: (1) A series of Pr0.8Ca0.2MnO3/BaTiO3 heterojunctions with different relative thickness have been prepared on (001) oriented SrTiO3 single crystal substrates. The hysteresis loop measurements show that the thickness is 9 unit cell height (u. C.) The Pr0.8Ca0.2MnO3 films are in ferromagnetic phase below 10K, and the results of PPM show that 5u. C. Thick BaTiO3 still has ferroelectric properties. It is determined that the optimized composite barrier is Pr0.8Ca0.2MnO3 (9 u. C.) / BaTiO3 (5 u. C.). (2) to prepare LaNiO3/Pr0.8Ca0.2MnO3/BaTiO3/La0.7Sr0.3MnO3 epitaxial heterostructure. The prototype devices of multi-iron tunneling junctions were obtained by ion beam etching and other micromachining methods. The test results show that the device has four distinct non-volatile resistance states, the tunneling resistance is about 100 and the tunneling magnetoresistance is about 24. It is also found that the polarization direction of the ferroelectric barrier can modulate the spin polarizability of Pr0.8Ca0.2Mn03. Furthermore, the tunneling magnetoresistance of the device is affected. (3) the ferroelectric domain relaxation phenomenon of BaTiO3 thin films with different thickness is different, 7 u. C. In ultrathin BaTiO3 films, the area of ferroelectric domains changes slowly, but the polarization intensity becomes smaller, while in BaTiO3 thin films with 40nm thickness, the relaxation is achieved by decreasing the area of ferroelectric domains. The temperature has a great influence on the ferroelectric domain retention of Pb (Zr0.1Ti0.9) O 3 thin films, and the higher the temperature, the worse the domain retention. The shape of ferroelectric domain affects the relaxation time, and the closer the ferroelectric domain is to the circle, the slower the relaxation is, and the better the retention is.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TP333;O484.4
，
本文編號(hào)：2350125
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