Controlled nanostructuration of polycrystalline tungsten thin films

Abstract

Nanostructured tungsten thin films have been obtained by ion beam sputtering technique stopping periodically the growing. The total thickness was maintained constant while nanostructure control was obtained using different stopping periods in order to induce film stratification. The effect of tungsten sublayers' thicknesses on film composition, residual stresses, and crystalline texture evolution has been established. Our study reveals that tungsten crystallizes in both stable aand metastable b-phases and that volume proportions evolve with deposited sublayers' thicknesses. a-W phase shows original fiber texture development with two major preferential crystallographic orientations, namely, a-Wh110i and unexpectedly a-Wh111i texture components. The partial pressure of oxygen and presence of carbon have been identified as critical parameters for the growth of metastable b-W phase. Moreover, the texture development of a-W phase with two texture components is shown to be the result of a competition between crystallographic planes energy minimization and crystallographic orientation channeling effect maximization. Controlled grain size can be achieved for the a-W phase structure over 3 nm stratification step. Below, the b-W phase structure becomes predominant. V C 2013 AIP Publishing LLC. [http://dx.

Pulsed laser synthesis of carbon-overdoped tungsten with a body-centered orthorhombic structure and planar defects

“…simple cubic type β-W. (Note that β-W is a metastable precursor at nanoscale (<3 nm) 21 and high temperature as indicated by its larger ambient cell parameter (a = 0.505 nm for β-W and 0.5036 nm for A15 isostructural W 3 O) 22 than that of α-W (0.3164 nm, JCPDS file 04-0806). The inward diffusion of C into α-W and/or β-W then triggered lattice shuffling and long range ordering to form faulted BCO and/or OBCO-type W analogous to martensitic transformation of C-dissolved γ-Fe as martensite with a body centered tetragonal (bct) structure upon rapid quenching.…”

“…13) 1 and stability as an α-type bcc structure (space group Im3m) with a positive Clausius-Clapeyron (ΔT/ΔP) slope in a wide P-T range. 2 Having high mechanical strength and hardness (21)(22)(23)(24)(25), 3 good creep resistance, metal barrier performance and patternability, 4 excellent electrical conductivity 5 and fair chemical stability, 6 nanostructured W was shown to be useful as a cold-cathode material and for application in high-temperature devices. 7,8 Nanostructured W also performed excellently as an absorbing layer in X-ray masks and mirrors, 9 photonic crystals, 10 interconnectors on Sibased devices, 11,12 and metallization layers 13 by the selective crystalline polymorphs in the films.…”

Comparative study of the mechanical properties of nanostructured thin films on stretchable substrates

“…29 Phase analysis by XRD measurements shows that W crystallites exhibit two different phases: the equilibrium pure W phase, called a-W which has a bodycentered cubic-bcc-structure (space group Im-3 m) and a second one called b-W having an A15 cubic structure (space group Pm-3n) which is stabilized by a low impurity (O, C) concentration. 30 The volume fraction of the b-W phase has been estimated to be about 10% by the method given in Ref. 28.…”

Amorphous, ultra-nano- and nano-crystalline tungsten-based coatings grown by Pulsed Laser Deposition: mechanical characterization by Surface Brillouin Spectroscopy

“…However, PS limit is represented by the inability to finely control film structure at the atomic scale, which often results in undesired material properties and failure of the coating [9,10]. Alternatively, in order to finely control film structure, morphology and stoichiometry, a variety of physical-(PVD) and chemical-(CVD) vapour deposition techniques is available for W coatings deposition [11,12,13,14]. Pulsed Laser Deposition (PLD) is one of the most versatile PVD techniques, by which both mono-or multi-elemental films such as metals, compounds and carbon based materials, also replicating complicated or unusual target stoichiometry can be deposited [15,16,17,18,19,20,21].…”