LUMINESCENT SILICON NANOSTRUCTURES VIA TIN OXIDE DOPING

Abstract

Tin oxide ( SnO2 )-doped Si nanorings of diameter in the range of 100 nm to 170 nm with an average width of 25 nm are synthesized by off-axis laser ablation (PLD) and are characterized by different techniques. The AFM observations show that the surface morphological features of films depend on the tin oxide concentration. The bandgap energies of undoped quantum dots are found to be 2.29 eV, while it decreases to 2.15 eV and 1.5 eV for 3 wt.% and 0.1 wt.% SnO2 -doped samples, respectively. The increase in the value of bandgap energy can be attributed to size reduction of particles. The Raman spectra of SnO2 -doped films are characterized by a broad Raman band with intensity maximum around 478 cm-1. Raman spectrum shows frequency shift which may be due to changes in the Si – O bond length or Si – O – Si bond angle. The activation energy at higher temperature is found to be 16.99 meV for 3 SnSi 209, 21 meV for 0.1 SnSi 209 and 18.1 meV for undoped silicon which shows that defect levels are present in all the samples, the conduction is due to the presence of holes. The synthesized films exhibit PL peak in the visible region. The PL emission peak and PL intensity depend on dopants and it is concluded that luminescence does not originate from localized states in gap but from extended states. The size and shape of nanostructures depend on the SnO2 concentration and the doping effects can be used as a significant guideline for tuning the electronic and optical properties of Si .