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In view of the influence of variability of low-frequency noise frequency on noise prevention in real life, we present a novel two-dimensional tunable phononic crystal plate which is consisted of lead columns deposited in a silicone rubber plate with periodic holes and calculate its bandgap characteristics by finite element method. The low-frequency bandgap mechanism of the designed model is discussed simultaneously. Accordingly, the influence of geometric parameters of the phononic crystal plate on the bandgap characteristics is analyzed and the bandgap adjustability under prestretch strain is further studied. Results show that the new designed phononic crystal plate has lower bandgap starting frequency and wider bandwidth than the traditional single-sided structure, which is due to the coupling between the resonance mode of the scatterer and the long traveling wave in the matrix with the introduction of periodic holes. Applying prestretch strain to the matrix can realize active realtime control of low-frequency bandgap under slight deformation and broaden the low-frequency bandgap, which can be explained as the multiple bands tend to be flattened due to the localization degree of unit cell vibration increases with the rise of prestrain. The presented structure improves the realtime adjustability of sound isolation and vibration reduction frequency for phononic crystal in complex acoustic vibration environments.

High-quality low Sn-content GeSn film has been grown on tensile strained Ge/Si (100) substrate using a physical vapor deposition reactor and no subsequent annealing was carried out after the deposition of the film. High Resolution X-ray diffraction (HR-XRD) measurement was performed to estimate the crystallinity and the residual strain in the Ge layer. Secondary-ion mass spectrometry (SIMS) and X-ray photoelectron spectrometer (XPS) show Sn incorporation of the film is approximately 3%. High-resolution transmission electron microscopy (TEM) and atomic force microscopy (AFM) results show that the crystallinity of the film is quite good and it shows a smooth surface (RMS = 0.744 nm) in 5 µm × 5 µm scan. Raman spectroscopy and photoluminescence (PL) measurements were carried out to study the structural and optical properties of the film. Room-temperature PL of the film was observed and it results in a decrease in the difference between Γ and L valleys of tensile strained Ge (0.21%) from 87 meV to 76 meV, which makes this method promising for obtaining Pseudo-direct bandgap group IV films.

In recent years, wireless energy transmission technology has developed rapidly and has received increasing attention in the industry. For microwave wireless energy transfer system applications, Ge Schottky diodes as the core components of the rectifier circuit are commonly used. Compared with Ge semiconductor, strained Ge semiconductor on Si substrate has the advantages of compatibility with Si process, low cost, and high electron mobility. It is an ideal replacement material for Ge semiconductor applications. In view of this, based on the model of the relationship between the performance of strained Ge semiconductor on Si substrate Schottky diodes and the geometric parameters of the device and the physical parameters of the material, Silvaco TCAD and ADS simulation software are jointly used to propose a novel strained Ge semiconductor on Si substrate Schottky diode for microwave rectification circuit. Simulation results show that the strained Ge semiconductor on Si substrate Schottky diode has a rectification efficiency of 70.1% when the input of the rectifier circuit is 20 dBm, the load resistance is R = 1000 Ω, and the load capacitance is C = 100 pF. Compared with traditional Ge Schottky diodes, this optimal operating point is closer to a low energy density, which is beneficial to a wide range of energy absorption. Studies have shown the feasibility of replacing Ge Schottky diodes. The research in this paper can provide valuable reference for the design and development of the core components of the rectifier circuit of the microwave infinite energy transmission system.

In the study of acoustic characteristics of micro-scale surface phononic crystal, the band gap characteristics below 100 MHz need to be further optimized. In this work, a piezoelectric surface phononic crystal with a composite column composed of nickel balls and epoxy backing is proposed. The finite element method is used to calculate the band gap characteristics and displacement vector field of the model. The influence of column radius on the band structure is studied, and meanwhile, the effect of the multi-layer composite column structure on the band gap is discussed via increasing the number of elements in the composite column, while the reason for the opening of the high-order band gap is analyzed in detail by combining the vibration mode. Furthermore, the temperature adjustability of the band gap is further studied. The results show that the spherical composite column deposition structure can open a wider complete band gap of surface acoustic wave in a lower frequency range than the existing inverse conical surface phononic crystal structure with the same lattice constant (Hsu J C, Lin F S 2018 Jpn. J. Appl. Phys. 57 07LB01). The restricted cavity mode is easily formed between the hard boundaries with the increase of column radius, which provides a possible way for low-order vibration modes to open high-order band gaps. There exist mode inheritance and energy coupling between adjacent modes, which leads the band gap to flatten and anti-flatten. Moreover, the real-time adjustment of band gap frequency by external temperature field can be realized via introducing the temperature-sensitive material epoxy resin into the structure. The band gap frequency range can be effectively reduced by increasing the number of composite cylinder layers, while the multi-vibrator structure can generate multipole resonance coupling with traveling wave and finally open a complete band gap between high-order frequency bands. This work provides a theoretical reference for analyzing the low-frequency band gap mechanism of micron-scale surface phononic crystal.

The mechanism of high stress in silicon nitride thin film is studied systematically in this paper. The effects of the various process parameters on the stress in silicon nitride thin film deposited by PECVD are analyzed and discussed. The silicon nitride thin film with high compressive and tensile stress has been deposited on the optimized process parameters and the compressive and tensile stress are up to-1.38GPa and 866MPa, respectively. Finally, the method of further improving the stress in silicon nitride thin film is presented.

Mobility is one of the most important properties of semiconductor material, and it has a great impact on the property of MOS devices.In this paper, the influence of ionizing impurity scattering, acoustic phonon scattering and intervalley scattering to strained-Si(101) material is discussed.In addition, a calculation of the electron mobility in Strained-Si(101) material is made using the average momentum relaxation time method described in Ref[1]. The results show that the electron mobility increases gradually for both [001] and [100] orientations while for [010] orientation increases rapidly with the increasing Ge fraction x.

Solving the Schrödinger equation with strain Hamiltonian and combining with KP theory, we obtained the conductivity effective mass and density of states effective mass of strained Si1-xGex(001) in this paper. On the basis of conductivity effective mass and density of states effective mass, considered of Fermi golden rule and Boltzman collision term approximation theory, scattering rate model was established in strained Si1-xGex(001). Based on the conductivity effective mass and scattering rate models we discussed the dependence of electron mobility on stress and doping concentration in strained Si1-xGex(001), it shows that electron mobility decrease with the increasing of stress and doping concentration. This result can provide valuable references to the research of electron mobility of strained Si1-xGexmaterials and the design of devices.

Germanium-tin films with rather high Sn content (28.04% and 29.61%) are deposited directly on Si (100) and Si (111) substrates by magnetron sputtering. The mechanism of the effect of rapid thermal annealing on the Sn surface segregation of Ge1 −x Sn x films is investigated by x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The x-ray diffraction (XRD) is also performed to determine the crystallinities of the Ge1−x Sn x films. The experimental results indicate that root mean square (RMS) values of the annealed samples are comparatively small and have no noticeable changes for the as-grown sample when annealing temperature is below 400 °C. The diameter of the Sn three-dimensional (3D) island becomes larger than that of an as-grown sample when the annealing temperature is 700 °C. In addition, the Sn surface composition decreases when annealing temperature ranges from 400 °C to 700 °C. However, Sn bulk compositions in samples A and B are kept almost unchanged when the annealing temperature is below 600 °C. The present investigation demonstrates that the crystallinity of Ge1−x Sn x /Si (111) has no obvious advantage over that of Ge1−x Sn x /Si (100) and the selection of Si (111) substrate is an effective method to improve the surface morphologies of Ge1−x Sn x films. We also find that more severe Sn surface segregation occurs in the Ge1−x Sn x /Si (111) sample during annealing than in the Ge1−x Sn x /Si (100) sample.

The analysis of threading dislocation density (TDD) in Ge-on-Si layer is critical for developing lasers, light emitting diodes (LEDs), photodetectors (PDs), modulators, waveguides, metal oxide semiconductor field effect transistors (MOSFETs), and also the integration of Si-based monolithic photonics. The TDD of Ge epitaxial layer is analyzed by etching or transmission electron microscope (TEM). However, high-resolution x-ray diffraction (HR-XRD) rocking curve provides an optional method to analyze the TDD in Ge layer. The theory model of TDD measurement from rocking curves was first used in zinc-blende semiconductors. In this paper, this method is extended to the case of strained Ge-on-Si layers. The HR-XRD scan is measured and Ge (004) single crystal rocking curve is utilized to calculate the TDD in strained Ge epitaxial layer. The rocking curve full width at half maximum (FWHM) broadening by incident beam divergence of the instrument, crystal size, and curvature of the crystal specimen is subtracted. The TDDs of samples A and B are calculated to be 1.41 × 108 cm−2 and 6.47 × 108 cm−2, respectively. In addition, we believe the TDDs calculated by this method to be the averaged dislocation density in the Ge epitaxial layer.

The intrinsic carrier concentration is the important parameter for researching strained Si1-xGex materials properties and evaluating Si-based strained devices parameters. In this paper, at the beginning of analyzing the band structure of strained Si1-xGex/(101)Si, the dependence of its effective densities of states for the conduction and valence bands (Nc, Nv) and its intrinsic carrier concentration (ni) on Ge fraction (x) and temperature were obtained. The results show that ni increases significantly due to the effect of strain in strained Si1-xGex/(101)Si. Furthermore, Nc and Nv decrease with increasing Ge fraction (x). In addition, it is also found that as the temperature becomes higher, the increase in Nc and Nv occurs. The results can provide valuable references to the understanding on the Si-based strained device physics and its design.

This paper presents and designs a UWB, low voltage, high linearity, folded CMOS direct down-conversion mixer in zero-IF receiver. The proposed mixer uses inverter, self-biasing and constant Gm biasing circuit. Also, inductor in LC resonating network is used to get rid of the negative effect of parasitic capacitor in this paper. Consequently, all performances of the mixer are effectively improved. This design is based on 0.18μm CMOS technology of SMIC (Semiconductor Manufacturing International Corporation), the simulation results show the conversion gain of 7dB, the NF of 13.8dB (the IF frequency is 20MHz), the IIP3 of 13.4dBm. The circuit operates at the supply voltage of 1.8V and dissipates 11mW. The dynamic range of total receiver can be effectively improved because of high linearity of the mixer.

This paper presents one of bistable jump phenomena observed in rotor system supported on uncentralized squeeze film dampers which occurs in the subcritical speed range of rotor. The jumping tendency of this bistable jump is jumping up in acceleration and jumping down in deceleration and is without the transposition of disk mass centre. The behaviors, especially the latter, are different from the bistable jump behaviors reported to date. The reason for occurrence of the subcritical speed bistable jump is explained by a Duffing equation with the varied stiffness and the exciting force which amplitude is proportional to the square of rotating speed of rotor.