Black silicon structures

The first optically black silicon structures were probably made by anodization as early as the 1950-1960s. Koltun studied films generated at lower current densities than Uhlir and Turner (Uhlir 1956 Turner 1958 Koltun 1964). He described their persistent black color being due to a high degree of dispersion of silicon. Interestingly, he also recorded reflectivity fi"om his photocells, but focused on the infrared rather than the visible range (Koltun 1964). 

Figure 17 SEM images (Lu etal., 2013) of femtosecond laser fabrication performed in SFg gas atmosphere to create black silicon structures.

Lin C-H, Dimitrov DZ, Du C-H, Lan C-W (2010) Influence of surface structure on the performance of black-silicon solar cell. Phys Stat Solid C7(ll-12) 2778-2784 Lin T-C, Shiu S-C, Pun K-L, Syu H-J, Lin C-F (2012) Layer transfer of crystalline Si thin film by metal-assisted chemical etching concerning different H2O2/HF ratios. In 38th IEEE Photovoltaic Specialists Conference (PVSC), Austin (USA), pp 000346-000349 Lipinski M (2008) Macroporous texturing of multicrystalline silicon for solar cells. Arch Metall Mater 53(1) 185-187... 

CNT and silicon structures are electrically conductive, thus they can be imaged using a conventional scanning electron microscope (SEM). In Figure 2, it can be observed that the CNT-GAC were scattered and not well-aligned. The layers of the wall cannot be seen clearly. After the adsorption experiment, it is observed that there were some black spots on the surface of the CNT-GAC. The spots showed that adsorption process had occurred on the CNT-GAC surface. 

Murias et al. (2012) described using the DRIE etching process for the formation of black silicon (pyramid-like structures in this case) using an SF6/O2/CH4 gas mixture. The authors reported that the reflectance of silicon was reduced from 30% to 1%, and suggested that this technique be used in low-cost solar cell manufacture. 

Phosphoric Acid Fuel Cell This type of fuel cell was developed in response to the industiy s desire to expand the natural-gas market. The electrolyte is 93 to 98 percent phosphoric acid contained in a matrix of silicon carbide. The electrodes consist of finely divided platinum or platinum alloys supported on carbon black and bonded with PTFE latex. The latter provides enough hydrophobicity to the electrodes to prevent flooding of the structure by the electrolyte. The carbon support of the air elec trode is specially formulated for oxidation resistance at 473 K (392°F) in air and positive potentials. 

Pure silicon carbide is colorless, but iron impurities normally impart an almost black color to the crystals. Carborundum is an excellent abrasive because it is very hard, with a diamondlike structure that fractures into pieces with sharp edges (Fig. 14.43). 

Under pressure black phosphorus transforms first to a modification that corresponds to gray arsenic. At an even higher pressure this is converted to the a-polonium structure. Then follows a hexagonal-primitive structure, which has also been observed for silicon under pressure (p. 122), but that hardly ever occurs otherwise. Above 262 GPa phosphorus is body-centered cubic this modification becomes superconducting below 22 K.. 

Exists in two adotropic modifications. Crystalline sihcon is made up of grayish-black lustrous needle-hke crystals or octahedral platelets cubic structure Amorphous sdicon is a brown powder. Other physical properties are density 2.33g/cm3 at 25°C melts at 1,414°C high purity liquid silicon has density 2.533 g/cm at its melting point vaporizes at 3,265°C vapor pressure 0.76 torr at 2,067°C Mohs hardness 6.5. Brinell hardness 250 poor conductor of electricity dielectiric constant 13 critical temperature 4°C calculated critical pressure 530 atm magnetic susceptibility (containing 0.085%Fe) 0.13x10 insoluble in water dissolves in hydrofluoric acid or a mixture of hydrofluoric and nitric acids soluble in molten alkalies. 

Figure 3.7 Molecular structure of [(Cp )Ca N(SiMe t)2l(thf>l calcium, nitrogen and silicon atoms are shown as black spheres, oxygen and carbon atoms are white. Selected bond lengths Ca-N 2.30(1), Ca-O 2.35(1), Ca-M 2.397A...

Figure 3.10 The structure of [BalNiSiMc il hlthfi ] Barium and nitrogen atoms are shown as black spheres, silicon atoms are grey and carbon and oxygen atoms are white. Selected bond lengths Ba-NI 2.587(6), Ila i 2 2.596(6), Ba-OI 2.745(6), Ba 02 2.717(6)A...

Figure 8.1 Illustration of the structure of crystallized [flMe, Si)2Al(NH2)2 3AII. Aluminium atoms are shown as black spheres, silicon atoms are dark grey and nitrogen and carbon atoms are white. Selected bond lengths AI1-N1 2.022(4), AII-N2 2.017(5), AI1-N3 2.022(3), AI2-N1 1.935(4), AI3-N2 1.936(4), AI3-N3 1.923(5), AII-AI2 2.911(3), AI1-AI3 2.905(2) A...

This chapter describes the preparation and examination of ceramic matrix composites realized by the addition of different carbon polymorphs (carbon black nanograins, graphite micrograins, carbon fibers and carbon nanotubes) to silicon nitride matrices. In the following sections, structural, morphological and mechanical characteristics of carbon-containing silicon nitride ceramics are presented. 

FIGURE 29 The crystal structure of RBisSis, projected onto the (110) plane. Polyhedra indicate B12 icosahedra, small gray circles are silicon atoms, and large black circles represent rare earth atoms. 

As in carbon-black-filled EPDM and NR rubbers, the physical network in silica-filled PDMS has a bimodal structure [61]. A loosely bound PDMS fraction has a high density of adsorption junctions and topological constraints. Extractable or free rubber does virtually not interact with the silica particles. It was found that the density of adsorption junctions and the strength of the adsorption interaction, which depends largely on the temperature and the type of silica surface, largely determine the modulus of elasticity and ultimate stress-strain properties of filled silicon rubbers [113]. 

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