本文選題：相變存儲器 + 硅銻碲�。� 參考：《吉林大學(xué)》2015年碩士論文

【摘要】：相變存儲器是一種新型的非易失性半導(dǎo)體存儲器。相變存儲器中存儲信息的載體是相變材料，相變材料在一定外界條件的作用下可以發(fā)生晶相和非晶相之間的快速可逆相變，同時兩相之間存在明顯的光學(xué)或者電學(xué)性質(zhì)的差異。目前的相變材料中研究最廣泛的是Ge2Sb2Te5，但是Ge2Sb2Te5的非晶穩(wěn)定性還不夠好，在制作器件中難以承受高溫工藝，同時功耗較高。為了解決這些問題，人們又構(gòu)建了其他非晶穩(wěn)定性更好的相變材料組分，硅銻碲材料就是其中之一。 實驗上得到的硅銻碲材料最佳配比為SixSb2Te3(3x3.5)，其中Sb2Te3的非晶相不穩(wěn)定，加入硅元素之后得到的硅銻碲材料表現(xiàn)出了良好非晶穩(wěn)定性。實驗上發(fā)現(xiàn)，硅銻碲材料相變過程中會發(fā)生相分離，硅始終保持非晶狀態(tài)，非晶硅與碲化銻形成納米尺度下互相包裹的網(wǎng)狀結(jié)構(gòu)，這些網(wǎng)狀結(jié)構(gòu)中存在大量的硅和碲化銻的界面。一般來說，界面處會表現(xiàn)出不同于體材料性質(zhì)，我們認為這些硅和碲化銻界面結(jié)構(gòu)對穩(wěn)定非晶相方面起著非常重要的作用，本文利用第一性原理分子動力學(xué)模擬，建立非晶硅和非晶碲化銻界面的原子結(jié)構(gòu)模型，通過研究界面成鍵特性與電子結(jié)構(gòu)探究硅提高碲化銻非晶穩(wěn)定性的內(nèi)在原因。 本文共分為四章，第一章對相變存儲器和相變材料的研究背景進行介紹，同時介紹一些國內(nèi)外科研工作者的研究進展。 第二章，介紹研究方法。對第一性原理、密度泛函理論、分子動力學(xué)模擬進行簡單的介紹。 第三章，利用分子動力學(xué)模擬建立非晶硅和非晶碲化銻的界面結(jié)構(gòu)，從成鍵結(jié)構(gòu)和電子結(jié)構(gòu)兩方面進行分析，并與體相非晶碲化銻進行對比，結(jié)果表明，在界面結(jié)構(gòu)中，碲元素的成鍵結(jié)構(gòu)從原來p電子成鍵結(jié)構(gòu)轉(zhuǎn)變成sp3雜化成鍵與p電子鍵共存的結(jié)構(gòu)，同時碲化銻部分的電子局域程度明顯升高，這兩種變化使得碲化銻非晶和晶相結(jié)構(gòu)上的相似性被破壞，并且不利于形成晶相中共振鍵，這就是非晶硅提高碲化銻非晶穩(wěn)定性的內(nèi)在原因。 第四章，介紹對三種相變材料Ge15Sb85、Sb2Te、Sb2Te3相變特性的研究。在對非晶的Ge15Sb85研究中，，我們發(fā)現(xiàn)Ge在非晶Ge15Sb85中就存在聚集的現(xiàn)象，這也是這種材料容易相分離的原因。另外我們發(fā)現(xiàn)利用分子動力學(xué)模擬得到的Sb2Te，Sb2Te3晶相呈現(xiàn)出結(jié)構(gòu)上有序，但成分上無序的特點，我們認為相變材料實際相變過程中的晶相可能呈現(xiàn)這種結(jié)構(gòu)有序而成分無序的結(jié)構(gòu)，這也可能是相變材料能夠快速相變的原因。
[Abstract]:Phase change memory (PCM) is a new type of non-volatile semiconductor memory.The carrier of information stored in phase change memory is phase change material. Under certain external conditions, phase change can occur rapidly and reversible between crystalline phase and amorphous phase, and there are obvious differences in optical or electrical properties between the two phases.Ge2Sb2Te5 is the most widely studied phase change material at present, but the amorphous stability of Ge2Sb2Te5 is not good enough, and it is difficult to withstand high temperature process and high power consumption in fabricating devices.In order to solve these problems, other phase change materials with better amorphous stability have been constructed, among which the silicon antimony tellurium material is one of them.The optimum ratio of SiSb _ 2TE _ 3N _ 3x 3.5N is obtained by experiments. The amorphous phase of Sb2Te3 is unstable, and the Si-antimony-tellurium material with silicon element exhibits good amorphous stability.It is found that phase separation occurs in the process of phase transformation of antimony tellurium and the amorphous state of silicon remains. The amorphous silicon and antimony telluride form a netted structure wrapped in each other at nanoscale.There are a large number of interfaces between silicon and antimony telluride in these network structures.Generally speaking, the interfacial properties are different from those of bulk materials. We think that these interfacial structures of silicon and antimony telluride play a very important role in stabilizing the amorphous phase.The atomic structure model of the interface between amorphous silicon and amorphous antimony telluride was established. The intrinsic reasons for improving the amorphous stability of antimony telluride were investigated by studying the bonding characteristics and electronic structure of the interface.This paper is divided into four chapters. In the first chapter, the research background of phase change memory and phase change material is introduced, and the research progress of some researchers at home and abroad is also introduced.The second chapter introduces the research methods.The first principle, density functional theory and molecular dynamics simulation are briefly introduced.In chapter 3, the interfacial structure of amorphous silicon and amorphous antimony telluride is established by molecular dynamics simulation. The bonding structure and electronic structure are analyzed, and compared with bulk amorphous antimony telluride. The results show that, in the interfacial structure,The bonding structure of tellurium changed from the original p-electron bonding structure to the coexistence of sp3 heterogenetic bond and p-electron bond, and the electronic localization of antimony telluride part increased obviously.These two changes destroy the similarity between amorphous and crystalline structure of antimony telluride and are not conducive to the formation of resonance bonds in the crystalline phase, which is the intrinsic reason why amorphous silicon improves the stability of amorphous antimony telluride.In chapter 4, the phase transition characteristics of three kinds of phase change materials Ge15Sb85Sb2TeSb2Te3 are introduced.In the study of amorphous Ge15Sb85, we found that GE aggregates in amorphous Ge15Sb85, which is the reason for the easy phase separation of this material.In addition, we find that the crystal phase of SB _ 2TeN _ (SB _ 2TE _ 3) obtained by molecular dynamics simulation has the characteristics of ordered structure, but disordered composition. We think that the crystal phase of phase change material in the actual phase transition process may present this kind of ordered structure and disordered composition structure.This may also be the reason for the rapid phase transition of phase change materials.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TP333

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本文編號：1750198