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Plasmonic metastructures have become valuable platforms for manipulating light based on polarization. While traditional approaches have focused on sorting light through front- or back-scattering, recent advances underscore the potential of in-plane light routing—guiding and separating photons across the surface of the metastructure itself. In this study, we investigate how lateral asymmetry in nanoantenna design—introduced along the direction of in-plane light propagation rather than the axis of illumination—can be leveraged for efficient polarization sorting. We focus on metasurfaces composed of arrays of both symmetric and asymmetric gold nanoantennas. Our results reveal that such structural asymmetry enables two distinct modes of operation: in one, photons with different polarizations are directed along separate in-plane paths; in the other, they follow the same axis but are emitted at different angles depending on their polarization. We further examine the spectral dependence of this sorting behavior and demonstrate that asymmetric metastructures can realize four-way polarization sorting, each with unique anisotropic characteristics. Our simulation results provide insight into how phase modulation of the scattered light—coupled into the substrate beneath the metasurface—is influenced by nanoantenna asymmetry. These findings pave the way for compact, on-chip implementations of the planar spin Hall effect and for simplified metasurfaces suited to sensing, optical switching, and beam steering applications. 

Nanohybrids of graphene and colloidal semiconductor quantum dots (QDs/Gr) provide a promising quantum sensing scheme for photodetection. Despite exciting progress made in QDs/Gr photodetectors in broadband from ultraviolet to short-wave infrared, the device performance is limited in middle-wave infrared (MWIR) detection. A fundamental question arises as to whether the thermal noiseinduced dark current and hence poor signal-to-noise ratio in conventional uncooled MWIR photodetectors persist in QDs/ Gr nanohybrids. Herein, we investigated noise, responsivity (R*), and specific detectivity (D*) in HgTe QDs/Gr nanohybrids, revealing that the noise and R* are decoupled in nanohybrids and each can be optimized independently toward its theoretical limit. Specifically, the noise in the QDs/Gr nanohybrids is dominated by that of graphene with a negligible effect from the dark current in HgTe QDs and can be optimized to its intrinsic limit by removing charge doping of adsorbed polar molecules on graphene. Furthermore, the R* is proportional to the photoconductive gain enabled by the strong quantum confinement in QDs and Gr. Achieving high gain in the MWIR spectrum, however, is challenging and requires elimination of charge traps primarily from the surface states of the narrow-bandgap semiconductor HgTe QDs. Using grain-rotation-induced grain-coalescence growth of single-layer and core/shell HgTe QDs, we show the that HgTe QDs surface states caused by Te deficiency can be dramatically suppressed, resulting in high gain up to 4.0 × 107 in the MWIR spectrum. The optimized noise and R* have led to high uncooled MWIR D* up to 2.4 × 1011 Jones, making nanohybrids promising to surpass the fundamental dark-current limit in conventional photodetectors. 

Single-atom catalysts have the advantage of high chemical efficiency, which requires atomic-scale control during catalyst formation. In order to address this challenge, this work explores the synthesis of single-atom platinum (SA-Pt) catalysts using atomic-layer deposition (ALD) on vertical graphene (VG), in which a large number of graphene edges serve as energetically favorable nucleation sites for SA-Pt, as predicted by density functional theory calculations. Interestingly, SA-Pt has been achieved on VGs at low ALD cycle numbers of up to 60. With a further increase in the number of ALD cycles, an increasing number of Pt clusters with diameters <2 nm and Pt nanoparticles (NPs) with diameters >2 nm become dominant (nano-Pt @VG). This is in contrast to the observation of predominantly nano-Pt on other carbon nanostructures, such as carbon nanotubes and monolayer graphene, under the same ALD growth conditions, indicating that the edge states on VG indeed play a critical role in facilitating the formation of SA-Pt. Profound differences are revealed in a comparative study on H2 sensing. SA-Pt exhibits both a higher sensitivity and faster response than its nano-Pt counterpart by more than an order of magnitude, illustrating the high catalytic efficiency of SAPt and its potential for gas sensing and a variety of other catalytic applications. 

Colloidal quantum dots/graphene (QD/Gr) nanohybrids have been studied intensively for photodetection in a broadband spectrum including ultraviolet, visible, near-infrared, and shortwave infrared (UV−vis-NIR-SWIR). Since the optoelectronic process in the QD/Gr nanohybrid relies on the photogenerated charge carrier transfer from QDs to graphene, understanding the role of the QD−QD and QD−Gr interfaces is imperative to the QD/Gr nanohybrid photodetection. Herein, a systematic study is carried out to probe the effect of these interfaces on the noise, photoresponse, and specific detectivity in the UV−vis-NIR-SWIR spectrum. Interestingly, the photoresponse has been found to be negligible without a 3-mercaptopropionic acid (MPA) ligand exchange, moderate with a single ligand exchange after all QD layers are deposited on graphene, and maximum if it is performed after each QD layer deposition up to five layers of total QD thickness of 260−280 nm. Furthermore, exposure of graphene to C-band UV (UVC) for a short period of 4−5 min before QD deposition leads to improved photoresponse via removal of polar molecules at the QD/Gr interface. With the combination of the MPA ligand exchange and UVC exposure, optimal optoelectronic properties can be obtained on the PbS QD/Gr nanohybrids with high specific detectivity up to 2.6 × 1011, 1.5 × 1011, 5 × 1010, and 1.9 × 109 Jones at 400, 550, 1000, and 1700 nm, respectively, making the nanohybrids promising for broadband photodetection. 

Surface-enhanced Raman spectroscopy (SERS) is an important analytical tool with ultrahigh sensitivity that depends on electromagnetic mechanism (EM) and chemical mechanism (CM). The CM relies on efficient charge transfer between the probe molecules and SERS substrates, which means engineering the molecule attachment and the energy level alignment at the molecule/substrate interface is critical to optimal CM enhancement. Herein, we report enhanced CM of Rhodamine 6G (R6G) on graphene SERS substrates using combined C-band ultraviolet (UVC) irradiation and Pt nanoparticle (Pt-NPs) decoration using atomic layer deposition (ALD). An enhancement of 270% was obtained in the former, which is ascribed to the graphene surface activation and p-doping on graphene for improved R6G molecule attachment and charge transfer by its surface change from hydrophobic to hydrophilic and the down-shift of the Fermi energy (p-doping) after UVC exposure. The Pt-NPs decoration adds an additional enhancement of 250% by further p-doping graphene, which shifts the graphene’s Fermi energy to promote charge (hole) transfer at the R6G/graphene interface. Remarkably, the combination of the UVC irradiation and Pt-NPs decoration has led to enhanced R6G SERS sensitivity of 5 × 10−9 M, which represents a two-orders of magnitude enhancement over that on the pristine graphene and illustrates the importance of graphene engineering for optimal probe molecule attachment and the energy level alignment at the molecule/graphene interface toward achieving high-performance SERS biosensing. 

Abstract Ultrathin (sub-2 nm) Al₂O₃/MgO memristors were recently developed using anin vacuoatomic layer deposition (ALD) process that minimizes unintended defects and prevents undesirable leakage current. These memristors provide a unique platform that allows oxygen vacancies (V_O) to be inserted into the memristor with atomic precision and study how this affects the formation and rupture of conductive filaments (CFs) during memristive switching. Herein, we present a systematic study on three sets of ultrathin Al₂O₃/MgO memristors with V_O-doping via modular MgO atomic layer insertion into an otherwise pristine insulating Al₂O₃atomic layer stack (ALS) using anin vacuoALD. At a fixed memristor thickness of 17 Al₂O₃/MgO atomic layers (∼1.9 nm), the properties of the memristors were found to be affected by the number and stacking pattern of the MgO atomic layers in the Al₂O₃/MgO ALS. Importantly, the trend of reduced low-state resistance and the increasing appearance of multi-step switches with an increasing number of MgO atomic layers suggests a direct correlation between the dimension and dynamic evolution of the conducting filaments and the V_Oconcentration and distribution. Understanding such a correlation is critical to an atomic-scale control of the switching behavior of ultrathin memristors. 

Abstract In the carbon nanotubes film/graphene heterostructure decorated with catalytic Pt nanoparticles using atomic layer deposition (Pt-NPs/CNTs/Gr) H 2 sensors, the CNT film determines the effective sensing area and the signal transport to Gr channel. The former requires a large CNT aspect ratio for a higher sensing area while the latter demands high electric conductivity for efficient charge transport. Considering the CNT’s aspect ratio decreases, while its conductivity increases ( i.e. , bandgap decreases), with the CNT diameter, it is important to understand how quantitatively these effects impact the performance of the Pt-NPs/CNTs/Gr nanohybrids sensors. Motivated by this, this work presents a systematic study of the Pt-NPs/CNTs/Gr H 2 sensor performance with the CNT films made from different constituent CNTs of diameters ranging from 1 nm for single-wall CNTs, to 2 nm for double-wall CNTs, and to 10–30 nm for multi-wall CNTs (MWCNTs). By measuring the morphology and electric conductivity of SWCNT, DWCNT and MWCNT films, this work aims to reveal the quantitative correlation between the sensor performance and relevant CNT properties. Interestingly, the best performance is obtained on Pt-NPs/MWCNTs/Gr H 2 sensors, which can be attributed to the compromise of the effective sensing area and electric conductivity on MWCNT films and illustrates the importance of optimizing sensor design. 

Abstract Continuous device downsizing and circuit complexity have motivated atomic-scale tuning of memristors. Herein, we report atomically tunable Pd/M1/M2/Al ultrathin (<2.5 nm M1/M2 bilayer oxide thickness) memristors using in vacuo atomic layer deposition by controlled insertion of MgO atomic layers into pristine Al₂O₃atomic layer stacks guided by theory predicted Fermi energy lowering leading to a higher high state resistance (HRS) and a reduction of oxygen vacancy formation energy. Excitingly, memristors with HRS and on/off ratio increasing exponentially with M1/M2 thickness in the range 1.2–2.4 nm have been obtained, illustrating tunneling mechanism and tunable on/off ratio in the range of 10–104. Further dynamic tunability of on/off ratio by electric field is possible by designing of the atomic M2 layer and M1/M2 interface. This result probes ways in the design of memristors with atomically tunable performance parameters.