Formation of silicon nanoparticles by a pressure induced nucleation mechanism

• Published in: Nanoscale 2013-04, Vol.5 (8), p.3266-3271
• Main Authors: Kang, Myung-Koo, Kim, Si Joon, Kim, Hyun Jae
• Format: Article
• Language: English
• Subjects: Density; Grain size; Lasers; Liquids; Nanostructure; Nucleation; Silicon; Silicon dioxide
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c3nr34178j

Formation of silicon nanoparticles (SiNPs) was achieved using excimer laser crystallization of an amorphous Si (a-Si) thin film using a SiO 2 capping layer (C/L) with improved thin-film transistor (TFT) performance due to the enlarged grain size of polycrystalline Si (poly-Si). After laser irradiation of an a-Si thin film covered with C/L, fluctuation in the surface morphology of the C/L was observed above the critical laser energy density ( E cr ) with the formation of SiNPs. The grain size of the poly-Si layer after crystallization increased abruptly at the same time. A non-uniform pressure distribution beneath the SiO 2 C/L was proposed for the initiation of nucleation, which is named pressure induced nucleation (PIN) mechanism. Following nucleation, the release of latent heat made it difficult for the remnant liquid Si to solidify and the volume increased due to the density difference between the liquid and solid Si. Consequently, the pressure on the liquid Si caused SiNPs to sprout through the SiO 2 C/L as grains grew from the low temperature to high temperature point. This study offers not only a simple method to fabricate SiNPs with controllable size/density but also larger grain size with lower laser energy density, which leads to higher TFT performance. Si nanoparticles and polycrystalline Si were formed using laser crystallization of an amorphous Si thin film with a SiO 2 capping layer.