θ–2θ XRD patterns for the as-deposited films A20, A180, B20, B180, C20, and C180 obtained immediately following deposition. The measured film thicknesses are given in Table I. The solid and dotted vertical lines mark the positions of the Bragg peaks for α-W and β-W structures, respectively. For α-W, the four Bragg peaks are, from left to right, (110), (200), (211), and (220). For β-W, the nine Bragg peaks are, from left to right, (200), (210), (211), (222), (320), (321), (400), (420), and (421).
Dark-field transmission electron micrographs for the nominally 5-nm-thick films B5 (a) and C5 (b) and the nominally 10-nm-thick films B10 (c) and C10 (d). The selected area diffraction patterns are shown as insets in the upper right.
Sections of the θ–2θ XRD patterns for films B5, B10, C5, and C10. The solid vertical lines in the patterns correspond to the (110) reflection of α-W, while the dotted vertical lines correspond in order from left to right to the (110), (200), and (211) reflections of β-W.
Plan-view electron phase contrast TEM image of film B20 in the as-deposited state. The phase contrast image was formed by using a large enough objective aperture to include both the transmitted beam and some of the diffracted beams.
Cross-sectional dark-field transmission electron micrograph of film B180 in the as-deposited state. This image was formed by using the (110) reflection.
(Color online) (a) Out-of-plane α-(110) XRD peaks of films B20, B30, B180, C20, C30, and C180 in the as-deposited state. The experimentally observed peaks (black solid lines) were deconvoluted into the primary α-W (red open circles) and secondary α-W (blue open squares) peaks. (b) The average (110) peak positions for films B20–B180, obtained from in-plane and out-of-plane XRD θ–2θ scans are shown as a function of thickness. The dotted horizontal line represents the expected peak position for unstrained α-W using the value of lattice parameter given in Ref. 30. (c) The difference in the (110) interplanar spacing of primary α-W (circles) and secondary α-W (squares) along the film normal direction relative to the unstrained interplanar spacing is shown as a function of film thickness. The half-closed circle represents the two identical data points (d) The integrated intensity ratios (secondary α-W)/(primary α-W + secondary α-W) for the unencapsulated films (B20–B180) and encapsulated films (C20–C180) from (a) are shown as a function of thickness.
Resistivity as a function of thickness for films B5–B180 (circles) and C5–C180 (squares) in the as-deposited state (closed symbols) and after annealing at 850 °C for 2 h (open symbols). The resistivity of film C5 after the annealing treatment is not shown due to film agglomeration in the absence of the encapsulant.
Film identification, base pressure prior to film deposition, film thickness, and film resistivities in the as-deposited and annealed states. The number of grains measured and the grain size for a subset of the annealed films are also given. Films were annealed at 850 °C for 2 h.
Summary of deposition methods and the corresponding thick-film resistivities for polycrystalline W films reported in the literature.
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