A functional probe with bowtie aperture and bull's eye structure for nanolithograph

The bowtie aperture surrounded by concentric gratings(the bull’s eye structure) integrated on the near-field scanning optical microscopy(NSOM) probe(aluminum coated fiber tip) for nanolithography has been investigated using the finite-difference time domain(FDTD) method.By modifying the parameters of the bowtie aperture and the concentric gratings,a maximal field enhancement factor of 391.69 has been achieved,which is 18 times larger than that obtained from the single bowtie aperture.Additionally,the light spot depends on the gap size of the bowtie aperture and can be confined to sub-wavelength.The superiority of the combination of the bowtie aperture and the bull’s eye structure is confirmed,and the mechanism for the electric field enhancement in this derived structure is analyzed.     

Improving lithographic masks with the assistance of indentations

Indentations etched on the output surface of a metallic mask are proposed to produce fine lithographic patterns with a resolution of 500 nm using the finite-difference time domain(FDTD) method.Such a designed mask is capable of enhancing near field lithography(NFL) resolution more than three times compared with the structure without indentations.The simulation results show that the interference disturbance between the adjacent lithographic channels can be eliminated efficiently by employing the indentations.As a straightforward consequence,the channel-to-channel interspaces can be shortened significantly,maintaining a uniform field distribution and high contrast.     

染料敏化太阳能电池中染料分子共轭π桥的扩展

以染料分子D5为原型, 采用不同类型和数量的共轭桥单元来设计D-π-A 型有机分子. 采用密度泛函理论(DFT)和含时密度泛函理论(TDDFT)来模拟计算分子的形貌、分子轨道能级以及紫外-可见光谱, 为染料敏化太阳能电池(DSSCs)的敏化分子寻找适合的共轭桥. 采用“次甲基链”、“呋喃环”或“噻吩环”、“次甲基链和呋喃环”或“次甲基链和噻吩环”作为共轭桥单元, 使得分子的吸收光谱依次红移. 随着共轭桥单元的增加, 分子的吸收光谱有剧烈的红移, 但随着共轭桥单元数量的进一步增加, 分子吸收光谱的红移现象减弱. 分子的最低未占据分子轨道(LUMO)能级逐渐降低, 而最高占据分子轨道(HOMO)能级逐渐升高. 采用3个“次甲基链和呋喃环”或者“次甲基链和噻吩环”作为共轭桥时, HOMO能级已经高于氧化还原电解质的能级, 而在极性溶液中, 由2个“次甲基链和噻吩环”单元作为有机分子的共轭桥时, 分子的HOMO能级已经高于氧化还原电解质的能级了. 采用“次甲基链和呋喃环”或“次甲基链和噻吩环”单元作为有机分子的共轭桥时, 吸收光谱有明显的红移,但对于DSSCs的敏化分子, 这样的共轭桥单元只能有1-2个, 不宜过多.     

Control of plasmonic wave propagating in nanocavity with tooth-shaped configuration

Characteristics of plasmonic wave propagating in nanocavity formed by two silver films are studied numerically. The groove etched inside wall of the top film makes it possible to control the propagation when light goes through the top film along a nanoslit into the cavity. It is found that the transmission wave through the channel of groove etched side can be filtered linearly with the groove of a certain depth; while the other side is still open for this wave and its intensity can be enhanced periodically with the variable groove position in both films, which are explained well based on the interference of plasmonic waves in the system.