Characterization of CVD Diamond Films by Optical Spectroscopies
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CHARACTERIZATION SPECTROSCOPIES
OF
CVD
DIAMOND
FILMS
BY
OPTICAL
JOEL W. AGER III', SUNG HAN", RON S. WAGNER***, LAWRENCE S. PAN ***,D.R. KANIA..... AND STEPHEN M. LANE .... *Center for Advanced Materials, Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720 "**Department of Nuclear Engineering, University of California at Berkeley, Berkeley, California 94720 ***Electronics Division, D429, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 ****Laser Program of Lawrence Livermore National Laboratory, L-476, Livermore, California 94550 *****Crystallume, Menlo Park, CA 94025 ABSTRACT Raman and photoluminescence spectroscopy was used to investigate radiation damage by 5 MeV He' ions at room temperature in prototype CVD-diamond detector material. Amorphization of the diamond is not observed at fluences up to 8x10' 5 cm 2 . A threshold behavior is seen in the formation of the H3 vacancy-dinitrogen color center. The defect is not 2 a linear behavior increase in H3 observed for fluences in the range 1.6x1012 to 1.6xl0x3 cma; 14 5 intensity is observed over the range 1.6x10 to 1.6x10" cm 2 . The formation mechanism of the H3 color center under He' irradiation involves a self-annealing effect that allows vacancies to diffuse to, and complex with, nitrogen complexes. INTRODUCTION CVD diamond films have been proposed as rugged photoconductive detectors forradiation and particles with energies greater than the indirect gap of 5.5 eV. The presence of extended and point defects, both in the as-grown material and induced by the operating environment, will affect the performance of practical detectors. Defect characterization methods are required in order to determine operating conditions for diamond detectors. Raman spectroscopy is used routinely in CVD diamond manufacturing to monitor levels of non-diamond carbon and to provide a rough measure of defect density [1]. Photoluminescence (PL) spectroscopy has been used extensively to identify and monitor intrinsic and extrinsic defects in natural and synthetic diamonds [2]. In this work, we use Raman and PL characterization to evaluate lattice damage in an ongoing study on the effects of radiation damage on diamond detector performance. EXPERIMENTAL The single-crystal, natural type IHa diamond (2 mm x 2 mm x 200 p.m thick), was supplied by DubbleDee Harris Corp. High-mobility diamond films (120 gm thick) were grown by microwave CVD at Crystallume [3,4]. A series of CVD and natural samples is used in this study. Five pieces from a CVD sample and the natural Ia sample were exposed to 5 MeV He'
Mat. Res. Soc. Symp. Proc. Vol. 302. ©1993 Materials Research Society
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ions at beam current of ca. 15 nA at total fluences of 1.6x10 12 cm 2 to 1.6x10' 5 cm 2 . A 0.5 mm diameter mask was used to define the irradiated area. The details of the irradiation process have been described in a previous report [5]. Raman and photoluminescence spectra were obtained using the 488 nm line of an Ar ion laser. The laser spot size in the macro sampling mode used
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