Electrical Properties in CVD Diamond Films
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ELECTRICAL PROPERTIES IN CVD DIAMOND FILMS S. Zhaoa, K.K. Gan", H. Kagana, R. Kassa, R. Malchowa, F. Morrowa, W. Palmera, C. Whitea, L.S. Panb, S. Hanb, D. Kaniab, M. Planoc, M. Landstrassc, M. Leed, S. Kimd, F. Sannesd, S. Schnetzerd, R. Stoned, G. Thomsond, y. Sugimotoe, A. Fryf, S. Kandag, S. Olseng. 'Department of Physics, The Ohio State University, Columbus, OH 43210; bLaser Division, Lawrence Livermore National Laboratory, Livermore, CA 94550; cCrystallume Inc., Menlo Park, CA 94025; 'Department of Physics, Rutgers University, Piscataway, NJ 08854; 'KEK National Laboratory, Tsukuba-shi, Ibaraki-ken, Japan 305; 'Physics Division, Superconducting Super Collider Laboratory, Dallas, TX 75237; gDepartment of Physics, University of Hawaii, Honolulu, HI 96822.
ABSTRACT The electrical properties associated with carrier mobility, p, and lifetime, r, have been investigated for the chemical vapor deposited (CVD) diamond films using charged particle-induced conductivity and time resolved transient photo-induced conductivity. The collection distance, d, the average distance which electron and hole depart when driven by an applied electric field E, was measured by both methods. The collection distance is related to the carrier mobility and lifetime by d = pEr. Our measurements show that the collection distance increases linearly with sample thickness for CVD diamond films. The collection distance at the growth side of the CVD diamond film is comparable to that of single crystal natural type Ha diamond; at the substrate side of the film, the collection distance is near zero. No saturation of the collection distance is observed for film thickness up to 500 microns.
INTRODUCTION The use of diamond films for radiation tolerant electronic applications has recently generated considerable interest. This is primarily due to diamond's extreme properties (radiation hardness, high mobility and large band gap etc.) and developments in the chemical vapor deposition growth process. In particular, the detection of radiation using diamond as the detector medium is being actively pursued for fast charge particle and photon detectors. Used in this manner, the detector performance is directly associated with the quality of the CVD diamond films. In the past few years, significant improvements in the quality and reduction of cost have been achieved. The collection distance, a characteristic of the electrical properties of diamond, was studied as a function of film thickness for polycrystalline CVD diamond films.
EXPERIMENTS AND RESULTS Polycrystalline CVD diamond typically grows in cone shaped columnar structures. The substrate side of the films begin with small grains, typically lpm or less. The average grain size on the growth side of the films increases with film thickness. The grains exhibit a preferred crystal orientation, usually (110), which was determined from Mat. Res. Soc. Symp. Proc. Vol. 302. ©1993 Materials Research Society
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x-ray diffraction studies. With the columnar structure along the growth direction, it is possible
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