High-Quality Large-Size Organic Crystals Prepared by Improved Physical Vapor Growth Technique and Their Optical Gain Properties

We have developed an improved physical vapor transport method. This method enables us to decrease the sublimation temperature of small organic molecules, and slow the weight loss process, and then regulate the degree of vapor saturation of materials. Large-size single-crystalline materials with high quality are successfully prepared from small organic functional molecules. The slice crystals are found to be single crystalline with high quality. The surface morphologies and structural information of grown crystals were characterized by optical microscope, atomic force microscopy (AFM), and X-ray diffraction (XRD) analysis. The results indicate that the growth mechanism of single crystals is a 2D nucleation, with elementary steps, large straight steps, and layer-by-layer growth.