N/B掺杂石墨烯的光学与电学性质

石墨烯因其独特的化学成键结构而拥有出色的化学、热学、机械、电学、光学特性.由于石墨烯为零带隙材料,限制了其在纳电子学领域的发展.因此,为了拓宽石墨烯的应用范围,研究打开石墨烯带隙的方法显得尤为重要.本文构建了本征石墨烯、N掺杂石墨烯、B掺杂石墨烯三种模型,研究了本征石墨烯和不同掺杂浓度下的N/B掺杂石墨烯的能带结构、电子态密度及光学与电学性质,包括吸收谱、反射谱、折射率、电导率和介电函数等.研究结果显示:1)本征石墨烯费米能级附近的电子态主要是由C-2p轨道形成,而N/B掺杂石墨烯费米能级附近的电子态主要是由C-2p和N-2p/B-2p轨道杂化形成;2)N/B掺杂可以引起石墨烯费米能级、光学与电学性质的改变,且使狄拉克锥消失,进而打开石墨烯带隙;3)N/B掺杂可以引起石墨烯光学和电学性质的变化,且对吸收谱、反射谱、折射率、介电函数影响较大,而对电导率影响较小.本文的结论可为石墨烯在光电子器件中的应用提供理论依据.

氮等离子体辅助脉冲激光沉积生长p型ZnO∶N薄膜的光学和电学性质(英文)

通过氮气等离子体辅助脉冲激光沉积(PLD)技术制备了氮掺杂氧化锌(ZnO∶N)薄膜。经过低温快速热退火(RTA)处理后,ZnO∶N薄膜呈现p型导电特性。利用X射线光电子能谱(XPS)、光致发光(PL)和霍尔测量对ZnO∶N薄膜中N的化学状态及其光学和电学性质进行了系列的研究。结果表明:所制得的p型ZnO∶N薄膜为高度补偿半导体;RTA工艺不仅可以激活薄膜中更多的N受主,还可以弱化由薄膜中的施主缺陷造成的自补偿效应。在低温PL光谱中观察到了3种与氮受主相关的光发射,并且通过自由电子-受主(FA)辐射复合光发射确定了薄膜中N受主的离化能(128 meV)。随着退火温度的升高,施主-受主对发射峰呈现了略微的红移现象,这可以通过势能波动模型加以理解。

Rubrene∶MoO3混合薄膜的制备及光学和电学性质

利用热蒸发技术在衬底温度为室温的硅衬底、氧化铟锡衬底和石英衬底上制备了红荧烯与氧化钼的混合薄膜.将两种材料放置于不同的坩埚中,通过控制蒸发源的温度来控制混合比例,制备了不同比例的混合薄膜.通过原子力显微镜对混合薄膜的表面形貌进行了测量,发现当红荧烯与氧化钼的比例为2:1时,薄膜表面的平整度最好;通过X射线衍射分析对混合薄膜的结晶性进行分析,发现不同浓度的混合薄膜均表现出非晶态特征.通过PL谱和吸收光谱研究了不同比例的混合薄膜的光学性质,从光致发光谱可以发现:混合薄膜在近红外区域有显著吸收,说明红荧烯在氧化钼诱导下产生中间能级,形成电荷转移络合物.从吸收谱知:除4:1外,其他比例的混合薄膜具有几乎相同的吸收峰.根据Tauc方程计算了混合薄膜的光学带隙,发现当红荧烯与氧化钼的比例为2:1时,混合薄膜的带隙最窄(-2.23 eV).制备了结构为Al/rubrene:MoO3/ITO的器件,测试了J-V特性,研究了混合薄膜的电学性质.发现当混合比例为4:1和2:1时,混合薄膜与金属电极的接触表现为欧姆接触.本研究显示出红荧烯和氧化钼的混合薄膜在近红外区域有潜在的应用前景,也为红荧烯和氧化钼的混合薄膜在有机光电器件的应用提供了基础.

First‑principles study on electronic structure,optical and magnetic properties of rare earth elements X(X=Sc,Y,La,Ce,Eu)doped with two‑dimensional GaSe

The electronic structure,magnetic,and optical properties of two-dimensional(2D)GaSe doped with rare earth elements X(X=Sc,Y,La,Ce,Eu)were calculated using the first-principles plane wave method based on den-sity functional theory.The results show that intrinsic 2D GaSe is a p-type nonmagnetic semiconductor with an indi-rect bandgap of 2.6611 eV.The spin-up and spin-down channels of Sc-,Y-,and La-doped 2D GaSe are symmetric,they are non-magnetic semiconductors.The magnetic moments of Ce-and Eu-doped 2D GaSe are 0.908μ_(B)and 7.163μ_(B),which are magnetic semiconductors.Impurity energy levels appear in both spin-up and spin-down chan-nels of Eu-doped 2D GaSe,which enhances the probability of electron transition.Compared with intrinsic 2D GaSe,the static dielectric constant of the doped 2D GaSe increases,and the polarization ability is strengthened.The ab-sorption spectrum of the doped 2D GaSe shifts in the low-energy direction,and the red-shift phenomenon occurs,which extends the absorption spectral range.The optical reflection coefficient of the doped 2D GaSe is improved in the low energy region,and the improvement of Eu-doped 2D GaSe is the most obvious.

锑掺杂二氧化锡(ATO)纳米颗粒:共沸蒸馏干燥法制备及隔热性能

以五水合四氯化锡、三氯化锑为原料,乙醇为溶剂,氨水为沉淀剂,乙酸异戊酯为共沸溶剂,共沸蒸馏干燥前驱体溶胶,650℃煅烧后制备了单分散不同锑掺杂量的掺锑二氧化锡(ATO)纳米颗粒。结果表明,锑含量对颗粒粒径、光电性质具有重要影响,10mol%锑掺杂量时,样品具有最低的电阻率以及最优良的光学性质(最高的可见光透过率与近红外屏蔽效果),电学性质。ATO与聚氨酯复合涂膜玻璃隔热测试表明,涂层薄膜具有优良的隔热效果,能够有效地减小热量的传递与扩散。

La,Ce,Nd掺杂SnO_2的电子结构和光学性质密度泛函理论研究（英文）

基于平面波赝势密度泛函理论,研究了La,Ce,Nd掺杂SnO2的电子结构和光学性质。计算结果表明,La附近的键长变化最大,而Nd附近的键长变化最小,这表明稀土掺杂SnO2引起的晶格畸变与掺杂原子的共价半径大小有关。能带结构表明,稀土掺杂可使SnO2的带隙变窄。La掺杂相比较本征SnO2,带隙减小了0.892 e V,Nd掺杂在SnO2的禁带中引入了3个能级。差分电荷密度分析表明,稀土掺杂使SnO2的电子重新分配且由于f电子的存在使其离子性增强。La原子失电子最多,Nd原子失电子最少,这和计算的能带结果是一致的。光学性质表明,介电函数的虚部和吸收函数因稀土掺杂出现了不同程度的红移,这和计算的能带结果非常吻合。

First-principles investigations of structural, mechanical, electronic and optical properties of U_3Si_2-type AlSc_2Si_2 under high pressure

The structural, elastic, electronic and optical properties for U3Si2-type AlSc2Si2 compound under pressure were systematically investigated by using the first-principles calculations. The values of elastic constants and elastic moduli indicate that AlSc2Si2 keeps mechanical stability under high pressure. The mechanical properties of AISc2Si2 are compared with those of Al3Sc. The results indicate that AlSc2Si2 is harder than AI3Sc. Anisotropic constant AU and 3D curved surface of elastic moduli predict that AISc2Si2 is obviously anisotropic under pressure. The electronic structure of AlSc2Si2 exhibits metallic character and the metallicity decreases with the elevated pressure. In addition, optical properties as a function of pressure were calculated and analyzed. The present work provides theoretical support for further experimental work and industrial applications.

Electronic Structure Magnetic Properties and Optical Properties of Co-doped AIN from First Principles

The electronic structure, magnetic properties, and optical properties of Co-doped AIN are investigated based upon the Perdew-Burke-Ernzerhof form of generalized gradient approximation within the density functional theory. The band gaps narrowing of AI1-x Cox N are found with the increase of Co concentrations. The analyses of the band structures and density of states show that AI1-xCoxN alloys exhibit a halfometallie character. Moreover, we have succeeded in demonstrating that Co doped AIN system in x = 0.125 is always antiferromagnetie, which is in good agreement with the experimental results. Besides, it is shown that the insertion of Co atom leads to redshift of the optical absorption edge. Finally, the optical constants of pure A1N and AI1-xCoxN alloy, such as loss function, refractive index and reflectivity, are discussed.

Effects of structures of molybdenum catalysts on selectivity in gas-phase propylene oxidation

Molybdenum-based catalysts for the gas-phase oxidation of propylene with air were investigated. Various types of silica-supported molybdenum oxide and molybdenum-bismuth mixed oxide cata- lysts were prepared from inorganic and organometallic molybdenum precursors using wet impregnation and physical vapor deposition methods. The epoxidation activities of the prepared cata- lysts showed direct correlations with their nanostructures, which were identified using transmission electron microscopy. The appearance of a partly or fully crystalline molybdenum oxide phase, which interacted poorly with the silica support, decreased the selectivity for propylene oxide for- mation to below 10%; non-crystalline octahedrally coordinated molybdenum species anchored on the support gave propylene oxide formations greater than 55%, with 11% propylene conversion. Electrochemical characterization of molybdenum oxides with various morphologies showed the importance of structural defects. Direct promotion by bismuth of the epoxidation reactivities over molybdenum oxides is disputed.

国内红外与光电子

由集成光电子国家重点联合实验室、香港中文大学、台湾成功大学共同主办的第一届中华光电子研讨会于1994年8月29日～9月2日在香港中文大学举行。参加这次讨论会的代表共有百余人。 本次研讨会就目前光电子发展概况、光电子和高速器件。

Au doping effects on electrical and optical properties of vanadium dioxides

Vanadium dioxides were fabricated on normal glass substrates using reactive radio frequency （RF） magnetron sputtering. The oxygen flow volume and annealed temperatures as growth parameters are systematically investigated. The electrical and opti- cal properties of VO2 and Au：VO2 thin films with different growth conditions are discussed. The semiconductor-metal phase transition temperature decreased by -10~C for the sample with Au doping compared to the sample without Au doping. How- ever, the optical transmittance of Au：VO2 thin films is much lower than that of bare VO2. These results show that Au doping has a marked effect on the electrical and optical properties.

Red fluorescent siloles with aggregation-enhanced emission characteristics

A series of new red fluorescent siloles consisting of a silole core and dimesitylboranyl substituent connected with a furan, thiophene, and selenophene bridges were synthesized and characterized. The optical properties, electronic structures, and electroluminescence （EL） performances were investigated. The emission wavelengths were red-shifted from the siloles with furan, to those with thiophene, and then selenophene. The thiophene, and selenophene-containing siloles, （MesB）2DTTPS, and （MesB）zDSTPS, showed the typical aggregation-enhanced emission （AEE） feature, while furan-containing one, （MesB）2DFTPS, showed slight emission decrease as the aggregate formation. Theoretical calculations were carried out to explain the difference in the optical properties. Undoped OLEDs using these red siloles as light-emitting layers were fabricated. The device of （MesB）2DTTPS exhibited the best performance. It radiated red EL emission at 589 nm, and afforded good maximum luminance, current, power, and external quantum efficiency of 13300 cd m^-2, 4.3 cd A^-1, 2.9 lm W^-1, and 1.8%, respectively.

Optical Properties of Laterally Aligned Si Nanowires for Transparent Electronics Applications

We have investigated the optical properties of laterally aligned Si nanowire （SiNW） arrays in order to explore their potential applicability in transparent electronics. The SiNW array exhibited good optical transparency in the visible spectral range with a transmittance of -90% for a NW density of -20-25 per 10 μm. In addition, polarization-dependent measurements revealed a variation in transmittance in the range of 80%-95% depending on the angle between the polarization of incident light and the NW axis. Using the SiNWs, we demonstrated that transparent transistors exhibit good optical transparency （greater than 80%） and showed typical p-type SiNW transistor characteristics.

Influence of annealing on the structural,optical and electrical properties of indium oxide films deposited on c-sapphire substrate

Indium oxide(In_2O_3) films were prepared on Al_2O_3(0001) substrates at 700 °C by metal-organic chemical vapor deposition(MOCVD).Then the samples were annealed at 800 °C,900 °C and 1 000 °C,respectively.The X-ray diffraction(XRD) analysis reveals that the samples were polycrystalline films before and after annealing treatment.Triangle or quadrangle grains can be observed,and the corner angle of the grains becomes smooth after annealing.The highest Hall mobility is obtained for the sample annealed at 900 °C with the value about 24.74 cm^2·V^(-1)·s^(-1).The average transmittance for the films in the visible range is over 90%.The optical band gaps of the samples are about 3.73 e V,3.71 e V,3.70 eV and 3.69 eV corresponding to the In_2O_3 films deposited at 700 °C and annealed at 800 °C,900 °C and 1 000 °C,respectively.

First-Principles Calculations on Electronic,Chemical Bonding and Optical Properties of Cubic Hf_3N_4

Electronic, chemicM bonding and optical properties of cubic Hf3N4 （ c-Hf3N4 ） are calculated using the first- principles based on the density functional theory （DFT）. The optimized lattice parameter is in good agreement with the available experimental and cedculational values. Band structure shows that c-Hf3N4 has direct band gap. Densities of states （DOS） and charge densities indicate that the bonding between Hf and N is ionic. The optical properties including complex dielectric function, refractive index, extinction coefficient, absorption coefficient, and refleetivity are predicted. Prom the theory of crystal-field and molecular-orbited bonding, the optical transitions of c-Hf3N4 affected by the electronic structure and molecular orbited are studied. It is found that the absorptive transitions of c-Hf3N4 compound are predominantly composed of the transitions from N T2 2p valence bands to Hf T2 （dxy, dxz, dyz） conduction bands.