KBr 基板上に作製されたバナジルフタロシアニン薄膜の結晶形態と非線形光学特性

Abstract

In this paper, VOPc thin films are produced with molecular beam epitaxy (MBE) technique on KBr substrate. The morphologies of VOPc thin films on KBr are studied by a x-ray diffraction (XRD), optical absorption spectra in the visible and infrared regions (UV/VIS), scanning electron microscopy (SEM) and reflection high energy electron diffraction (RHEED). The VOPc thin film deposited for 60 minutes at 80℃ on a KBr (100) substrate composes of unidirectionally-oriented single crystals. The VOPc thin film on KBr (100) surface is a epitaxial growth crystals. At Ts : 200℃, the average size of crystals is about 1×1×0.1μm^3. The VOPc film prepared with MBE method is dominated by epitaxially-grown crystals with increasing Ts. This means that molecules on KBr surface can migrate with increasing Ts to form epitaxially grown crystals. 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 optical single crystal are not well understood yet. We succeeded to prepare a large nonlinear single crystal. It was obtained with the control of substrate temperature, evaporation time and annealing time. We estimated the third order Nonlinear optical susceptibility χ^<(3)> from the TH intensity for VOPc single crystal. Its χ^<(3)> value estimated is 9.5×10^<10> esu. The value is 3 times higher than the value reported recently.