Tribological Properties of Fluorinated Amorphous Carbon Thin Films

Rubio‐Roy, Miguel; Corbella, Carles; Andújar, J.L.; Bertrán, E.

doi:10.5772/15394

Cited by 4 publications

(2 citation statements)

References 100 publications

(102 reference statements)

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“…Aluminium nitride (AlN) specifically has a wide band gap (6.3 eV), high decomposition temperature (2490°C), good dielectric properties and usually crystallizes in wurtzite structure (P6³mc) with the lattice parameters of a=0.311 nm and c=0.498nm, which is the reason why it is extensively studied [5,6]. Considerable interest arose in the last decade in the use of thin films of AlN for various applications, ranging from hard coatings and over-coatings for magneto-optic media to thin film transducers and GHz-band surface acoustic wave devices (SAW) 00010 [7][8][9]. However, AlN thin film deposited on a sapphire substrate usually contains a lot of lattice defects because of the large lattice mismatch, as well as the poor Al atom migration ability [10].…”

Section: Introductionmentioning

confidence: 99%

Reduction of dislocation density of aluminium nitride buffer layer grown on sapphire substrate

et al. 2016

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An aluminium nitride (AlN) buffer layer with 200 nm thickness was grown on (0001) sapphire substrate using the metal-organic vapour phase epitaxy (MOVPE) method in a low-pressure furnace, followed by a clean-up treatment of sapphire substrate at 1100 o C. Thereafter, the AlN buffer layer was annealed at a high temperature in the range of 1500 o C to 1700 o C for 2 hours under the atmosphere of N2+CO. The objective of this research is to determine the microstructure changes with different annealing temperatures. Cross-sectional TEM has revealed that, after annealing at 1500 o C, two types of defects remained in the AlN buffer layer: inverted cone shape domains and threading dislocations. The former domains were observed in an image taken with diffraction of g=0002, but not in an image with g=101 ̅ 0. The morphology and the diffraction condition for the image contrast strongly, suggesting that the domains are inversion domains. The threading dislocations were invisible in the image taken with the diffraction of g=0002, revealing that they were a-type dislocations. However, after annealing at 1600 o C, the inversion domains coalesced with each other to give a two-layer structure divided by a single inversion domain boundary at the centre of the AlN buffer layer. The density of threading dislocation was roughly estimated to be 5×10 9 cm -2 after annealing at 1500 o C, and to be reduced to 5×10 8 cm -2 after annealing at 1600 o C. These experimental results validate the fact that the annealing temperature around 1600 o C is high enough to remove the defects by the diffusion process. Therefore, it was discovered that high temperature annealing is an effective treatment to alter the microstructure of AlN thin films and remove defects by the diffusion process. Annealing at high temperature is recommended to increase the emission efficiency for fabrication of optoelectronic devices.

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Section: Introductionmentioning

confidence: 99%

Reduction of dislocation density of aluminium nitride buffer layer grown on sapphire substrate

et al. 2016

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“…1,9 This potential of fluorinated materials is mainly enabled by the unique properties of C−F bonds, specifically the high binding energy and low polarizability, which are also crucial to obtain chemically resistant, low-dielectric-constant materials to be used as lowfriction coatings. 10,11 Fluorinated polymers are emerging as solid lubricants and frequently used as fillers in many composites due to their low friction coefficients. 12,13 Furthermore, fluoropolymers like polytetrafluoroethylene (PTFE) are widely used in micro/ nanoelectromechanical systems (MEMS/NEMS) as lowfriction and antistiction coatings to improve the device performance.…”

Section: ■ Introductionmentioning

confidence: 99%

Adhesion and Friction Properties of Fluoropolymer Brushes: On the Tribological Inertness of Fluorine

et al. 2014

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The effects of fluorination on the adhesion and friction properties of covalently bound poly(fluoroalkyl methacrylate) polymer brushes (thickness ∼80 nm) were systematically investigated. Si(111) surfaces were functionalized with a covalently bound initiator via a thiol-yne click reaction to have a high surface coverage for initiator immobilization. Surface-initiated atom-transfer radical polymerization (SI-ATRP) was employed for the synthesis of four different fluoropolymer brushes (SPFx, where x = 0, 3, 7, or 17 F atoms per monomer), based on fluoroalkyl methacrylates. All polymer brushes were characterized with static contact angle measurements, X-ray photoelectron spectroscopy (XPS), and infrared absorption reflection spectroscopy (IRRAS). The polymer brushes exhibited an excellent hydrophobicity, with static water contact angles of up to 121° depending on the number of fluorine atoms per side chain in fluoroalkyl methacrylate. The degree of swelling was precisely studied by using ellipsometry in different solvents such as acetone, hexadecane, hexafluoroisopropanol, nonafluorobutyl methyl ether, and Fluorinert FC-40. The polymer brushes have shown nanoscale swelling behavior in all solvents except hexadecane. The grafting density decreased upon increasing fluorine content in polymer brushes from 0.65 chains/nm(2) (SPF0) to 0.10 chains/nm(2) (SPF17) as observed in Fluorinert FC-40 as a good solvent. Adhesion and friction force measurements were conducted with silica colloidal probe atomic force microscopy (CP-AFM) under ambient, dry (argon), and lubricating fluid conditions. SPF17 showed the lowest coefficient of friction 0.005 under ambient condition (RH = 44 ± 2%) and a further decrease with 50% under fluidic conditions. These polymer brushes also showed adhesion forces as low as 6.9 nN under ambient conditions, which further went down to 0.003 nN under fluidic conditions (Fluorinert FC-40 and hexadecane) at 10 nN force.

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