二苯基氧磷修饰的不对称三嗪主体材料的理论研究

近年来,电致磷光器件因其在全色显示和固体照明领域的潜在应用而备受关注.文中针对电致磷光器件中的主体材料,设计了基于二苯氧磷的一系列三嗪衍生物,并通过密度泛函理论（DFT）对三嗪衍生物进行了系统的量子化学理论研究.研究发现：三嗪核决定了该类材料具有较高的三线态能级（2.84 eV～3.02eV）,而其前沿轨道能级可通过二苯氧磷和咔唑修饰单元数量及其比例来逐级调控,最高占据轨道（HOMO）由咔唑决定,维持在-5.85 eV;而最低未占据轨道（LUMO）受二苯氧磷影响,可以从-1.42 eV降低到-2.33 eV,从而具有独立可调的LUMO能级.综合比较发现,具有两个咔唑和一个二苯氧磷的不对称三嗪（DCzPT）比较适合作为蓝光客体的主体材料,这是因为DCzPT不仅具有高的三线态能级（3.02 eV）和低的LUMO值（-1.74 eV）,而且具有较高的电子和空穴的传输能力.     

Fe、Co、Ni掺杂磷烯的第一性原理研究

本文基于第一性原理研究了Fe、Co、Ni在P位吸附和掺杂磷烯的稳定性、能带结构、态密度以及差分电荷密度分布.结果表明:在吸附体系中,Co在P位的吸附的稳定性强于Fe、Ni吸附体系;在掺杂体系中,Fe、Co、Ni在P位掺杂的的稳定性较强的是Ni掺杂体系.Fe、Co、Ni在P位吸附磷烯,可以较好的调控能带结构,从而得到可控性能的半导体材料.在P位掺杂Fe、Co、Ni原子的带隙值分别为0.52、0.56和0.4eV.在Fe、Co、Ni掺杂位点上,近邻的两个磷原子周围出现了电子聚集的现象;原因在于Fe、Co、Ni的4s轨道上都有两电子,而非金属的磷原子较容易得到电子.     

第一性原理计算Zr/S共掺杂锐钛矿相TiO_2的电子结构

利用基于密度泛函理论的第一性原理平面波赝势方法对Zr/S共掺杂锐钛矿相TiO2的晶格参数、电荷布居、能带结构、电子分态密度和吸收光谱进行了计算.计算结果表明:Zr/S共掺杂导致锐钛矿相TiO2的晶格畸变使其体积变大,共掺杂时Zr和S的电荷布居数与单掺杂前的布居数略有不同;Zr/S共掺杂还导致锐钛矿相TiO2的禁带宽度变大0.1eV,达到2.30eV,但是由于Zr/S共掺杂在TiO2禁带之内引入了杂质能级,这些杂质能级可以作为电子跃迁的"台阶"而降低电子从价带跃迁到导带所需的激发光子能量,这有可能是实验上制备的Zr/S共掺杂TiO2具有较高光催化活性的内在原因.     

背面氩离子轰击改善MOS系统界面特性和击穿特性

在室温下用低能量Ａｒ＾＋轰击ＭＯＳ电容器肾面，能改善ｉＯ２－Ｓｉ系统的界面特性和击穿特性。结果表明，随着轰击时间的增加，固定电荷密度、界面态密度和漏电流减少，高场击穿的比率增大，然后这些参数变化平缓并开始呈恶化趋势。轰击能量为５５０ｅＶ和束流密度为０．５ｍＡ／ｃｍ＾２时的效果比在３５０ｅＶ和０．３ｍＡ／ｃｍ＾２时的好。     

间隔装药对爆破破碎效果的影响

用空气，水和岩粉３种间隔材料进行了间隔装药爆破试验，研究了间隔对破碎块度的影响，得出了３种材料的临界间隔比例值。对比了该３种材料间隔与全长偶合装药的异同，讨论了间隔的位置、长度及间隔材料对爆破破碎效果的影响。     

H2O分子在石墨烯扶手型边缘吸附的研究

类似石墨表面,石墨烯可以吸附和脱附各种原子和分子,石墨烯比石墨具有更大表面积,因此,石墨烯的表面性能被广泛关注. 然而较少被关注的是石墨烯边缘C原子的性能. 石墨烯边缘C原子由于存在未配对的电子,因此具有更强的反应活性. 本文采用了SelfConsistentCharge Density Functional Tight Binding(SCCDFTB)方法对H2O分子在石墨烯扶手型边缘的吸附现象进行了研究. 研究发现,石墨烯边缘的峰位C原子具有很好的吸附性,吸附能大约为-0.109~-0.768     

有关“二极管特性曲线测定”实验的讨论

普通物理实验教材中,对“二极管特性曲线测定”实验未加讨论直接采用了Id＝Ie（exp（eV/kT）-1）的解析公式,要求由实验结果求出指数e/kT,从而求出电子电荷e,或波尔兹曼常数k,并和理论值比较,考察实验误差．这种要求由于实际结果偏离解析公式较大,因而不尽合理．本文讨论了有关实验结果,并对上述结论作了必要的说明．最后建议对该实验的要求作合理的调整,即主要考察V—A的一般关系．     

Self-organization of supramolecular helical dendrimers into complex electronic materials

The discovery of electrically conducting organic crystals and polymers has widened the range of potential optoelectronic materials, provided these exhibit sufficiently high charge carrier mobilities and are easy to make and process. Organic single crystals have high charge carrier mobilities but are usually impractical, whereas polymers have good processability but low mobilities. Liquid crystals exhibit mobilities approaching those of single crystals and are suitable for applications, but demanding fabrication and processing methods limit their use. Here we show that the self-assembly of fluorinated tapered dendrons can drive the formation of supramolecular liquid crystals with promising optoelectronic properties from a wide range of organic materials. We find that attaching conducting organic donor or acceptor groups to the apex of the dendrons leads to supramolecular nanometre-scale columns that contain in their cores pi-stacks of donors, acceptors or donor-acceptor complexes exhibiting high charge carrier mobilities. When we use functionalized dendrons and amorphous polymers carrying compatible side groups, these co-assemble so that the polymer is incorporated in the centre of the columns through donor-acceptor interactions and exhibits enhanced charge carrier mobilities. We anticipate that this simple and versatile strategy for producing conductive pi-stacks of aromatic groups, surrounded by helical dendrons, will lead to a new class of supramolecular materials suitable for electronic and optoelectronic applications.     

METALLIC PHASE AND INSULATING CHARACTER OF ALKALI-EARTH METAL DOPED C60①

The three dimensional EHMO crystal orbital calculations for crystalline Ba6 C60,Ca3 C60 and Ca5 C60 are reported. The ground state of partially doped Ca3 C60 is found to be insulating with an indirect energy gap of 0. 5eV. In contrast, the. Cas C60 forms a metallic conducting phase with a set of three half - filled bands crossing the Fermi level which is Found to locate close to a peak of the density of state. The character of crystal orbitals near the Fermilevel for both Ca3 C60 and Ca5 C60 is completely carbon - like. In both cases the Ca3 atoms are almost fully ionized and C60 molecules form a stable negative, charge state with six to ten additional electrons. The conductivity of Ba6 C60 is resute.4 from the incomplete charge tranfer. The valance charge of every Ba ion is about 0. 33. The total charge tranfer of six Ba atoms is almost the same as that of five Ca atoms.     

锂离子电池负极材料Li2MgSi的Li脱嵌性质研究

使用基于平面波展开的第一原理赝势法,研究了锂离子电池负极材料Li2MgSi在各种脱锂量下的锂脱嵌形成能、相应的体积变化、能带结构、电子态密度以及电荷密度分布.计算结果表明:脱锂量越大需要的能量越大,随脱锂量的变化,平均一个锂的脱嵌形成能在-1.21～-1.61 eV之间.脱锂过程中,体积先膨胀后收缩,整个过程中体积变化很大,是导致材料循环性能较差的重要原因.在脱锂过程中材料显示了由半导体性到金属性又到半导体性的特征.     

METALLIC PHASE AND INSULATING CHARACTER OF ALKALI-EARTH METAL DOPED C60

The three dimensional EHMO crystal orbital calculations for crystalline Ba6 C60,Ca3 C60 and Ca5 C60 are reported.The ground state of partially doped Ca3 C60 is found to be insulating with an indrect energy gap of 0.5eV.In contrast,the Ca5 C60 forms a metallic conducting phase with a set of three half-filled bands crossing the Fermi level which is Found to locate close to a peak of the density of state. The character of crystal orbitals near the Fermilevel for both Ca3 C60 and Ca5 C60 is completely carbon-like.In both cases the Ca3 atoms are almost fully ionized and C60 molecules form a stable negative charge state with six to ten additional electrons.The conductivity of Ba6 C60 is resuted from the incomplete charge tranfer.The valance charge of every Ba ion is about 0.33.The total charge tranfer of six Ba atoms is almost the same as that of five Ca atoms.     

锂离子电池负极材料Li2.5Cu0.5N的Li脱嵌性质

使用基于平面波展开的第一原理赝势法,计算了锂离子电池非碳基负极材料Li2.5Cu0.5N在各种脱锂量下的Li脱嵌形成能以及相应的体积变化,讨论了脱锂前后材料的电荷密度,电子状态密度等电子性质.计算表明,Li2.5Cu0.5N晶体中LiN层的锂的脱出能要比LiCu层的锂小得多,即LiN层中的锂更容易脱嵌.结果还表明,各种脱锂量的Li脱嵌能大致在-2.72～-4.08 eV/Li之间.当脱锂量小于30%,材料的体积变化较小,随着脱锂量的增大,材料的体积变化较大.     

自洽法计算非晶硅的带隙态密度

本文叙述了一个场效应电导测量氢化非晶硅(a—Si:H)带隙态密度的数据处理方法。该法放弃了对空间电荷区电荷、电场和电势分布的任何假设,采用电子占据局域态的费米统计分布和占据扩展态的玻耳兹曼分布,应用自洽的原理,能够在较大的能量范围内计算出a-Si:H的带隙态密度分布,运算过程中以电势V为自变量,减少了对电势、电场和电荷密度等量空间分布的计算,简化了分析,提高了精度,减少了运算量。应用该法计算出了a—Si:H样品的带隙态密度在费米能级以上0.1eV到0.45 eV能量范围内的分布,它的最小值在费米能级附近,约为10~(16)cm~(-3)·eV~(-1)。     

堇青石-莫来石和工业石蜡的低温节能特性对比研究

在自行搭建的低温余热能源回收系统上,以堇青石-莫来石蜂窝蓄热体和工业石蜡为蓄热材料,进行低品位能余热回收利用实验.考察蓄热体种类、主要工艺参数-换向周期等对余热回收率的影响,并结合工业石蜡DSC分析结果,探讨相变蓄热材料对蓄放热性能的影响机制.结果表明:合理换向周期为5分钟;蜂窝蓄热体的蓄放热速率均大于工业石蜡的蓄放热...     

A photovoltaic device structure based on internal electron emission

There has been an active search for cost-effective photovoltaic devices since the development of the first solar cells in the 1950s (refs 1-3). In conventional solid-state solar cells, electron-hole pairs are created by light absorption in a semiconductor, with charge separation and collection accomplished under the influence of electric fields within the semiconductor. Here we report a multilayer photovoltaic device structure in which photon absorption instead occurs in photoreceptors deposited on the surface of an ultrathin metal-semiconductor junction Schottky diode. Photoexcited electrons are transferred to the metal and travel ballistically to--and over--the Schottky barrier, so providing the photocurrent output. Low-energy (approximately 1 eV) electrons have surprisingly long ballistic path lengths in noble metals, allowing a large fraction of the electrons to be collected. Unlike conventional cells, the semiconductor in this device serves only for majority charge transport and separation. Devices fabricated using a fluorescein photoreceptor on an Au/TiO2/Ti multilayer structure had typical open-circuit photovoltages of 600-800 mV and short-circuit photocurrents of 10-18 micro A cm(-2) under 100 mW cm(-2) visible band illumination: the internal quantum efficiency (electrons measured per photon absorbed) was 10 per cent. This alternative approach to photovoltaic energy conversion might provide the basis for durable low-cost solar cells using a variety of materials.     

Bandgap modulation of carbon nanotubes by encapsulated metallofullerenes

Motivated by the technical and economic difficulties in further miniaturizing silicon-based transistors with the present fabrication technologies, there is a strong effort to develop alternative electronic devices, based, for example, on single molecules. Recently, carbon nanotubes have been successfully used for nanometre-sized devices such as diodes, transistors, and random access memory cells. Such nanotube devices are usually very long compared to silicon-based transistors. Here we report a method for dividing a semiconductor nanotube into multiple quantum dots with lengths of about 10nm by inserting Gd@C82 endohedral fullerenes. The spatial modulation of the nanotube electronic bandgap is observed with a low-temperature scanning tunnelling microscope. We find that a bandgap of approximately 0.5eV is narrowed down to approximately 0.1eV at sites where endohedral metallofullerenes are inserted. This change in bandgap can be explained by local elastic strain and charge transfer at metallofullerene sites. This technique for fabricating an array of quantum dots could be used for nano-electronics and nano-optoelectronics.     

对苯二甲酸-锌配合物的几何体态与电子结构

基于密度泛函理论,使用自洽投影缀加平面波方法,计算了对苯二甲酸 锌配合物(MOF-5)的体态几何与电子结构。经理论预测MOF 5是一种直接能隙半导体,价带极大值(VBM) 与导带极小值(CBM)都位于位于G(0, 0, 0)点,其直接能隙约为3.17eV,间接能隙约为3.18eV。通过对优化后的MOF-5晶体结构的分析,发现MOF-5晶体结构中的苯环沿着对位方向受到拉伸,同时沿着垂直于对位方向受到压缩,说明成键过程中对苯二甲酸分子的苯环发生了一定的变形。同时对优化后的MOF-5晶体进行总态密度图、分波态密度图及Mulliken电荷分析,发现Zn—O1键的键能大于Zn—O2键,Zn原子的4p轨道有电子分布,即Zn的s、p和d轨道均参与了成键。     

等离子体处理对碘掺杂PPS电导的影响

导电的PPS(聚对苯硫醚)的电导稳定性至今未得到解决,其根本原因是掺杂剂与PPS分子之间不能形成或不能永久形成电荷传递结合物。本文以不形成电荷传递结合物的掺杂剂碘(I)作为研究对象,在化学掺杂之后进行了等离子体处理,使PPT的电导率和稳定性大幅度提高,达到强掺杂剂的程度。红外吸收和二次离子质谱分析表明,经低温等离子体处理后,I和PPS之间形成(C_3 H_2S)~+和(HCIS)~+ 基团,电导的活化能从原始的2.0eV降低到0.2V,电导的机理是载流的热活化过程。     

含硼矿物复合材料对1keV;1eV及0.0253eV能量中子的屏蔽性能

以我国辽宁东部地区特有的硼铁矿原矿石、含硼铁精矿、富硼渣为原料,用蒙特卡罗方法研究了不同配比含硼矿物/环氧树脂复合材料对1 keV,1 eV,0.025 3 eV能量慢中子的屏蔽性能及影响因素,并与普通混凝土屏蔽材料进行了对比.结果表明:复合材料对1 keV中子的屏蔽性能随着氢元素质量分数的增加而增加;复合矿物材料对1 eV中子的屏蔽性能主要与复合材料中硼元素的质量分数及氢、硼元素的配比有关;硼元素质量分数是影响0.025 3 eV中子屏蔽性能的主要因素.各配比组成复合屏蔽材料对慢中子的屏蔽性能均强于普通混凝土,有望提高普通混凝土生物防护层对慢中子的防护性能,并为慢中子的屏蔽设计提供依据.