Photoluminescence Properties of CVD Diamond Excited by Ultra-Violet Synchrotron Radiation
- PDF / 348,354 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 115 Downloads / 175 Views
ABSTRACT Photoluminescence (PL) properties of microwave-assisted chemical-vapor- deposition (CVD) diamond have been studied using ultraviolet synchrotron radiation. The defect-related 5RL PL feature, which was not detected in cathodoluminescence (CL), was observed for both undoped and boron-doped (200ppm) CVD diamond. The defect formation in the thin nearsurface layer is discussed in relation to dependence of PL spectra on incident photon energy. In the case of boron-doped diamond, the boron-related peak was detected at 2.3eV while the band-A feature was not observed at 2.9eV. PL excitation (PLE) spectra associated with these emissions are also discussed in relation to absorption coefficients at energies above the band gap. INTRODUCTION Luminescence spectroscopy has been proven to be a sensitive technique for identification of impurities and other defects in semiconducting materials. Luminescence induced by ultra-violet radiation was used for many years in study of natural and synthetic diamonds [1]. The band structure of the ideal diamond is well understood from a theoretical point of view [2,3]. Recently, a number of works were conducted to characterize the growth process and to measure the properties of chemical-vapor-deposition (CVD) diamond [4-7]. However, photoluminescence (PL) experiments have been limited to measurements using excitation lights below the diamond band-gap energy diamond (5.5eV) simply because high intensity and high-energy excitation sources were not conventionally available. In this work, low-temperature cathodoluminescence (CL) and PL were used to investigate radiative recombination processes in undoped and boron-doped CVD diamonds since both PL and CL are techniques sensitive to the near surface region of diamond. Because of large diamond absorption of excitation lights in the direct-transition energy range (>_7.0eV) [8], PL can be used for characterization of defect formation in the thin near surface layer as well as for study of diamond band structure using excitation spectra. EXPERIMENT Diamond films were grown on p'-Si substrates by means of microwave plasma CVD method. All the substrates used were subjected to ultrasonic pretreatment with diamond powders. The source gas used in the growth experiment consisted of 100 sccm CO (1 0%)-H2 (90%) mixture. In order to dope boron into diamond films, H2 gas was replaced by B2-I6-diluted H 2 gas. The growth conditions employed were as follows: total pressure 45 Torr, microwave power 250W and substrate temperature 9300C. The concentration of boron dopant in the reaction gases, estimated from boron-to-carbon (B/C) ratio , was 200 ppm in all the doping experiments. PL measurements were carried out in a chamber with pressures below 10 8Torr using synchrotron 717
Mat. Res. Soc. Symp. Proc. Vol. 423 0 1996 Materials Research Society
radiation from the 750-MeV storage ring located in the Institute for Molecular Science, Okazaki, Japan. A toroidal-grating monochromator was used to select photon energy ranging from 6.0eV to 13.8eV. For PL measurement
Data Loading...
