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