Design and Fabrication of Low-microwave loss Coplannar Waveguide and precise V groove on Silicon Substrate for Optoelectronic Packaging - art. no. 601938

Optoelectronic packaging has become a most important factor that influences the final performance and cost of the module. In this paper, low microwave loss coplanar waveguide(CPW) on high resistivity silicon(HRS) and precise V groove in silicon substrate were successfully fabricated. The microwave attenuation of the CPW made on HRS with the simple process is lower than 2 dB/cm in the frequency range of 0 similar to 26GHz, and V groove has the accuracy in micro level and smooth surface. These two techniques built a good foundation for high frequency packaging and passive coupling of the optoelectronic devices. Based on these two techniques, a simple high resistivity silicon substrate that integrated V groove and CPW for flip-chip packaging of lasers was completed. It set a good example for more complicate optoelectronic packaging.

Optical properties of inGaAs/GaAs quantum wells grown by Sb-assisted molecular beam epitaxy

It is found that both methods using either continuous Sb supply or pre-deposition of a very thin Sb layer are efficient for the Sb-assisted molecular beam epitaxy growth of highly strained InGaAs/GaAs quantum wells (QWs). The emission of QWs is extended to long wavelength close to 1.25 mu m with high luminescence efficiency at room temperature. The influence of rapid thermal annealing (RTA) on the photoluminescence intensity critically depends on the annealing temperature and duration for highly strained QWs. A relatively low RTA temperature of 700 degrees C with a short duration of 10 s is suggested for optimizing the annealing effect. (c) 2005 Elsevier B.V. All rights reserved.

Effect of microwave on formation/decomposition of natural gas hydrate

Natural gas hydrate (NGH) reservoirs have been considered as a substantial future clean energy resource and how to recover gas from these reservoirs feasibly and economically is very important. Microwave heating will be taken as a promising method for gas production from gas hydrates for its advantages of fast heat transfer and flexible application. In this work, we investigate the formation/decomposition behavior of natural gas hydrate with different power of microwave (2450MHZ), preliminarily analyze the impact of microwave on phase equilibrium of gas hydrate,and make calculation based on van der Waals-Platteeuw model. It is found that microwave of a certain amount of power can reduce the induction time and sub-cooling degree of NGH formation, e.g., 20W microwave power can lead to a decrease of about 3A degrees C in sub-cooling degree and the shortening of induction time from 4.5 hours to 1.3 hours. Microwave can make rapid NGH decomposition, and water from NGH decomposition accelerates the decomposition of NGH with the decomposition of NGH. Under the same pressure, microwave can increase NGH phase equilibrium temperature. Different dielectric properties of each composition of NGH may cause a distinct difference in temperature in the process of NGH decomposition. Therefore, NGH decomposition by microwave can be affected by many factors.

Electron injection assisted phase transition in a nano-Au-VO2 junction

The semiconductor-metal transition of vanadium dioxide (VO2) thin films epitaxially grown on C-plane sapphire is studied by depositing Au nanoparticles onto the thermochromic films forming a metal-semiconductor contact, namely, a nano-Au-VO2 junction. It reveals that Au nanoparticles have a marked effect on the reduction in the phase transition temperature of VO2. A process of electron injection in which electrons flow from Au to VO2 due to the lower work function of the metal is believed to be the mechanism. The result may support the Mott-Hubbard phase transition model for VO2.

In situ hydrate dissociation using microwave heating: Preliminary study

In this work, we investigate the dissociation behavior of natural gas hydrate in a closed system with microwave (MW) heating and hot water heating. The hydrate was formed at temperatures of 1-4 degrees C and pressures of 4.5-5.5 MPa. It was found that the gas hydrate dissociated more rapidly with microwave than with hot water heating. The rate of hydrate dissociation increased with increasing microwave power, and it was a function of microwave power. Furthermore, the temperature of the hydrate increased linearly with time during the microwave radiation.

Experimental observation of negative lateral displacements of microwave beams transmitting through dielectric slabs

It was theoretically predicted that when a beam of light travels through a thin slab of optically denser medium in the air, the emerging beam from the slab will suffer a lateral displacement that is different from the prediction of geometrical optics, that is, the Snell's law of refraction and can be zero and negative as well as positive. These phenomena have been directly observed in microwave experiments in which large angles of incidence are chosen for the purpose of obtaining negative lateral displacements. (C) 2005 Elsevier B.V. All rights reserved.

Laser irradiation cell photothermal therapy assisted by gold nanoparticles

The strong absorption of gold nanoparticles in the visible spectral range allows the localized generation of heat in a volume of only a few tens of nanometer. The efficient conversion of strongly absorbed light by plasmonic gold nanoparticles to heat energy and their easy bioconjugation suggest that the gold nanoparticles can be used as selective photothermal agents in molecular cell targeting. The selective destruction of alkaline phosphatase, the permeabilization of the cell membrane and the selective killing of cells by laser irradiating gold nanoparticles were demonstrated. The potential of using this selective technique in molecularly targeted photothermal therapy and transfection is discussed.

Synthesis of novel hexagon SnO2 nanosheets in ethanol/water solution by hydrothermal process

The novel hexagon SnO2 nanosheets are successfully synthesized in ethanol/water solution by hydrothermal process. The samples are characterized by X-ray diffraction (XRD), infrared ray (IR) and transmission electron microscopy (TEM). By changing the reaction conditions, the size and the morphology can be controlled. Comparison experiments show that when the temperature increased from 140 degrees C to 180 degrees C, the edge length of the hexagon nanoparticles increases from 300-450 nm to 700-900 nm. On the other hand, by adjusting the ratios of water to ethanol from 2 to 0.5, SnO2 nanoparticles with different morphologies of triangle and sphere are obtained. When the concentration of NaOH is increased from 0.15 M to 0.30 M, a hollow ring structure can be obtained. (c) 2006 Elsevier B.V. All rights reserved.

Fabrication of Silicon-Based Template-Assisted Nanoelectrode Arrays and Ohmic Contact Properties Investigation

A convenient fabrication technology for large-area, highly-ordered nanoelectrode arrays on silicon substrate has been described here, using porous anodic alumina (PAA) as a template. The ultrathin PAA membranes were anodic oxidized utilizing a two-step anodization method, from Al film evaporated on substrate. The purposes for the use of two-step anodization were, first, improving the regularity of the porous structures, and second reducing the thickness of the membranes to 100 similar to 200 nm we desired. Then the nanoelectrode arrays were obtained by electroless depositing Ni-W alloy into the through pores of PAA membranes, making the alloy isolated by the insulating pore walls and contacting with the silicon substrates at the bottoms of pores. The Ni-W alloy was also electroless deposited at the back surface of silicon to form back electrode. Then ohmic contact properties between silicon and Ni-W alloy were investigated after rapid thermal annealing. Scanning electron microscopy (SEM) observations showed the structure characteristics, and the influence factors of fabrication effect were discussed. The current voltage (I-V) curves revealed the contact properties. After annealing in N-2 at 700 degrees C, good linear property was shown with contact resistance of 33 Omega, which confirmed ohmic contacts between silicon and electrodes. These results presented significant application potential of this technology in nanosize current-injection devices in optoelectronics, microelectronics and bio-medical fields.

LO-PHONON-ASSISTED TUNNELING IN ASYMMETRIC DOUBLE-WELL STRUCTURES WITH THICK BARRIERS

Nonresonant electron tunneling between asymmetric double quantum wells in AlxGa1-xAs/GaAs systems has been investigated by using steady-state and time-resolved photoluminescence spectra. Experimental evidence of LO-phonon-assisted tunneling through thick barriers has been obtained by enhancing excitation power densities or applying electric fields perpendicular to the well plane. LO-phonon-assisted tunneling times have also been estimated from the variation of the decay time of the narrow-well photoluminescence with applied electric fields. Our findings suggest that LO phonons in the barriers play an important role in the tunneling transfer.