Atomically precise vacancy-assembled quantum antidots

Patterning antidots, which are regions of potential hills that repel electrons, into well-defined antidot lattices creates fascinating artificial periodic structures, leading to anomalous transport properties and exotic quantum phenomena in two-dimensional systems. Although nanolithography has brought conventional antidots from the semiclassical regime to the quantum regime, achieving precise control over the size of each antidot and its spatial period at the atomic scale has remained challenging. However, attaining such control opens the door to a new paradigm, enabling the creation of quantum antidots with discrete quantum hole states, which, in turn, offer a fertile platform to explore novel quantum phenomena and hot electron dynamics in previously inaccessible regimes. Here we report an atomically precise bottom-up fabrication of a series of atomic-scale quantum antidots through a thermal-induced assembly of a chalcogenide single vacancy in PtTe2. Such quantum antidots consist of highly ordered single-vacancy lattices, spaced by a single Te atom, reaching the ultimate downscaling limit of antidot lattices. Increasing the number of single vacancies in quantum antidots strengthens the cumulative repulsive potential and consequently enhances the collective interference of multiple-pocket scattered quasiparticles inside quantum antidots, creating multilevel quantum hole states with a tunable gap from the telecom to far-infrared regime. Moreover, precisely engineered quantum hole states of quantum antidots are geometry protected and thus survive on oxygen substitutional doping. Therefore, single-vacancy-assembled quantum antidots exhibit unprecedented robustness and property tunability, positioning them as highly promising candidates for advancing quantum information and photocatalysis technologies.

Gate-Tunable Resonance State and Screening Effects for Proton-Like Atomic Charge in Graphene

The ability to create a robust and well-defined artificial atomic charge in graphene and understand its carrier-dependent electronic properties represents an important goal toward the development of graphene-based quantum devices. Herein, we devise a new pathway toward the atomically precise embodiment of point charges into a graphene lattice by posterior (N) ion implantation into a back-gated graphene device. The N dopant behaves as an in-plane proton-like charge manifested by formation of the characteristic resonance state in the conduction band. Scanning tunneling spectroscopy measurements at varied charge carrier densities reveal a giant energetic renormalization of the resonance state up to 220 meV with respect to the Dirac point, accompanied by the observation of gate-tunable long-range screening effects close to individual N dopants. Joint density functional theory and tight-binding calculations with modified perturbation potential corroborate experimental findings and highlight the short-range character of N-induced perturbation.

Strong carrier lifetime enhancement in GaAs nanowires coated with semiconducting polymer

The ultrafast charge carrier dynamics in GaAs/conjugated polymer type II heterojunctions are investigated using time-resolved photoluminescence spectroscopy at 10 K. By probing the photoluminescence at the band edge of GaAs, we observe strong carrier lifetime enhancement for nanowires blended with semiconducting polymers. The enhancement is found to depend crucially on the ionization potential of the polymers with respect to the Fermi energy level at the surface of the GaAs nanowires. We attribute these effects to electron doping by the polymer which reduces the unsaturated surface-state density in GaAs. We find that when the surface of nanowires is terminated by native oxide, the electron injection across the interface is greatly reduced and such surface doping is absent. Our results suggest that surface engineering via π-conjugated polymers can substantially improve the carrier lifetime in nanowire hybrid heterojunctions with applications in photovoltaics and nanoscale photodetectors.

Immune Response of Broiler Chickens Fed Diets Supplemented with Different Level of Chromium Methionine under Heat Stress Conditions

The objectives of this study were to investigate the immune responses of broiler chickens fed diets supplemented with different level of chromium methionine (CrMet) in heat stress (HS) condition. Two hundred and eighty eight male broiler chickens (Ross 308) were allocated to four treatment groups (supplementation with 0, 200, 400 or 800 ppb Cr in the form of CrMet) in a completely randomized design. The experiment was conducted at heat stressed condition and all birds were kept under temperature of 33±2°C. Antibody titers against Newcastle disease virus (NDV) and infectious bronchitis virus (IBV), heterophil to lymphocyte ratios (H/L), and concentration of plasma cortisol (CPC) were measured at 21 and 42 d. At 42 days of age two birds were chosen randomly from each replicate, slaughtered, spleen and bursa of Fabricius were collected, weighed and expressed as a percentage of live body weight. Antibody titers against NDV and IBV at 21 and 42 days of age in broiler fed supplemental CrMet were higher than in broiler chickens fed control diet (p<0.05). CPC level in broiler chickens fed CrMet were significantly (p<0.05) decreased. Increases in lymphocyte counts and consequently a decrease in heterophil to lymphocyte ratios in broiler chickens fed 800 ppb Cr were observed at 21 and 42 d. Supplementation with CrMet had no significant effect on lymphoid organs of broilers. The results suggest that dietary CrMet supplementation at a level of 800 ppb can improve some immune responses of broiler chickens under heat stress conditions.