Lattice mismatch and crystal growth of monoclinic KY1-xYbx(WO4)2/KY(WO4)2 layers by liquid phase epitaxy

Monoclinic layers of KY1-xYbx (WO4)(2) with a thickness of up to 330 mu m were grown on KY(WO4)(2) substrates by liquid phase epitaxy (LPE) using K2W2O7 solvent. The layers grown from solutions of up to 7.5 at.% substitution of Y by Yb generally had flat surfaces on {010} and {110} crystal faces with no macroscopic defects at the layer/substrate interface. Already at 10 at.% of Yb substituting Y, some defects at the interface tend to appear and increase for higher concentrations. The layers grown on {310} and {(1) over bar 11} faces show more growth instabilities even at low Yb concentrations. The thermal evolutions of the lattice mismatches between the epilayer and the substrate for {010}, {110}, {310} and {(1) over bar 11} faces were calculated to range from 0.55% at 1273 K to -0.31% at 298 K. The optical spectroscopic studies carried out with these samples agree well with Yb-doped KYW bulk crystals, the measured absorption and calculated (by the reciprocity method) emission cross-sections at 981 nm with E parallel to N-m being sigma(abs) = 12.5 x 10(-20) cm(2) and sigma(em) = 15.8 x 10(-20) cm(2), respectively.