Nanostructured surfaces

Comparison of optical spectra of cylindrical and rough nanowires with silver nanoparticles
Havryliuk O.O., Tkachuk O. I., Semchuk O.Yu., Biliuk А.А. 

Chuiko Institute of Surface Chemistry NAS of Ukraine. 17 Ganeral Naumova Str., Kyiv-03164, Ukraine. 
E-mail: gavrylyuk.oleksandr@gmail.com

Today, solar energy is a promising area of research. Despite the great achievements, reducing costs and improving the efficiency of solar cells will always be two big challenges in this area. It has been experimentally demonstrated that Si nanowires with rough surfaces exhibit poor thermal transport properties as compared to bulk structures or even nanowires with well-controlled surfaces [1]. However, the question remains how the optical characteristics of structures with rough and cylindrical nanowires differ.
The absorption spectra of structures with cylindrical and rough silicon nanowires were calculated by the FDTD method. The following structure parameters were used for the calculation: diameter and length of nanowires - 100 and 2000 nm, respectively; diameter of silver nanoparticles - 100 nm.
Calculations showed that in the wavelength range of 300-600 nm significant differences in the absorption spectrum are not observed. If we consider structures without silver nanoparticles, we observe a slight increase in the absorption coefficient in the structure with cylindrical nanowires in the wavelength range of 600-800 nm compared with the structure with rough nanowires.
When silver nanoparticles are introduced into the spaces between nanowires, we observe the appearance of surface plasmon resonance (SPR). For a structure with cylindrical nanowires, the SPR is observed at a wavelength of 870 nm, and for a structure with rough nanowires, the SPR peak is shifted to the long-wavelength region by 910 nm. Moreover, in the structure with rough nanowires, interference effects (Fabry-Perot effect) are less pronounced.
In further studies, it is planned to calculate the optical spectra of such structures with non-periodic distribution of silver nanoparticles, which is most often observed in the experiment.
 
1.	Luisier M. Investigation of thermal transport degradation in rough Si nanowires // J. Appl. Phys. 1.-2011.-110.-P.074510.