Nature | Vol 577 | 16 January 2020 | 349that is clearly resolved from the background, demonstrating success-
ful direct detection of neutrons (Fig. 4a). The pulse-height spectrum
shows a broad full-energy peak corresponding to the neutron-capture
reaction close to the dark-current noise background edge. When cad-
mium shielding (0.125-inch-thick; 1 inch = 2.54 cm) was placed in front
of the device to block most of the thermalized neutrons, the count rate
was reduced by 87%. This reduction stems from the high absorption of
neutrons below the cadmium cutoff energy (0.5 eV; ref.^22 ). The energy
resolution of this neutron-capture peak was 69.7%. This response is
very promising at this early stage.
An ideal neutron detector should be insensitive to γ-rays to ensure
that false neutron counts are not generated from incident γ radiation.
The ability of the LiInP 2 Se 6 device to discriminate against γ-rays was
evaluated on a thicker detector (~0.5 mm) exposed to a 0.2-mCi^57 Co
γ-radiation source (a photon flux multiple orders of magnitude higher
than the neutron source discussed earlier). Despite the higher flux, the
pulse-height spectra of the ambient background and under direct γ
irradiation shown in Fig. 3c are essentially identical, demonstrating
the negligible γ sensitivity of this material.
In conclusion, LiInP 2 Se 6 is the first, to our knowledge, direct thermal-neu-
tron semiconductor detector with intrinsic^6 Li to demonstrate a resolved
full-energy neutron peak above the background. Further improvements
in the neutron detection efficiency could be achieved by the growth of
larger single crystals, such as through the Bridgman growth method. Fur-
thermore, spectroscopic^241 Am α-particle detection is achieved with 13.9%
energy resolution. The excellent semiconducting properties and radiation
response achieved here demonstrate that LiInP 2 Se 6 has the potential to
transform neutron detection technology, which relies almost exclusively
on scintillation paradigms, and usher in the semiconductor modality for
direct-conversion thermal-neutron detection.
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availability are available at https://doi.org/10.1038/s41586-019-1886-8.
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