Investigation of Ag-bulk/glassy-phase/Si heterostructures of printed Ag contacts on crystalline Si solar cells

The interface structure of screen-printed silver contacts on a crystalline silicon solar cell has been studied by transmission electron microscopy (TEM). TEM results confirmed that the glassy-phase plays an important role in contact properties. There are at least three different microstructures present in optimal fired contacts. The location where silver-bulk directly contacts silicon is observed through SEM, and this is actually a very thin glass layer in between. In addition, high-density silver embryos on silicon were found for samples fired optimally. The results presented in this study suggest that Ag-bulk/thin-glass-layer/Si contact is the most decisive path for current transportation.     

Planar array stack design aided by rapid prototyping in development of air-breathing PEMFC

The polymer electrolyte membrane fuel cell (PEMFC) is one of the most important research topics in the new and clean energy area. The middle or high power PEMFCs can be applied to the transportation or the distributed power system. But for the small power application, it is needed to match the power requirement of the product generally. On the other hand, the direct methanol fuel cell (DMFC) is one of the most common type that researchers are interested in, but recently the miniature or the micro-PEMFCs attract more attention due to their advantages of high open circuit voltage and high power density.     

Fabrication of organic flexible electrodes using transfer stamping process

A transfer stamping process is proposed to fabricate micro-scale organic flexible electrodes. With different adhesion forces of the transferring interfaces, ink/mold and ink/substrate, patterns are formed from the relief features of the elastomeric mold to the substrate without residual layer, and no complex pre-process and steps are needed. To estimate the deformation during pressing, the sagging height of the mold is analyzed with finite element method (FEM). Two conductive polymers, PEDOT:PSS and silver paste, are transferred from the flat relief features of the mold to the PET substrate. The coating characteristics and problems are discussed. The transfer stamping process is also employed to fabricate electrodes on the dielectric/ITO film and to form an organic flexible capacitance. This paper demonstrates the potential of transfer stamping in fabricating organic electronic components, such as organic integrated circuit, OLED and OTFT.     

A dual-phase charge pump circuit with compact size

In this paper, a regulated dual-phase charge pump with compact size is presented. By means of a nano-ampere switched-capacitor voltage reference (SCVR) circuit, the dual-phase charge pump regulator can reduce the quiescent current and the output ripple. Besides, a new power stage is proposed to define the stability of the overall system. Owing to the design of buffer stage, the charge pump regulator can extend bandwidth and increase phase margin. Thus, the transient response and driving capability can be improved. Beside, the proposed automatic body switching circuit can efficiently drive the bulk of the power p-type MOSFETs to avoid leakage and potential latch-up. This chip was fabricated by TSMC 0.35 μm, 3.3 V/5 V 2P4 M CMOS technology. The input voltage range varies from 2.9 to 4.9 V for the lithium battery and the output voltage is regulated at 5 V. Experimental results demonstrate the charge pump can provide 50 mA maximum load current without any oscillation problems.     

Fabrication of 1.55 μm VCSELs on Si using metallic bonding

Using AuGeNiCr multilayered metals as the wafer bonding medium, long-wavelength GaInAsP/InP vertical cavity surface emitting lasers employing Al-oxide/Si as the upper and lower distributed Bragg reflectors were fabricated on Si substrate with the bonding interface formed outside the vertical cavity surface emitting laser cavity. Laser emission at 1.545 μm was measured under pulsed operations near room temperature. The low-temperature metallic bonding process demonstrates a great potential in device fabrication     

Parallel transport: a new transport layer paradigm for enabling Internet quality of service

The transport layer in the network protocol stack serves as a liaison between the application and the underlying network. Any quality of service provided by the network thus has to be effectively translated by the transport layer protocol in order to be enjoyed by the applications. In this article, we argue for a fundamental rethinking of the transport layer design to facilitate such QoS delivery. We identify the key requirement for a QoS enabling transport layer protocol as the ability to effectively handle multiplicity in terms of user differentiation levels, network resources, and service models. However, TCP, the transport layer protocol predominantly used in the Internet, is unable to support such multiplicity due to its single-state design. We extend TCP to a parallel transport layer protocol called parallel TCP (pTCP) that can tackle the different dimensions of multiplicity, and hence enable varying classes of QoS to applications. We discuss the applicability of pTCP in three specific domains with different levels of network support for QoS, and present simulation results substantiating our arguments.     

Aircraft type recognition in satellite images

This paper proposes a hierarchical classification algorithm to accurately recognise aircraft in satellite images. Before recognition, a novel symmetry-based algorithm is proposed to estimate an aircraft's optimal orientation for rotation correction. Then, distinguishable features are derived from each aircraft for aircraft recognition. However, different features have different discrimination abilities to recognise the types of aircraft. Therefore, a novel booting algorithm is proposed to learn a set of proper weights from training samples for feature integration. Owing to this integration, significant improvements in terms of recognition accuracy and robustness can be achieved. Last, a hierarchical recognition scheme is proposed to recognise the types of aircraft by using the area feature, first for a rough categorisation on which detailed classifications are then achieved using several suggested features. Experiments were conducted on a wide variety of satellite images. Experimental results reveal the feasibility and validity of the proposed approach in recognising aircraft in satellite images.     

A low-phase-noise K-band CMOS VCO

A novel circuit topology for low-phase-noise voltage controlled oscillators (VCOs) is presented in this letter. By employing a PMOS cross-coupled pair with a capacitive feedback, superior circuit performance can be achieved especially at higher frequencies. Based on the proposed architecture, a prototype VCO implemented in a 0.18-/spl mu/m CMOS process is demonstrated for K-band applications. From the measurement results, the VCO exhibits a 510-MHz frequency tuning range at 20GHz. The output power and the phase noise at 1-MHz offset are -3dBm and -111dBc/Hz, respectively. The fabricated circuit consumes a dc power of 32mW from a 1.8-V supply voltage.     

Intermetallic growth of wire-bond at 175°C high temperature aging

Two types of samples were applied in this wire-bond evaluation work for an Al-pad diffusion process. One was finished product for the cross-section examination of wire-bond and the other was without compound encapsulant used for the plane view examination of wire-bond interface. These samples were aged at 175 C in air from 0 h to 1008 h. It is found that the normal product which was ready on board existed ∼1 μm Au₂Al and Au₅Al₂ phases. The Au₂Al phase was then transformed to Au₅Al₂ phase in a 4 ∼ 72 h aging period. The Au₄Al phase formed along with the Au₅Al₂ phase in 72 h to 240 h aging period showing some porosity within the reacted phases. The total phase thickness increased to ∼4μm after 240 h aging. The Au₄Al phase became the major phase after 336 aging h. The reacted phase layer thickness increased to ∼6 μm and reached the steady state. A titanium-rich thin layer was also induced within the reacted phase layer. Three ternary phases as AlAu₂Ti, AlAuTi, and Al₂Au₂Ti are found in this titanium-rich layer. In particular, Al₂Au₂Ti could be a new phase.     

Design and fabrication of deep submicron CMOS technology compatible suspended high-Q spiral inductors

In this paper, deep submicron complementary metal-oxide-semiconductor (CMOS) process compatible high-Q suspended spiral on-chip inductors were designed and fabricated. In the design, the electromagnetic solver, SONNET, and the finite element program, ANSYS, were used for electrical characteristics, maximum endurable impact force, and thermal conduction simulations, respectively. Based on the design, suspended spiral inductors with different air cavity structures, i.e., diamond opening, circle opening, triangle opening, and full suspended with pillar supports were developed for various applications. Among these structures, the suspended inductor with pillar support possesses the highest Q/sub max/ (maximum of quality factor) of 6.6 at 2 GHz, the least effective dielectric constant of 1.06, and the lowest endurable impact force 0.184 Newton. On the other hand, the spiral inductor with diamond opening has a lowest Q/sub max/ of 4.3, the largest effective dielectric constant of 3.44 and highest endurable impact force 4 Newton. The former is suitable for station telecommunication applications in which the mechanical vibration is not a serious concern, while the latter can be used for mobile telecommunication applications subject to strong mechanical vibrations. Additionally, the conventional on-chip spiral inductor embraced by SiO/sub 2/ with a dielectric constant of 4 was prepared for comparison and found its Q/sub max/ is 3.8 at 1.2 GHz.