Luminescence line shape of free excitons in natural diamond

Abstract

The radiative recombination of free excitons in diamond has been previously reported by Dean et al. /l/. They showed that the valence band splitting due to spin-orbit interaction must be taken into account for a good understanding of their line shape. Their experiments were performed a t high temperature (T > 77 K) and with a relatively low resolution.In our experiments we used a cathodoluminescence apparatus, working in pulsed mode, described in preceding publications /2, 3/. The main characteristics are briefly recalled: 2 z < 1 n s for 0 < I < 2 A/cm , rise time: pulse length 8 : 10 n s < 8 < 1000 ns, acceleration voltage U: 20 kV < U < 100 kV.We worked generally with the following experimental conditions: 2 I * 1.6 A/cm , U = 50 kV, repetition rate f = 800 Hz.High injection r a t e s can be reached, so that we could observe the free exciton luminescence a t low temperature, down to about 4.2 K. The intensity of this line decreases very quickly below 77 K. We worked with a sample of "natural diamond", type I1 b.On Fig, 1 is reported the main emission line of free excitons a t 80 K. The maximum is situated a t 5.275 eV, as previously observed by Dean et al. /l/.The width a t half height is much l a r g e r than predicted when the valence band split off by the spin-orbit interaction is neglected.

Intrinsic exciton transitions of isotopically purified 13C studied by photoluminescence and transmission spectroscopy

“…It should be noted that although one previous study measured the luminescence and absorption spectra for N.A. C and 13 C, the fine structure splitting was not fully resolved due to their relatively high experimental temperatures (liquid nitrogen temperatures). 22) In addition, Hazama et al conducted those experiments at liquid helium temperatures, they did not target isotopically purified diamond (only N.A.…”

“…However, the intrinsic optical properties of diamond are not fully understood despite their potential applications such as deep-ultraviolet lightemitting devices. 9) For example, fine structure splitting parameters of diamond such as the spin-orbit interaction constant, [10][11][12][13][14][15] the electron-hole exchange interaction constant, [16][17][18][19][20] and the mass-anisotropy splitting parameter 21) have not reached a consensus on their quantitative values. In addition, the fine structure splitting of isotopically purified diamond has yet to be studied.…”

“…C) and isotopically purified ( 13 C) diamond should lead to efficient deep-ultraviolet light-emitting devices using isotopic homojunction engineering. 23) Herein the fine structure splitting of intrinsic exciton transitions is observed using photoluminescence and transmission spectroscopies for 13 C and N.A. C at liquid helium temperatures.…”

“…The thickness is about 300 μm. The third sample, 13 C HPHT , was grown by the HPHT method using commercial 13 C carbon powder as the carbon source and a Ni-2wt% Ti alloy as the growth medium. 27) 13 C HPHT is composed of at least 99% 13 C. The boron concentration is almost comparable to that of the N.A.…”

Cathodoluminescence de défauts dans le diamant naturel

“…Son histoire scientifique est malheureusement mal connue, en particulier nous ne pouvons savoir avec certitude s'il a été volontairement irradié ou si les défauts contenus dans ce cristal proviennent a) Une luminescence proche du gap due à la recombinaison d'excitons libres piégés sur des impuretés peu profondes ; l'analyse de ces raies est présentée par ailleurs [2].…”