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On-chip coherent light source has always been fascinating and intriguing due to its various potential applications. In the past decades, there has been some progress in the development of chip coherent light (e.g., nanolaser, Bose-Einstein condensation and nonlinear optical effects). However, these methods strictly depend on materials and extreme experimental conditions, and are usually not tunable. Here, a hybrid structure is designed which combines a chirped surface plasmon metasurface with a monolayer transition metal dichalcogenide (TMDC) to achieve a coherent second harmonic generation (SHG) covering the entire visible light spectrum. Using only finite number of metallic grooves, a continuous resonance tuning is obtained. By translating the metasurface in space, a space-frequency locking SHG is demonstrated. Although the Q factor of the surface plasmon cavity is low, its near-field enhancements of both fundamental and SH waves are still obvious. Significantly, the broad linewidth of plasmonic cavity leads to a large degree of overlap between adjacent localized modes, that enables the tuning of the output wavelength continuously at room temperature. Meanwhile, the exciton resonance also plays an important role. This monolithic tunable device demonstrates the potentials of 2D material-plasmon hybrid metasurface and to construct an efficient broadband tunable on-chip coherent light source.

Plasmonics have been well investigated on photodetectors, particularly in IR and visible regimes. However, for a wide range of ultraviolet (UV) applications, plasmonics remain unavailable mainly because of the constrained optical properties of applicable plasmonic materials in the UV regime. Therefore, an epitaxial single‐crystalline aluminum (Al) film, an abundant metal with high plasma frequency and low intrinsic loss is fabricated, on a wide bandgap semiconductive gallium nitride (GaN) to form a UV photodetector. By deliberately designing a periodic nanohole array in this Al film, localized surface plasmon resonance and extraordinary transmission are enabled; hence, the maximum responsivity (670 A W−1) and highest detectivity (1.48 × 1015 cm Hz1/2 W−1) is obtained at the resonance wavelength of 355 nm. In addition, owing to coupling among nanoholes, the bandwidth expands substantially, encompassing the entire UV range. Finally, a Schottky contact is formed between the single‐crystalline Al nanohole array and the GaN substrate, resulting in a fast temporal response with a rise time of 51 ms and a fall time of 197 ms. To the best knowledge, the presented detectivity is the highest compared with those of other reported GaN photodetectors., Aluminum plasmonics is merged as an advancement tool to boost GaN a superior complementary metal oxide semiconductor (CMOS) compatible UV photodetector. By introducing a single‐crystalline Al nanohole array on a GaN substrate, it enables ultraviolet plasmons and Schottky barrier, and thus demonstrates excellent performance in entire UV regime: maximum responsivity (670 A W−1), highest detectivity (1.48 × 1015 cm Hz1/2 W−1), and fast temporal response.

A hybrid graphene–insulator–metal (GIM) platform is proposed with a supported surface plasmon polariton (SPP) wave that can be manipulated by breaking Lorentz reciprocity. The ZnO SPP nanowire lasers on the GIM platforms are demonstrated up to room temperature to be actively modulated by applying external current to graphene, which transforms the cavity mode from the standing to propagation wave pattern. With applying 100 mA external current, the laser threshold increases by ≈100% and a 1.2 nm Doppler shift is observed due to the nonreciprocal propagation characteristic. The nanolaser performance also depends on the orientation of the nanowire with respect to the current flow direction. The GIM platform can be a promising platform for integrated plasmonic system functioning laser generation, modulation, and detection., Plasmonic nanolasers are incorporated into the hybrid graphene–insulator–metal platform that can break the Lorentz reciprocity by applying external current to graphene in order to actively modulate the laser threshold. Room temperature laser modulation demonstrates that the laser threshold increases by ≈100% with applying 140 mA external current.

Twisting between two stacked monolayers modulates periodic potentials and forms the Moiré electronic superlattices, which offers an additional degree of freedom to alter material property. Considerable unique observations, including unconventional superconductivity, coupled spin-valley states, and quantized interlayer excitons are correlated to the electronic superlattices but further study requires reliable routes to study the Moiré in real space. Scanning tunneling microscopy (STM) is ideal to precisely probe the Moiré superlattice and correlate coupled parameters among local electronic structures, strains, defects, and band alignment at atomic scale. Here, a clean route is developed to construct twisted lattices using synthesized monolayers for fundamental studies. Diverse Moiré superlattices are predicted and successfully observed with STM at room temperature. Electrical tuning of the Moiré superlattice is achieved with stacked TMD on graphite.

Raman and SIMS studies of Mg-doped InN films with a Mg content from NMg = 3.3 × 1019 to 5.5 × 1021 cm–3 are reported. Lattice dynamics of hexagonal InN with substitutional impurities and vacancies has been investigated theoretically and calculated Raman spectra were compared with experimental ones. It is concluded that Raman spectroscopy is a good tool for quantitative characterization of Mg-doped InN. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report the unusual photoluminescence (PL) properties of vertically aligned InN nanorod arrays grown on Si(111) with a Si3N4 buffer layer. The optimum growth conditions of InN nanorods are obtained by controlling the III/V ratio and the growth temperature. Structural characterization by X-ray diffraction and scanning electron microscopy indicates that individual nanorods are wurtzite InN single crystals with the growth direction along the c-axis. Near-infrared PL from InN nanorods is clearly observed at room temperature. However, in comparison to the PL from InN epitaxial films, the PL from InN nanorods is significantly lower in efficiency and exhibit anomalous temperature dependence. We propose that these unusual PL properties are results of considerable structural disorder (especially for the low-temperature grown InN nanorods) and strong surface electron accumulation effect. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of proton irradiation on the optical and electrical properties of n-InN with charge carrier concentrations of 2 - 5 x 10 18 cm -3 have been investigated. Strong changes in photoluminescence spectra and electrical parameters of irradiated n-InN are discussed. Proton irradiation of n-InN results in the appearance of shallow donors in large concentrations. Comparison with the effects observed on heavily degenerate n-InN after proton irradiation leads to the conclusion that these irradiation-produced donors are native defects, most likely vacancies on the nitrogen sublattice.

Metal and semiconductor nanoparticles display fascinating size-dependent structural, electronic, optical, magnetic, and chemical properties, which make them promising materials to be tailored and functionalized as fundamental building blocks for emerging nanotechnology applications. Because of the strong dependence of nanoparticle properties on their quantum-scale dimensions, the synthesis of nanoparticles with a small size and shape variation is of key importance. At present, size-, shape-, composition-, and surface-chemistry-controlled nanoparticles can be synthesized by colloidal-solution methods for a wide range of materials. Furthermore, strategies have been developed in which monodispersed nanoparticles can form self-assembled, long-range nanoparticle lattices (2D and 3D) under appropriate conditions. The next important challenge for emerging nanotechnological applications (chemical and biological sensing, electronics, optoelectronics) is to perform controlled and hierarchical self-assembly of monodispersed nanoparticles from the solution phase into ordered and specifically designed nanoparticle structures immobilized on solid-surface templates. In this paper, we report an approach for controlled assembly of metal (Au) and semiconducting (CdSe/ZnS core/shell) thiol-terminated nanoparticles onto electrically patterned Si3N4/SiO2/Si (NOS) electret films with an unprecedented resolution. In the past few years, several important breakthroughs in scanning-probe-based lithographic techniques using tip-induced local electrochemical reactions of self-assembled monolayers (SAMs) or tip-induced local-transport processes, such as dip-pen nanolithography, were developed for fabricating surface templates, which can be used to assemble nanoparticles on solid supports. In these techniques, the patterning process is realized by molecular reaction or transport through a water meniscus that naturally occurs between the tip and sample under ambient conditions. Therefore, the typical resolution and writing speed of such techniques is controlled by parameters such as probe scan speed, temperature, humidity, and molecule type. Furthermore, the reaction or transport rate is limited by the reaction or ink-transport process. As a result, these types of lithographic mechanism limit the line-writing speed to the range 0.1–10 lm s and the dotwriting time to the range of a few milliseconds to tens of seconds per dot (size-dependent) under ambient conditions. Recently, electrostatic-force-based assembly of nanoparticles has been proposed as a general, precise, and reliable methodology for such purposes. In the most direct type of electrostatic-force-based assembly, charge patterns are created by scanning-probe or microcontact charging techniques onto electret materials via electronor hole-tunneling processes. As the electret materials can retain electric charge or polarization for a long time, these charge patterns can be used as templates for assembling charged or polarizable nanoparticles. The major advantage of electrostatic lithography is that, in contrast to diffusion processes, the patterning speed can be enhanced over three orders of magnitude. However, because electrostatic forces scale with surface area and particle size, nanoscale electrostatic assembly of nanoparticles is a formidable task. Xerography (a form of electrophotography) is currently one of the prevailing methods for pattern generation or replication, with ∼ 100 lm resolution. In this process, charged toner particles (with diameters in the range of several micrometers) are attracted by electrostatic-charge patterns (latent electrostatic images) created on a photosensitive electret, and the images are developed with these toner particles. Very recently, nanoscale xerography (nanoxerography) using an electrical microcontact printing process or a scanningprobe-based process was proposed as a means for nanoscale pattern generation or replication. In this work, by using an optimized electret structure (NOS dielectric stack), improved local-charging conditions under high vacuum, and chemically modified nanoparticles (5 nm thiol-terminated gold colloids, see the literature and the Experimental section for the synthesis procedure), we are able to perform selective attachment of gold colloidal nanoparticles onto the patterned electret in a toluene solution at a resolution of ∼ 30 nm. Furthermore, in our process, only a C O M M U N IC A IO N S

The exact solution of the Thomas–Fermi equation for a planar accumulation layer of a degenerate semiconductor is presented. The obtained results are compared with theoretical literature data. The applicability of the solution is demonstrated by using results of electrochemical capacitance–voltage measurements and photoluminescence data for n-InN epilayers. It has been found that the difference between the electron concentrations estimated from the Hall and photoluminescence measurements is a measure of the electron content in the accumulation layer with acceptable accuracy. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)