Characterization of Flame Grown Diamond Films by Luminescence and EPR
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FILMS BY
L. PEREIRA *,E. PEREI RA*,C.TA VARES*,M. NETO*, A.CREMADES**, J.PIQUERAS**, J.JIMENEZ***, P.MARTIN *Departamento de Fisica, Universidade de Aveiro, 3800 Aveiro, Portugal "*Departamento de Ffsica de Materiales, Facultad de Ciencias Ffsicas, Universidad Complutense de Madrid, 28040 Madrid,Spain ***Departamento de Ffsica de la Materia Condensada ETSII, 47011 Valladolid, Spain
ABSTRACT Flame grown diamond films, depending on the growth conditions may present various amounts of diamond like carbon (DLC) besides the diamond phase. A correlation of the morphology with the secondary electron emission, cathodoluminescence, photoluminescence, EPR and Raman data is presented for samples grown using in different ratios of oxygen and acetylene.
INTRODUCTION The acethylene torch synthesis of diamond films is a simple way of obtaining diamond thin films [1]. The possibility of doping the films during the growth with different dopants offers an unique way of defect introduction that may give useful properties to the films for optoelectronic applications [2]. Therefore, a detailed study of the growth conditions and the properties of the films is required. there are already some reports on the cathodoluminescence of diamond films [3,4], a few on photoluminescence [5] and EPR [6]. Nevertheless, a correlation between the different results is seldom made. In the present work we show a detailed study of the characteristics of diamond films grown by the torch flame method, correlating the growth conditions with the film properties. EXPERIMENTAL The samples were observed in the emissive and CL modes at 77 K in a Hitachi S-2500 scanning microscope at voltages of 10 kV. To record the spectra an optical lens was used to focus the light on a waveguide feeding the light to an Oriel 78215 computer controlled monochromator. 811
Mat. Res. Soc. Symp. Proc. Vol. 358 01995 Materials Research Society
Raman spectra were obtained with a DILOR X-Y Raman spectrometer coupled with a metallographic microscope that allowed to probe small volumes with a lateral resolution better than I pm, allowing the study of micronsize structures. Excitation was made with the 514.5 nm line of an Ar+ laser. Different structural features of the films were selected for these measurements. Time resolved photoluminescence ms-/as range was recorded with a SPEX 1934 C Phosphorimeter. The sample is excited by a Xenon flash with a pulse duration of 3/pm. The steady state spectra are excited by a Xe 250 W lamp. The spectra are obtained with a 1702/ 04 spectrometer coupled to a SPEX DM-lB computer. The temperature of the samples was head constant within 0.2 K from 10 K to room temperature in a closed cycle helium temperature. Photoluminescence and cathodoluminescence spectra have been corrected for the spectral dependence of the optical set up. EPR spectra were obtained in a BRUKER ESP 300 spectrometer. All the EPR spectra were obtained at room temperature, after calibration of the spectrometer with a DPPH sample. SAMPLE PREPARATION The samples were grown by the torch
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