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Yap C.M.,IIa Technologies Pte Ltd. 17 | Tarun A.,IIa Technologies Pte Ltd. 17 | Xiao S.,IIa Technologies Pte Ltd. 17 | Misra D.S.,IIa Technologies Pte Ltd. 17
Diamond and Related Materials | Year: 2016

This study describes the growth of 13C-enriched (100)-oriented diamond single crystals by the MPCVD (microwave plasma chemical vapour deposition) process. All crystals are at least 6 × 6 mm2 in area and 0.5-1.0 mm in thickness. The samples with nominal 13C percentages (R = [13C] / [13C + 12C]) of 0.011 (natural abundance), 0.10, 0.21, 0.24 and 0.34 were obtained by controlling the flow of the carbon-13 and carbon-12 methane feed gases. To obtain thicker and near-colourless quality 13C-enriched diamond, 190 ppm of nitrogen was added into the gas mixture. The shift towards lower frequency in the Raman peak positions and decrease in the thermal conductivities of the near-colourless crystals with increasing 13C percentages are similar to previous studies of isotopically-controlled diamond grown with no nitrogen additive. The images of the structural defects associated with 13C-enrichment obtained by spatially-resolved X-ray rocking curve measurement show distinct patterned structures that runs parallel to the < 100 > direction. Moreover, the broadening in the line width of the nuclear magnetic resonance (NMR) peak from sp3 13C correlates with increasing R. We also expand the study by injecting 500 ppm of nitrogen. Higher nitrogen concentration leads to the formation of brown crystals. The brown crystals show far greater 13C NMR peak intensity than the near-colourless. This suggests that paramagnetic nitrogen impurities in the brown crystals hasten the spin-lattice relaxation time of the 13C nuclear spin that resulted in higher intensity. The isotopic splitting observed for the localized vibrational mode of the NVH0 defect in brown crystals is attributed to the co-existence of both the 13C (3114.2 cm- 1) and 12C (3123.5 cm- 1). Unlike the isotopic splitting observed for NVH0 defect, the peak position of the Ns + defect shifts towards lower frequency as R increases. Not only have we demonstrate the growth of bigger isotopically-controlled diamond single crystals, the results shown here have provided a framework to further investigate the interplay between 13C atoms and nitrogen impurity. © 2015 Elsevier B.V. All rights reserved.


Tarun A.,IIa Technologies Pte Ltd. 17 | Lee S.J.,IIa Technologies Pte Ltd. 17 | Yap C.M.,IIa Technologies Pte Ltd. 17 | Finkelstein K.D.,Cornell University | Misra D.S.,IIa Technologies Pte Ltd. 17
Diamond and Related Materials | Year: 2015

Radiation detectors based on diamond are highly favored for particle physics research due to the superior radiation hardness. In this work, we investigate the influence of impurities and crystalline imperfections on the charge collection efficiency (CCE) of single crystal diamond. Seventeen (17) ultra-low fluorescent diamond samples grown by microwave plasma chemical vapor deposition method from IIa Technologies PTE LTD are pre-selected for this study. The measured CCE of all samples using 241Am (α-particles) as ionizing source are analyzed together with the concentration of trace impurities and crystalline imperfection in the crystal. The amounts of impurities are quantified from integrated fluorescence intensity arising from the nitrogen vacancies (NV) created during different CVD growth process conditions. The crystal imperfections are assessed by X-ray rocking curves from X-ray topography images obtained at the Cornell High Energy Synchrotron Source. The CCE decays rapidly as the intensity of NV (I NV ), phonon sideband approaches that of diamond 2nd order Raman peak which follows the relation: CCEINV=100/1+INV1.052. The energy resolution, δE/E (ratio of the energy spectrum width to the most probable peak) highly correlates with broader rocking curve width distribution. Prime novelty statement: This work provides an understanding on the most important factors that contribute to degradation of charge collection efficiency (CCE) in diamond based detectors and sensors. The CCE decays rapidly as the intensity of nitrogen vacancy phonon sideband approaches that of diamond 2nd order Raman peak which follows the relation: CCEINV=100/1+INV1.052. The energy resolution, that is the ratio of the energy spectrum width to the most probable peak, highly correlates with broader X-ray rocking curve width distribution. © 2015 Elsevier B.V.

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