Photoluminescence Studies of Li-Doped Si Nanocrystals

Eva Klimešová,Václav Hol,Jiří Vacík,Ivan Pelant

doi:10.5772/56925

Abstract

We investigate the optical properties of Li-doped Si nanocrystals (both freestanding and matrix-embedded), which are potentially an important material for the new generation of lithium-ion batteries. Our samples contain 10 – 100 Li atoms per one Si nanocrystal and their lattice is slightly expanded. The photoluminescence (PL) spectra of the S-band of Li-doped Si nanocrystals are blue-shifted by ∼30nm compared to the undoped Si nanocrystals and their PL lifetime is correspondingly shorter. The F-band emission is almost unaffected by Li doping. The observed changes in the PL performance are probably caused by Si lattice expansion induced by Li insertion. The reported spectral blue shift is favourable for certain photonic applications.

Highlights

Si nanocrystals (SiNCs) are a widely investigated nanomaterial because their optical and mechanical properties are different from bulk Si and, in many cases, more favourable for various applications [1,2,3]
We investigated Li‐doped SiNCs that are a relevant material for Li‐ion batteries
We showed that PL properties of Si nanocrystals are modified after doping with Li

Summary

Introduction

Si nanocrystals (SiNCs) are a widely investigated nanomaterial because their optical and mechanical properties are different from bulk Si and, in many cases, more favourable for various applications [1,2,3]. Bulk Si – the predominant material in electronics – has an indirect band gap and exhibits a very inefficient luminescence. Light sources for optoelectronics, such as light‐emitting diodes (LEDs) or lasers, cannot be directly produced from bulk Si and the applications of Si cannot be extended from electronics to optoelectronics and photonics. Contrary to bulk Si, SiNCs with sizes of several nanometres exhibit visible photoluminescence at room temperature [4] and are a prospective material for optoelectronic light‐ emitting devices [1, 3]. For the development of a Si‐ based laser a photoluminescence (PL) spectrum at shorter wavelengths is desirable because it reduces free carrier absorption that is one of the most significant competing mechanisms acting against optical gain in SiNCs [9]

Methods

Results

Discussion

Conclusion