本文選題：分子器件　切入點(diǎn)：負(fù)微分電導(dǎo)效應(yīng)　出處：《山東師范大學(xué)》2017年碩士論文

【摘要】：隨著科技的不斷進(jìn)步,微觀器件越來越小型化,人們對(duì)微觀世界的認(rèn)識(shí)也越來越廣泛,研究單個(gè)分子器件的功能特性也取得了不俗的成果,并且伴隨著實(shí)驗(yàn)和理論的完善,出現(xiàn)了不同種類的分子器件,例如:分子導(dǎo)線、分子開關(guān)、分子傳感器等等。其中分子傳感器中的負(fù)微分電導(dǎo)(NDC)效應(yīng)就是分子器件中的一個(gè)十分理想的功能特性,并且得到了越來越多的關(guān)注和研究。本文利用密度泛函理論(DFT)和非平衡格林函數(shù)(NEGF)方法研究了低偏壓下以9,10-二氫蒽為核心的單硫醇化芳香基亞乙炔分子(簡(jiǎn)稱為TADHA分子)器件的NDC效應(yīng)以及影響其NDC效應(yīng)的外界因素。在低偏壓下取得較大的NDC效應(yīng)是單分子器件的一個(gè)非常理想的功能特性。依據(jù)Perrin M.L.等人研究的TADHA分子,由于其是由兩個(gè)共軛分支組成,所以TADHA分子是一個(gè)可以拉伸、壓縮的非剛性分子。而且他們的實(shí)驗(yàn)研究結(jié)果顯示該分子結(jié)在較低偏壓狀態(tài)下呈現(xiàn)出了優(yōu)異的NDC效應(yīng)。為了解釋低偏壓狀態(tài)下呈現(xiàn)出的優(yōu)異的NDC效應(yīng),我們?cè)赑errin M.L.等人的實(shí)驗(yàn)基礎(chǔ)上對(duì)TADHA分子結(jié)進(jìn)行了拉伸和壓縮計(jì)算,討論了電極之間的距離改變對(duì)分子結(jié)的NDC效應(yīng)的影響。結(jié)果顯示在對(duì)分子結(jié)進(jìn)行拉伸和壓縮的過程中,存在著一個(gè)能量最低的電極距離,即平衡距離。在電極的平衡距離下由于外界偏壓作用引起HOMO和HOMO-1能級(jí)的劈裂,使得分子結(jié)在較低偏壓下產(chǎn)生了明顯的負(fù)微分電導(dǎo)。隨著電極距離的縮短,分子結(jié)的電流和負(fù)微分電導(dǎo)行為都隨之變大;相反由平衡距離處開始拉伸兩電極時(shí),分子結(jié)的負(fù)微分電導(dǎo)慢慢變小直至最后消失,而當(dāng)NDC效應(yīng)消失后,分子結(jié)又呈現(xiàn)出了整流特性�？紤]到一般分子器件的組裝是在溶液環(huán)境中進(jìn)行的,若分子結(jié)組裝后干燥不徹底,仍然會(huì)存有部分水吸附在分子結(jié)附近,為此,我們就嘗試研究了將單個(gè)或多個(gè)水分子吸附在TADHA功能分子上,擬探究H20的吸附是否會(huì)對(duì)較低偏壓下的NDC效應(yīng)產(chǎn)生影響。結(jié)果顯示H2O的吸附作用對(duì)分子器件的電子傳輸特性和負(fù)微分電導(dǎo)效應(yīng)存在不同程度的影響,具體表現(xiàn)在:單個(gè)或兩個(gè)H20吸附對(duì)分子器件的負(fù)微分電導(dǎo)影響較小,隨著吸附H20的數(shù)目的增加,對(duì)電輸運(yùn)的影響也越來越明顯;并且H20吸附位置不同,其對(duì)分子器件的電輸運(yùn)性質(zhì)影響也不同。除此之外,H20吸附還導(dǎo)致了分子結(jié)的對(duì)稱性被破壞,所以分子結(jié)也出現(xiàn)了整流特性。并且H20的吸附位置不同,對(duì)電輸運(yùn)性質(zhì)和NDC效應(yīng)的影響也不同,具體表現(xiàn)在:吸附位置越靠近分子結(jié)的中間部分,對(duì)NDC效應(yīng)影響越明顯。除此之外,我們進(jìn)一步研究了 F2的吸附效應(yīng)對(duì)TADHA功能分子的NDC效應(yīng)的影響。理論結(jié)果顯示,F2的吸附抑制了 NDC效應(yīng)的產(chǎn)生,并且導(dǎo)致低偏壓下的電流、電導(dǎo)變小。但是同時(shí),F2的吸附使得分子結(jié)不對(duì)稱性增加,出現(xiàn)了較大的整流比,整流效果變強(qiáng),而且F2的吸附位置越靠近TADHA分子中間位置,最大整流比越大,整流效果越明顯。本論文一共有六個(gè)章節(jié)的內(nèi)容:第一章是綜述,對(duì)分子電子學(xué)領(lǐng)域的主要研究?jī)?nèi)容和研究現(xiàn)狀進(jìn)行了簡(jiǎn)單的介紹;第二章是本論文中的理論部分,主要包括DFT理論和NEGF方法;第三章主要討論了電極距離的改變對(duì)TADHA分子結(jié)的負(fù)微分電導(dǎo)效應(yīng)的影響,發(fā)現(xiàn)在適宜的電極距離下,兩個(gè)電極之間的距離越小,NDC效應(yīng)越明顯;第四章討論了 H20的吸附效應(yīng)對(duì)TADHA分子結(jié)的電輸運(yùn)特性的影響,探究了不同數(shù)目的H20吸附在TADHA分子結(jié)的不同位置處時(shí)對(duì)負(fù)微分電導(dǎo)效應(yīng)的影響;第五章討論了氣體小分子(具有強(qiáng)氧化性的F2)對(duì)低偏壓下的負(fù)微分電導(dǎo)的影響,可以看出F2的吸附對(duì)分子結(jié)的負(fù)微分電導(dǎo)起到了抑制作用,不同吸附位置處的抑制作用也不相同;第六章對(duì)研究的工作做出了總結(jié),并對(duì)接下來將要開展的工作進(jìn)行了展望。
[Abstract]:With the continuous progress of science and technology, more and more micro device miniaturization, understanding of the microscopic world is more and more widely, functional properties of single molecule devices have also achieved good results, and with perfect theory and experiment, the different kinds of molecular devices, such as molecular wires, molecular switch, molecular the sensor and so on. The negative differential conductance sensor (NDC) molecules in an ideal function effect is in molecular devices, and get more and more attention and research. By using the density functional theory (DFT) and non equilibrium Green function (NEGF) method to study the single thiol 9,10- two hydrogen anthracene core under low bias of aryl ethynylene molecular (TADHA molecules) external factors NDC effect devices as well as the influence of the NDC effect. The larger NDC effect under low bias is single An ideal function sub device. On the basis of TADHA molecular Perrin M.L. et al, because it is composed of two conjugate branches, so the TADHA molecule is a non rigid molecule can stretch, compression. And experimental study on their results show that the molecular junction at low bias state show NDC effect is excellent. In order to explain the low bias condition showed excellent NDC effect in our experimental based on TADHA Perrin M.L. et al. Molecular junctions were tensile and compression calculation, discusses the distance between the electrodes change on NDC effect of molecular junctions. The results showed that the tensile and compression process in the molecular junction, there is a lowest energy electrode distance, namely the balance distance. In the distance between the electrodes due to external bias caused by HOMO and HOMO-1 energy level splitting, the molecular junction in The low bias has a negative differential conductance significantly. With the shorter distance of electrodes, current molecular junctions and negative differential conductance behavior increases; instead the balance begins at a distance stretching two electrode, negative differential conductance of the molecular junction slowly decreases until it finally disappeared, and when the NDC effect disappeared after the molecular node presents rectification characteristics. Considering the general assembly of molecular devices is carried out in solution in the environment, if the molecular junction after assembly will still not completely dry, water adsorption in the near molecular junction therefore, we try to study the adsorption of single or multiple functions of water molecules in the TADHA molecules. To explore H20 whether the adsorption will affect the NDC effect on the low bias. The results show that the electronic transmission characteristics of adsorption of H2O on molecular devices and negative differential conductance effect has different effect, the specific performance In: single or two H20 negative differential conductance effect on the adsorption of smaller molecular devices, with the increase in the number of H20 adsorption, the influence of electrical transport is becoming more and more obvious; and the H20 adsorption at different positions on the electrical transport properties of molecular devices have different effects. In addition, the adsorption of H20 to the symmetry of the molecular junction was destroyed, so molecular junctions also appeared different adsorption sites and rectifying properties. H20, the influence of electrical transport properties and NDC effect is different, specific performance in the middle part of the adsorption position near the molecular junction, the NDC effect more obvious influence. In addition, we further studied the effect of NDC F2 on the effect of adsorption effect of TADHA molecules. The theoretical results show that the adsorption of F2 inhibited the NDC effect, and lead to the current low bias, the conductance decreases. But at the same time, the adsorption of F2 molecules do not make The symmetry of the increase, there was greater than the effect of rectification, rectification and strong adsorption position of F2 is close to the middle position of the TADHA molecule, the maximum rectification ratio increases, the rectification effect is more obvious. This thesis consists of six chapters: the first chapter is the summary, makes a brief introduction to the field of molecular electronics. The main research contents and research status; the second chapter is the theoretical part of this paper, mainly including the DFT theory and NEGF method; the third chapter the effects of negative differential conductance effect of electrode distance changes on the TADHA molecular junction are discussed in this paper, found in the appropriate electrode distance, the distance between the two electrodes is smaller, NDC the effect is more obvious; the fourth chapter discusses the adsorption effect of H20 transport on the characteristics of TADHA molecular junction, explores a different number of H20 adsorption at different locations of the TADHA junction effect of negative differential conductance Ring; the fifth chapter discusses the small gas molecules (strong oxide F2) effect on the negative differential conductance under low bias voltage, it can be seen that F2 adsorption to the inhibition of negative differential conductance of molecular junctions, inhibition of different adsorption position is not the same; the sixth chapter of the research work made summary and the next work to be carried out are discussed.

【學(xué)位授予單位】：山東師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN601

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本文編號(hào)：1687593