Structural model of sputtered fluorinated amorphous silicon

Abstract

Structure of a fluorinated amorphous-silicon alloy (a-Si:F), which is produced by the sputtering of Si in mixtures of Ar and SiF4 gases, is studied by transmission electron microscope (TEM). As a special technique to study the localization of both atomic species and particular types of Si-F configuration, the change of TEM micrograph due to anisotropic chemical etching of samples is observed, and it is compared with the similar changes in infrared absorption spectra and the Rutherford backscattering spectra. The evolved gases from heated a-Si:F are also analyzed to determine the role of Ar atoms in the microstructure. It is found that a-Si:F film consists of many small grains of a-Si network, and that both Si-F4 bonds and Ar atoms are localized at the grain boundary. Based on these results, the most possible structural model for a-Si:F, which suggests key factors to improve the properties, is presented.

Neutron scattering studies of hydrogenated, deuterated and fluorinated amorphous silicon

“…More recent studies [46] report the gradual orthopara conversion of the trapped D 2 in the deuterium analogue at 4.2 K and outline the effects of annealing and deposition rate on these properties [45]. In addition to the high-pressure H 2 found in hydrogenated amorphous silicon, molecular SiF 4 is also known to exist in the fluorine-doped derivatives [51][52][53][54]. For samples prepared by photochemical vapour deposition, Langford et al [54] have suggested that these SiF 4 molecules are contained within cages of much the same size as those containing the molecular H 2 in the hydrogenated material.…”

The Role of Fluorine in Implanted Amorphous Silicon

“…In particular, the presence of fluorine atoms suppresses the regrowth rate (5).Spear and LeComber (10) demonstrated in 1975 that the doping of a-Si is possible by the incorporation of hydrogen atoms. Since then intense research has been carried out on a-Si based alloys to study the resultant structures and properties, aiming at improving the material quality of a-Si for device applications (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). Fluorinated amorphous silicon (a-Si:F) is a promising material for its stability against heating.…”

“…For example, it is well known that voids are present in a-Si films prepared by the GD or the thermal evaporation method (17). It has also been shown that a-Si:F films prepared by sputtering of Si in mixtures of Ar and SiF4 gases consist of many small grains of a-Si network, with both Si-F4 bonds and Ar atoms localized at the grain boundaries (20). These undesired microstructures can seriously affect the material quality.…”