Effect of laser annealing on crystallinity of the Si layers in Si/SiO2 multiple quantum wells

Abstract We report on continuous-wave laser induced crystallisation processes occurring in Si/SiO 2 multiple quantum wells (MQW), prepared by remote plasma enhanced chemical vapour deposition of amorphous Si and SiO 2 layers on quartz substrates. The size and the volume fraction of the Si nanocrystals in the layers were estimated employing micro-Raman spectroscopy. It was found that several processes occur in the Si/SiO 2 MQW system upon laser treatment, i.e. amorphous to nanocrystalline conversion, Si oxidation and dissolution of the nanocrystals. The speed of these processes depends on laser power density and the wavelength, as well as on the thickness of Si-rich layers. At optimal laser annealing conditions, it was possible to achieve ∼100% crystallinity for 3, 5 and 10 nm thickness of deposited amorphous Si layers. Crystallization induced variation of the light absorption in the layers can explain the complicated process of Si nanocrystals formation during the laser treatment.

[1]  Continuous-wave laser annealing of free-standing Si∕SiO2 superlattice: Modification of optical, structural, and light-emitting properties , 2006 .

[2]  Lorenzo Pavesi,et al.  Will silicon be the photonic material of the third millenium? * , 2003 .

[3]  Juergen Reif,et al.  Influence of local heating on micro-Raman spectroscopy of silicon , 2003 .

[4]  M. Först,et al.  Influence of excitonic singlet-triplet splitting on the photoluminescence of Si∕SiO2 multiple quantum wells fabricated by remote plasma-enhanced chemical-vapor deposition , 2006 .

[5]  L. Khriachtchev,et al.  Thermal annealing of Si/SiO2 materials: Modification of structural and photoluminescence emission properties , 2002 .

[6]  W. Li,et al.  Visible light emission from single layer Si nanodots fabricated by laser irradiation method , 2006 .

[7]  M. Räsänen,et al.  Laser-controlled stress of Si nanocrystals in a free-standing Si∕SiO2 superlattice , 2006 .

[8]  L. Canham.  Silicon quantum wire array fabrication by electrochemical and chemical dissolution of wafers , 1990 .

[9]  H. Richter,et al.  FTIR spectroscopic system with improved sensitivity , 2006 .

[10]  Structural and optical properties of Si/SiO2 multi-quantum wells , 2007 .

[11]  L. Ley,et al.  Optical properties and transport in microcrystalline silicon prepared at temperatures below 400 °C , 1981 .

[12]  Residual stress in Si nanocrystals embedded in a SiO2 matrix , 2006 .

[13]  Melvin Lax,et al.  Temperature rise induced by a laser beam , 1977 .

[14]  I. Gregora,et al.  Applicability of Raman scattering for the characterization of nanocrystalline silicon , 1999 .

[15]  T. Tada,et al.  Giant heating of Si nanoparticles by weak laser light: Optical microspectroscopic study and application to particle modification , 2005 .

[16]  P. Fauchet,et al.  Thermal crystallization of amorphous Si/SiO2 superlattices , 1999 .