Quantum Beam Science Research

5-4

Use of Diamonds for Single Ion Detection－ Real-Time Detection of Ion Impact Position by Fluorescence of Nitrogen Vacancy Centers －Fig.5-9 Photograph of diamonds irradiated by ultravioletlight
Photographs of diamonds containing dense nitrogen (left),electron-irradiated diamonds (middle), and diamonds
containing NV centers after thermal treatment (right). The
colors are peculiar to the impurities and defects.

No irradiation

15

N 56 MeV

20Ne 75 MeV

40

Ar 150 MeV

84

Kr 322 MeV

129Signal intensity (a.u.)

6000
5000

NV 04000
3000

NV

Normalized counts (a.u.)

120 µm

‒

2000
1000
0560

600

640

680

720

760

Wavelength (nm)

Xe 454 MeV

0Fig.5-10 Photoluminescence spectrum of created NVcenter
After electron irradiation and thermal treatment, thediamonds contain electrically neutral NV 0 centers and−negatively charged NV centers.

Fig.5-11 CCD images when an ion strikes a diamond
When an ion strikes a diamond containing NV centers, thevery weak luminescence light from the ion impact position issuccessfully detected.

A single ion causes temporary malfunctions and permanentfailures in semiconductors, which are called single event
effects (SEEs). To use semiconductors in harsh radiation
environments such as space, it is necessary to clarify themechanism of SEEs. This requires a technique for detecting asingle ion in real time. The technique of detecting the positionof fluorescence induced by a single ion on a luminescent sheet
is currently used. Therefore, we are exploring a luminescentsheet having strong fluorescence intensity capable ofdetecting a single ion. In this study, we focus on the featuresof nitrogen-vacancy defects (NV centers), which efficiently
absorb ultraviolet light and emit high-intensity fluorescence.
First, diamonds containing dense NV centers werecreated from synthetic diamonds containing dense nitrogen
impurities. By irradiating the sample with a 2 MeV electron
beam, vacancies were introduced into the diamond by thedisplacement damage mechanism. After electron irradiation,
thermal treatment at 800 °C was performed for 2 h. By

combining nitrogen impurities with vacancies, we successfully
created a diamond containing dense NV centers (Fig.5-9).
Photoluminescence spectrum analysis clearly revealed thatelectrically neutral NV0 centers and negatively charged NV
centers were created (Fig.5-10). As shown in the figure,additional defects other than NV centers were not found. Next,
the sample was irradiated with several ions at various energies.
A measurement system consisting of a highly sensitive CCD
camera and an image intensifier was developed. Using thesystem, fluorescence was successfully detected in real time
(Fig.5-11). The spots are detected in the diamonds containing
NV centers, but not in those without NV centers. This resultis regarded as demonstrating a fundamental technology forelucidating the mechanism of SEEs that reduce the reliabilityof semiconductors.
This work was partially supported by the Strategic
Japanese–German Joint Research Program of the Japan
Science and Technology Agency (JST).

Reference
Onoda, S. et al., Diamonds Utilized in the Development of Single Ion Detector with High Spatial Resolution, Transactions of the Materials Research Societyof Japan, vol.37, no.2, 2012, p.241-244.
JAEA R&D Review 201365