氧化物异质结中界面相变诱导的阻变特性研究

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谷婷

11849409

硕士

物理学

陈朗

2020-05-28

2020-06-04

哈尔滨工业大学

深圳

随着信息技术的快速发展，铁电存储器作为一种新型的非易失性存储器，具有功耗低、耐久性好、易于调控等优点，受到了广泛关注，但是铁电阻变存储器目前也面临一些问题，铁电材料漏电流太大，高低阻态之间差异太小导致存储界限不明显。因此，本文期望通过利用铁电极化反转诱导La1-xSrxMnO3 (LSMO)中的空穴在界面积聚和耗散的特性，从而触发LSMO在相位边界的穿越，使铁电阻变存储器的开关比更明显，提高铁电阻变器件的阻变性能。本文成功制备了高质量的La1-xSrxMnO3 (x = 0, 0.15, 0.2, 0.3)薄膜。通过改变Pb(Zr0.2Ti0.8)O3 (PZT)薄膜的生长温度，制备了致密、均匀的高质量PZT薄膜。研究了PZT薄膜厚度对Pt/PZT/La0.7Sr0.3MnO3异质结的铁电性能和阻变性能的影响，当PZT薄膜厚度为72 nm时，异质结中的PZT薄膜漏电流密度低、铁电性能较好。本文制备了La0.7Sr0.3MnO3薄膜和PZT/La0.7Sr0.3MnO3薄膜，测试得到它们的金属绝缘相的转变温度分别为330 K和 250 K，说明PZT的极化反转可以调控LSMO的相变。在此基础上，通过改变铁电异质结中的相变调控层LSMO，设计并制备了四种Pt/PZT/La1-xSrxMnO3 (x = 0, 0.15, 0.2, 0.3)/La0.7Sr0.3MnO3铁电异质结结构。研究了四个异质结的铁电性能，四个异质结的电滞回线为饱和状态，极化强度大致相同，说明四个异质结之间阻变性能的差异与铁电性无关。通过改变扫描电压的大小，测试了四个异质结的阻变性能，得到Pt/PZT/La0.8Sr0.2MnO3/ La0.7Sr0.3MnO3铁电异质结的开关比最大，达到了7.2×104，并且该铁电异质结的阻变效应在正负电压下的差距最明显，这是因为该异质结中的相变调控层La0.8Sr0.2MnO3处于铁磁金属态和铁磁绝缘态的临界点，PZT铁电层的铁电极化反转能够诱导La0.8Sr0.2MnO3薄膜层中的空穴在界面积聚和耗散，触发La0.8Sr0.2MnO3在相位临界点之间穿越；Pt/PZT/La0.7Sr0.3MnO3铁电异质结的开关比为7×104；而Pt/PZT/La0.85Sr0.15MnO3/La0.7Sr0.3MnO3铁电异质结的开关比明显降低了，最大的开关比为4×104；Pt/PZT/LaMnO3/La0.7Sr0.3MnO3铁电异质结的开关比最小，为7×103，这是因为LaMnO3 (LMO)薄膜在室温下为反铁磁绝缘态。对四种异质结进行可靠性测试，四种异质结均具有优异的连续擦写操作能力和数据保持能力。

With the development of information technology, as a new type of non-volatile memory, ferroelectric memory has the advantages of low power consumption, good duration and easy regulation. But ferroelectric memory is also facing some problems, such as the leakage current of ferroelectric materials is too large, the difference between high and low resistance states is too small. Therefore, it is expected that ferroelectric polarization reversal can induce the accumulation and dissipation of holes in LSMO at the interface, so as to trigger the phase change of LSMO and to make the ON/OFF ratio of ferroelectric memory more obvious, the resistance performance of ferroelectric memory can be improved. In this paper, high quality La1-xSrxMnO3 (x = 0, 0.15, 0.2, 0.3) films were prepared by pulsed laser deposition. By changing the substrate temperature of PZT film, uniform and high quality PZT films were prepared. The effect of PZT film thickness on ferroelectric properties and resistance properties of Pt/PZT/LSMO heterojunction was studied. When the thickness of PZT film is 72 nm, the leakage current density of PZT film in the heterojunction is low and the ferroelectric performance of PZT film is good. Next, La0.7Sr0.3MnO3 and PZT/La0.7Sr0.3MnO3 films were prepared, and the transition temperatures of their metal-insulation phases were measured to be 330 K and 250 K, it indicates that the polarization reversal of PZT can regulate the phase change of LSMO. On this basis, by changing the screened layer LSMO in ferroelectric heterojunction, the Pt/PZT/La1-xSrxMnO3 (x = 0, 0.15, 0.2, 0.3)/La0.7Sr0.3MnO3 ferroelectric heterojunctions were designed and fabricated. The ferroelectric properties of four heterojunctions were studied, the hysteresis loop of the four heterojunctions is in the saturated state, and the polarization intensity was the same, indicating that the difference in the resistance performance between the four heterojunctions was independent of ferroelectricity. The resistance behavior of four heterojunctions was tested by setting different scan voltages, we can obtain the ON/OFF ratio of Pt/PZT/La0.8Sr0.2MnO3/La0.7Sr0.3MnO3 is the largest, which is 7.2×104, and the difference between positive and negative voltage is the most obvious, this is because the screened layer La0.8Sr0.2MnO3 is at the critical point of ferromagnetic metal state and ferromagnetic insulation state, ferroelectric polarization reversal can induce the accumulation and dissipation of holes in the La0.8Sr0.2MnO3 film at the interface, thus trigger the crossing of La0.8Sr0.2MnO3 between the critical point and improve the resistance performance of the heterojunction; the ON/OFF ratio of Pt/PZT/La0.7Sr0.3MnO3 is 7×104; the ON/OFF ratio of Pt/PZT/La0.85Sr0.15MnO3/La0.7Sr0.3MnO3 was significantly reduced, and the maximum ON/OFF ratio is 4×104; the maximum ON/OFF ratio of Pt/PZT/LaMnO3/La0.7Sr0.3MnO3 can only reach 103, this is because the LMO film is in an anti-ferromagnetic insulation state at room temperature. The reliability test of four heterojunctions was carried out, and the four heterojunctions all can erase continuously and have good data retention.

铁电二极管 阻变 相变 铁电极化 电场调控

ferroelectric diodes resistive switching phase change ferroelectric polarization electric control

中文

联合培养

南方科技大学

谷婷. 氧化物异质结中界面相变诱导的阻变特性研究[D]. 深圳. 哈尔滨工业大学,2020.