电荷俘获存储器的过擦现象

基于密度泛函理论的第一性原理平面波超软赝势方法和VASP软件对电荷俘获存储器过擦现象进行了分析研究.通过形成能的计算,确定了含有氮空位缺陷的Si3N4和含有间隙氧缺陷的Hf O2作为研究的对象;俘获能的计算结果表明两种体系对电子的俘获能力比对空穴的大,因而对两体系擦写载流子确定为电子.分别计算了Hf O2和Si3N4擦写前后的能量、擦写前后电荷分布变化、吸附能和态密度,以说明过擦的微观机理.对能量和擦写电荷变化的研究,表明Si3N4相比于Hf O2,其可靠性较差,且Si3N4作为俘获层,在一个擦写周期后,晶胞中电子出现减少现象;界面吸附能的研究表明,Si3N4相比于Hf O2在缺陷处更容易与氧进行电子交换;最后,通过对态密度的分析表明Si3N4和Hf O2在对应的缺陷中均有缺陷能级俘获电子,前者为浅能级俘获,后者为深能级俘获.综上分析表明,Si3N4在氮空位的作用下,缺陷附近原子对电子的局域作用变弱,使得Si3N4作为俘获层时,材料本身的电子被擦出,使得擦操作时的平带偏移电压增大,导致存储器发生过擦.本文的研究结果揭示了过擦的本质,对提高电荷俘获存储器的可靠性以及存储特性有着重要的指导意义.     

Anisotropic evolution of 4-brane in a 6D generalized Randall-Sundrum model

We investigate a 6 D generalized Randall-Sundrum brane world scenario with a bulk cosmological constant.Each stress-energy tensor T_(ab)~i on the brane is shown to be similar to a constant vacuum energy.This is consistent with the Randall-Sundrum model,in which each 3-brane Lagrangian yielded a constant vacuum energy.By adopting an anisotropic metric ansatz,we obtain the 5 D Friedmann-Robertson-Walker field equations.In a slightly later period,the expansion of the universe is proportional to the square root of time,t~(1/2),which is similar to the period of the radiation-dominated regime.Moreover,we investigate the case with two a(t) and two b(t).In a large range of t,we obtain the 3 D effective cosmological constant Λ_(eff)=-2Ω/30,which is independent of the integral constant.Here,the scale factor is an exponential expansion,which is consistent with our present observation of the universe.Our results demonstrate that it is possible to construct a model that solves the dark energy problem,while guaranteeing a positive brane tension.     

基于衣康酸配体构筑的两个锌配合物的合成、结构和荧光性质

通过水热法合成了两种锌配位聚合物{[Zn（ic）（bip）]·2H₂O}_n（1）和[Zn（ic）（bpe）]_n（2）（H₂ic=衣康酸,bip=3,5-二（1-咪唑基）吡啶,bpe=1,2-二（4-吡啶基）乙烯）,并通过X射线单晶衍射和元素分析对其结构进行了表征。配合物1和2均为含有一维金属-羧酸链的二维（4,4）格子层结构。此外,对它们的热重、粉末X射线衍射和固体荧光性能进行了考察。与配体bip相比,1的发射光谱发生了明显的蓝移（⁷8 nm）,可能归因于配体到金属的电荷转移;2显示与游离的bpe配体相似的荧光性质,轻微的红移可能是因为与金属离子之间的配位作用导致的。     

One-dimensional Coordination Polymers Assembled into Two Supramolecular Frameworks with High Stability

The dual ligand system of V-shaped 5-(4-carboxy-2-nitrophenoxy)-isophthalic acid(Hcn-H2ipa) and dipyridy-type molecules produces two new coordination polymers: {[Ni(cn-Hipa)(bpa)(H2O)3]·1.5H2O}n 1 and {[Cu(Hcn-ipa)(ppe)2]}n 2(bpa = 1,2-bis(4-pyridyl)ethane, and ppe = trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene). Two complexes have been characterized by single-crystal X-ray diffraction, elemental analysis, IR, and thermogravimetric analysis(TGA). Complex 1 is of monoclinic system, space group C2 with a = 25.936(3), b = 7.6100(10), c = 16.558(2), β = 105.9470(10)°, V = 3142.4(7) ?3, Dc = 1.415 g/cm3, Mr = 669.23, Z = 4, F(000) = 1388, μ = 0.687 mm-1, the final R = 0.0397 and w R = 0.0967 for 12070 observed reflections with I 2σ(I). Complex 2 belongs to the triclinic system, space group P1 with a = 10.165(5), b = 14.946(7), c = 15.506(11) ?, α = 106.461(7), β = 102.454(8), γ = 107.861(5)°, V = 2029(2) ?3, Dc = 1.266 g/cm3, Mr = 773.20, Z = 2, F(000) = 794, μ = 0.595 mm-1, the final R = 0.0538 and w R = 0.1378 for 15488 observed reflections with I 2σ(I). Two complexes show that the 1D polymeric chains are cohered together by extensive H-bonds to complete stable supramolecular microporous frameworks.     

Syntheses,Structures and Characteristics of Two New Cu(Ⅱ) Coordination Polymers Based on 4-tert-butyl-phthalate and Different Bis(1,2,4-triazol-1-yl) Co-Ligands

Two new Cu(II) coordination polymers, [Cu2(tbph)2(btb)2]n(1) and {[Cu2(tbph)2-(bth)2]·H2O}n(2),(H2tbph = 4-tert-butyl-phthalic acid, btb = 1,4-bis(1,2,4-triazol-1- yl)butane, bth = 1,6-bis(1,2,4-triazol-1-yl)hexane), have been synthesized and characterized by elemental analysis, FT-IR and X-ray single-crystal diffraction. Complex 1 has a 2D sql layer. Complex 2 shows a(3,4)-connected 2D sheet with a(4.64.8)(4.82) topology. The thermal behavior of the two corresponding complexes has briefly been investigated.     

两个以3-硝基邻苯二甲酸为配体构筑的锌和钴配位聚合物的合成、晶体结构和性质

通过水热法合成了2种配位聚合物{[Zn(3-Nbdc)(bpmp)]·H₂O}_n (1)和{[Co(3-Nbdc)(bpmp)(H₂O)]·H₂O}_n (2)(3-Nbdc^2-=3-硝基邻苯二甲酸根, bpmp=1, 4-二(4-吡啶甲基)哌嗪), 并通过X-射线单晶衍射、元素分析和红外光谱对其结构进行了表征。配合物1和2均为二维(4, 4)格子层结构, 其中1含有双核单元, 2含有螺旋金属羧酸链。此外, 对它们的热重、粉末X-射线衍射、固体荧光和磁性性能进行了考察。1显示与游离的3-硝基邻苯二甲酸相似的荧光性质, 锌离子的配位环境和配体之间的耦合作用对其荧光性能几乎没有影响。2在低温区表现出铁磁耦合作用, 高温区的χ_MT值降低主要是由于八面体钴的自旋轨道耦合导致的。     

基于半刚性的4-羧基苯乙酸和富氮共配体组装的Zn(Ⅱ)/Cd(Ⅱ)配位聚合物的合成、结构和性质

采用溶剂热法合成了一系列Zn（Ⅱ）/Cd（Ⅱ）配位聚合物：{[Zn（cbaa）（bpmp）_0.5（H₂O）]·2H₂O}_n（1）、[Zn（cbaa）（bip）]_n（2）、[Cd（cbaa）（Hizb）]_n（3）和[Cd₂（cbaa）₂（itmb）（H₂O）]_n（4）（H₂cbaa=4-羧基苯乙酸;bpmp=1,4-二（4-吡啶甲基）哌嗪;bip=3,5-双（1-咪唑基）吡啶;Hizb=2-（4-咪唑-1-基苯基）-1H-苯并咪唑;itmb=1-（咪唑-1-基）-4-（1,2,4-三唑-1-基甲基）苯）。X射线单晶衍射结果表明,半刚性的4-羧基苯乙酸和富氮辅助配体构筑形成了4个多样化拓扑结构的配位聚合物。化合物1和2是Zn（Ⅱ）配位聚合物：1是由2个Zn-羧酸盐链之间通过富氮配体桥连形成的一维梯形结构,而2是由Zn-羧酸盐链之间通过富氮配体拓展形成的二维单层结构;化合物3和4是Cd（Ⅱ）配位聚合物：3是由Cd-O无机链之间通过羧酸配体的桥连拓展形成的二维单层结构,富氮配体作为伸出层平面的悬臂仅仅起到结构修饰作用,而4则形成了Cd-羧酸盐空旷双层结构,富氮配体填充在层内空腔中,从而导致了致密双层结构的产生。另外,考察了4个化合物的热稳定性和光致发光性能。     

A (4,2)-connected niobium phosphate Na13Nb3P6O28F2 with a unique 6.12-net layer: synthesis, structure and ion exchange properties

A severely interrupted (4,2)-connected niobium phosphate, Na(13)Nb(3)P(6)O(28)F(2), with a unique 6.12-net topology sheet and novel structure type has been synthesized under mild hydrothermal conditions, and its ion exchange properties preliminarily investigated.     

密度泛函理论研究氧空位对HfO2晶格结构和电学特性影响?

HfO2因高k值、热稳定性良好和相对Si导带偏移良好等特点,作为电荷俘获型存储器栅介质材料得到了广泛研究。为了明确高k俘获层提高CTM电荷俘获效率的原因,运用基于密度泛函理论的第一性原理计算,研究了氧空位引起HfO2的晶格变化及其影响计算结果显示优化后氧空位最近邻氧原子间距明显减小,次近邻O与Hf间距变化稍小。优化后氧空位明显改变局部晶格,而对较远晶格影响逐渐减弱,即引起了局部晶格变化深能级和导带电子态密度主要是Hf原子贡献,而价带则是O原子贡献。优化后各元素局部电子态密度和总电子态密度都明显大于未优化体系,局部电子态密度之和比总电子态密度小。优化后俘获电荷主要在氧空位周围和相邻氧原子上,而未优化时电荷遍布整个体系。优化后缺陷体系电荷局域能增大,电荷量增加时未优化体系电荷局域能明显减小,即晶格变化无饱和特性对电荷局域影响大。说明晶格变化对电荷的俘获能力较强,有利于改善存储器特性。     

Two New Coordination Polymers Containing Metal-carboxylate Helix

Two novel compounds, {[Cd(nbdc)(bpp)(H2O)]·H2O}n 1 and {[Cd(nbdc)(dpds)-(H2O)]·H2O}n 2(H2nbdc = 4-nitro-1,2-benzenedicarboxylic acid, bpp = 1,3-bis(4-pyridyl)propane and dpds = 4,4ˊ-dipyridyldisulfide), were solvothermally synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis(TGA), fluorescent analysis and single-crystal X-ray diffraction. Complex 1 is of monoclinic system, space group P21/c with a = 14.4370(17), b = 8.4090(10), c = 19.168(2) , β = 104.5050(10)°, V = 2252.8(5) 3, Dc = 1.639 g/cm3, Mr = 555.81, Z = 4, F(000) = 1120, μ = 1.022 mm-1, the final R = 0.0269 and wR = 0.0599 for 16656 observed reflections with I 2σ(I). 2 is isostructural to 1 with a = 14.4175(11), b = 8.4737(7), c = 18.0120(14) , β = 106.7220(10)°, V = 2107.5(3)3, Dc = 1.821 g/cm3, Mr = 577.85, Z = 4, F(000) = 1152, μ = 1.287 mm-1, the final R = 0.0280 and wR = 0.0705 for 15136 observed reflections with I 2σ(I). Both complexes present intimately related structures featuring infinite Cd-carboxylate helix of [CdⅡ(nbdc)(H2O)]n connected by bpp(or dpds) molecule to produce the 2D layer frameworks.