Journal
NANO LETTERS
Volume 19, Issue 6, Pages 4043-4051Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.9b01417
Keywords
Chromium thiophosphate; magnetic semiconductor; photooxidation; energy transfer; encapsulation
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Funding
- National Research Foundation of Korea [NRF-2015R1A2A1A15052078, NRF-2016R1A2B3010390]
- Institute for Information & Communications Technology Promotion (IITP) grant - Ministry of Science, ICT & Future Planning of Korea [B0117-16-1003]
- Institute for Basic Science (IBS), Korea [IBS-R014-A1]
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Many two-dimensional (2D) semiconductors represented by transition metal dichalcogenides have tunable optical bandgaps in the visible or near IR-range standing as a promising candidate for optoelectronic devices. Despite this potential, however, their photoreactions are not well understood or controversial in the mechanistic details. In this work, we report a unique thickness-dependent photoreaction sensitivity and a switchover between two competing reaction mechanisms in atomically thin chromium thiophosphate (CrPS4), a two-dimensional antiferromagnetic semiconductor. CrPS4 showed a threshold power density 2 orders of magnitude smaller than that for MoS2 obeying a photothermal reaction route. In addition, reaction cross section quantified with Raman spectroscopy revealed distinctive power dependences in the low and high power regimes. On the basis of optical in situ thermometric measurements and control experiments against O-2, water, and photon energy, we proposed a photochemical oxidation mechanism involving singlet O-2 in the low power regime with a photothermal route for the other. We also demonstrated a highly effective encapsulation with Al2O3 as a protection against the destructive photoinduced and ambient oxidations.
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