Atomic-scale surface control and second-harmonic generation in GdxY(1-x)Ca4O(BO3)3 thin films grown by combinatorial laser molecular-beam epitaxy

We studied the atomic-scale, growth control and second-harmonic generation (SHG) properties of GdxY1-xCa4O(BO3)(3) thin films. Combinatorial laser mol ecular-beam epitaxy was employed to optimize the growth conditions of the f ilm. Ultrasmooth GdxY1-xCa4O(BO3)(3) thin films with step-and-terrace struc ture were obtained by using atomically controlled GdCa4O(BO3)(3) substrates . The dependence of SHG intensity on the fundamental wave polarization angl e was studied for the epitaxial film on (010) GdCa4O(BO3)(3) substrate in c omparison for the randomly oriented film on (0001) sapphire substrate. It w as found that only the epitaxially grown film clearly exhibited a fourfold SHG intensity showing type-II phase-matching direction. (C) 2001 American I nstitute Of Physics.