Dispersion characteristics of nanometer-scaled silicon rib waveguides

We investigate the dispersion properties of nanometer-scaled silicon waveguides with channel and rib cross section around the optical fiber communication wavelength and systematically study their relationship with the key structural parameters of the waveguide. The simulation results show that the introduction of an extra degree of freedom in the rib depth enables the rib waveguide more flexible in engineering the group velocity dispersion (GVD) compared with the channel waveguide. Besides, we get the structural parameters of the waveguides that can realize zero-GVD at 1550 nm.

A COMPARATIVELY LOW-QUALITY SILICON MATERIAL IMPROVED FOR SOLAR-CELL FABRICATION

A comparatively low-quality silicon wafer (with a purity of almost-equal-to 99.9%) was adopted to form a silicon-on-defect-layer (SODL) structure featuring improved crystalline silicon near the defect layer (DL) by means of proton implantation and subsequent annealing. Thus, the SODL technique provides an opportunity to enable low-quality silicon wafers to be used for fabrication of low-cost solar cells.

NEW TYPE OF SILICON MATERIAL WITH VERY HIGH-QUALITY SURFACE-LAYER ON INSULATING DEFECT LAYER

A new-type silicon material, silicon on defect layer (SODL) was proved to have a very high quality surface microstructure which is necessary for commercially feasible high-density very large scale integrated circuits (VLSI). The structure of the SODL material was viewed by transmission electron microscopy. The SODL material was also proved to have a buried defect layer with an insulating resistivity of 5.7 x 10(10) OMEGA-cm.

Silicon: the promising material for phontonic integrated circuits platform

The development of optical network demands integrated arid multiple functionality modules to lowing cost and acquire highly reliability. Among the various contender materials to be photonic integrated circuits platform, silicon exhibits dominant characteristics and is the most promising platform materials. The paper compares the characteristics of some candidate materials with silicon and reviews recent progress in silicon based photonic integration technology. Tile challenges to silicon for optical integration for optical networking application arc also indicated.

Effects of helium and oxygen common implantation in silicon wafer

Defect engineering for SiO2] precipitation is investigated using He-ion implantation as the first stage of separation by implanted oxygen (STMOX). Cavities are created in Si by implantation with helium ions. After thermal annealing at different temperatures, the sample is implanted with 120keV 8.0 x 10(16) cm(-2) O ions. The O ion energy is chosen such that the peak of the concentration distribution is centred at the cavity band. For comparison, another sample is implanted with O ions alone. Cross-sectional transmission electron microscopy (XTEM), Fourier transform infrared absorbance spectrometry (FTIR) and atomic force microscopy (AFM) measurements are used to investigate the samples. The results show that a narrow nano-cavity layer is found to be excellent nucleation sites that effectively assisted SiO2 formation and released crystal lattice strain associated with silicon oxidation.

Comparison of the properties of GaN grown on complex Si-based structures

With the aim of investigating the possible integration of optoelectronic devices, epitaxial GaN layers have been grown on Si(Ill) semiconductor-on-insulator (SOI) and on Si/CoSi2/Si(111) using metalorganic chemical vapor deposition. The samples are found to possess a highly oriented wurtzite structure, a uniform thickness, and abrupt interfaces. The epitaxial orientation is determined as GaN(0001)//Si(111), GaN[1120]//Si[110], and GaN[1010]//Si[112], and the GaN layer is tensilely strained in the direction parallel to the interface. According to Rutherford backscattering/channeling spectrometry and (0002) rocking curves, the crystalline quality of GaN on Si(111) SOI is better than that of GaN on silicide. Room-temperature photoluminescence of GaN/SOI reveals a strong near-band-edge emission at 368 nm (3.37 eV) with a full width at half-maximum of 59 meV. (c) 2005 American Institute of Physics.

Heteroepitaxial growth of novel SOI material Si/gamma-Al2O3/Si

In this paper, we report the fabrication of Si-based double hetero-epitaxial SOI materials Si/gamma-Al2O3/Si. First, single crystalline gamma-Al2O3 (100) insulator films were grown epitaxially on Si(100) by LPCVD, and then, Si(100) epitaxial films were grown on gamma-Al2O3 (100)/Si(100) epi-substrates using a CVD method similar to silicon on sapphire (SOS) epitaxial growth. The Si/gamma-Al2O3 (100)/Si(100) SOI materials are characterized in detail by RHEED, XRD and AES techniques. The results demonstrate that the device-quality novel SOI materials Si/gamma-Al2O3 (100)/Si(100) has been fabricated successfully and can be used for application of MOS device.

Heteroepitaxial growth of novel SOI material Si/gamma-Al2O3/Si

In this paper, we report the fabrication of Si-based double hetero-epitaxial SOI materials Si/gamma-Al2O3/Si. First, single crystalline gamma-Al2O3 (100) insulator films were grown epitaxially on Si(100) by LPCVD, and then, Si(100) epitaxial films were grown on gamma-Al2O3 (100)/Si(100) epi-substrates using a CVD method similar to silicon on sapphire (SOS) epitaxial growth. The Si/gamma-Al2O3 (100)/Si(100) SOI materials are characterized in detail by RHEED, XRD and AES techniques. The results demonstrate that the device-quality novel SOI materials Si/gamma-Al2O3 (100)/Si(100) has been fabricated successfully and can be used for application of MOS device.

碳化硅中氦离子高温注入引入的缺陷及其退火行为的光谱研究

对氦(He)离子高温(600K)注入6H-SiC中的辐照缺陷,在阶梯温度退火后演化行为的拉曼光谱和室温光致发光谱的特征进行了分析.这两种方法的实验结果表明,离子注入所产生晶格损伤的程度与注入剂量有关;高温退火导致损伤的恢复,不同注入剂量造成的晶格损伤需要不同的退火温度才可恢复.在阶梯温度退火下呈现出了点缺陷的复合、氦-空位团的产生、氦泡的形核、长大等特性.研究表明:高温(600K)注入在一定剂量范围内是避免注入层非晶化的一个重要方法,为后续利用氦离子注入空腔掩埋层吸杂或者制备低成本、低缺陷密度的绝缘层上碳化硅(SiCOI)材料提供了可能.

硅在大豆低钾胁迫中的作用

钾是作物生长发育的必需矿质元素，缺钾对大豆产量和营养品质影响显著。硅是植物的有益元素，在低钾胁迫条件下，硅对大豆生长是否有改善作用还未见相关报道，本研究以对低钾敏感的不同基因型大豆品种（铁丰35和铁丰31）为试验材料，在低钾条件下（1 mmol L-1)，施加Na2SiO3，通过大豆生物量、根系形态学、生理学和抗氧化物酶活性等参数的变化，研究硅在大豆缺钾胁迫生长中的作用。主要研究结果如下： 1低钾胁迫对大豆生长发育和生理指标形状的影响 与正常钾生长条件（5 mmol L-1）相比，对低钾敏感的基因型大豆品种铁丰35，低钾胁迫使铁丰35品种主根、侧根，过氧化氢 (H2O2)和丙二醛含量(MDA)，根系和叶片的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)活性和光合特性指标等发生显著变化，同样地，铁丰31品种根系的SOD、CAT、POD活性和MDA含量也发生显著变化。相反，铁丰31品种的其它形态学和生理学指标参数受低钾胁迫影响差异不显著。 2 Si和Na+对大豆生长发育和生理过程中低钾胁迫的减缓作用 为探明Si对大豆生长发育和生理过程中低钾胁迫的减缓作用，我们将Na2SiO3分别设立3个浓度处理水平(0.1, 2.0, 5.0 mmol L-1)，对照CK0：5.0 mmol/L KNO3+0.0 mmol/L Na2SiO3，副对照CK1：1.0 mmol/L KNO3+4.0mmol/L NaCl，其中以Si2处理是2个品种减缓低钾胁迫效应最好的，对大豆生长发育和促进大豆根、茎和叶内钾浓度含量，低钾胁迫使SOD、POD、CAT活性，H2O2和MDA含量，以及光合特性(Pn, WUE)等指标参数得以显著地改善，但Na2SiO3对低钾敏感品种铁丰35的减缓作用远大于对低钾不敏感的品种铁丰31。为排除Na2SiO3中Na+对低钾大豆的生长作用，用等浓度NaCl进行检验，结果表明，Na+可以部分地减缓低钾胁迫，并且这减缓作用远小于等浓度的Si。本试验结果说明Si通过改变几个关键的生理过程，进而提高低钾胁迫条件下，大豆生长发育的表达活力，以有效地改善低钾对大豆生长的胁迫。 3 Si通过提高抗氧化胁迫进而减缓大豆生长发育中低钾胁迫 低钾胁迫使大豆地上和地下生物产量与对照CK0相比显著减少，增施Na2SiO3前后大豆其根冠比、过氧化氢积累、钾含量、膜质过氧化产物和抗氧化物酶活性变化显著。另外，Na2SiO3显著减缓了低钾胁迫使大豆根冠比、提高了低钾大豆根、茎、叶内钾浓度，Si还减缓了过氧化氢 (H2O2)和丙二醛含量(MDA)，这说明Si抑制了低钾的过氧化胁迫，显著地抑制了因低钾胁迫而使超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)等活性的升高，这些酶活性提高效应被施加的Na2SiO3消除，这些结果表明，Si通过提高抗氧化胁迫能力，进而减缓大豆生长发育的低钾胁迫，对低钾胁迫有非常重要的减缓调控作用。

A Si-based tunable narrow-band flat-top filter with multiple-step-type Fabry-Perot cavity structure

In the optical network, the quick and accurate alignment with wavelength is an important issue during the channel detection. At this point, a filter having flat-top response characteristic is an effective solution. Based on multiple-step-type Fabry-Perot cavity structure, a novel all-Si-based thermooptical tunable flat-top filter with narrow-band has been fabricated, using our patent silicon-on-reflector bonding technology. The device demonstrated a 1-dB flat-top width of 1 nm, 3-dB band of 3 nm, free spectra range of 8 nm, and the tuning range of 4.6 nm was obtained under the applied voltage of 4 V.

Characterization of stress induced in SOS and Si/gamma-Al2O3/Si heteroepitaxial thin films by Raman spectroscopy

Raman spectroscopy technique has been performed to investigate the stress induced in as-grown silicon-on-sapphire (SOS), solid-phase-epitaxy (SPE) re-grown SOS, and Si/gamma-Al2O3/Si double-heteroepitaxial thin films. It was demonstrated that the residual stress in SOS film, arising from mismatch and difference of thermal expansion coefficient between silicon and sapphire, was reduced efficiently by SPE process, and that the stress in Si/gamma-Al2O3/Si thin film is much smaller than that of as-grown SOS and SPE upgraded SOS films. The stress decrease for double heteroepitaxial film Si/gamma-Al2O3/Si mainly arises from the smaller lattice mismatching of 2.4% between silicon top layer and the gamma-Al2O3/Si epitaxiial composite substrate, comparing with the large lattice mismatch of 13% for SOS films. It indicated that gamma-Al2O3/Si as a silicon-based epitaxial substrate benefits for reducing the residual stress for further growth of silicon layer, compared with on bulk sapphire substrate. (c) 2005 Elsevier B.V. All rights reserved.

EFFECT OF SURFACE-STRUCTURES UPON ULTRATHIN-FILM INTERFERENCE-FRINGES

Effect of surface structures upon ultrathin film interference fringes generated from extremely thin films or epitaxial layers grown on semiconductor wafers has been studied. Since dark regions of fringes correspond to the places where the thin films are destroyed or absent, the fringes are investigated to detect uneven surfaces with undesired structures. Therefore, surface microstructures can be detected and characterized effectively by the modification of the fringes.

The cost estimate for a novel cheap solar cell

The estimate for the lowest cost of SODL (silicon on defect layer) solar cell is made according to the price standard of present market. The estimate shows that the PV (photovoltaics) energy costs can be reduced from today's 25-30 cents/(kW h) to 7-8 cents/(kW h) which is comparable with the present cost of electricity generated by traditional energy sources such as fossil and petroleum fuels. The PV energy costs could be reduced to a value lower than 7-8 cents(kW h) by developing SODL technology. The SODL solar cell manufacture featuring simple processes is suitable to large scale automated assembly lines with high yield of large area cells. Some new ideas are suggested, favoring the further reduction in the cost of commercial solar cells.

Ferromagnetic MnSb Films Consisting of Nanorods and Nanoleaves

Ferromagnetic MnSb films were synthesized on Si wafers by physical vapor deposition. X-ray diffraction revealed that the films primarily consisted of MnSb alloy. Nanorods and nanoleaves were observed in the MnSb films by field-emission scanning electron microscopy. These nanorods had an average diameter of 20nm and a length of up to hundreds of nanometers. The nanoleaves had a width and thickness of about 100 and 20nm, respectively. Magnetic hysteresis loops were measured by an alternative gradient magnetometer, and the loops showed strong geometrical anisotropy.