Patterning of ferroelectric β′-Gd₂(MoO ₄)₃ crystal lines on the glass surface by transition metal atom heat processing

Lines consisting of ferroelectric β′-Gd₂(MoO ₄)₃ crystals are patterned on the surface of NiO (2 mol%)-doped 21.25Gd₂O₃·63.75MoO₃· 15B₂O₃ glass by continuous wave (cw) Nd: YAG laser irradiations with a wavelength of λ = 1064 nm, where laser energies absorbed by Ni²⁺ ions are converted to the local heating of surrounding Ni²⁺ ions. The surface morphology of crystals in the patterned lines is clarified from confocal scanning laser microscope observations. β′-Gd₂(MoO₄)₃ crystal lines patterned by laser irradiations with a power of 0.73 W and a scanning speed of 2.5 μm/s show a smooth surface with a bump (width: 9 μm, height: 3 μm), and it is suggested from polarized micro-Raman scattering spectra that β′ -Gd₂(MoO₄) ₃ crystals might orient along the laser scanning direction. The present study demonstrates that the transition metal atom heat processing, i.e., a combination of cw Nd:YAG laser and Ni²⁺ ions, is a novel technique for spatially selected crystallization in rare-earth containing glasses.