惨杂钙钛矿钴氧化物异质结的制备及特性研究

发布时间：2018-05-20 12:32

本文选题：钙钛矿钴氧化物 + 异质结　；参考：《西安科技大学》2016年硕士论文

【摘要】：本文采用脉冲沉积技术(PLD)分别在n型0.7wt%Nb-SrTiO3(100)基片上制备(La_(1-x)Pr_x)_(0.7)Sr0.3CoO3(x=0,0.2,0.4,0.6,0.8)和La_(0.82)Sr_(0.18)Co_(1-x)Cr_xO_3(x=0,0.2,0.4,0.6,0.8,1.0)系列异质结。通过X射线衍射(XRD)、原子力显微镜(AFM)、低温测试系统和光电测试系统对制备的异质结的晶体结构、表面形貌、输运特性和光伏特性进行了表征及研究分析。主要结论如下:1.XRD和AFM测试表明系列异质结样品均呈现出良好的外延生长特性,薄膜沿着基底晶向择优生长,样品表面颗粒致密均匀,起伏度较小,生长质量良好。通过椭圆偏振光谱仪测得异质结的薄膜厚度范围为90-110 nm。2.对于(La_(1-x)Pr_x)_(0.7)Sr_(0.3)CoO_3/Nb-SrTiO_3系列异质结,Pr离子的掺入导致材料的晶格结构发生改变,各异质结由于薄膜与基底晶格的失配度不同而表现出不同的输运特性。随着温度的增加,结间势垒降低,耗尽层变窄,异质结的整流特性减弱。3.在激光的照射下,(La_(1-x)Pr_x)_(0.7)Sr_(0.3)CoO_3/Nb-SrTiO_3系列异质结样品中可以测试到持续的光电压,在473 nm激光照射下的光电压高于532 nm激光照射下的光电压,x=0.8的异质结样品的光电压最大值随着温度升高而降低。对光生电压上升沿和下降沿拟合后发现下降时间常数即非平衡载流子的寿命在较大的ms量级且随温度的升高而减小。4.在La_(0.82)Sr_(0.18)Co_(1-x)Cr_xO_3/Nb-SrTiO3系列异质结中,Cr离子掺杂量比较低的异质结样品具有很好地整流性,当掺杂比例较高时界面漏电机制主要为欧姆导电,主要是由于Cr离子与Co离子之间发生电子跃迁使得材料中的载流子浓度增加。5.激光的照射下,在x=0和x=0.4的La_(0.82)Sr_(0.18)Co_(1-x)Cr_xO_3/Nb-SrTiO3样品中观察到持续光电压的产生,473 nm激光照射下的光电压高于532 nm激光照射下的光电压,x=0的异质结样品的光电压最大值随温度的升高先升高后降低,通过对光生电压下降沿的指数函数拟合后发现非平衡载流子寿命的下降时间常数随温度升高而减小,且低温下具有较大的值,在改善光伏器件性能方面具有比较重要的研究意义。
[Abstract]:A series of heterojunctions have been prepared by pulse deposition technique (PLD) on n type Nb-SrTiO3O _ (100) substrates, respectively. A series of heterostructures have been prepared on n type Nb-SrTiO3O _ (100) substrates. The crystal structure, surface morphology, transport and photovoltaic properties of the heterojunction were characterized and analyzed by X-ray diffraction (XRD), atomic force microscope (AFM), low temperature measurement system and photoelectric measurement system. The main conclusions are as follows: 1. XRD and AFM measurements show that the heterojunction samples exhibit good epitaxial growth characteristics. The films grow in preferential direction along the substrate crystal direction. The surface particles of the films are compact and uniform, the fluctuation is small, and the growth quality is good. The thickness range of heterojunction films measured by elliptical polarization spectrometer is 90-110nm.2. The doping of pr ions in the Nb-SrTiO3 series heterojunction leads to the change of the lattice structure of the material. The heterostructures show different transport characteristics due to the mismatch between the thin films and the substrate lattice, because of the difference in the mismatch between the thin films and the substrate lattices. With the increase of temperature, the interjunction barrier decreases, the depletion layer becomes narrower, and the rectifying characteristic of heterojunction weakens by .3. The persistent photovoltage can be measured in the Lasta1-xSrTiO3 series heterojunction samples. The maximum photovoltage of the heterojunction samples with 473 nm laser irradiation is higher than that with 532 nm laser irradiation x 0.8 heterojunction sample. The maximum photovoltage of the heterojunction sample with 0.3s / s CoO3 / Nb-SrTiO3 heterojunction can be decreased with the increase of the temperature, and the photovoltage of the heterojunction sample with the laser irradiation of 473 nm is higher than that of the heterojunction sample with the laser irradiation of 532nm, and the maximum of the photovoltage of the heterojunction sample is decreased with the increase of temperature. After fitting the rising edge and descending edge of photogenerated voltage, it is found that the decreasing time constant, that is, the lifetime of the non-equilibrium carrier is in the larger Ms order and decreases with the increase of temperature. In La_(0.82)Sr_(0.18)Co_(1-x)Cr_xO_3/Nb-SrTiO3 series heterojunction samples with low doping amount of Cr ion have good rectifying property. The main mechanism of interface leakage is ohmic conduction when doping ratio is high. It is mainly due to the electron transition between Cr ion and Co ion that the carrier concentration in the material increases by .5. Under laser irradiation, It was observed that the maximum photovoltage of heterojunction samples exposed to 473 nm laser was higher than that of heterojunction sample with 532nm laser irradiation. The maximum photovoltage of heterojunction samples increased first and then decreased with the increase of temperature. By fitting the exponential function of the drop edge of photogenerated voltage, it is found that the decreasing time constant of non-equilibrium carrier lifetime decreases with the increase of temperature, and has a large value at low temperature. In improving the performance of photovoltaic devices has more important research significance.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O611.4

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