{'fraction_non_alphanumeric': 0.02485089463220676, 'fraction_numerical': 0.006958250497017893, 'mean_word_length': 5.29375, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Initial Stage of Preferential Sputtering in Cu–Pt Alloy Studied by Sputtered Neutrals Mass Spectrometry

Nonresonant multiphoton ionization sputtered neutrals mass spectrometry (NRMPI-SNMS) was used to measure a codeposited Cu–Pt alloy film to elucidate how preferential sputtering proceeds with ion bombardment. For this, we have newly developed a compact coevaporator which enables preparation of Cu–Pt alloy film of homogeneous composition from the surface to the bulk in a specimen chamber. The present study has revealed that the ratio of sputtered Cu atoms to Pt atoms is ∼9.3 at the very initial stage of sputtering for a Cu–Pt alloy surface of which surface composition under ion bombardment is assessed to be Cu(88 at.%)–Pt at the topmost surface together with by the successive atomic layers of homogeneous composition of Cu(68.2 at.%)–Pt. This result has clearly indicated that Cu atoms are preferentially sputtered through atomic collisions caused entirely by the kinetic process of sputtering.