Silicon amorphous thin films

Figures High mass resoiution mass spectrum obtained from a phosphorus-doped amorphous silicon hydride thin film using a magnetic sector ion microanalyzer. The peak is well separated from the hydride iirterferences.

Lustig, N. Kanicki J. (1989). Gate dielectric and contact effects in hydrogenated amorphous silicon-silicon nitride thin-film transistors, J. Appl. Phys., Vol. 65, 3951-3957, ISSN 0003-6951... 

Silicon oxides (SiOx) are the most widely used thin films in silicon microelectronic and micromechanical devices. Similar to silicon nitride (Section 5.5.4), these amorphous films exhibit dielectric properties. Silicon oxide is often utilized as part of a dielectric membrane, as a passivation or insulating layer, or as a sacrificial layer, which can be etched with hydrofluoric acid (HF)-containing etchants. Two different approaches to forming a silicon oxide thin film are... 

Daves, W., Krauss, A., Behnel, N., Haublein, V., Bauer, A., Frey, L., 2011. Amorphous silicon carbide thin films (a-SiC H) deposited by plasma-enhanced chemical vapor deposition as protective coatings for harsh environment applications. Thin Solid Films 519,5892—5898. http //dx.doi.Org/10.1016/j.tsf.2011.02.089. 

Amorphous Thin Films Currently, thin amorphous films of silicon nitride for applications as masking layers and as diffusion barriers during semiconductor processing are produced by gas-phase reactions of silicon tetrachloride or silane with ammonia, in the presence of hydrogen as carrier gas. Today, the standard GVD process is augmented by complex molecular excitation methods that include PACVD, laser-excited GVD (LECVD) and photosensitized GVD (PHCVD) enhance-... 

The FTIR spectra of fluorine-doped silicon dioxide thin films were used to characterise these species. " The IR spectra of amorphous SiO H (2.0 > x > 0) films include vSiOSi bands near 1050 and 1150cm 5SiOSi near 800 Features from vSiO were studied in the IR spectra of Si02.P205 films prepared by micro-pressure... 

Stoichiometry has long been used by solid-state chemists to control the final products of a reaction. However, traditional synthetic techniques do not have the ability to control reaction intermediates and all stable phases will form as illustrated in Figure 2. For example, in the iron-silicon system, thin film diffusion couples have been used to determine the sequence of phase formation (79). FeSi was always found to nucleate first, followed by the crystallization of FeSi2 at the FeSi-Si interface and FeSi3 at the FeSi-Fe interface. The following paragraphs provide evidence that stoichiometry of the amorphous intermediates can be used to control nucleation to obtain the desired crystalline compounds directly. Thus, we use stoichiometry to control the mechanism of the reaction. 

TETRA(SILYL)METHANE, (H3Si)4C, A VOLATILE CARBOSILANE FOR THE CHEMICAL VAPOR DEPOSITION OF AMORPHOUS SILICON CARBIDE THIN FILMS... 

Amorphous thin films of silicon and germanium were prepared by physical vapor deposition using a bell jar thermal evaporator (Fig. 2.4b]. A charge of elemental material was evaporated under a... 

Figure 2.9 Bright-field TEM images of amorphous thin films of (a) silicon and (b) germanium prepared by evaporation. The corresponding electron diffraction patterns are shown in the insets.

Figure 2.10 Voltage profile and differential capacity from amorphous thin films of silicon (a and b) and germanium [c and d) for cycles 1,25, and 50.

For the silicon film, an initial discharge capacity of 3500 mAh/g, and charge capacity of 2500 mAh/g were measured, which yields a columbic efficiency of 71% for the first cycle. Upon subsequent cycling, the electrode exhibited a rather stable specific capacity 2000 mAh/g with a columbic efficiency of 98% on cycle 9. After 20 cycles, the amorphous thin film exhibited a mean capacity loss of only 8 mAh/g per cycle. The differential capacity plot (Fig. 2.10b)... 

Amorphous Silicon. Amorphous alloys made of thin films of hydrogenated siUcon (a-Si H) are an alternative to crystalline siUcon devices. Amorphous siUcon ahoy devices have demonstrated smah-area laboratory device efficiencies above 13%, but a-Si H materials exhibit an inherent dynamic effect cahed the Staebler-Wronski effect in which electron—hole recombination, via photogeneration or junction currents, creates electricahy active defects that reduce the light-to-electricity efficiency of a-Si H devices. Quasi-steady-state efficiencies are typicahy reached outdoors after a few weeks of exposure as photoinduced defect generation is balanced by thermally activated defect annihilation. Commercial single-junction devices have initial efficiencies of ca 7.5%, photoinduced losses of ca 20 rel %, and stabilized efficiencies of ca 6%. These stabilized efficiencies are approximately half those of commercial crystalline shicon PV modules. In the future, initial module efficiencies up to 12.5% and photoinduced losses of ca 10 rel % are projected, suggesting stabilized module aperture-area efficiencies above 11%. 

Fig. 4. Some electronic device applications using amorphous silicon (a) solar cell, (b) thin-fiLm transistor, (c) image sensor, and (d) nuclear particle detector.

Microscopic sheets of amorphous silica have been prepared in the laboratory by either (/) hydrolysis of gaseous SiCl or SiF to form monosilicic acid [10193-36-9] (orthosihcic acid), Si(OH)4, with simultaneous polymerisation in water of the monosilicic acid that is formed (7) (2) freesing of colloidal silica or polysilicic acid (8—10) (J) hydrolysis of HSiCl in ether, followed by solvent evaporation (11) or (4) coagulation of silica in the presence of cationic surfactants (12). Amorphous silica fibers are prepared by drying thin films of sols or oxidising silicon monoxide (13). Hydrated amorphous silica differs in solubility from anhydrous or surface-hydrated amorphous sdica forms (1) in that the former is generally stable up to 60°C, and water is not lost by evaporation at room temperature. Hydrated sdica gel can be prepared by reaction of hydrated sodium siUcate crystals and anhydrous acid, followed by polymerisation of the monosilicic acid that is formed into a dense state (14). This process can result in a water content of approximately one molecule of H2O for each sdanol group present. 

Textured Tin Oxide Films Produced by Atmospheric Pressure Chemical Vapor Deposition from Tetramethyltin and Their Usefulness in Producing Light Trapping in Thin-Film Amorphous Silicon Solar Energy Mater., 18 263-281 (1989)... 

The thickness of a photovoltaic cell is chosen on the basis of its ability to absorb sunlight, which in turn depends on the bandgap and absorption coefficient of the semiconductor. For instance, 5 nm of crystalline silicon are required to absorb the same amount of sunlight as 0.1 nm of amorphous silicon and 0.01 nm of copper-indium diselenide. Only MBE and MOCVD are capable of producing such extremely thin films.i l... 

A thin film of tin oxide with a rough texture, produced by MOCVD from tetramethyl tin, (CH3)4Sn, deposited on an amorphous silicon cell provides a light-trapping surface, which enhances the efficiency of the device. 

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