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Dynamic plasmonics with the real-time active control capability of plasmonic resonances attracts much interest in the communities of physics, chemistry, and material science. Among versatile reconfigurable strategies for dynamic plasmonics, electrochemically driven strategies have garnered most of the attention. We summarize three primary strategies to enable electrochemically dynamic plasmonics, including structural transformation, carrier-density modulation, and electrochemically active surrounding-media manipulation. The reconfigurable microstructures, optical properties, and underlying physical mechanisms are discussed in detail. We also summarize the most promising applications of dynamic plasmonics, including smart windows, structural color displays, and chemical sensors. We suggest more research efforts toward the widespread applications of dynamic plasmonics.

Samples (Cu0.5Tl0.5)Ba2Ca2Cu3-xKxO10-δ (x = 0, 1, 2, 2.5, 3) and Tl1.0Ba2Ca2K3O10-δ were synthesized to study the effect of electron donor atoms at the copper planar sites CuO2 to better understand process of superconductivity in oxides. The samples were synthesized following the two-step solid-state reaction method, and analyzed using x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray fluorescence spectroscopy (XRF), resistivity (RT), and Fourier-transform infrared (FTIR) absorption measurements. By using the software VESTA (visualization for electronic and structural analysis), we have successfully drawn the crystal structures of all the samples. From room temperature to the onset of superconductivity, our samples showed metallic variation in resistivity, with zero resistivity at the critical temperature (Tc, R = 0) staying around 93 K. In the Tl1.0Ba2Ca2K3O10-δ samples, copper Cu (3d9) atoms were entirely removed from the charge reservoir layer (i.e., Tl1.0Ba2O4-δ charge reservoir layer) the samples showed semiconducting behavior with variable range Mott hopping (VRH) conductivity with an energy gap of 2.41 meV. The FTIR absorption spectrum demonstrated the planar oxygen mode, as well as the apical oxygen modes. Tl-OA-Cu(2) and Cu(1)-OA-Cu(2) were stiffened with the doping of K(4s1) at the CuO2 planar sites, confirming intrinsic doping of K atoms. Excess conductivity studies (FIC) of the Cu0.5Tl0.5Ba2Ca2Cu3-xKxO10-δ (x = 1, 2, 2.5, 3) samples revealed an increase in the coherence length along the c-axis ξc(0), the Fermi velocity of superconducting carriers VF, inter-layer coupling J, and the energy needed to break apart the Cooper pairs when compared with the un-doped Cu0.5Tl0.5Ba2Ca2Cu3O10-δ, sample. Doped alkali atoms provide a larger density of free carriers in the superconducting planes rising superconductivity parameters. Higher free carrier density provided by the doped alkali atoms at room temperature to the conducting planes enhanced the electron–hole recombination process which brings them to the optimal doping level, thereby promoting the critical temperature and superconducting parameters to superior values. The Turning of the Tl1Ba2Ca2K3O10-δ samples semiconducting has shown that the presence of a spin-bearing entity in the unit cell is important for the occurrence of high Tc superconductivity, and the interplay of spin and charge density waves induces superconductivity in oxide samples at high temperatures.

Two-dimensional (2D) materials with reversible phase transformation are appealing for their rich physics and potential applications in information storage. However, up to now, reversible phase transitions in 2D materials that can be driven by facile nondestructive methods, such as temperature, are still rare. Here, we introduce ultrathin Cu 9 S 5 crystals grown by chemical vapor deposition (CVD) as an exemplary case. For the first time, their basic electrical properties were investigated based on Hall measurements, showing a record high hole carrier density of ∼ 10 22 cm −3 among 2D semiconductors. Besides, an unusual and repeatable conductivity switching behavior at ∼ 250 K were readily observed in a wide thickness range of CVD-grown Cu 9 S 5 (down to 2 unit-cells). Confirmed by in-situ selected area electron diffraction, this unusual behavior can be ascribed to the reversible structural phase transition between the room-temperature hexagonal β phase and low-temperature β′ phase with a superstructure. Our work provides new insights to understand the physical properties of ultrathin Cu 9 S 5 crystals, and brings new blood to the 2D materials family with reversible phase transitions.

This paper discusses the use of an approximated charge carrier density to model an organic thin-film transistor (OTFT) using a double exponential density of states. Traditionally, published work employs a single exponential density of states and Gaussian density of states. On the contrary, this paper employs a double exponential density of states in the Fermi integral to evaluate the charge carrier density for the OTFT. We consider two exponential density of states, one rateled to the tail region and one to a deep region, in addition to various associated parameters. The distribution of localized trap states between the highest and lowest orbital is expressed as a density of states, one for the tail states and one for the deep states. Tail states are better described by the Gaussian function, while deep states are better described by the exponential density of states. Therefore, if we require that the two regions be defined by a single function, then the function should be a sum of the two, the exponential and the Gaussian, to more accurately describe the complete region. The double exponential density of states is employed to evaluate and approximate the Fermi integral using various mathematical methods, so that the error is lower for various parameters.

A central challenge in making two-dimensional (2D) material-based devices faster, smaller, and more efficient is to control their charge carrier density at the nanometer scale. Traditional gating techniques based on capacitive coupling through a gate dielectric cannot generate strong and uniform electric fields at this scale due to divergence of the fields in dielectrics. This field divergence limits the gating strength, boundary sharpness, and minimum feature size of local gates, precluding certain device concepts (such as plasmonics and metamaterials based on spatial charge density variation) and resulting in large device footprints. Here we present a nanopatterned electrolyte gating concept that allows locally creating excess charges by combining electrolyte gating with an ion-impenetrable e-beam-defined resist mask. Electrostatic simulations indicate high carrier density variations of Δn ∼ 1014 cm−2 across a length of only 15 nm at the mask boundaries on the surface of a 2D conductor. We implement this technique using cross-linked poly(methyl methacrylate), experimentally prove its ion-impenetrability and demonstrate e-beam patterning of the resist mask down to 30 nm half-pitch resolution. The spatial versatility enables us to demonstrate a compact mid-infrared graphene thermopile with a geometry optimized for Gaussian incident radiation. The thermopile has a small footprint despite the number of thermocouples in the device, paving the way for more compact high-speed thermal detectors and cameras.

This paper analyzes the effect of a HfAlO x dielectric in a dual-channel (DC)single-gate (SG) metal oxide semiconductor high-electron-mobility transistor (DCSG-MOSHEMT) on improving device performance metrics. The small-signal analog/RF and noise performance of the device are explored in detail. The physics-based TCAD simulator tool is utilized to characterize the device. A peak drain current of 1.52 mA/µm is achieved due to superior sheet carrier density ( n s ) of 1.5×10 18 cm −3 and low ON resistance. Further, a high positive threshold voltage ( V T ) of 0.214 V and a peak transconductance of 1.8 ms/µm is achieved with HfAlO x as the dielectric. Moreover, high cutoff frequency ( f T ) of 530 GHz and maximum frequency of oscillation ( f max ) of 840 GHz at V ds  = 0.5 V is achieved. The device exhibits a minimum noise figure of 1.32 dB at V gs  = 0.3 V and V ds  = 0.5 V. With low noise over a large bandwidth and high-frequency performance, this device can be utilized to design low-noise amplifiers (LNA) for broadband applications.

A TiN-based substrate with high reusability presented high-sensitivity refractive index measurements in a home-built surface plasmon resonance (SPR) heterodyne phase interrogation system. TiN layers with and without additional inclined-deposited TiN (i-TiN) layers on glass substrates reached high bulk charge carrier densities of 1.28 × 1022 and 1.91 × 1022 cm−3, respectively. The additional 1.4 nm i-TiN layer of the nanorod array presented a detection limit of 6.1 × 10−7 RIU and was higher than that of the 46 nm TiN layer at 1.2 × 10−6 RIU when measuring the refractive index of a glucose solution. Furthermore, the long-term durability of the TiN-based substrate demonstrated by multiple processing experiments presented a high potential for various practical sensing applications.

A semiconductor is a material that has electrical properties somewhere in the middle, between those of an insulator and a conductor. It is neither a good insulator nor a good conductor (called a semiconductor). It has very few free electrons because its atoms are closely grouped together in a crystalline pattern called a crystal lattice, however, electrons are still able to flow, but only under special conditions. One of the principal characteristics of semiconductors is that they can be doped with impurities to alter their electrical properties. The semiconductor properties are characterized by the band theory. This model states that an electron in a solid can only take on energy values within certain ranges called permitted bands, which are separated by other bands called band gaps. These materials are mainly used in electronics (diodes, transistors, etc.), microelectronics for integrated circuits, solar cells and optoelectronic devices such as light emitting diodes (LEDs). III-V semiconductors are of great interest because of their properties, they are robust, have a high thermal conductivity and a direct band gap. Devices and circuits in the III-V semiconductor group were always known by their high speed, but also by their expensive production and lower integration compared to silicon-based ones. In this paper, models for the effective density of states (Nc and Nv) in the conduction and valence bands, intrinsic carrier density ni, temperature dependence of the energy band gap (Eg) and doping dependence of the energy band gap (Eg) of aluminum gallium arsenide (AlxGa1 – xAs) semiconductors are analyzed using MATLAB for different values of x (0 ≤ x ≤ 1).

In the present study, the surface properties of carbon steel were investigated to examine its corrosion behavior after the doping of cobalt via thermal diffusion at different temperatures for 1 to 4 h in three atmospheres: oxidative, reductive and inert. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), potentiodynamic analysis (PDA), Mott-Schottky (MS) studies, quantometer analysis (QA), and X-ray diffraction (XRD) were used to investigate the samples. The MS studies confirmed that a semiconductor is formed onto the surface of carbon steel. According to the EIS data and the CV curves, in the most of samples, the electrical characteristic was similar to the Schottky diode SB-540. For the cobalt-doped samples, the results of the PDA curves showed that the surface of the most of samples was protected through passivity and in some cases by trans-passivity process. It was found that by increasing the polarization resistance ( R p ) the rate of corrosion reaction is reduced, so the lowest corrosion rate corresponds to the temperatures of 650 ℃ (in the inert atmosphere and doping time of 2 h), 950 ℃ (in the oxidative and doping time of 2 h) and 550 ℃ (in the reductive atmosphere and doping time of 1 h). The electron acceptor and donor’s carrier density ( N d and N a ) values were calculated to specify the n-type or p-type semiconductors formed at different temperatures and atmospheres. The XRD spectra of the samples showed the formation of Co 3 Fe 7 , CoFe 2 O 4 , Fe 3 O 4 , Fe 24 O 32 , Fe 2 O 3 , Fe 7 O 0.088 , Fe 7 C 3 , CoC 8 , C 3 N 4 , Co 3 (Co(CN) 6 ) 2 , Co(N(CN) 2 ) 2 , FeN 0.076 , Fe 8 N structures. Graphical Abstract

Pseudo-satellite technology has excellent compatibility with the BDS satellite navigation system in terms of signal systems. It can serve as a stable and reliable positioning signal source in signal-blocking environments. User terminals can achieve continuous high-precision positioning both indoors and outdoors without any modification to the navigation module. As a result, pseudo-satellite indoor positioning has gradually emerged as a research hotspot in the field. However, due to the complex and variable indoor radio propagation environment, signal propagation is interfered with by noise, multipath, non-line-of-sight (NLOS) propagation, etc. The geometric relation-based localization algorithm cannot be applied in indoor non-line-of-sight environments. Therefore, this paper proposes a pseudo-satellite fingerprint localization method based on the discriminative deep belief networks (DDBNs). The method acquires the model parameters of pseudo-satellite multi-carrier noise density signal strength in non-line-of-sight indoor spaces through a greedy unsupervised learning method and gradient descent-supervised learning method. It establishes a mapping relationship between the implied features of the pseudo-satellite multi-carrier noise density signal strength and indoor location, enabling pseudo-satellite fingerprint matching localization in indoor non-line-of-sight environments. In this paper, the performance of the positioning algorithm is verified in dynamic and static scenarios through numerous experiments in a laboratory environment. Compared to the commonly used localization algorithms based on fingerprint library matching, the results demonstrate that, in indoor non-line-of-sight test conditions, the system’s 2D static positioning has a maximum error of less than 0.24 m, an RMSE better than 0.12 m, and a 2σ (95.4%) positioning error better than 0.19 m. For 2D dynamic positioning, the maximum error is less than 0.36 m, the average error is 0.23 m, and the 2σ positioning error is better than 0.26 m. These results effectively tackle the challenge of pseudo-satellite indoor positioning in non-line-of-sight environments.