Nanoparticle deposition in hydrogenated amorphous silicon films during rf plasma deposition

Abstract

Particles of 2–14 nm diameter, representing 10−4–10−3 of the film volume, are observed by scanning tunneling microscopy (STM) in thin films of hydrogenated amorphous silicon (a-Si:H) grown by rf-plasma-enhanced deposition using optimized conditions. The particles are produced in the discharge and incorporated in the film during growth, in contradiction to expected particle trapping by discharge sheath fields. The interfaces between the nanoparticles and the homogeneous film can produce low-density regions that form electronic defects in a-Si:H films.

Surface roughening during plasma-enhanced chemical-vapor deposition of hydrogenated amorphous silicon on crystal silicon substrates

“…These images are excluded from the analysis in this paper, but are the subject of a previous publication. 21 The undoped a-Si:H typically has a low-field resistivity Ͼ10 9 ⍀ cm. A calculation of spreading resistance for current injected from a subnanometer point contact using this number suggests that it would be impossible to conduct these tunneling currents through the films.…”

“…20 Pockets of clustered H atoms are reported by NMR measurements. 21 These types of features make the density of a-Si:H ϳ5% lower than crystalline silicon ͑c-Si͒. Our previous scanning tunneling microscope ͑STM͒ studies of a-Si:H films revealed a surprisingly wide variety of topographic features, including the incorporation of nanoparticles in the films from the plasma.…”

“…Our previous scanning tunneling microscope ͑STM͒ studies of a-Si:H films revealed a surprisingly wide variety of topographic features, including the incorporation of nanoparticles in the films from the plasma. 21,22 In this paper we focus on the homogeneous regions of thin films of a-Si:H, which represent the vast majority of the film volume. These measurements should correlate with techniques that average over large regions of the film surface.…”

Fullerene and nanotube formation in cool terrestrial “dusty plasmas”

“…7 These cause nonuniformity in the deposited films, and in extreme cases lead to unacceptable contamination rendering the material unusable for electronic applications. 8 This has led to a number of publications focused on understanding the formation, dynamics, and consequences of these terrestrial dusty plasmas, with regard to silicon-based PECVD dust. 9 However, the development of amorphous hydrogenated carbon ͑a-C:H͒ 10 devices formed from a methane precursor, for example, is still very much in its infancy, and little attention has so far been paid to the nature of carbonaceous dusty plasmas.…”

Influence of hydrogen atoms on the growth of carbon based nanoparticles and of thin films from reactive plasmas

“…Even when they are so small that they are not able to cause any damage during the plasma processing of micro components they may be embedded into the film matrix changing the film properties and forming defects and voids at the interface with the surrounding film [34]. Sometimes the incorporation of the nanoparticles is wanted in plasma processing of the film because this is the only way to achieve desirable properties as for example in the case of photoluminescent thin films deposited in silane plasma with embedded crystalline clusters with sizes of 1 to 5 nm [35].…”