Fluorescent Decay Time and Energy Response of γ-CuI Crystal

doi:10.15541/jim20160262

Abstract

Abstract:

γ-CuI crystal was prepared by using slow solvent evaporation method. The optical transmission spectrum reveals that the crystal is transparent with band gap of 2.96 eV. Two near-band-edge emission peaks are located at 410 nm, 430 nm, and an iodine related defect emission band near 720 nm of the crystal appear under UV excitation. The emission band near 720 nm can be suppressed by iodine annealing, while a new and relative strong near-band-edge emission peaked at 420 nm appears. Decay times of emission peaks and band of γ-CuI crystals were measured by using streak camera. The results show that the decay times of all near-band-edge emission peaks are tens of picosecond, which indicates that γ-CuI crystal is one of the fastest scintillators, but the decay time of the emission band near 720 nm is mainly tens of nanosecond. γ-CuI crystal presents a near-band-edge emission peaked at 435 nm and a broad emission band near 680 nm under X-ray excitation. The energy response of the near- band-edge emission to X-ray shows that the emission has a relatively high response to X-ray when the X-ray energy is less than 49.1 keV.

Key words: γ, -CuI crystal, ultrafast scintillator, decay time, energy response to X-ray

CLC Number:

O734

LI Feng-Rui, GU Mu, HE Hui, CHANG Li-Hua, WEN Wei-Feng, LI Ze-Ren, CHEN Liang, LIU Jin-Liang, OUYANG Xiao-Ping, LIU Xiao-Lin, LIU Bo, HUANG Shi-Ming,NI Chen. Fluorescent Decay Time and Energy Response of γ-CuI Crystal[J]. Journal of Inorganic Materials, 2017, 32(2): 163-168.

Figures/Tables 10

Fig. 1 Measurement schematic of decay time

Fig. 2 Measurement schematic of energy response to X-ray

Table 1 Type of filters

Emission	410 nm	420 nm	430 nm	720 nm	400-450 nm
Model	BP410-10K	BP420-10K	BP430-10K	BP740-280K	Non-standard part
Peak wavelength/nm	411	423	431	750	424
FWHM/nm	10	10	10	280	50
Transmittance/%	65	72	72	72	89

Table 2 Average energy of X-ray emitted by different targets

Target	Fe	Cu	Ge	Zr	Ag	Sn	Nd	Dy	W	Au
E_X/keV	6.7	8.1	10.4	16.7	23.5	26.9	39.5	49.1	63.0	73.0

Fig. 3 XRD (a) and EDS (b) patterns of CuI crystal

Fig. 4 Transmission spectrum of γ-CuI crystal

Fig. 5 Photoluminescence of γ-CuI crystal (a), and the streak camera images and temporal profiles of the emissions near 410 nm (b), 430 nm (c) and 720 nm (d), respectively

Table 3 Decay time of the emission peaks (band) of γ-CuI crystal

Emission	410 nm		430 nm		720 nm
Decay time	τ=24.6 ps	I=100%	τ=46.7 ps	I=100%	τ₁=5.92 ns	I₁=34%
Decay time	τ=24.6 ps	I=100%	τ=46.7 ps	I=100%	τ₂=67.04 ns	I₂=66%

Fig. 6 Photoluminescence of I2 annealed γ-CuI crystal (a) and streak camera image and temporal profile of the emission at 420 nm of γ-CuI crystal (b)

Fig. 7 X-ray excited luminescence of γ-CuI and PbWO4 crys- tals (a) and energy response of γ-CuI crystal to X-ray (b)

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