化学气相反应法制备Zr-Si-C涂层

为了提高Zr-Si-C涂层与基体的结合强度,基于粉末埋入反应辅助涂覆工艺,采用新型化学气相反应法在SiC陶瓷表面制备Zr-Si-C涂层.SiC陶瓷基片被包埋于Zr-1%(质量分数)I2混合粉体中,在850～1 100 ℃进行化学气相反应.碘促进Zr原子向SiC陶瓷表面的传输,Zr与SiC之间的扩散反应导致在SiC表面生成连续的Zr-Si-C复合涂层.采用X射线衍射、扫描电镜结合X射线能谱分析以及相图分析确定了涂层微结构及相组成.结果表明:复合涂层内层为ZrC、中间层为Zr2Si-ZrC1-x复相区、外层为ZrC1-x.通过测量涂层厚度研究了涂层的生长动力学,在850～1 100 ℃范围内,涂层生长符合抛物线规律,活化能为(210±20)kJ/mol.     

Optical properties of metallic films for vertical-cavity optoelectronic devices

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.     

Sense and nonsense in hierarchical regression analysis: Comment on Smyth.

Contrasts ANCOVA via hierarchical regression analysis with hierarchical analyses used by L. D. Smyth (see record 1983-07281-001) in his article on psychopathology as a function of neuroticism. It is shown that Smyth's analyses did not address the hypotheses he wished to test and that the results yielded by these analyses are meaningless. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The dependence of the output Stokes parameters on the state of an arbitrarily located polarization controller in PMD mitigation schemes

The dependence of the instantaneous Stokes parameters, at the output of a transmission system, on the state of a polarization controller (PC) located anywhere in the system is analytically derived. Based on the analytical formalism, a novel characterization technique is introduced and used for finding the PC state that yields a maximum degree of polarization and optimal bit-error rate.     

Formation of composition-modulated alloys by electrodeposition

A method has been developed to produce composition-modulated alloys by electrodeposition. The method was demonstrated for the copper-nickel couple. Salts of the two component metals are dissolved in a common electrolyte and the potential is alternately pulsed for fixed durations between values above and below the reduction potential of the less noble component. Co-deposition of the nobler metal into the other metal layer is diminished by setting unfavourable diffusion conditions during the more cathodic pulse. Modulation was achieved down to 0.8 nm thick layers. The resulting composition-modulated alloys were analysed by Auger spectroscopy and X-ray diffraction.     

Spectral shift and broadening of DFB lasers under direct modulation

The spectrum of DFB lasers, directly modulated at 144 and 622 Mb/s, is found to be considerably wider than the modulating random sequence rate. The broadening, which may be as high as ten times the data bandwidth, is accounted for by frequency changes (chirp) along each bit, incorporating a recently observed short time constant on the order of 10-20 ns. These changes will also introduce a few gigahertz spectral shifts as a function of the bit rate