Tunable Surface Plasmon Resonance in Sn-Doped Zn-Cd-O Alloyed Nanocrystals

Aliovalent ion doped n-type semiconductor nanocrystals (NC) have presently gained high interest in semiconductor research for their potential applications in plasmonics, transparent conducting oxide (TCO), and high speed optical device. For most of the cases the plasmonic absorbance band appears in the near infrared region (NIR) but it is rarely observed in visible wavelength for aliovalent ion doped semiconductor nanocrystals. In this article, we report the synthesis of Sn-doped ZnO monodispersed nanocrystals and their unique plasmonic absorbance property which is tunable from the visible to the NIR region (550 nm to >3000 nm) by varying the Sn dopant concentration and the degree of Cd-alloying. We have studied the surface enhanced Raman spectroscopy (SERS) of the 4-mercaptopyridine (4-MPy) molecule using Sn:ZnO NC thin film as SERS substrate and found a high enhancement factor value. A TCO thin film with a good figure of merit value has been prepared by Sn:ZnCd-O alloyed NCs by taking advantage of high electron density and high mobility of electrons of doped alloyed NCs. Application as SERS substrate and TCO are excellent features of Sn-doped Zn1-xCdxO NCs.