抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 μm complementary metal–oxide–semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the current or expected materials to be used in processing for CMOS devices, (f) process compatibility, and (g) reliability. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. A review of current work and literature in the area of alternate gate dielectrics is given. Based on reported results and fundamental considerations, the pseudobinary materials systems offer large flexibility and show the most promise toward success...

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High-κ gate dielectrics: Current status and materials properties considerations

There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

Coinage metals, such as Au, Ag, and Cu, have been important materials throughout history.1 While in ancient cultures they were admired primarily for their ability to reflect light, their applications have become far more sophisticated with our increased understanding and control of the atomic world. Today, these metals are widely used in electronics, catalysis, and as structural materials, but when they are fashioned into structures with nanometer-sized dimensions, they also become enablers for a completely different set of applications that involve light. These new applications go far beyond merely reflecting light, and have renewed our interest in maneuvering the interactions between metals and light in a field known as plasmonics.2–6

In plasmonics, the metal nanostructures can serve as antennas to convert light into localized electric fields (E-fields) or as waveguides to route light to desired locations with nanometer precision. These applications are made possible through a strong interaction between incident light and free electrons in the nanostructures. With a tight control over the nanostructures in terms of size and shape, light can be effectively manipulated and controlled with unprecedented accuracy.3,7 While many new technologies stand to be realized from plasmonics, with notable examples including superlenses,8 invisible cloaks,9 and quantum computing,10,11 conventional technologies like microprocessors and photovoltaic devices could also be made significantly faster and more efficient with the integration of plasmonic nanostructures.12–15 Of the metals, Ag has probably played the most important role in the development of plasmonics, and its unique properties make it well-suited for most of the next-generation plasmonic technologies.16–18

1.1. What is Plasmonics?
Plasmonics is related to the localization, guiding, and manipulation of electromagnetic waves beyond the diffraction limit and down to the nanometer length scale.4,6 The key component of plasmonics is a metal, because it supports surface plasmon polariton modes (indicated as surface plasmons or SPs throughout this review), which are electromagnetic waves coupled to the collective oscillations of free electrons in the metal.

While there are a rich variety of plasmonic metal nanostructures, they can be differentiated based on the plasmonic modes they support: localized surface plasmons (LSPs) or propagating surface plasmons (PSPs).5,19 In LSPs, the time-varying electric field associated with the light (Eo) exerts a force on the gas of negatively charged electrons in the conduction band of the metal and drives them to oscillate collectively. At a certain excitation frequency (w), this oscillation will be in resonance with the incident light, resulting in a strong oscillation of the surface electrons, commonly known as a localized surface plasmon resonance (LSPR) mode.20 This phenomenon is illustrated in Figure 1A. Structures that support LSPRs experience a uniform Eo when excited by light as their dimensions are much smaller than the wavelength of the light.



Figure 1

Schematic illustration of the two types of plasmonic nanostructures discussed in this article as excited by the electric field (Eo) of incident light with wavevector (k). In (A) the nanostructure is smaller than the wavelength of light and the free electrons ...



In contrast, PSPs are supported by structures that have at least one dimension that approaches the excitation wavelength, as shown in Figure 1B.4 In this case, the Eo is not uniform across the structure and other effects must be considered. In such a structure, like a nanowire for example, SPs propagate back and forth between the ends of the structure. This can be described as a Fabry-Perot resonator with resonance condition l=nλsp, where l is the length of the nanowire, n is an integer, and λsp is the wavelength of the PSP mode.21,22 Reflection from the ends of the structure must also be considered, which can change the phase and resonant length. Propagation lengths can be in the tens of micrometers (for nanowires) and the PSP waves can be manipulated by controlling the geometrical parameters of the structure.23

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Controlling the synthesis and assembly of silver nanostructures for plasmonic applications

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

/pdf/present-and-future-of-surface-enhanced-raman-scattering-34aqgcm385.pdf

Present and Future of Surface-Enhanced Raman Scattering

Metal as floating gate (FG) in combination with high-k interpoly dielectrics (IPD) is seen as a possible solution to continue the scaling of NAND Flash technology node beyond 25nm. We have investigated the thermal stability of TaN metal as FG in combination with Hf based high-k IPD stacks. IPD leakage is found to worsen with high temperature anneal and causing degraded memory behavior. Comparative leakage study of high-k dielectrics on metal and Si substrates were performed through metal-insulator-metal (MIM) and metal-insulator semiconductor (MIS) structures. The leakage degradation was observed to be higher in case of MIM, which was attributed to the higher degree of dielectric crystallization on metal. The thermal stability of the high-k IPD on TaN metal FG memory structure has to be improved for potential application in future NAND flash memory.

Investigation of Thermal Stability of High-kappa Interpoly Dielectrics in TaN Metal Floating Gate Memory Structures

This work presents the interfacial properties of hafnium-doped SiO2 films via N and P metal oxide semiconductor (MOS) materials, MOS-capacitor, and N and P metal oxide semiconductor field effect transistor (MOSFET) characterization. The results indicate that HfSixOy films (a) have excellent transistor characteristics; (b) remain amorphous through high-temperature processing; (c) are compatible with N+ and P+ polysilicon electrodes; (d) have lower gate leakage than SiO2 of the same equivalent oxide thickness (EOT); and (e) have a dielectric constant of ∼8. Therefore, the hafnium-doped SiO2 films are at-tractive as a dielectric material and offer a technologically relevant gate-stack node for insertion, prior to deployment of high-K dielectrics.

N and P metal oxide semiconductor field effect transistor characteristics of hafnium-doped SiO2 gate dielectrics

An oxygen doped microcrystalline silicon (μc-Si) deposition process is developed by mixing small amounts of nitrous oxide (N2O) with silane (SiH4) in a rapid thermal chemical vapor deposition (RTCVD) reactor. The effects of oxygen doping on the properties of RTCVD μc-Si films are studied. Experimental results show that the RTCVD process provides high deposition rates for μc-Si and polycrystalline silicon (polySi) films at elevated deposition temperatures and pressures. The surface roughness of the RTCVD μc-Si films can be significantly reduced compared to that of conventional LPCVD polySi films. Steep side walls can be realized due to the small grain size of the μc-Si films. The sheet resistance of BF2 doped μc-Si films is slightly higher than that of BF2 doped polySi films, whereas sheet resistances of P and As doped μc-Si films are much higher than those of the corresponding P and As doped polySi films. Measurements of the catastrophic breakdown strength of metal-oxide-semiconductor (MOS) capacitors indicate that the quality of gate electrodes fabricated using μc-Si is improved relative to that of MOS capacitors fabricated using polySi gate electrodes.

Effects of oxygen doping on properties of microcrystalline silicon film grown using rapid thermal chemical vapor deposition

This work investigates the changes in response to ozone and humidity of Atomic Layer Deposited (ALD) tin dioxide (SnO 2 ) sensors operated at room temperature and integrated into a portable platform over several weeks. The impact of humidity is highlighted as it relates to immediate changes in ozone response and in slower changes where the history of exposure influences the surface kinetics while the adsorbed gas species attempt to reach an equilibrium state.

Room temperature ozone and humidity response evolution of atomic layer deposited SnO 2 sensors

This chapter discusses field effect transistors. The development of field effect devices continued with moderate progress until the early 1960s, when the metal-oxide-silicon field effect transistor (MOSFET) emerged as a prominent device. This device quickly became popular in semiconductor memories and digital integrated circuits. Today, the MOSFET dominates the integrated circuit technology, and it is responsible for the computer revolution of the 1990s. This chapter begins by discussing the basic theory of the MOSFET, beginning with its fundamental building block, the MOS capacitor. The MOSFET is the building block of the current ultra large scale integrated circuits (ICs). The growth and complexity of MOS ICs are continually increasing over the years to enable faster and denser circuits. Further, the chapter presents an overview of less common field effect devices used only in specific applications. Their coverage is limited to a qualitative explanation of the operating principles and basic equations.

Veena Misra

Papers

Investigation of Thermal Stability of High-kappa Interpoly Dielectrics in TaN Metal Floating Gate Memory Structures

N and P metal oxide semiconductor field effect transistor characteristics of hafnium-doped SiO2 gate dielectrics

Effects of oxygen doping on properties of microcrystalline silicon film grown using rapid thermal chemical vapor deposition

Room temperature ozone and humidity response evolution of atomic layer deposited SnO 2 sensors

3 – Field Effect Transistors