Erbium silicates

The modem silicon-based microelectronics led to the miniaturization of electronic devices. However, delays caused by metallic intercoimec-tions became a bottleneck for the improvement of their performances. One possible solution of this problem is to use optical intercoimections for the transfer of information, and, therefore, silicon compatible materials and devices that are able to generate, guide, amplify, switch, modulate, and detect light are needed. Rare earth silicates with luminescent rare earths and compatibility with silicon may be a good choice for these applications (Miritello et al., 2007). Miritello et al. presented the study on nanocrystalline erbium silicate thin films fabricated on silicon/silica substrates. The obtained films exhibit strong photoluminescence emission around 1540 nm with room temperature excitation by 488 ran Ar laser. 

In the study of the kinetics of the decay of erbium PL we used a semiconductor laser radiating at 658 nm wavelength with a variable pulse time. The energy of photons of this laser corresponds to the transitions between the tail states of the valence band and the conduction band of the amorphous silicon, but it is significantly smaller that the width of the forbidden gap of the dielectric nanocrystals of erbium silicate. The intensity decay of erbium PL after the end of the pumping pulse is well described by two exponents with the characteristic times of 27 ps for the fast component (Ifts,) and 200 ps for the slow component (Liow)- The presence in the decay kinetics of two components with strongly... 

Figure 3. The ratio of components of erbium PL decay at the wavelengh of 1.54 pm depending on the duration of the excitation pulse. Black circles are experimental findings, white circles are calculated data. In the insert the scheme of erbium excitation is shown for erbium in amorphous silicon with erbium silicate nanociystals.

S708>, and 2-phenyl-l,3-dioxolanes are cleaved cleanly to diols by the use of catalytic erbium triflate <20050BC4129>. A titanium silicate molecular sieve is effective in catalyzing methanolysis of l,3-dioxolan-2-one to give ethanediol and dimethyl carbonate <1996CC2281>. 

In addition to the above, preparation in w/o microemulsions of nanoparticles of various other types of compounds, viz. silica-coated iron oxide, Fe203-Ag nanocomposite, oxides of ytrium, erbium, neodymium, vanadium and cobalt, titanates of barium and lead, ferrites of barium, strontium, manganese, cobalt and zinc, oxide superconductors, aluminates, zirconium silicate, barium tungstate, phosphates of calcium, aluminium and zinc, carbonates of calcium and barium, sulphides of molybdenum and sodium, selenides of cadmium and silver etc. have been reported. Preparative sources and related elaboration can be found in [24]. 

A third group of sodium rare earth silicates is formed by the smallest lanthanides from erbium to lutetium and yttrium. The original description of the stmctures as Pbn2j (Maksimov et al., 1967) was later changed to Pcn2i, for NaYSi04 (Merinov et al., 1979) after a different choice of axes. This structure is isostmctural with Ca2Si04, but with the octahedrally coordinated calcium atoms replaced by sodium and rare earth atoms. 

The rare earth elements form mixed disilicates with alkali metals of M3RSi207. There are two different structure types - hexagonal and orthorhombic. K3EuSi207 is the only example that has been found of the first type (Bondar et al., 1965b). Mixed disilicates with sodium and lanthanides from erbium to lutetium, yttrium and scandium exhibit the second stmcture type (Maksimov et al., 1969). The structure is similar to that of the sheet-like silicates of vermiculite, nontronite, etc., and consists of isolated 81307 groups joined together by NaOj, Na04 and ROg polyhedra (Skshat et al., 1969) (fig. 43). 

J. Du, A.N. Cormack, The structure of erbium doped sodium silicate glasses. J. Non-Cryst. Solids 351, 2263-2276 (2005)... 

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