Investigation of Microwave Surface-Wave Plasma Deposited SiO_x Coatings on Polymeric Substrates

In this paper, we reported nano-scale SiOx coatings deposited on polyethylene terephthalate （PET） webs by microwave surface-wave assisted plasma enhanced chemical vapor deposition for the purpose of improving their barrier properties. Oxygen （O2） and hexamethyl- disiloxane （HMDSO） were employed as oxidant gas and Si monomer during SiOx deposition, re- spectively. Analysis by Fourier transform infrared spectroscope （FTIR） for chemical structure and observation by atomic force microscopy （AFM） for surface morphology of SiO~ coatings demon- strated that both chemical compounds and surface feature of coatings have a remarkable influence on the coating barrier properties. It is noted that the processing parameters play a critical role in the barrier properties of coatings. After optimization of the SiOx coatings deposition conditions, i.e. the discharge power of 1500 W, 2 ： 1 of O2 ： HMDSO ratio and working pressure of 20 Pa, a better barrier property was achieved in this work.

Catalyst-Free Growth of Graphene by Microwave Surface Wave Plasma Chemical Vapor Deposition at Low Temperature

Catalyst-free graphene films has been synthesized by microwave (MW) surface wave plasma (SWP) chemical vapor deposition (CVD) using hydrogenated carbon source on silicon substrates at low temperature (500℃). The synthesized process is simple, low-cost and possible for application on transparent electrodes, gas sensors and thin film resistors. Analytical methods such as Raman spectroscopy, transmission electron microscopy (TEM) and four points prove resistivity measurement and UV-VIS-NIR spectroscopy were employed to characterize properties of the graphene films. The formation of multilayer of graphene on silicon substrate was confirmed by Raman spectroscopy and TEM. It is possible to grow graphene directly on silicon substrate (without using catalyst) due to high radical density of MW SWP CVD. In addition, we also observed that the hydrogen had significant role for quality of graphene.

Study and Modeling of Human Biological Tissue Exposed to High Frequency Electromagnetic Waves

The main objective of this proposed article is to provide explanations to justify the validity of the results of the studies of the interaction between the electromagnetic fields and the human body. It can also find direct applications in the characterization and modeling of the macroscopic electrical properties of the biological media for assessing the effects of fields induced by electromagnetic radiation sources in the human body to set up new standards on the Human exposure to electromagnetic fields. To do this, we have taken into account the different physical phenomena of propagation of a hyper-frequency electromagnetic plane wave and on the other hand, the experimental values in order to model the electrical behavior of human biological tissues based on an equivalent electronic circuit model composed of capacities, resistance and reel, which assimilates the biological tissues of the skin, grease, blood. This model using the characteristic impedance of the dielectric support makes it possible to evaluate the voltage induced by the electromagnetic waves of the hyper-frequencies in the studied biological system. The results of the simulations obtained from computer tools demonstrate that the hyper-frequency electromagnetic waves can result in an elevation of the electrical potential of the biological tissues. Despite this potential is a decreasing function of the penetration depth.

High-frequency gravitational waves having large spectral densities and their electromagnetic response

Various cosmology models, brane oscillation scenarios, interaction of interstellar plasma with intense electromagnetic radiation, and even high-energy physics experiments （e.g., Large Hadron Collider （LHC）） all predict high frequency gravitational waves （HFGWs, i.e., high-energy gravitons） in the microwave band and higher frequency region, and some of them have large energy densities. Electromagnetic （EM） detection to such HFGWs would be suitable due to very high frequencies and large energy densities of the HFGWs. We review several typical EM detection schemes, i.e., inverse Gertsenshtein effect （G-effect）, coupling of the inverse G effect with a coherent EM wave, coupling of planar superconducting open cavity with a static magnetic field, cylindrical superconducting closed cavity, and the EM sychro-resonance system, and discuss related minimal detectable amplitudes and sensitivities. Furthermore, we give some new ideas and improvement ways enhancing the possibility of measuring the HFGWs. It is shown that there is still a large room for improvement for those schemes to approach and even reach up the requirement of detection of HFGWs expected by the cosmological models and high-energy astrophysical process.

High-performance microwave absorption enabled by Co_(3)O_(4) modified VB-group laminated VS_(2) with frequency modulation from S-band to Ku-band

High performance microwave absorption(MA)materials especially those with tunable frequency are highly desirable for telecommunication industries and military camouflage in the information era.Herein,we constructed hierarchical heterostructures based on VB-group laminated vanadium disulfide(VS_(2))nanosheets embedded with cobalt tetroxide(Co_(3)O_(4))nanoparticles.The highly dispersed Co_(3)O_(4)nanoparticles generate strong electromagnetic coupling networks that could enhance the loss properties of MA materials.Moreover,the interconnected VS_(2)layered network results in dipolar/interfacial polarization,multiple reflection and scattering favorable for the enhanced MA performance.Impressively,the maximum reflection loss of the VS_(2)/Co_(3)O_(4)hybrids containing 10%Co_(3)O_(4)can reach 57.96 dB at a thin thickness of 1.57 mm,and the bandwidth with an RL value less than-10 dB is as large as 3.5 GHz.The effective MA band could be adjusted in a range of 15.1 GHz(2.9-18 GHz)from S to Ku bands by the increase in thickness from 1.2 mm to 5.5 mm.The results show that the synergistic effect of multiple loss mechanisms and good impedance matching could be the reasons for strong MA capability in nearly all frequency bands,and thus,the high-performance and lightweight MA materials could be developed by the VS_(2)/Co_(3)O_(4)hybrids.

Design of 35 GHz 1 Watt GaAs pHEMT Power Amplifier MMIC

By using 0.15 μm GaAs pHEMT （pseudomorphic high electron mobility transistor） technology,a design of millimeter wave power amplifier microwave monolithic integrated circuit （MMIC） is presented.With careful optimization on circuit structure,this two-stage power amplifier achieves a simulated gain of 15.5 dB with fluctuation of 1 dB from 33 GHz to 37 GHz.A simulated output power of more than 30 dBm in saturation can be drawn from 3 W DC supply with maximum power added efficiency （PAE） of 26%.Rigorous electromagnetic simulation is performed to make sure the simulation results are credible.The whole chip area is 3.99 mm2 including all bond pads.