Chemical erosion of amorphous hydrogenated boron films

Abstract

Amorphous-hydrogenated boron (a-B:H) and carbon (a-C:H) thin films were prepared by radio-frequency plasma deposition using (B2H6+H2) or CH4 as a precursor gas. The film composition and density were investigated by ion-beam analysis. The films were eroded by hydrogen electron cyclotron resonance plasmas at floating potential and by atomic hydrogen dissociated by a hot filament. The temperature of the substrates was increased during the erosion process from 330 to 680 K. Erosion rates were measured in situ by ellipsometry. a-B:H films are shown to be much more resistant to erosion by hydrogen ions (H+) and atomic hydrogen (H0) than a-C:H films. In contrast to a-C:H films, no chemical erosion of a-B:H films by H0 was observed at temperatures below 600 K. Ion energies lower than the threshold energy for physical sputtering cause measurable erosion rates for a-B:H films. It is concluded that this is a synergistic effect of simultaneous H0 and H+ bombardment and it is designated as ion-induced chemical erosion.

Study on formation and shape of carbon nanotips depending on ion bombardment

“…where z 1 and z 2 are the atomic numbers of the ion and carbon, E the ion energy, n the atomic density of the carbon film and d is the nearest-neighbor distance [11] and they are 86.28 atoms nm À3 and 0.134 nm [12,13], respectively. In Ref.…”

Synergistic etch rates during low-energetic plasma etching of hydrogenated amorphous carbon

“…1,10,13,14,16-18,40,47,48 The kinetic energy of the incident ions is thereby below the threshold for physical sputtering (32 eV for H þ ; 58 eV for Ar þ ). 13 When the ions transfer sufficient kinetic energy for the erosion of a CH 3 (or higher C x H y ) radical group, but do not break any bonds themselves, the process is called ion-assisted chemical erosion. 13 Chemical sputtering is a similar process, in which the incident ions do break carbon bonds within their surface penetration depth.…”

“…13 When the ions transfer sufficient kinetic energy for the erosion of a CH 3 (or higher C x H y ) radical group, but do not break any bonds themselves, the process is called ion-assisted chemical erosion. 13 Chemical sputtering is a similar process, in which the incident ions do break carbon bonds within their surface penetration depth. [17][18][19]49,50 The incident hydrogen radicals immediately passivate the newly formed DBs, thereby creating hydrocarbon groups that will eventually desorb.…”

“…II). 13,17,19 The ion energy is thereby higher than the binding energy ($ 3 À 5 eV) for the carbon bonds, yet lower than the threshold for physical sputtering ($ 32 À 58 eV). The difference between both mechanisms lies in the role of the incident ions.…”

“…10 Previous studies of carbon etching -with ion energies between 10 eV and 5 keV -have established several etch mechanisms in literature. [11][12][13][14][15][16][17][18] Two of those mechanisms, i.e. chemical sputtering and ion-assisted chemical erosion, describe a synergistic effect in the etch rate when simultaneously exposing a-C:H to both radicals and ions (see also Sec.…”