Interactions of fragment ions of tetradecane with solid surfaces

Vapors of tetradecane (C14H30) were ionized by electron bombardment. The generated fragment ions such as C3H7, C6H13, and C12H25 ions were separated by an E × B filter (Wien filter) and accelerated toward Si(1 0 0) substrates. Thickness measurements showed that thin films were deposited on the Si substrates by C3H7- and C6H13-ion irradiation, although the Si substrate surface was predominantly sputtered by C12H25 ions. Rutherford backscattering spectroscopy showed that the irradiation damage by the fragment-ion beams decreased with the increasing molecular weight of the fragment ions at the same acceleration voltage. Furthermore, Raman spectra as well as X-ray photoelectron spectroscopy measurements showed that DLC films were formed by C3H7- and C6H13-ion irradiation with the film thickness being larger in case of C3H7. On the contrary, for C12H25-ion irradiation, chemical sputtering occurred by surface reactions of hydrogen and methyl radicals with silicon atoms. The chemical reaction at the irradiated substrate surface could be enhanced by the higher temperatures achieved by the high energy–density irradiation effect of the polyatomic ions.