ORCID Profile
0000-0002-1467-3105
Current Organisation
National Institute for Materials Science
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In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Probability Theory | Stochastic Analysis and Modelling | Statistics |
Publisher: American Chemical Society (ACS)
Date: 08-03-2021
Publisher: American Physical Society (APS)
Date: 08-12-2022
Publisher: American Chemical Society (ACS)
Date: 26-10-2023
Publisher: American Chemical Society (ACS)
Date: 11-08-2023
Publisher: American Chemical Society (ACS)
Date: 21-07-2020
Publisher: American Chemical Society (ACS)
Date: 18-05-2022
Publisher: Springer Science and Business Media LLC
Date: 16-08-2021
DOI: 10.1038/S41467-021-24925-9
Abstract: Engineering non-linear hybrid light-matter states in tailored lattices is a central research strategy for the simulation of complex Hamiltonians. Excitons in atomically thin crystals are an ideal active medium for such purposes, since they couple strongly with light and bear the potential to harness giant non-linearities and interactions while presenting a simple s le-processing and room temperature operability. We demonstrate lattice polaritons, based on an open, high-quality optical cavity, with an imprinted photonic lattice strongly coupled to excitons in a WS 2 monolayer. We experimentally observe the emergence of the canonical band-structure of particles in a one-dimensional lattice at room temperature, and demonstrate frequency reconfigurability over a spectral window exceeding 85 meV, as well as the systematic variation of the nearest-neighbour coupling, reflected by a tunability in the bandwidth of the p-band polaritons by 7 meV. The technology presented in this work is a critical demonstration towards reconfigurable photonic emulators operated with non-linear photonic fluids, offering a simple experimental implementation and working at ambient conditions.
Publisher: Springer Science and Business Media LLC
Date: 23-05-2015
Publisher: AIP Publishing
Date: 24-07-2023
DOI: 10.1063/5.0155311
Abstract: Reliable methods to create quantum emitters in hexagonal boron nitride (hBN) are highly sought after for scalable applications in quantum photonic devices. Specifically, recent efforts have focused on defects in hBN with a zero phonon line at 2.8 eV (436 nm). Here, we employ carbon-doped hBN crystals that were irradiated by an electron beam to generate these emitters and perform annealing treatments to investigate the stability of the emitters. We find that the blue emitters are stable up to ∼800 °C. However, upon annealing to 1000 °C, the emitters disappear, and a family of other emitters appears in the region of hBN that had been irradiated by an electron beam. Our findings contribute to the understanding of emitter species and emitter formation in hBN.
Publisher: American Chemical Society (ACS)
Date: 22-09-2021
Publisher: Research Square Platform LLC
Date: 28-10-2021
DOI: 10.21203/RS.3.RS-1008445/V1
Abstract: An increase in power consumption necessitates a low-power circuit technology to extend Moore’s law. Low-power transistors, such as tunnel field-effect transistors (TFETs) 1-5 , negative-capacitance field-effect transistors (NC-FETs) 6 , and Dirac-source field-effect transistors (DS-FETs) 7-10 , have been realised to break the thermionic limit of the subthreshold swing (SS). However, a low-power diode rectifier, which breaks the thermionic limit of an ideality factor (η) of 1 at room temperature, has not been proposed yet. In this study, we have realised a DS diode, which exhibits a steep-slope characteristic curve, by utilising the linear density of states (DOSs) of graphene 7 . For the developed DS diode, η 1 for more than two decades of drain current with a minimum value of 0.8, and the rectifying ratio is large ( 10 5 ). The realisation of a DS diode paves the way for the development of low-power electronic circuits.
Publisher: American Chemical Society (ACS)
Date: 22-04-2020
Publisher: American Chemical Society (ACS)
Date: 23-11-2020
Publisher: American Chemical Society (ACS)
Date: 05-10-2021
Publisher: Springer Science and Business Media LLC
Date: 15-09-2021
DOI: 10.1038/S41467-021-25747-5
Abstract: Monolayers of transition metal dichalcogenides are ideal materials to control both spin and valley degrees of freedom either electrically or optically. Nevertheless, optical excitation mostly generates excitons species with inherently short lifetime and spin/valley relaxation time. Here we demonstrate a very efficient spin/valley optical pumping of resident electrons in n-doped WSe 2 and WS 2 monolayers. We observe that, using a continuous wave laser and appropriate doping and excitation densities, negative trion doublet lines exhibit circular polarization of opposite sign and the photoluminescence intensity of the triplet trion is more than four times larger with circular excitation than with linear excitation. We interpret our results as a consequence of a large dynamic polarization of resident electrons using circular light.
Publisher: Springer Science and Business Media LLC
Date: 20-12-2021
Publisher: American Chemical Society (ACS)
Date: 08-06-2023
Publisher: Springer Science and Business Media LLC
Date: 30-05-2022
DOI: 10.1038/S41467-022-30645-5
Abstract: Engineering the properties of quantum materials via strong light-matter coupling is a compelling research direction with a multiplicity of modern applications. Those range from modifying charge transport in organic molecules, steering particle correlation and interactions, and even controlling chemical reactions. Here, we study the modification of the material properties via strong coupling and demonstrate an effective inversion of the excitonic band-ordering in a monolayer of WSe 2 with spin-forbidden, optically dark ground state. In our experiments, we harness the strong light-matter coupling between cavity photon and the high energy, spin-allowed bright exciton, and thus creating two bright polaritonic modes in the optical bandgap with the lower polariton mode pushed below the WSe 2 dark state. We demonstrate that in this regime the commonly observed luminescence quenching stemming from the fast relaxation to the dark ground state is prevented, which results in the brightening of this intrinsically dark material. We probe this effective brightening by temperature-dependent photoluminescence, and we find an excellent agreement with a theoretical model accounting for the inversion of the band ordering and phonon-assisted polariton relaxation.
Publisher: American Chemical Society (ACS)
Date: 03-11-2022
Publisher: Springer Science and Business Media LLC
Date: 04-11-2021
DOI: 10.1038/S41467-021-26715-9
Abstract: The emergence of spatial and temporal coherence of light emitted from solid-state systems is a fundamental phenomenon intrinsically aligned with the control of light-matter coupling. It is canonical for laser oscillation, emerges in the superradiance of collective emitters, and has been investigated in bosonic condensates of thermalized light, as well as exciton-polaritons. Our room temperature experiments show the strong light-matter coupling between microcavity photons and excitons in atomically thin WSe 2 . We evidence the density-dependent expansion of spatial and temporal coherence of the emitted light from the spatially confined system ground-state, which is accompanied by a threshold-like response of the emitted light intensity. Additionally, valley-physics is manifested in the presence of an external magnetic field, which allows us to manipulate K and K’ polaritons via the valley-Zeeman-effect. Our findings validate the potential of atomically thin crystals as versatile components of coherent light-sources, and in valleytronic applications at room temperature.
Publisher: Wiley
Date: 24-02-2021
Abstract: Due to Fermi level pinning (FLP), metal‐semiconductor contact interfaces result in a Schottky barrier height (SBH), which is usually difficult to tune. This makes it challenging to efficiently inject both electrons and holes using the same metal—an essential requirement for several applications, including light‐emitting devices and complementary logic. Interestingly, modulating the SBH in the Schottky–Mott limit of de‐pinned van der Waals (vdW) contacts becomes possible. However, accurate extraction of the SBH is essential to exploit such contacts to their full potential. In this study a simple technique is proposed to accurately estimate the SBH at the vdW contact interfaces by circumventing several ambiguities associated with SBH extraction. Using this technique on several vdW contacts, including metallic 2H‐TaSe 2 , semi‐metallic graphene, and degenerately doped semiconducting SnSe 2 , it is demonstrated that vdW contacts exhibit a universal de‐pinned nature. Superior ambipolar carrier injection properties of vdW contacts are demonstrated (with Au contact as a reference) in two applications, namely, a) pulsed electroluminescence from monolayer WS 2 using few‐layer graphene (FLG) contact, and b) efficient carrier injection to WS 2 and WSe 2 channels in both n‐type and p‐type field effect transistor modes using 2H‐TaSe 2 contact.
Publisher: American Chemical Society (ACS)
Date: 26-07-2023
Publisher: American Chemical Society (ACS)
Date: 22-10-2020
Publisher: Research Square Platform LLC
Date: 05-04-2023
DOI: 10.21203/RS.3.RS-2606377/V1
Abstract: Hexagonal boron nitride (hBN) has been a centre of interest due to its ability to host several bright quantum emitters at room temperature. However, the identification of the observed emitters remains challenging due to spectral variability as well as the lack of atomic defect structure information. In this work, we report two new blue quantum emitters with zero phonon line (ZPL) centred around 460 nm and 490 nm in hBN powders. We further demonstrate that the blue emissions can be created by high temperature annealing or high energy ion irradiation in exfoliated hBN flakes. Scanning transmission electron microscopy (STEM) reveals that the dominant defect structures present in ion irradiated s le are vacancy-type (V x ) and adatom(intercalant)-type (A x ). Together with first principle GW-BSE (Bethe-Salpeter equation) calculation, the observed blue emissions at 490 nm may be due to boron intercalants (B int ). Our results not only discover a new group of blue quantum emissions in hBN, but also provide an insight on the physical origin of the emissions by correlating the emission wavelength with local atomic structures in hBN.
Publisher: Research Square Platform LLC
Date: 23-02-2023
DOI: 10.21203/RS.3.RS-2516689/V1
Abstract: Atomic defects in two-dimensional (2D) semiconductors are promising single exciton traps for achieving quantum emission. However, excessively high density of defects often makes it impractical to optically address the quantum nature of such quasi-particles, preventing strategic exciton engineering. Here, we report a versatile strategy for dilute acceptor impurity doping of monolayer WS 2 , which enables the study of isolated bound excitons. We observe two distinct types of acceptor-bound excitons: one of them is characterized by a large binding energy, allowing its observation at room temperature and the other by an extremely narrow linewidth ( 1 meV), showing strong resemblance to quantum emitters in WSe 2 . Polarization-resolved spectroscopy and magnetic field dependence reveal their strong contribution of free exciton character. In particular, the latter type exhibits characteristics of acceptor-bound dark excitons. Our work demonstrates dilute impurity doping as a promising strategy towards optically addressable quantum states in monolayer semiconductors.
Publisher: American Chemical Society (ACS)
Date: 03-05-2023
Publisher: Springer Science and Business Media LLC
Date: 26-07-2022
DOI: 10.1038/S41467-022-31849-5
Abstract: An increase in power consumption necessitates a low-power circuit technology to extend Moore’s law. Low-power transistors, such as tunnel field-effect transistors (TFETs), negative-capacitance field-effect transistors (NC-FETs), and Dirac-source field-effect transistors (DS-FETs), have been realised to break the thermionic limit of the subthreshold swing (SS). However, a low-power rectifier, able to overcome the thermionic limit of an ideality factor (η) of 1 at room temperature, has not been proposed yet. In this study, we have realised a DS diode based on graphene/MoS 2 /graphite van der Waals heterostructures, which exhibits a steep-slope characteristic curve, by exploiting the linear density of states (DOSs) of graphene. For the developed DS diode, we obtained η 1 for more than four decades of drain current (η ave_4dec 1) with a minimum value of 0.8, and a rectifying ratio exceeding 10 8 . The realisation of a DS diode represents an additional step towards the development of low-power electronic circuits.
Publisher: Wiley
Date: 08-04-2023
Abstract: Monolayers (MLs) of transition‐metal dichalcogenides host efficient single‐photon emitters (SPEs) usually associated to the presence of nanoscale mechanical deformations or strain. Large‐scale spatial control of strain would enhance the scalability of such SPEs and allow for their incorporation into photonic structures. Here, the formation of regular arrays of strained hydrogen‐filled one‐layer‐thick micro‐domes obtained by H‐ion irradiation and lithography‐based approaches is reported. Typically, the H 2 liquefaction for temperatures T K causes the disappearance of the domes preventing their use as potential SPEs. Here, it is shown that the dome deflation can be overcome by hBN heterostructuring, that is by depositing thin hBN flakes on the domes. This leads to the preservation of the dome structure at all temperatures, as found by micro‐Raman and micro‐photoluminescence (µ‐PL) studies. Eventually, spatially controlled hBN‐capped WS 2 domes show the appearance, at 5 K, of intense emission lines originating from localized excitons, which are shown to behave as quantum emitters here. The electronic properties of the emitters are addressed by time‐resolved µ‐PL yielding time decays of 1–10 ns, and by magneto‐µ‐PL measurements. The latter provide an exciton magnetic moment a factor of two larger than the value observed in planar strain‐free MLs.
Publisher: American Chemical Society (ACS)
Date: 16-05-2022
Abstract: In artificial van der Waals (vdW) layered devices, twisting the stacking angle has emerged as an effective strategy to regulate the electronic phases and optical properties of these systems. Along with the twist registry, the lattice reconstruction arising from vdW interlayer interaction has also inspired significant research interests. The control of twist angles is significantly important because the moiré periodicity determines the electron propagation length on the lattice and the interlayer electron-electron interactions. However, the moiré periodicity is hard to be modified after the device has been fabricated. In this work, we have demonstrated that the moiré periodicity can be precisely modulated with a localized laser annealing technique. This is achieved with regulating the interlayer lattice mismatch by the mismatched lattice constant, which originates from the variable density of sulfur vacancy generated during laser modification. The existence of sulfur vacancy is further verified by excitonic emission energy and lifetime in photoluminescence measurements. Furthermore, we also discover that the mismatched lattice constant has the equivalent contribution as the twist angle for determining the lattice mismatch. Theoretical modeling elaborates the moiré-wavelength-dependent energy variations at the interface and mimics the evolution of moiré morphology.
Publisher: IOP Publishing
Date: 19-12-2022
Abstract: The possibility of almost linear tuning of the band gap and of the electrical and optical properties in monolayers (MLs) of semiconducting transition metal dichalcogenide (S-TMD) alloys opens up the way to fabricate materials with on-demand characteristics. By making use of photoluminescence spectroscopy, we investigate optical properties of WSSe MLs with a S/Se ratio of 57/43 deposited on SiO 2 /Si substrate and encapsulated in hexagonal BN flakes. Similarly to the ‘ parent ’ WS 2 and WSe 2 MLs, we assign the WSSe MLs to the ML family with the dark ground exciton state. We find that, in addition to the neutral bright A exciton line, three observed emission lines are associated with negatively charged excitons. The application of in-plane and out-of-plane magnetic fields allows us to assign undeniably the bright and dark (spin- and momentum-forbidden) negative trions as well as the phonon replica of the dark spin-forbidden complex. Furthermore, the existence of the single photon emitters in the WSSe ML is also demonstrated, thus prompting the opportunity to enlarge the wavelength range for potential future quantum applications of S-TMDs.
Publisher: Springer Science and Business Media LLC
Date: 23-08-2021
DOI: 10.1038/S41598-021-95700-5
Abstract: Two-dimensional layered materials offer the possibility to create artificial vertically stacked structures possessing an additional degree of freedom— the interlayer twist . We present a comprehensive optical study of artificially stacked bilayers (BLs) MoS $$_2$$ 2 encapsulated in hexagonal BN with interlayer twist angle ranging from 0 $$^{\\circ }$$ ∘ to 60 $$^{\\circ }$$ ∘ using Raman scattering and photoluminescence spectroscopies. It is found that the strength of the interlayer coupling in the studied BLs can be estimated using the energy dependence of indirect emission versus the A $$_\\text {1g}$$ 1g –E $$_\\text {2g}^1$$ 2g 1 energy separation. Due to the hybridization of electronic states in the valence band, the emission line related to the interlayer exciton is apparent in both the natural (2H) and artificial (62 $$^\\circ $$ ∘ ) MoS $$_2$$ 2 BLs, while it is absent in the structures with other twist angles. The interlayer coupling energy is estimated to be of about 50 meV. The effect of temperature on energies and intensities of the direct and indirect emission lines in MoS $$_2$$ 2 BLs is also quantified.
Publisher: American Chemical Society (ACS)
Date: 30-04-2021
Publisher: AIP Publishing
Date: 17-08-2020
DOI: 10.1063/5.0013092
Abstract: Monolayer transition metal dichalcogenide semiconductors, with versatile experimentally accessible exciton species, offer an interesting platform for investigating the interaction between excitons and a Fermi sea of charges. Using hexagonal boron nitride encapsulated monolayer MoSe2, we study the impact of charge density tuning on the A and B series of exciton Rydberg states, including A:1s, A:2s, B:1s, and B:2s. The doping dependence of the A:2s state provides an opportunity to examine such interactions with greatly reduced exciton binding energy and more spatially diffuse structures, and we found that the impact of the Fermi sea becomes much more dramatic compared to the A:1s state. Using photoluminescence upconversion, we verify that the B:2s exciton state displays similar behavior when interacting with the Fermi sea despite being well above the bare bandgap in energy. Photoluminescence and reflection spectra of the A:1s state show clear evidence that the interaction of the exciton with a Fermi sea is best described by the exciton–polaron model, rather than a trion model. Our experimental results demonstrate that overall features of charge interaction are quite generic and highly robust, offering key insights into the dressed many body states in a Fermi sea.
Publisher: American Physical Society (APS)
Date: 26-05-2022
Publisher: American Chemical Society (ACS)
Date: 09-11-2022
Publisher: American Chemical Society (ACS)
Date: 11-06-2021
Publisher: Research Square Platform LLC
Date: 25-05-2021
DOI: 10.21203/RS.3.RS-533063/V1
Abstract: The emergence of two-dimensional (2D) magnetic crystals and moiré engineering of van der Waals materials has opened the door for devising new magnetic ground states via competing interactions in moiré superlattices. Although a suite of interesting phenomena, including multi-flavor magnetic states, noncollinear magnetic states, moiré magnon bands and magnon networks, has been predicted in twisted bilayer magnetic crystals, nontrivial magnetic ground states have yet to be realized. Here, by utilizing the stacking-dependent interlayer exchange interactions in CrI3, we demonstrate in small-twist-angle CrI3 bilayers a noncollinear magnetic ground state. It consists of antiferromagnetic (AF) and ferromagnetic (FM) domains and is a result of the competing interlayer AF coupling in the monoclinic stacking regions of the moiré superlattice and the energy cost for forming AF-FM domain walls. Above a critical twist angle of ~ 3°, the noncollinear state transitions to a collinear FM ground state. We further show that the noncollinear magnetic state can be controlled by electrical gating through the doping-dependent interlayer AF interaction. Our results demonstrate the possibility of engineering new magnetic ground states in twisted bilayer magnetic crystals, as well as gate-voltage-controllable high-density magnetic memory storage.
Publisher: Wiley
Date: 15-01-2021
Start Date: 09-2020
End Date: 11-2024
Amount: $419,778.00
Funder: Australian Research Council
View Funded Activity