Dissertation
Dissertation > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Non-metallic elements and their compounds > Part Ⅳ family of non-metallic elements (carbon and silicon ) and its compounds > Carbon C

Photoluminescence Studies of Optical Centres in Electron-irradiated Diamond

Author WangKaiYue
Tutor LiZhiHong
School Tianjin University
Course Materials Science
Keywords Diamond Electron irradiation Photoluminescence Optical centre
CLC O613.71
Type PhD thesis
Year 2012
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This thesis mainly focused on determining the natural structures and chargestates of the optical centres in diamonds by using low-temperature photoluminescence(PL), following electron irradiation. A great number of related samples were involved;including ultrapure CVD diamonds, low-nitrogen Ⅱa diamonds, high nitrogen HTHPand CVD diamonds, and boron doped HTHP diamonds as well as some isotope-dopeddiamonds such as13C,15N,11B and so on.Both ultrapure and type Ⅱa diamonds only presented Raman signal inlow-temperature PL spectra, while lots of interstitial-and vacancy-related zerophonon lines were created in the range of500~600nm except GR1signal afterelectron irradiation. The3H centre and the rather strong lines at515.8nm,533.5nmand580nm were commonly observed in those samples, which we concluded are allassociated with the interstitials aggregation. The migration experiments suggest thatthe3H centre, and580nm centre have lower migration energy, but the533.5nm and515.8nm centres are harder to move out of the irradiated region.PL spectra of high-nitrogen Ib diamonds showed, in addition to the Raman line, avery strong NV signal. Another centre, named H3, which is caused by the trapping ofa vacancy by two neighbouring substitutional nitrogen atoms (a so-calledA-aggregation), was sometimes observed in PL spectra of type Ia diamonds. Afterelectron irradiation, the523.7nm and626.3nm centres were created in HTHP highnitrogen-doped diamonds in addition to the commonly observed3H and GR1luminescence. All these centres were enhanced by increase of the nitrogen content ofthe diamond except the GR1signal which decreased. The PL results indicated that the626.3nm centre was due to a nitrogen-interstitial complex, but no clear conclusionwas found for the523.7nm centre.The well-known ND1, TR12and389nm centres were obtained in the PL spectraof the nitrogen containing samples with a325nm excitation at liquid heliumtemperature. The TR12centre is probably related to a C interstitial complex because ithas a high energy local mode at509nm. The389nm line has been demonstratedpreviously resulting from C interstitial and nitrogen complex. The higher nitrogen samples yielded stronger389nm but weaker TR12luminescence.The DB1centre was found to be of considerable interest in the boron-doped typeⅡb diamonds, following electron irradiation because of its thermochromic andphotochromic behaviour. There is some evidence implying that the DB1centre is apositively charged defect, and it is strengthened after uv exposure. This remarkableenhancement was annealed out after annealing at200℃, but could be re-introduced byfurther uv exposure.

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