{"title":"Mechanism of Perfluoropolyether Lubricant Decomposition and SiOx Smear Growth in Heat-Assisted Magnetic Recording","authors":"Hiroshi Tani, Renguo Lu, Shinji Koganezawa","doi":"10.1007/s11249-026-02205-1","DOIUrl":null,"url":null,"abstract":"<div><p>Perfluoropolyether (PFPE) lubricants in heat-assisted magnetic recording (HAMR) hard disk drives are exposed to extreme thermal conditions at the head–disk interface, where local surface temperatures reach 300–400 °C. Under these conditions, PFPE decomposition is promoted, potentially generating HF-related fluoride species that may affect silicon oxide (SiO<sub>x</sub>) smear growth on the near-field transducer surface. This study investigates PFPE decomposition and SiO<sub>x</sub> smear growth through four experiments. Accelerated-aging tests in sealed glass ampoules demonstrate that hydroxyl-terminated PFPE lubricants decompose under high temperature and elevated pressure, with glass corrosion products detected by time-of-flight secondary ion-mass spectrometry (TOF–SIMS) providing strong indirect evidence for HF-related fluoride species generation. Moisture accelerates decomposition. TOF–SIMS analysis of commercial HAMR smear suggests that surface silanol groups may serve as SiO<sub>x</sub> precursors and reveals an inverse relationship between HF- and SiO<sub>2</sub>-related ion intensities. Temperature-dependent analysis is consistent with thermally activated Si migration from the magnetic layer and silanol decomposition above 300 °C. Laser-heating experiments with lubricant film thicknesses of 7, 10, and 15 Å show that increasing film thickness is associated with increased HF-related fluoride species generation and decreased SiO<sub>x</sub> accumulation. A three-step tribochemical mechanism is proposed: Si species react with adsorbed water to form silanol groups; these groups decompose under laser heating, potentially generating volatile silicon monoxide; and silicon monoxide may transform into SiO<sub>x</sub>, potentially inhibited by HF-related fluoride species. These findings highlight the importance of lubricant film thickness and moisture control in balancing SiO<sub>x</sub> smear formation and HF-related corrosion at the HAMR head–disk interface.</p><h3>Graphical Abstract</h3>\n<div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":806,"journal":{"name":"Tribology Letters","volume":"74 4","pages":""},"PeriodicalIF":3.5000,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Tribology Letters","FirstCategoryId":"5","ListUrlMain":"https://link.springer.com/article/10.1007/s11249-026-02205-1","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, CHEMICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Perfluoropolyether (PFPE) lubricants in heat-assisted magnetic recording (HAMR) hard disk drives are exposed to extreme thermal conditions at the head–disk interface, where local surface temperatures reach 300–400 °C. Under these conditions, PFPE decomposition is promoted, potentially generating HF-related fluoride species that may affect silicon oxide (SiOx) smear growth on the near-field transducer surface. This study investigates PFPE decomposition and SiOx smear growth through four experiments. Accelerated-aging tests in sealed glass ampoules demonstrate that hydroxyl-terminated PFPE lubricants decompose under high temperature and elevated pressure, with glass corrosion products detected by time-of-flight secondary ion-mass spectrometry (TOF–SIMS) providing strong indirect evidence for HF-related fluoride species generation. Moisture accelerates decomposition. TOF–SIMS analysis of commercial HAMR smear suggests that surface silanol groups may serve as SiOx precursors and reveals an inverse relationship between HF- and SiO2-related ion intensities. Temperature-dependent analysis is consistent with thermally activated Si migration from the magnetic layer and silanol decomposition above 300 °C. Laser-heating experiments with lubricant film thicknesses of 7, 10, and 15 Å show that increasing film thickness is associated with increased HF-related fluoride species generation and decreased SiOx accumulation. A three-step tribochemical mechanism is proposed: Si species react with adsorbed water to form silanol groups; these groups decompose under laser heating, potentially generating volatile silicon monoxide; and silicon monoxide may transform into SiOx, potentially inhibited by HF-related fluoride species. These findings highlight the importance of lubricant film thickness and moisture control in balancing SiOx smear formation and HF-related corrosion at the HAMR head–disk interface.
期刊介绍：
Tribology Letters is devoted to the development of the science of tribology and its applications, particularly focusing on publishing high-quality papers at the forefront of tribological science and that address the fundamentals of friction, lubrication, wear, or adhesion. The journal facilitates communication and exchange of seminal ideas among thousands of practitioners who are engaged worldwide in the pursuit of tribology-based science and technology.
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