Phosphonate self-assembled monolayers on aluminum surfaces

Abstract

Substrates of aluminum (Al) deposited by physical vapor deposition onto Si substrates and then chemically reacted with perfluorodecylphosphonic acid (PFDPAlSi), decylphosphonic acid (DPAlSi), and octadecylphosphonic acid (ODPAlSi) were studied by x-ray photoelectron spectroscopy (XPS), contact angle measurements, atomic force microscopy (AFM), and friction force microscopy, a derivative of AFM, to characterize their surface chemical composition, roughness, and micro-/nanotribological properties. XPS analysis confirmed the presence of perfluorinated and nonperfluorinated alkylphosphonate molecules on the PFDPAlSi, DPAlSi, and ODPAlSi. The sessile drop static contact angle of pure water on PFDPAlSi was typically more than 130 degrees and on DPAlSi and ODPAlSi typically more than 125 degrees indicating that all phosphonic acid reacted AlSi samples were very hydrophobic. The surface roughness for PFDPAlSi, DPAlSi, ODPAlSi, and bare AlSi was approximately 35 nm as determined by AFM. The surface energy for PFDPAlSi was determined to be approximately 11 mNm by the Zisman plot method compared to 21 and 20 mNm for DPAlSi and ODPAlSi, respectively. Tribology involves the measure of lateral forces due to friction and adhesion between two surfaces. Friction, adhesion, and wear play important roles in the performance of micro-/nanoelectromechanical systems. PFDPAlSi gave the lowest adhesion and coefficient of friction values while bare AlSi gave the highest. The adhesion and coefficient of friction values for DPAlSi and ODPAlSi were comparable.

Organic corrosion inhibitors: where are we now? A review. Part IV. Passivation and the role of mono- and diphosphonates

“…Hoque et al [43] 18 provided > 125°, which indicates strong hydrophobization of the Al/Si surface. In the following work [44], studies were carried out on oxidized Al, and APhC 8 was studied instead of APhC 10 F 17 .…”

Influence of chain ordering on frictional properties of self-assembled monolayers (SAMs) in nano-lubrication

“…Alkylphosphonic acids are also an important class of SAM molecules because of their ability to assemble on a number of oxide surfaces, such as tantalum oxide, aluminum oxide, silicon oxide, iron oxide, copper oxide, and mica, and to form robust surface films [78][79][80][81][82][83][84][85][86][87][88][89][90][91][92]. Compared to SAMs of fatty acids, alkanethiols, and alkylsilanes, which have been studied extensively, phosphonic acid-based SAMs have not received much attention [84].…”

“…Compared to SAMs of fatty acids, alkanethiols, and alkylsilanes, which have been studied extensively, phosphonic acid-based SAMs have not received much attention [84]. There has been increasing interest in forming monolayer lubricants with alkylphosphonate SAMs for Al-based substrates recently, particularly with the development of digital micromirror devices used in optical projection displays [81][82][83][84]93,94]. The phosphonic acid head group binds more strongly to metal oxide surfaces than carboxylic acid head group [85], and the increased binding stability leads to significant interest in phosphonic acid SAMs for applications in electronics and MEMS/NEMS.…”

Halogen-Free Phosphonate Ionic Liquids as Precursors of Abrasion Resistant Surface Layers on AZ31B Magnesium Alloy

“…Phosphorus-containing coatings, in particular phosphonate derivatives [1,53,54] are currently been studied as corrosion protective layers on magnesium alloys due to their biocompatibility. Phosphorus-containing ionic liquids have been extensively applied in corrosion protection of magnesium alloys [55][56][57][58][59][60][61][62][63][64].…”