Optical characterization of europium diphthalocyanine thin films

Thin films of europium diphthalocyanine were prepared on glass substrates by vacuum sublimation. The absorption and reflection spectra were recorded in the UV-Visible range. The B band absorption occurs at 360 nm and the Q band shows a doublet at 632 and 680 nm. From the absorption and reflectivity data, various optical parameters such as absorption coefficient (alpha), refractive index (n), extinction coefficient (k) and real and imaginary parts of the optical dielectric constant (epsilon.) were determined. (C) 2002

Step growth in single crystal diamond grown by microwave plasma chemical vapor deposition

Single crystal diamond films of varying quality are deposited using microwave plasma chemical vapor deposition (MPCVD) apparatus. Unpolished natural diamond seeds are used as substrates in the temperature (T-s) range 850-1200 degrees C. The gas mixture of methane (CH4), hydrogen (H,) and oxygen (0,) is used for the deposition of diamond. The deposition pressure is varied in the range 90 to 150 Torr. The films are characterized using scanning electron microscopy (SEM), Atomic force microscopy (AFM) and Raman spectroscopy techniques. The growth morphology of the films is found to be a sensitive function of the deposition parameters. The crystalline nature of the films change from polycrystalline to single crystal as we increase T, and for a certain set of parameters the filamentary growth of the diamond crystals can be seen. The films are polycrystalline in the range Of substrate temperature 850-900 degrees C and oriented grains of diamond crystals arc evident as the T, increases. The single crystal diamond growth is observed to proceed via the step growth mechanism with the evidence of bunching of the steps. Our study explores evolution of the growth of single crystal diamond in a wide range of parameters. (c) 2005 Elsevier B.V. All rights reserved