Gunnarsson Linda, Rindzevicius Tomas, Prikulis Juris, Kasemo Bengt, Käll Mikael, Zou Shengli, Schatz George C
Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
J Phys Chem B. 2005 Jan 27;109(3):1079-87. doi: 10.1021/jp049084e.
We report on the optical properties of single isolated silver nanodisks and pairs of disks fabricated by electron beam lithography. By systematically varying the disk size and surface separation and recording elastic scattering spectra in different polarization configurations, we found evidence for extremely strong interparticle interactions. The dipolar surface plasmon resonance for polarization parallel to the dimer axis exhibited a red shift as the interdimer separation was decreased; as expected from previous work, an extremely strong shift was observed. The scattering spectra of single particles and pairs separated by more than one particle radius can be well described by the coupled dipole approximation (CDA), where the particles are approximated as point dipoles using a modified dipole polarizability for oblate spheroids. For smaller particle separations (d < 20 nm), the simple dipole model severely underestimates the particle interaction, indicating the importance of multipolar fields and finite-size effects. The discrete dipole approximation (DDA), which is a finite-element method, describes the experimental results well even at d < 20 nm, including particles that have metallic bridges.
我们报道了通过电子束光刻制备的单个孤立银纳米盘及其对的光学性质。通过系统地改变盘尺寸和表面间距，并记录不同偏振配置下的弹性散射光谱，我们发现了粒子间极强相互作用的证据。对于平行于二聚体轴的偏振，偶极表面等离子体共振随着二聚体间间距减小而出现红移；正如先前工作所预期的，观察到了极强的红移。单个粒子以及间距超过一个粒子半径的粒子对的散射光谱可以通过耦合偶极近似（CDA）很好地描述，其中使用扁球体的修正偶极极化率将粒子近似为点偶极。对于较小的粒子间距（d < 20 nm），简单偶极模型严重低估了粒子相互作用，这表明多极场和有限尺寸效应的重要性。离散偶极近似（DDA）作为一种有限元方法，即使在d < 20 nm时也能很好地描述实验结果，包括具有金属桥的粒子。
