ORCID Profile
0000-0001-8586-127X
Current Organisations
Nanyang Technological University
,
Monash University
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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.
Surfaces and Structural Properties of Condensed Matter | Condensed Matter Physics | Electronic and Magnetic Properties of Condensed Matter; Superconductivity | Nanoelectronics
Expanding Knowledge in the Physical Sciences | Emerging Defence Technologies | Expanding Knowledge in Engineering | Solar-Photovoltaic Energy | Expanding Knowledge in Technology |
Publisher: American Chemical Society (ACS)
Date: 26-06-2023
Publisher: American Chemical Society (ACS)
Date: 23-08-2016
DOI: 10.1021/ACS.NANOLETT.6B02513
Abstract: The atomically precise doping of silicon with phosphorus (Si:P) using scanning tunneling microscopy (STM) promises ultimate miniaturization of field effect transistors. The one-dimensional (1D) Si:P nanowires are of particular interest, retaining exceptional conductivity down to the atomic scale, and are predicted as interconnects for a scalable silicon-based quantum computer. Here, we show that ultrathin Si:P nanowires form one of the most-stable electrical conductors, with the phenomenological Hooge parameter of low-frequency noise being as low as ≈10(-8) at 4.2 K, nearly 3 orders of magnitude lower than even carbon-nanotube-based 1D conductors. A in-built isolation from the surface charge fluctuations due to encapsulation of the wires within the epitaxial Si matrix is the dominant cause for the observed suppression of noise. Apart from quantum information technology, our results confirm the promising prospects for precision-doped Si:P structures in atomic-scale circuitry for the 11 nm technology node and beyond.
Publisher: IOP Publishing
Date: 25-01-2023
Abstract: Quantum technologies are poised to move the foundational principles of quantum physics to the forefront of applications. This roadmap identifies some of the key challenges and provides insights on material innovations underlying a range of exciting quantum technology frontiers. Over the past decades, hardware platforms enabling different quantum technologies have reached varying levels of maturity. This has allowed for first proof-of-principle demonstrations of quantum supremacy, for ex le quantum computers surpassing their classical counterparts, quantum communication with reliable security guaranteed by laws of quantum mechanics, and quantum sensors uniting the advantages of high sensitivity, high spatial resolution, and small footprints. In all cases, however, advancing these technologies to the next level of applications in relevant environments requires further development and innovations in the underlying materials. From a wealth of hardware platforms, we select representative and promising material systems in currently investigated quantum technologies. These include both the inherent quantum bit systems and materials playing supportive or enabling roles, and cover trapped ions, neutral atom arrays, rare earth ion systems, donors in silicon, color centers and defects in wide-band gap materials, two-dimensional materials and superconducting materials for single-photon detectors. Advancing these materials frontiers will require innovations from a erse community of scientific expertise, and hence this roadmap will be of interest to a broad spectrum of disciplines.
Publisher: American Physical Society (APS)
Date: 03-10-2019
Publisher: IOP Publishing
Date: 22-08-2023
Abstract: Ultra-low temperature scanning tunnelling microscopy and spectroscopy (STM/STS) achieved by dilution refrigeration can provide unrivalled insight into the local electronic structure of quantum materials and atomic-scale quantum systems. Effective isolation from mechanical vibration and acoustic noise is critical in order to achieve ultimate spatial and energy resolution. Here, we report on the design and performance of an ultra-low vibration (ULV) laboratory hosting a customized but otherwise commercially available 40 mK STM. The design of the vibration isolation consists of a T-shaped concrete mass block (∼55t), suspended by actively controlled pneumatic springs, and placed on a foundation separated from the surrounding building in a ‘room-within-a-room’ design. Vibration levels achieved are meeting the VC-M vibration standard at Hz, reached only in a limited number of laboratories worldwide. Measurement of the STM’s junction noise confirms effective vibration isolation on par with custom built STMs in ULV laboratories. In this tailored low-vibration environment, the STM achieves an energy resolution of 43 μ eV (144 mK), promising for the investigation and control of quantum matter at atomic length scales.
Publisher: IEEE
Date: 06-2010
Publisher: American Chemical Society (ACS)
Date: 20-11-2017
DOI: 10.1021/ACS.NANOLETT.7B02307
Abstract: 3D Dirac semimetals are an emerging class of materials that possess topological electronic states with a Dirac dispersion in their bulk. In nodal-line Dirac semimetals, the conductance and valence bands connect along a closed path in momentum space, leading to the prediction of pseudospin vortex rings and pseudospin skyrmions. Here, we use Fourier transform scanning tunneling spectroscopy (FT-STS) at 4.5 K to resolve quasiparticle interference (QPI) patterns at single defect centers on the surface of the line nodal semimetal zirconium silicon sulfide (ZrSiS). Our QPI measurements show pseudospin conservation at energies close to the line node. In addition, we determine the Fermi velocity to be ℏv
Publisher: American Chemical Society (ACS)
Date: 20-11-2017
Publisher: American Chemical Society (ACS)
Date: 15-12-2016
Publisher: IEEE
Date: 05-2012
Publisher: American Chemical Society (ACS)
Date: 27-02-2017
Publisher: American Chemical Society (ACS)
Date: 24-03-2014
DOI: 10.1021/NL4045026
Abstract: We demonstrate serial electron transport through a donor-based triple quantum dot in silicon fabricated with nanoscale precision by scanning tunnelling microscopy lithography. From an equivalent circuit model, we calculate the electrochemical potentials of the dots allowing us to identify ground and excited states in finite bias transport. Significantly, we show that using a scanning tunnelling microscope, we can directly demonstrate that a ∼1 nm difference in interdot distance dramatically affects transport pathways between the three dots.
Publisher: IEEE
Date: 06-2014
Publisher: Springer Science and Business Media LLC
Date: 20-10-2022
DOI: 10.1038/S41467-022-33676-0
Abstract: In one-dimensional (1D) systems, electronic interactions lead to a breakdown of Fermi liquid theory and the formation of a Tomonaga-Luttinger Liquid (TLL). The strength of its many-body correlations can be quantified by a single dimensionless parameter, the Luttinger parameter K , characterising the competition between the electrons’ kinetic and electrostatic energies. Recently, signatures of a TLL have been reported for the topological edge states of quantum spin Hall (QSH) insulators, strictly 1D electronic structures with linear (Dirac) dispersion and spin-momentum locking. Here we show that the many-body interactions in such helical Luttinger Liquid can be effectively controlled by the edge state’s dielectric environment. This is reflected in a tunability of the Luttinger parameter K , distinct on different edges of the crystal, and extracted to high accuracy from the statistics of tunnelling spectra at tens of tunnelling points. The interplay of topology and many-body correlations in 1D helical systems has been suggested as a potential avenue towards realising non-Abelian parafermions.
Publisher: AIP Publishing
Date: 03-2023
DOI: 10.1063/5.0130393
Abstract: In this work, we present an angle-resolved photoemission spectroscopy study of a 1T′-WTe2 monolayer epitaxially grown on NbSe2 substrates, a prototypical quantum spin Hall insulator (QSHI)/superconductor heterojunction. Angle-resolved photoemission spectroscopy data indicate the formation of electronic states in the bulk bandgap of WTe2, which are absent in the nearly free-standing WTe2 grown on the highly oriented pyrolytic graphite substrate, where an energy gap of ∼100 meV is reported. The results are explained in terms of hybridization effects promoted by the QSHI–superconductor interaction at WTe2/NbSe2 interfaces, in line with recent scanning probe microscopy investigation and theoretical band structure calculations. Our findings highlight the important role of interlayer interaction on the electronic properties and ultimately on the engineering of topological properties of the QSHI/superconducting heterostructure.
Publisher: American Physical Society (APS)
Date: 29-08-2016
Publisher: American Chemical Society (ACS)
Date: 02-01-2009
DOI: 10.1021/NL803196F
Abstract: Nanoscale control of doping profiles in semiconductor devices is becoming of critical importance as channel length and pitch in metal oxide semiconductor field effect transistors (MOSFETs) continue to shrink toward a few nanometers. Scanning tunneling microscope (STM) directed self-assembly of dopants is currently the only proven method for fabricating atomically precise electronic devices in silicon. To date this technology has realized in idual components of a complete device with a major obstacle being the ability to electrically gate devices. Here we demonstrate a fully functional multiterminal quantum dot device with integrated donor based in-plane gates epitaxially assembled on a single atomic plane of a silicon (001) surface. We show that such in-plane regions of highly doped silicon can be used to gate nanostructures resulting in highly stable Coulomb blockade (CB) oscillations in a donor-based quantum dot. In particular, we compare the use of these all epitaxial in-plane gates with conventional surface gates and find superior stability of the former. These results show that in the absence of the randomizing influences of interface and surface defects the electronic stability of dots in silicon can be comparable or better than that of quantum dots defined in other material systems. We anticipate our experiments will open the door for controlled scaling of silicon devices toward the single donor limit.
Publisher: American Physical Society (APS)
Date: 10-12-2014
Publisher: Springer Science and Business Media LLC
Date: 23-11-2018
DOI: 10.1038/S41534-018-0111-1
Abstract: Spin–orbit coupling (SOC) is fundamental to a wide range of phenomena in condensed matter, spanning from a renormalisation of the free-electron g -factor, to the formation of topological insulators, and Majorana Fermions. SOC has also profound implications in spin-based quantum information, where it is known to limit spin lifetimes ( T 1 ) in the inversion asymmetric semiconductors such as GaAs. However, for electrons in silicon—and in particular those bound to phosphorus donor qubits—SOC is usually regarded weak, allowing for spin lifetimes of minutes in the bulk. Surprisingly, however, in a nanoelectronic device donor spin lifetimes have only reached values of seconds. Here, we reconcile this difference by demonstrating that electric field induced SOC can dominate spin relaxation of donor-bound electrons. Eliminating this lifetime-limiting effect by careful alignment of an external vector magnetic field in an atomically engineered device, allows us to reach the bulk-limit of spin-relaxation times. Given the unexpected strength of SOC in the technologically relevant silicon platform, we anticipate that our results will stimulate future theoretical and experimental investigation of phenomena that rely on strong magnetoelectric coupling of atomically confined spins.
Publisher: American Physical Society (APS)
Date: 14-08-2023
Publisher: AIP Publishing
Date: 07-12-2015
DOI: 10.1063/1.4937576
Abstract: We demonstrate the charge sensing of a few-donor double quantum dot precision placed with atomic resolution scanning tunnelling microscope lithography. We show that a tunnel-coupled single electron transistor (SET) can be used to detect electron transitions on both dots as well as inter-dot transitions. We demonstrate that we can control the tunnel times of the second dot to the SET island by ∼4 orders of magnitude by detuning its energy with respect to the first dot.
Publisher: American Physical Society (APS)
Date: 24-03-2022
Publisher: IEEE
Date: 06-2017
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-01-2012
Abstract: One of the challenges in downsizing electronic circuits is maintaining low resistivity of wires, because shrinking their diameter to near atomic dimensions increases interface effects and can decrease the effectiveness of dopants. Weber et al. (p. 64 see the Perspective by Ferry ) created nanowires on a silicon surface with the deposition of phosphorus atoms through decomposition of PH 3 with a scanning tunneling microscope tip. A brief thermal annealing embedded these nanowires, which varied from 1.5 to 11 nanometers in width, into the silicon surface. Their resistivity was independent of width, and their current-carrying capability was comparable to that of thicker copper interconnects.
Publisher: IEEE
Date: 08-2007
Publisher: IEEE
Date: 09-2013
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3NR01796F
Abstract: Scanning tunneling microscope (STM) lithography has recently demonstrated the ultimate in device scaling with buried, conducting nanowires just a few atoms wide and the realization of single atom transistors, where a single P atom has been placed inside a transistor architecture with atomic precision accuracy. Despite the dimensions of the critical parts of these devices being defined by a small number of P atoms, the device electronic properties are influenced by the surrounding 10(4) to 10(6) Si atoms. Such effects are hard to capture with most modeling approaches, and prior to this work no theory existed that could explore the realistic size of the complete device in which both dopant disorder and placement are important. This work presents a comprehensive study of the electronic and transport properties of ultra-thin (<10 nm wide) monolayer highly P δ-doped Si (Si:P) nanowires in a fully atomistic self-consistent tight-binding approach. This atomistic approach covering large device volumes allows for a systematic study of disorder on the physical properties of the nanowires. Excellent quantitative agreement is observed with recent resistance measurements of STM-patterned nanowires [Weber et al., Science, 2012, 335, 64], confirming the presence of metallic behavior at the scaling limit. At high doping densities the channel resistance is shown to be insensitive to the exact channel dopant placement highlighting their future use as metallic interconnects. This work presents the first theoretical study of Si:P nanowires that are realistically extended and disordered, providing a strong theoretical foundation for the design and understanding of atomic-scale electronics.
Publisher: Springer Science and Business Media LLC
Date: 09-11-2015
DOI: 10.1038/NCOMMS9848
Abstract: Spin states of the electrons and nuclei of phosphorus donors in silicon are strong candidates for quantum information processing applications given their excellent coherence times. Designing a scalable donor-based quantum computer will require both knowledge of the relationship between device geometry and electron tunnel couplings, and a spin readout strategy that uses minimal physical space in the device. Here we use radio frequency reflectometry to measure singlet–triplet states of a few-donor Si:P double quantum dot and demonstrate that the exchange energy can be tuned by at least two orders of magnitude, from 20 μeV to 8 meV. We measure dot–lead tunnel rates by analysis of the reflected signal and show that they change from 100 MHz to 22 GHz as the number of electrons on a quantum dot is increased from 1 to 4. These techniques present an approach for characterizing, operating and engineering scalable qubit devices based on donors in silicon.
Publisher: Springer Science and Business Media LLC
Date: 13-04-2014
Abstract: Electron spins confined to phosphorus donors in silicon are promising candidates as qubits because of their long coherence times, exceeding seconds in isotopically purified bulk silicon. With the recent demonstrations of initialization, readout and coherent manipulation of in idual donor electron spins, the next challenge towards the realization of a Si:P donor-based quantum computer is the demonstration of exchange coupling in two tunnel-coupled phosphorus donors. Spin-to-charge conversion via Pauli spin blockade, an essential ingredient for reading out in idual spin states, is challenging in donor-based systems due to the inherently large donor charging energies (∼45 meV), requiring large electric fields (>1 MV m(-1)) to transfer both electron spins onto the same donor. Here, in a carefully characterized double donor-dot device, we directly observe spin blockade of the first few electrons and measure the effective exchange interaction between electron spins in coupled Coulomb-confined systems.
Publisher: American Physical Society (APS)
Date: 16-10-2015
Publisher: IOP Publishing
Date: 12-12-2006
Publisher: American Association for the Advancement of Science (AAAS)
Date: 03-03-2017
Abstract: Atomic engineering of donor-based spin qubits results in long lifetimes and high-fidelity two-qubit readout.
Publisher: Wiley
Date: 23-04-2021
Abstract: Atomically thin topological materials are attracting growing attention for their potential to radically transform classical and quantum electronic device concepts. Among them is the quantum spin Hall (QSH) insulator—a 2D state of matter that arises from interplay of topological band inversion and strong spin–orbit coupling, with large tunable bulk bandgaps up to 800 meV and gapless, 1D edge states. Reviewing recent advances in materials science and engineering alongside theoretical description, the QSH materials library is surveyed with focus on the prospects for QSH‐based device applications. In particular, theoretical predictions of nontrivial superconducting pairing in the QSH state toward Majorana‐based topological quantum computing are discussed, which are the next frontier in QSH materials research.
Publisher: Wiley
Date: 12-05-2017
Abstract: Few-layer black phosphorous (BP) has emerged as a promising candidate for next-generation nanophotonic and nanoelectronic devices. However, rapid ambient degradation of mechanically exfoliated BP poses challenges in its practical deployment in scalable devices. To date, the strategies employed to protect BP have relied upon preventing its exposure to atmospheric conditions. Here, an approach that allows this sensitive material to remain stable without requiring its isolation from the ambient environment is reported. The method draws inspiration from the unique ability of biological systems to avoid photo-oxidative damage caused by reactive oxygen species. Since BP undergoes similar photo-oxidative degradation, imidazolium-based ionic liquids are employed as quenchers of these damaging species on the BP surface. This chemical sequestration strategy allows BP to remain stable for over 13 weeks, while retaining its key electronic characteristics. This study opens opportunities to practically implement BP and other environmentally sensitive 2D materials for electronic applications.
Publisher: IEEE
Date: 06-2016
Publisher: IEEE
Date: 06-2014
Publisher: American Physical Society (APS)
Date: 02-08-2007
Publisher: AIP
Date: 2007
DOI: 10.1063/1.2730076
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6NR04327E
Abstract: Substoichiometric molybdenum disulphide (MoSx) nanosheets are successfully synthesised following a novel reductive route using hydrazine salts. The resulting two dimensional crystals are found to be highly monodispersed in thickness, forming exclusively 1.9 ± 0.2 nm thick bilayers. The lateral dimensions of the nanosheets are governed by the precursor bulk particle's size. Exploring a range of hydrazine derivatives with various degrees of steric hindrance leads to the conclusion that intercalation does not occur during the process and that exfoliation is instead facilitated by the reduction of Mo centres leading to the exfoliation of substoichiometric bilayers with distorted lattices. The lattice distortion is found to be persistent across all s les with XPS analysis pointing towards a S to Mo ratio of 1.2. The resulting material features an electronic bandgap of 2.1 eV, which is wider than that of pristine monolayer MoS2 with relatively longer radiative decay time.
Publisher: American Chemical Society (ACS)
Date: 12-07-2012
DOI: 10.1021/NL3012903
Abstract: Scalable quantum computing architectures with electronic spin qubits hosted by arrays of single phosphorus donors in silicon require local electric and magnetic field control of in idual qubits separated by ∼10 nm. This daunting task not only requires atomic-scale accuracy of single P donor positioning to control interqubit exchange interaction but also demands precision alignment of control electrodes with careful device design at these small length scales to minimize cross capacitive coupling. Here we demonstrate independent electrostatic control of two Si:P quantum dots, each consisting of ∼15 P donors, in an optimized device design fabricated by scanning tunneling microscope (STM)-based lithography. Despite the atomic-scale dimensions of the quantum dots and control electrodes reducing overall capacitive coupling, the electrostatic behavior of the device shows an excellent match to results of a priori capacitance calculations. These calculations highlight the importance of the interdot angle in achieving independent control at these length-scales. This combination of predictive electrostatic modeling and the atomic-scale fabrication accuracy of STM-lithography, provides a powerful tool for scaling multidonor dots to the single donor limit.
Publisher: AIP Publishing
Date: 20-07-2009
DOI: 10.1063/1.3186031
Abstract: We have fabricated a nanoscale ring of phosphorus dopants in silicon using a scanning tunneling microscope to pattern a hydrogen resist layer. Low-temperature magnetotransport measurements reveal both aperiodic universal conductance fluctuations and periodic Aharonov–Bohm oscillations. From the ratio of the h/e and h/2e components of the Aharonov–Bohm oscillations, we estimate a phase coherence length of ≃100 nm at a temperature T=100 mK. This is in agreement with previous results from weak localization measurements on low-dimensional dopant devices in silicon.
Publisher: American Chemical Society (ACS)
Date: 26-02-2016
Abstract: Hybrid organic-inorganic perovskite materials have received substantial research attention due to their impressively high performance in photovoltaic devices. As one of the oldest functional materials, it is intriguing to explore the optoelectronic properties in perovskite after reducing it into a few atomic layers in which two-dimensional (2D) confinement may get involved. In this work, we report a combined solution process and vapor-phase conversion method to synthesize 2D hybrid organic-inorganic perovskite (i.e., CH3NH3PbI3) nanocrystals as thin as a single unit cell (∼1.3 nm). High-quality 2D perovskite crystals have triangle and hexagonal shapes, exhibiting tunable photoluminescence while the thickness or composition is changed. Due to the high quantum efficiency and excellent photoelectric properties in 2D perovskites, a high-performance photodetector was demonstrated, in which the current can be enhanced significantly by shining 405 and 532 nm lasers, showing photoresponsivities of 22 and 12 AW(-1) with a voltage bias of 1 V, respectively. The excellent optoelectronic properties make 2D perovskites building blocks to construct 2D heterostructures for wider optoelectronic applications.
Start Date: 2016
End Date: 2019
Funder: Australian Research Council
View Funded ActivityStart Date: 01-2013
End Date: 09-2018
Amount: $2,645,586.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2016
End Date: 12-2016
Amount: $373,536.00
Funder: Australian Research Council
View Funded Activity