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In-Te及In-Se硫系薄膜可调光电性质研究
中文摘要

硫系材料以其优良的光学性质和电学特性,引起了研究人员的广泛关注,并在红外探测成像、光纤传输、逻辑电路、非易失性存储、神经网络等领域具有广阔的应用前景。然而,随着技术的发展,人们对硫系材料表现出丰富的物理特性需求更加强烈,目前硫系材料物理特性的调制方法和机制还存在很多问题,需要进一步深入研究。 本文以In-Te和In-Se两种二元硫系材料为研究对象,利用磁控溅射方法制备了不同的薄膜样品和忆阻器件,主要针对其相变特性、阻变特性和光学特性进行了分析研究,并详细讨论了两种材料物理特性的调制方法和机制。具体研究内容如下: 首先,研究了In₂Te₅薄膜材料物理特性受不同退火温度的影响和受厚度变化的调制。结果表明,In₂Te₅薄膜内部结构、透过率、光学常数、光学带隙以及非线性吸收系数等特性参数受退火温度的调控比较明显,在400℃退火条件下,有部分Te单质析出;44 nm厚度的In₂Te₅薄膜由于量子效应,表现出明显的饱和吸收,与其它厚度的薄膜反饱和吸收形成了鲜明的对比。同时,研究了退火温度对In₂Se₃薄膜物理特性的调制,结果表明,晶态和非晶态下的In₂Se₃薄膜光学特性差异很大,高温400℃退火条件下,有部分Se单质析出。In₂Se₃薄膜受退火温度的调制没有In₂Te₅薄膜明显,其内部缺陷态密度比In₂Te₅薄膜高,对于相变存储而言,In₂Te₅材料要优于In₂Se₃材料。 其次,研究分析了不同Ti掺杂浓度的InTe薄膜特性,结果表明,通过Ti掺杂浓度可以简单、有效的调制InTe物理特性,掺杂过程中Ti逐渐取代In形成了Ti-Te;材料内部载流子浓度随着Ti掺杂浓度的增加变高;由于Burstein-Moss效应,光学带隙受Ti掺杂调制比较明显,随其浓度的增加而变大;Ti掺杂对非线光学特性影响比较明显,在高载流子浓度条件下,非线性吸收中载流子吸收比例不能被忽略。 最后,研究分析了基于In₂Te₅和In₂Se₃介电材料的三明治结构的忆阻器特性。结果表明,两者都表现出明显的双极性忆阻特性;其内部导电机制符合陷阱受限的空间电荷受限的导电机制(Traped-SCLC);忆阻器I-V特性受电流注入方式影响比较大;Ag/In₂Te₅/W忆阻器和Ag/In₂Te₅/ITO忆阻器具有良好的可靠性和数据保持能力,通过调节电极的方式可以改变忆阻器的特性;基于In₂Se₃介电材料的忆阻器具有良好的可靠性和数据保持能力,在上电极(TE)和下电极(BE)具相似功函数条件下(Ta/In₂Se₃/Ag),正负偏压扫描过程中表现出对称性,而上下电极功函数具有一定差异的条件下(Ag/In₂Se₃/ITO、Ta/In₂Se₃/ITO),正负偏压扫描过程中表现出非对称性,电极的功函数对忆阻特性具有明显的调制作用;由于Ag和Ta属于不同的活性电极,从而Ag/In₂Se₃/ITO和Ta/In₂Se₃/ITO忆阻器表现出不同特性,活性电极Ag导致大电流注入,而惰性电极Ta导致小电流注入;通过改变电极的方式可简单、有效的调制基于硫系材料忆阻器特性;相比In₂Te₅材料,In₂Se₃材料更适合做阻变非易失性存储器;两类忆阻器都表现出电阻连续变化的能力,对于多值存储、逻辑运算、可编程电路及类神经元模拟等方向具有潜在应用价值。 关键词:硫系薄膜,相变特性,钛掺杂,磁控溅射,非线性光学吸收,忆阻特性,空间电荷受限导电 中图分类号:O474,O484,O469,O439

英文摘要

Due to its excellent optical and electrical properties, chalcogenide materials have attracted wide attention from researchers. And they have wide application prospects in IR detection, optical fiber transmission, logic circuits, non-volatile storage and neural network, etc. However, with the development of technology, more physical properties of chalcogenide materials are needed to build. There are still many problems in the modulation methods and mechanisms. Further research is needed. In this paper, two kinds of binary system chalcogenide materials (In-Te、 In-Se) are chose to be investigated. Different thin film samples and memristor devices are prepared by the magnetron sputtering method. Then the phase changed 、 resistance swtiching and optical properties are analyzed by various methods. The modulation methods and mechanisms of the physical properties are discussed in detail. The specific research contents are as follows: First, the physical properties of In₂Te₅ thin film materialsb under the different annealing temperatures processing and the different thickness are investigated. The results show that the internal structure, optical transmittance, optical constants, optical band gap and nonlinear absorption coefficient of In₂Te₅ films are modulated apparently by the annealing processing. The Te is precipitated,when the annealing temperature reachs at 400℃. The In₂Te₅ film with 44 nm thickness shows obviously saturated absorption due to the quantum effect, which is in sharp contrast to the reverse absorption of other thin films. Meanwhile, the modulation physical properties of In₂Se₃ thin films by the annealing processing ware studied. The results show that the optical properties of In₂Se₃ thin films under crystalline and amorphous state exhibit obvious differently. And the Se is precipitated,when the annealing procesing reachs at 400℃. Compare with the In₂Se₃ thin film, the In₂Te₅ thin film is modulated apparently by annealing processing. The internal defect state density in In₂Se₃ thin film is higher than that in In₂Te₅ thin film. For the phase change storage, the In₂Te₅ material is better than In₂Se₃ material. Secondly, the properties of In Te films with different Ti doping concentrations were studied. The results show that the physical properties of In Te can be easily and effectively modulated by Ti doping concentration. In the process of doping, Ti gradually replaced In to form Ti-Te. The carrier concentration in the film increases with the increasing of Ti doping concentration. As the Burstein-Moss effect, The optical band gap is changed obviously by Ti doping and increases with the increasing of Ti doping concentration. The effect of Ti doping on non-linear optical properties is obvious. Under the high carrier concentration, the ratio of carrier absorption in non-linear absorption can not be ignored. Finally, the characteristics of the memristors based on In₂Te₅ and In₂Se₃ dielectric materials by sandwich structure were analyzed. The results show that memristors exhibit obvious bipolar characteristics. And the internal conduction mechanism is consistent with the traped space charge limited conduction mechanism. The I-V characteristic is greatly influenced by the current injection mode. The characteristics of Ag/In₂Te₅/W and Ag/In₂Te₅/ITO with good reliability and data retention can be changed by adjusting the electrode. The memristors based on In₂Se₃ dielectric material have good reliability and data retention. Symmetry was shown in the process of positive and negative bias under the TE and BE with close work function (Ta/In₂Se₃/Ag), while the asymmetry was observed under the TE and BE with distinguish work function (Ag/In₂Se₃/ITO and Ta/In₂Se₃/ITO). The electrode work function can be as a tool to modulate the memristor characteristics. As the active electrode Ag leading to large current injection and the inert electrode Ta leading to small current injection, it is a simple and effective method to modulate memristor characteristics by changing the electrode. Compared to In₂Te₅, the In₂Se₃ is more suitable for resistive non-volatile memory. But the two kinds of memristors exhibit the resistance can changed continuously, which have potential application value for multi-level storage, logic operation, programmable circuits and neural network. Key words: Chalcogenide thin film, Phase change characteristics, Titanium doping, Magnetron sputtering, Nonlinear optical absorption, Resistance switching characteristics, Traped SCLC Classification Code : 0474 , 0484 , 0469 , 0439

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