Third-harmonic generation and growth mechanism of vanadyl-phthalocyanine single crystals prepared on KBr substrate by molecular beam epitaxy

Abstract

Vanadyl-phthalocyanine (VOPc) single crystals were prepared on KBr (1 0 0) substrate by molecular beam epitaxy (MBE). The second and third-harmonic generations of nonlinear optical thin films are proportional to the square of the thickness. Therefore, it is important to prepare a large nonlinear optical single crystal. However, the conditions to prepare a large nonlinear optical single crystal are not well understood yet. In this paper, we succeeded to prepare a large nonlinear single crystal. It was obtained with the control of substrate temp., evap. time and annealing time. The orientation and nonlinear property of VOPc single crystal prepared by the MBE method were also studied. The size of maximum single crystal prepared on KBr is 4×9×0.16 μm. The absorption spectrum of sample has an absorption peak at 790 nm. It reveals that the growth of single crystal gradually grow to a large crystal merging small crystals and also suggest that the VOPc single crystal is monoclinically grown from the results of RHEED pattern and UV/VIS spectrum. We estimated the third-order nonlinear optical susceptibility χ (3) from the TH intensity for VOPc single crystal monoclinically grown on KBr. Its χ (3) value estimated is 8.5×10 −10 esu. The value is 3 times higher than the value reported recently.