24P050-P
Ion-beam induced visible luminescence of Er2O3
酸化エルビウムの可視域イオンビーム誘起蛍光Daiji Kato, Hiroyuki A. Sakaue, Izumi Murakami, Teruya Tanaka, Takeo Muroga and Akio Sagara
加藤太治, 坂上裕之，村上 泉，田中照也，室賀健夫，相良明男
National Institute for Fusion Science322-6, Oroshi-cho, Toki, Gifu 509-5292, Japan
核融合科学研究所 〒509-5292 岐阜県土岐市下石町322-6

Ion-beam luminescence of sintered Er2O3 samples irradiated by Ar+ ion-beams was measured in avisible range. Three luminescence bands observed at 640-690, 540-580, and 490-520 nm are due
to intra-4f transitions of Er3+ (4f11) in the sample. The clean Stark spectrum of the luminescenceband at 640-690 nm suggests that the emitter Er3+ is situated in the C2 cation sites of pure Er2O3.
Each Stark component has the Lorentzian profile having a ~1012 Hz width in frequency. However,
the resonance broadening accounts only 1 % of the total width.
1. Introduction
Er2O3 electric insulating coating is being
developed for reduction of the MHD pressure dropin Li/V-alloy blanket systems [1]. It wasdemonstrated that the Er2O3 coating serves also as atritium permeation barrier of blanket systems madeof other breeder and coolant such as Flibe andLi-Pb [2]. However, neutron damages of the coatingin fusion reactors are a big concern. Ion-beamdamages are often used to simulate the neutron
damages. Changes in crystallinity of the irradiatedsample may be inferred from changes in ion-beam
induced luminescence spectra, because opticaltransitions of trivalent Er ions (Er3+) in the Er2O3
crystals are known rather strong and sharp [3]. The
ground state of Er3+ has an incomplete 4f sub-shell(4f11). The intra-4f transitions from lower excitedstates to the ground state are observed as theluminescence in Infrared and visible ranges. Tanakaet al. [4] investigated the ion-beam induced visible
luminescence of Er2O3 coating samples irradiatedby 100 keV H+ and Ar+ ion-beams at Osaka Univ.
The similar measurements have recently been
undertaken using an apparatus in NIFS in order tounderstand relations between the crystallinity andthe luminescence spectra. In the present study, thevisible luminescence spectra of sintered Er2O3
samples bombarded by Ar+ ion-beams weremeasured.
2. Experimental apparatus
The experimental apparatus consists of anion-beam source, a collision chamber, and a CCDspectrometer. The ion source is a part of medium
current ion implanter (ULVAC IM-200MH-FB)
used for semiconductor production (Freeman-type)in NIFS [5]. Ion-beam extracted from the Freeman
ion source was introduced into the collisionchamber after analyzing the mass to charge ratio bya magnet. We could use primary Ar+ ion beam ofabout 0.1 ~ several μA in current at 33, 50, and 70
keV in kinetic energy. In the collision chamber, amovable stage made of stainless steels was installed
to set the sintered Er2O3 sample disk (25 mmφ × 1mm). To the ion-beam axis, the sample surface wasleaned 45 degrees and placed (see Fig. 1). An
electrode with a hole of 5 mm diameter was placedin front of the sample. The electrode surface wasbiased -100 V to retard secondary electrons fromthe irradiated sample. The stage can be moved indirection parallel to the ion-beam axis.

Fig.1. Schematic illustration of the collision chamber
and the visible spectrometer.

After passing through a quartz window and theultra violet (UV) condenser lens, the light from thetarget sample was focused onto the entrance slit (30μm) of a spectrometer equipped with a charge
coupled device (CCD). The optical axis crosses
with the ion-beam axis and the sample surface atright angle and 45 degree, respectively.
3. Result and Discussion
Fig. 2 shows a luminescence spectrum obtainedby Ar+ ion-beams at incident energy of 33 keV.
Three luminescence bands are observed in thespectrum at 640-690, 540-580, and 490-520 nm,
which are assigned to the intra-4f transitions fromexcited states of 4F9/2, 4S3/2, and 4F7/2 to the groundstate, 4I15/2, respectively. Narrow emission lines of
sputtered neutral Er are also identified in thespectrum. Stark component in the luminescenceband at 640-690 nm are clearly resolved whereas
those in the other two bands cannot be identified.
Fig.3 shows the Stark spectrum in the band at640-690 nm together with 4F9/2 - 4I15/2 transition
wavelengths of Er3+ in the C2 cation sites of pureEr2O3 [6]. Each peak has the Lorentzian profile
having a ~1012 Hz width in frequency. The largeline width may be ascribed to perturbation byambient particles around the emitter, namely Er3+.
The broadening by mutual interaction between
nearby Er3+, i.e. the resonance broadening, is givenby,
wr  3

g1  e 2 f 
N ,g 2  40 m0 (1)where g’s are statistical weights of the upper andthe lower Stark levels, m electron mass, f theoscillator strength of the electric-dipole transition,
ω0 the transition frequency, and N the particle
number density of the emitter. The oscillator
strength values of doped Er3+ ions in Y2O3 [7] andEr3+ number density of the perfect Er2O3 crystal areadopted. However, it turns out that the resonancebroadening accounts only 1 % of the total width.
It is puzzling that the clean Stark spectrum of theluminescence band at 640-690 nm appears
suggesting no ion-beam damage at the local area ofthe emitter, because SRIM code [8] simulations
give 432 displacements in the target per incident
Ar+ at 33 keV. For a better understanding, variationof the intensity and the profile of the luminescenceband are to be investigated changing the ion-beamcurrent and the incident energy.
Acknowledgments
The present work is supported by UFFF029.

Fig.2. Measured luminescence spectrum. The
spectrum was obtained using a grating of 300
Grooves/mm. Reflectivity of the grating decreases withthe wavelength, and quantum efficiency of the CCD isalmost uniform over the whole wavelength range of thepresent interest.

Fig.3. Stark spectrum of the luminescence band at
640-690 nm. Dash-dotted lines indicate 4F9/2 - 4I15/2
transition wavelengths of Er3+ in the C2 cation sites ofpure Er2O3.
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