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

The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

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A comprehensive review of zno materials and devices

We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Band parameters for III–V compound semiconductors and their alloys

We present models for the optical functions of 11 metals used as mirrors and contacts in optoelectronic and optical devices: noble metals (Ag, Au, Cu), aluminum, beryllium, and transition metals (Cr, Ni, Pd, Pt, Ti, W). We used two simple phenomenological models, the Lorentz-Drude (LD) and the Brendel-Bormann (BB), to interpret both the free-electron and the interband parts of the dielectric response of metals in a wide spectral range from 0.1 to 6 eV. Our results show that the BB model was needed to describe appropriately the interband absorption in noble metals, while for Al, Be, and the transition metals both models exhibit good agreement with the experimental data. A comparison with measurements on surface normal structures confirmed that the reflectance and the phase change on reflection from semiconductor-metal interfaces (including the case of metallic multilayers) can be accurately described by use of the proposed models for the optical functions of metallic films and the matrix method for multilayer calculations.

Optical properties of metallic films for vertical-cavity optoelectronic devices.

We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature an...

Band parameters for nitrogen-containing semiconductors

Polarized micro-Raman measurements were performed to study the phonon modes of Fe, Sb, Al, Ga, and Li doped ZnO thin films, grown by pulsed-laser deposition on c-plane sapphire substrates. Additional modes at about 277, 511, 583, and 644 cm−1, recently assigned to N incorporation [A. Kaschner et al., Appl. Phys. Lett. 80, 1909 (2002)], were observed for Fe, Sb, and Al doped films, intentionally grown without N. The mode at 277 cm−1 occurs also for Ga doped films. These modes thus cannot be related directly to N incorporation. Instead, we suggest host lattice defects as their origin. Further additional modes at 531, 631, and 720 cm−1 seem specific for the Sb, Ga, and Fe dopants, respectively. Li doped ZnO did not reveal additional modes.

Raman scattering in ZnO thin films doped with Fe, Sb, Al, Ga, and Li

Infrared dielectric function spectra and phonon modes of high-quality, single crystalline, and highly resistive wurtzite ZnO films were obtained from infrared (300–1200 cm−1) spectroscopic ellipsometry and Raman scattering studies. The ZnO films were deposited by pulsed-laser deposition on c-plane sapphire substrates and investigated by high-resolution x-ray diffraction, high-resolution transmission electron microscopy, and Rutherford backscattering experiments. The crystal structure, phonon modes, and dielectric functions are compared to those obtained from a single-crystal ZnO bulk sample. The film ZnO phonon mode frequencies are highly consistent with those of the bulk material. A small redshift of the longitudinal optical phonon mode frequencies of the ZnO films with respect to the bulk material is observed. This is tentatively assigned to the existence of vacancy point defects within the films. Accurate long-wavelength dielectric constant limits of ZnO are obtained from the infrared ellipsometry anal...

Infrared dielectric functions and phonon modes of high-quality ZnO films

We present a unified theoretical approach to electromagnetic plane waves reflected or transmitted at arbitrarily anisotropic and homogeneous layered systems. Analytic expressions for the eigenvalues for the four-wave components inside a randomly oriented anisotropic medium are reported explicitly. As well, the partial transfer matrix for a slab of a continuously twisted biaxial material at normal incidence is described. Transition matrices for the incident and exit media are presented. Hence, a complete analytical 4\ifmmode\times\else\texttimes\fi{}4 matrix algorithm is obtained using Berreman's 4\ifmmode\times\else\texttimes\fi{}4 differential matrices [D. W. Berreman, J. Opt. Soc. Am. 62, 502 (1972)]. The algorithm has a general approach for materials with linear optical response behavior and can be used immediately, for example, to analyze ellipsometric investigations. \textcopyright{} 1996 The American Physical Society.

Polarization-dependent optical parameters of arbitrarily anisotropic homogeneous layered systems.

Spectroscopic ellipsometry in the infrared spectral range is used for comprehensive analysis of the anisotropic dielectric response of sapphire. We determine the ordinary and extraordinary infrared complex dielectric functions as well as all infrared-active phonon modes of single crystal $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ for wavelengths from 3 to 30 \ensuremath{\mu}m. Data were acquired from high-symmetry orientations of a-plane and c-plane surfaces cut from bulk crystals. A simple classification scheme is developed, which allows identification of the total reflection bands for p- and s-polarized light in anisotropic materials with multiple phonon branches. We employ a factorized form of the dielectric function for superior best-fit calculation of the infrared ellipsometry spectra adjusting frequencies and damping parameters of the transverse and longitudinal phonon modes with ${A}_{2u}$ and ${E}_{u}$ symmetry separately. A generalized Lowndes condition for the damping parameters is derived and found satisfied for the ${A}_{2u}$ and ${E}_{u}$ branches. Excellent agreement with phonon mode literature values is obtained, and improper use of selection rules reported previously for calculation of the sapphire dielectric functions is revised [Harman, Ninomiya, and Adachi, J. Appl. Phys. 76, 8032 (1994)]. The dielectric function model will become useful for infrared ellipsometry investigation of multiple-layer structures grown on $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ substrates such as group-III nitride heterostructures.

Infrared dielectric anisotropy and phonon modes of sapphire

Infrared spectroscopic ellipsometry (IRSE) over the wave-number range from 300 to 1200 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ is used to determine the anisotropic room-temperature optical properties of highly resistive, Si-doped n-type and Mg-doped p-type \ensuremath{\alpha}-GaN. The approximately 1-\ensuremath{\mu}m-thick films were deposited on c-plane sapphire by molecular beam epitaxy without a buffer layer. The free-carrier concentrations are obtained from Hall measurements. The IRSE data are analyzed through model calculations of the infrared optical dielectric functions parallel (\ensuremath{\parallel}) and perpendicular (\ensuremath{\perp}) to the c axis of the \ensuremath{\alpha}-GaN films. We obtain the thin-film phonon frequencies and broadening values and the optical mobility and effective-mass parameters for n- and p-type \ensuremath{\alpha}-GaN. In agreement with Perlin et al. [Appl. Phys. Lett. 68, 1114 (1996)] we determine the effective electron masses as ${m}_{e,\ensuremath{\perp}}{/m}_{0}=0.237\ifmmode\pm\else\textpm\fi{}0.006$ and ${m}_{e,\ensuremath{\parallel}}{/m}_{0}=0.228\ifmmode\pm\else\textpm\fi{}0.008.$ For p-type GaN with hole concentration ${N}_{h}=8\ifmmode\times\else\texttimes\fi{}{10}^{17}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ we find ${m}_{h}{/m}_{0}=1.40\ifmmode\pm\else\textpm\fi{}0.33,$ which agrees with recent theoretical studies of the Rashba-Sheka-Pikus parameters in wurtzite GaN. However, no substantial anisotropy of the effective hole mass is obtained to within 25%. The ellipsometry data also allow for derivation of the model quantities ${\ensuremath{\epsilon}}_{\ensuremath{\infty},j}$ $(j=\ensuremath{\perp},\ensuremath{\parallel}),$ which are almost isotropic but may vary between 4.92 and 5.37 depending on whether the films are undoped or doped. In heavily-Si-doped n-type \ensuremath{\alpha}-GaN we observe a thin carrier-depleted surface layer and additional infrared-active vibrational modes at 574, 746, and 851 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. Raman measurements of the GaN films are also performed, and the results are compared to those obtained from the IRSE investigations.

Mathias Schubert

Papers

Raman scattering in ZnO thin films doped with Fe, Sb, Al, Ga, and Li

Infrared dielectric functions and phonon modes of high-quality ZnO films

Polarization-dependent optical parameters of arbitrarily anisotropic homogeneous layered systems.

Infrared dielectric anisotropy and phonon modes of sapphire

Free-carrier and phonon properties of n- and p-type hexagonal GaN films measured by infrared ellipsometry