Micro and Nanostructures最新文献

This paper proposed a meta material model with low-frequency wide band gap and band gap tunability, optimized its structure as a multibranch chain structure, and analyzed the band gap relationship of above two models based on Brag's theorem and finite element method. Among them, the fan base structure has a band gap of 65.92 % within 20,000 Hz, and the band gap is optimized to low-frequency after the structure is optimized, and the band gap reaches 75.94 % within 10,000 Hz. The effects of the ligament width and the thickness of the center parcel layer on the band gap distribution of the structure are also discussed, and the wave transmission characteristics in the structure are explored by group and phase velocities to verify the acoustic performance of the structure. The results show that the smaller the ligament thickness is, the lower the first band gap opening frequency of the structure is; when the thickness of the central wrapping layer is increased, the structure develops the band gap at the center frequency of 3000 Hz to a lower frequency and generates an ultra-wide band gap at the center frequency of 6000 Hz. These findings can provide a new idea for low-frequency vibration isolation and noise reduction.

In this work, we have implemented Ge source Selective buried oxide (SELBOX) Tunnel FET for photo sensing applications in the visible range of spectrum for wavelength (λ = 300–700) nm. The various electrical parameters are extracted under dark and illumination states considering the presence and absence of trap charges at the interface of gate oxide and semiconductor. It is seen that at illumination state, the drain current degrades at low gate voltage and presence of traps lead to reduced tunnelling rate. Further, the spectral sensitivity, responsivity, and signal to noise ratio (SNR) are extracted for this TFET based photosensor with variation in λ. Result reveals that spectral sensitivity, responsivity, and signal to noise ratio (SNR) are 20.8, 0.5, and 49.5 dB, respectively, at λ = 300 nm. Further, the presence of trap charges result in degradation of these parameters. Finally, a comparative study of optical parameters with the existing data is highlighted.

Organic photodetectors (OPDs) have received wide attention for the weak-light signals sensitivity and promising application in imaging, and optical communication. While limited light absorption due to low carrier mobility of organic active layer. ZnO nanorods (NRs) possesses excellent photoelectric and light-trapping properties have been used in OPDs. Herein, for the first time, ZnO NRs were hydrothermal synthesized based on Kaolinite-ZnO (KAZN) seed layer. Kaolinite is a natural substance that originates from layered silicate minerals, possess unique crystal chemical properties. The KAZN NRs exhibits a smaller grain size, enhanced crystallinity and significantly enhanced light-scattering (average Haze increased 36 % from 300 to 800 nm) compared with ZnO NRs. Meanwhile, KAZN NRs have a narrower band gap, leading to superior photoelectric emission. The resulting KAZN NRs OPDs showed an enhancement in responsivity (Rs) by 44 % and achieved an impressively high On/Off ratio (18,744), representing a remarkable increase of 1800 %@ 440 nm. The noise equivalent power (NEP) has decreased by an order of magnitude at full test band. The significant improvement can be attributed to the introduction of Kaolinite, which alters the NRs crystal structure and effectively reduces OPDs dark current while enhancing photocurrent. Our research provides a simple and cost-effective approach for improving light-scattering characteristics and optoelectronic performance for ZnO based-photovoltaic devices.

This research delves into the influence of hydrostatic pressure on the structural, electronic, and optical characteristics of the cubic halide perovskite KSrCl₃. The reduction in interatomic distance caused by pressure has a considerable effect on the unit cell volume and lattice constant of this perovskite. As pressure increases, the electronic band gap closes, transferring from the ultraviolet to the visible spectrum. This phenomenon increases the efficiency of optoelectronic devices by simplifying the transition of electrons from the valence band to the conduction band. In addition, the material becomes more appropriate for use in a variety of optoelectronic applications when the band gap changes from indirect to direct at pressures of about 50 GPa. A comprehensive optical analysis suggests that KSrCl₃ holds potential applications in surgical tools, integrated circuits, QLED, OLED, solar cells, waveguides, and materials designed for solar heat reduction. The tolerance factor “t" confirms the stability of the KSrCl3 phase across the applied pressure range, and the formation energy values with negative values show the attained thermodynamic stability.

In recent technology, Nano Ribbon FET (NR-FET) is an emerging device due to its enhanced effective width than other FET devices. In this paper, the electrical parameters including self-heating effect (SHE) for NRFET is presented. The drain current (I_D), transconductance (g_m), transconductance generation factor (TGF = g_m/I_D), and cut-off frequency (f_c) are highlighted in NRFET with/without considering SHE. It is observed that various electrical parameters are degraded by significant amount in the presence of SHE for NR-FET. The g_m is changed from 1.45 to 0.725 mS in presence of SHE, whereas, f_c is reduced to 2.47 THz from 4.5 THz in presence of SHE for NRFET. Further, the effect of variation in width and height of ribbon in NRFET on e-density, drain current, and transconductance are reported with/without including SHE. Result reveals that with increased width/height, the performance of NRFET is enhanced and this is further degraded with including SHE. Finally, the important parameters like lattice temperature and thermal resistance (R_th) are calculated for NRFET. The calculated lattice temperature and R_th are 375.2 K and 1.534 K/μWatt, respectively.

Shrinking MOSFETs suffer performance hits due to short-channel effects and leakage. Junctionless transistors JLTs emerge as promising alternatives due to simpler fabrication and better gate control. This paper investigates the analog and RF performance characteristics of n-type Silicon-Based Double Gate Junctionless Transistors with varying channel lengths (15 nm, 20 nm, and 25 nm) This study evaluates analog device performance through critical parameters: drain current density (I_d), transconductance (g_m), output resistance (R_O), intrinsic gain (g_mR_O), and transconductance generation factor (g_m/I_d). These parameters assess current handling, gain characteristics, and design efficiency, providing a comprehensive analysis for analog circuit applications. Results indicate that the device having 15 nm channel length exhibits a transconductance which is 25.38 % more than the 20 nm variant and drain current which is 44.7 % more than the latter, suggesting its superior performance to devices with longer channel lengths. In addition, the RF performance of the devices is evaluated using the small signal model of the device. This work further investigates the high-frequency response of the devices using key figures of merit (FoMs): gate capacitances (C_gs, C_gd, C_gg), cut-off frequency (f_T), and maximum oscillation frequency (f_MAX). These parameters quantify the influence of parasitic capacitances on switching speed and the maximum useable frequency for analog and RF applications. Analyzing C_gs, C_gd, and C_gg reveals the impact of gate control on high-frequency operation. The device having 15 nm channel length, exhibits an increase of 47.29 % in f_T and 68.97 % increase in f_MAX compared to device having 20 nm channel length. The findings underscore the significance of channel length optimization in enhancing the Analog and RF performance of n-type Silicon-based Double Gate Junctionless Transistors.

The influence of bismuth (Bi) nanoparticles on single-crystal iron (Fe) under rigid ball rolling-sliding friction conditions is investigated using molecular dynamics simulations.Various aspects such as frictional force, dislocation length, dislocation configuration, and frictional surface are examined, along with the characteristics of bismuth particles at different depths of inclusion during wear provide partial theories for the application of free-cutting steels containing Bi. The results indicate that the morphology of wear chips accumulation and the lattice structure of wear chips depend significantly on the different forms of Bi inclusions and rotation periods of rigid ball. The extracted atomic displacement vectors theoretically explain the reasons for different accumulation morphologies and reveal atomic trajectories for subsurface damage due to inward movements. Furthermore, comparing the friction force curves between specimens with inclusions and pure Fe demonstrates that the softer Bi particles soften the workpiece, leading to corresponding wear and damage even at lower friction forces compared to the pure Fe model. Additionally, the study finds that dislocations play a dominant role in wear damage, with Bi particles hindering dislocation slip, as evidenced by the significant inhibition of Von Mises stresses by bismuth. Bi also prevents dislocation nucleation within itself, avoiding deeper wear damage to the iron matrix after slip, ultimately resulting in less severe subsurface frictional damage in the inclusion model compared to pure iron. Deeper inclusions significantly induce the generation of high-energy dislocations during wear, attributed to Bi aiding in strain energy storage, thereby higher strain energy for dislocations in Fe media.

In this paper, we first characterize a superlattice structure created by repeating a heterostructure formed from two armchair graphene nanoribbon (AGNR) segments with different widths. We investigate the electronic and transport properties of this structure by varying its widths and lengths to demonstrate the tunability of its overall band gap. The plot of the local density of states shows the formation of localized states at the low band gap segments of the superlattice. The superlattice is then used as a barrier to create a double barrier quantum well (DBQW) to design a proposed resonant tunneling diode (RTD) structure. We observe this device's negative differential resistance (NDR) operation for a range of bias voltages between the contacts. We study the effect of dimensional parameters on the RTD performance. The non-equilibrium Green's function method, based on a tight-binding model, is employed for numerical computation.

The p-type ohmic contact of GaN laser diodes has been optimized in several ways. The heavily doped p-GaN contact layer obtained by using delta-doping method, which effectively suppressed the self compensation effect of Mg ions during the heavy doping. By optimizing the delta-doping period, temperature, and thickness of the p-GaN contact layer, the activation energy of Mg atoms is reduced, and the hole concentration in the surface contact layer is further increased. Finally, the specific contact resistivity of the p-type ohmic contact of the GaN laser, measured more accurately by using the transmission line module, was successfully reduced to the order of 1E-3 Ω cm².

In this study, we propose a theoretical simulation of the type-I step quantum well obtained from GeSn/SiGeSn to scan a wide range of telecommunication wavelengths and obtain near-infrared optical modulators. At T = 300 K, the band discontinuities and energy gap between stretched Ge_1−xSn_x and relaxed Si_0.1Ge_0.9−ySn_y due to the acquisition of the heterostructure were calculated.

Then, optimization of this heterostructure based on (Si) GeSn was performed using the solid theory model to balance out the composition y of Si_0.1Ge_0.9-ySn_y relaxed and thickness of Ge_0.91Sn_0.09 QWs. The eigenenergies and their related wavefunctions are computed by solving the Schrödinger equation using the finite difference method under the framework of the effective mass approximation. Depending on the y concentration, the energy levels of the electron and the heavy hole, the change of transition energies and oscillator strength were examined for different well widths. Additionally, the absorption coefficient with y concentration and structure parameters were examined.

From the findings obtained, it was determined that this material group is very important to obtain high efficiency from electro-absorption modulators covering the 1.55 μm wavelength range.