Abstract
A new diagnosis method for the discriminative detection of laser-accelerated multi-MeV carbon ions from background oxygen ions utilizing solid-state nuclear track detectors (SSNTDs) is ...proposed. The idea is to combine two kinds of SSNTDs having different track registration sensitivities: Bisphenol A polycarbonate detects carbon and the heavier ions, and polyethylene terephthalate detects oxygen and the heavier ions. The method is calibrated with mono-energetic carbon and oxygen ion beams from the heavy ion accelerator. Based on the calibration data, the method is applied to identify carbon ions accelerated from multilayered graphene targets irradiated by a high-power laser, where the generation of high-energy high-purity carbon ions is expected. It is found that 93 ± 1% of the accelerated heavy ions with energies larger than 14 MeV are carbons. The results thus obtained support that carbon-rich heavy ion acceleration is achieved.
The 2-D semiconductors have been recognized as promising channel materials for the ultimately scaled transistor technologies beyond silicon. An essential technology enabler for 2-D semiconductor ...electronics is the development of dielectric materials interfaced with 2-D semiconductors. In this review article, we overview different types of dielectric materials that are suitable for different application scenarios, including high-<inline-formula> <tex-math notation="LaTeX">{k} </tex-math></inline-formula> gate dielectrics, low-<inline-formula> <tex-math notation="LaTeX">{k} </tex-math></inline-formula> spacers, and thermal management materials under the paradigm of 2-D semiconductor electronics. A material selection guideline for dielectric materials and the key process technology modules are discussed in detail. A special emphasis is made on how each of the dielectric technologies may enable the further scaling and practical applications of 2-D semiconductor transistors. The state-of-the-art device technologies are summarized, and the remaining challenges toward practical applications are discussed from the industrial perspective.
Abstract
Extended red emission (ERE) is a broad feature in the spectral region of 500–900 nm commonly observed in a wide range of circumstellar and interstellar environments. Although the ...observational constraints for ERE are well established, definitive identifications of the carriers and associated processes complying with these constraints remain unanswered. We report a plausible two-step model involving far-ultraviolet (UV)-irradiated single-layer graphene (SLG), considered as large polycyclic aromatic hydrocarbons, to meet these constraints and supported by laboratory experiments. The far-UV-treated SLG, producing structural defects and graphene quantum dots, showed photoluminescence excitation spectrum extending from the far-UV to UV–visible region, hence meeting the requirements of far-UV light and high photon conversion efficiency. Furthermore, a photoluminescence band shifted from ∼585 to ∼750 nm for high-dose-exposed SLG agrees with the observed redshift of the ERE band in regions under a greater far-UV radiation density.
Development of n-/p-type semiconducting graphenes is a critical route to implement in graphene-based nanoelectronics and optronics. Compared to the p-type graphene, the n-type graphene is more ...difficult to be prepared. Recently, phosphorous doping was reported to achieve air-stable and high mobility of n-typed graphene. The phosphorous-doped graphene (P-Gra) by ion implantation is considered as an ideal method for tailoring graphene due to its IC compatible process; however, for a conventional ion implanter, the acceleration energy is in the order of kiloelectron volts (keV), thus severely destroys the sp2 bonding of graphene owing to its high energy of accelerated ions. The introduced defects, therefore, degrade the electrical performance of graphene. Here, for the first time, we report a low-damage n-typed chemical vapor deposition (CVD) graphene by an industrial-compatible ion implanter with an energy of 20 keV where the designed protection layer (thin Au film) covered on as-grown CVD graphene is employed to efficiently reduce defect formation. The additional post-annealing is found to heal the crystal defects of graphene. Moreover, this method allows transferring ultraclean and residue-free P-Gra onto versatile target substrates directly. The doping configuration, crystallinity, and electrical properties on P-Gra were comprehensively studied. The results indicate that the low-damaged P-Gra with a controllable doping concentration of up to 4.22 at % was achieved, which is the highest concentration ever recorded. The doped graphenes with tunable work functions (4.85–4.15 eV) and stable n-type doping while keeping high-carrier mobility are realized. This work contributes to the proof-of-concept for tailoring graphene or 2D materials through doping with an exceptional low defect density by the low energy ion implantation, suggesting a great potential for unconventional doping technologies for next-generation 2D-based nanoelectronics.
Zinc oxide (ZnO) is a stable, direct bandgap semiconductor emitting in the UV with a multitude of technical applications. It is well known that ZnO emission can be shifted into the green for visible ...light applications through the introduction of defects. However, generating consistent and efficient green emission through this process is challenging, particularly given that the chemical or atomic origin of the green emission in ZnO is still under debate. In this work we present a new method, for which we coin term desulfurization, for creating green emitting ZnO with significantly enhanced quantum efficiency. Solution grown ZnO nanowires are partially converted to ZnS, then desulfurized back to ZnO, resulting in a highly controlled concentration of oxygen defects as determined by X-ray photoelectron spectroscopy and electron paramagnetic resonance. Using this controlled placement of oxygen vacancies we observe a greater than 40-fold enhancement of integrated emission intensity and explore the nature of this enhancement through low temperature photoluminescence experiments.
Abstract
The scaling of transistors with thinner channel thicknesses has led to a surge in research on two-dimensional (2D) and quasi-2D semiconductors. However, modulating the threshold voltage (
V
...T
) in ultrathin transistors is challenging, as traditional doping methods are not readily applicable. In this work, we introduce a optical-thermal method, combining ultraviolet (UV) illumination and oxygen annealing, to achieve broad-range
V
T
tunability in ultrathin In
2
O
3
. This method can achieve both positive and negative
V
T
tuning and is reversible. The modulation of sheet carrier density, which corresponds to
V
T
shift, is comparable to that obtained using other doping and capacitive charging techniques in other ultrathin transistors, including 2D semiconductors. With the controllability of
V
T
, we successfully demonstrate the realization of depletion-load inverter and multi-state logic devices, as well as wafer-scale
V
T
modulation via an automated laser system, showcasing its potential for low-power circuit design and non-von Neumann computing applications.
Ferroelectric semiconductor α‐In2Se3 has gained significant attention due to its favorable physical characteristics, including an appropriate bandgap (≈1.4 eV) for semiconductor devices, ...intercorrelated out‐of‐plane and in‐plane polarization, and high Curie temperature (>200 °C). Combining its semiconducting and ferroelectric properties, α‐In2Se3 holds promise for developing many innovative applications. However, the large‐scale synthesis of uniform layered α‐In2Se3 for practical use and a comprehensive understanding of its phase transition during synthesis are lacking. In this study, layered α‐In2Se3 on amorphous SiO2 substrates at a cm2‐scale is successfully synthesized and explored its phase transition during synthesis, by using a 2D solid‐phase crystallization (2DSPC) method with a SiO2 encapsulation. The formation of highly crystalline 2D layered α‐In2Se3 is observed through the real‐time β‐phase to α‐phase transition at room temperature. The electrical (field‐effect mobility µFE ≈ 1 cm2 V−1s−1), optical, and ferroelectric properties of the synthesized α‐In2Se3 thin films are further investigated. This study contributes to the understanding and control of stoichiometry and phases of In2Se3 and provides an efficient approach for synthesizing large‐area 2D layered α‐In2Se3.
In this study, large‐area 2D layered ferroelectric semiconductor α‐In2Se3 on amorphous SiO2 substrates is successfully synthesized at a cm2‐scale and explored its phase transition during synthesis through a 2D solid‐phase crystallization (2DSPC) method with a SiO2 encapsulation. The formation of highly crystalline 2D layered α‐In2Se3 is observed through the real‐time β‐phase to α‐phase transition at room temperature.
Abstract
Single molecules are elusive and often produce misleading signals. Surface‐enhanced Raman spectroscopy (SERS) is one of the few techniques capable of verifying the presence of single ...molecules. To achieve the goal, the bianalyte proof is favored by researchers as it relies on the statistical analysis of thousands of spectra, rather than the fluctuating signals observed at limited spots. Since the hotspot of SERS is extremely small (<10 nm), less than 1% of the adsorbed molecules can deliver boosted Raman intensities, making the capture of single molecules a rare event. Here, the proof with single‐molecule signals covering 89.6% of the scanned spots is presented. This is achieved by plasmonically coupling subsurface InGaN quantum dots (QDs) to every Au nanoparticle on the SERS substrate. The QD‐Au complexes extend the plasmonic fields far away from the metallic nanojunction, redefining the bianalyte rule for single‐molecule detection.
The multilayer HfSe2 on sapphire is first fabricated by the ion beam‐assisted process combining ion implantation with the post annealing. The A1g mode of HfSe2 is shown in the Raman spectrum, the ...X‐ray photoelectron spectroscopy results indicate the existence of Hf–Se bonding, and the transmission electron microscopy analysis exactly identifies the crystal structure of HfSe2. The six‐layered (6L) octahedral HfSe2 (1T‐HfSe2), whose band structure is well realized by utilizing photoluminescence spectroscopy compared with the results of the density functional theory calculation, is formed via the Hf selenization during annealing.
The 6L 1T‐HfSe2 on sapphire, synthesized by the ion beam‐assisted process, possesses two photoluminescence peaks corresponding to the direct bandgaps with the band splitting of conduction bands at Γ‐point in theory.
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