Growth of CsLiB₆O₁₀ thin films on Si substrate by pulsed laser deposition using SiO₂ and CaF₂ as buffer layers

Abstract

CsLiB₆O₁₀ (CLBO) thin films are grown on Si (100) and (111) substrates using lower index SiO₂ and CaF₂ as buffer layers by pulsed KrF (248 nm) excimer laser ablation of stoichiometric CLBO targets over a temperature range of 425 to 725°C. A CaF₂ buffer layer is grown on Si by laser ablation while SiO₂ is prepared by standard thermal oxidation. From extended x-ray analysis, it is determined that CaF₂ is growth with preferred orientation on Si (100) at temperatures lower than 525°C while on Si (111) substrate, CaF₂ is grown epitaxially over the temperature range; this agrees well with observed reflection high energy electron diffraction patterns. X-ray 2θ-scans indicate that crystalline CLBO are grown on SiO₂/Si and CaF₂/Si (100). Analysis of reflectance spectra from CLBO/SiO₂/Si yields the absorption edge at 182 nm. Surface roughness of the CaF₂ and CLBO/CaF₂/Si film are 19 and 15 nm, respectively. This relatively rough surface caused by the ablation of wide bandgap CaF₂ and CLBO limits the application of CLBO for waveguiding measurement.