THE MAGNESIUM DIFFUSED LAYER CHARACTERISTICS OF A LITHIUM-NIOBATE SINGLE-CRYSTAL WITH MAGNESIUM-ION INDIFFUSION

A Mg-ion indiffusion process was applied to lithium niobate single cry stal substrates with a deposited magnesium oxide thin film. By means o f electron probe microanalysis and X-ray diffraction analysis, the ME concentration distribution along the depth of the magnesium diffused l ayer was obtained and the activation energy for Mg-ion indiffusion was determined to be 288 KJ/mol. It was also determined that the magnesiu m diffused layer exhibits a crystal structure of an unknown compound f rom the Mg-Li-Nb-O ternary system. It is proposed that this unknown co mpound and MgNb2O6, which form during a solid state reaction between t he thin layer of MgO and the lithium niobate crystal in a Li2O-rich at mosphere, are the real sources for Mg-ion indiffusion into lithium nio bate. The high activation energy and the appearance of this unknown co mpound in the magnesium diffused layer suggest that Mg-ions diffuse su bstitutionally into the lithium niobate crystal. Mechanisms causing a decrease in the refractive index of the Mg diffused layer are also dis cussed.