Surface-State Assisted Carrier Recombination and Optical Nonlinearities in Bulk to 2D Nonlayered PtS

Abstract

Cooperite, or platinum sulfide (PtS), is a rare mineral that generally exists as microscale, irregularly shaped crystallites. The presence of impurities, in both naturally occurring and synthesized samples, has hindered the study of its optical properties in the past. In this work, we prepare large-scale, uniform PtS films in bulk to two-dimensional form through the thermally assisted conversion method. An abnormal trend is observed in linear spectral studies whereby the optical bandgap narrows as the film thickness decreases. A model based on the continuous distribution of carriers in real space, which can be regarded as a quantum well normal to the plane, is used to describe the thickness-dependent carrier recombination phenomenon. In the nonlinear optical measurements, PtS exhibits ultrafast saturable absorption and self-defocusing properties in the visible region, which are dominated by the resonant electronic nonlinearities.

Electronic and structural characterisation of polycrystalline platinum disulfide thin films

“…Previous research has shown that at lower pressure, or lower sulfur content, lms with PtS stoichiometry are obtained. 35 This simple method avoids the need for exotic, expensive or hazardous precursors and is essentially a scalable process suitable for producing large-area polycrystalline lms.…”

“…Under typical reaction conditions for the sulfurisation of Pt, the non-layered material PtS, rather than PtS 2 , has been reported as the dominant product. 35 When considering the sulfurisation of Pt, the reaction parameters must be considered and carefully tuned to obtain an appreciable yield of PtS 2 . 34 Transmission Electron Microscopy (TEM) is a powerful and widely-used technique for the characterisation of 2D materials.…”

Donor-Acceptor Type Reduced Graphene-Oxide and a Tin-Selenide Nanohybrid With Broad and Ultrafast Optical Limiting Properties

“…In particular, many studies were done to investigate both saturable absorption (SA) [1][2][3] and RSA [4,5] of two-dimensional (2D) materials, which are two typical NLO absorption properties of 2D materials. Non-linear optical properties of diverse 2D materials were investigated, including black phosphorus [6][7][8], transition metal dichalcogenides (TMDCs) [9,10], topological insulator [11][12][13], SnS [14,15], etc. The non-linear absorption properties of atomically-thin 2D-materials are exploited as saturable absorbers [16][17][18][19], optical diodes [20,21], and optical limiters [22].…”

Large 3rd Order Optical Kerr Nonlinearity in 2D PdSe2 Dichalcogenide Films for Integrated Nonlinear Photonic Chips

“…However, at higher photon energies, the boundelectron contribution to the n2 nonlinearity becomes negative, while the free-carrier nonlinearity is usually also negative. [33,44] We therefore infer that either, or both, processes contribute to the nonlinearity since we observed a negative Kerr nonlinearity for the PdSe2 film. This is further complicated by the fact that PdSe2 is an indirect bandgap material.…”

“…In theory, the optical nonlinear refraction originates mainly from the free-carrier and bound-electron nonlinearities. [33,[40][41][42][43][44] We assume that the two mechanisms co-exist in the PdSe2 film. It has been shown that, near the half-bandgap the two-photon resonance typically yields a positive n2.…”