An upgraded ultra-high vacuum magnetron-sputtering system for high-versatility and software-controlled deposition

et al. 2021

ACS Appl. Nano Mater.

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Introducing porosity is attractive for tailoring electronic, thermal, and mechanical properties of inorganic materials. Nanoporosity is typically either inherent in crystallographic channels in the structure or obtained by external templating during synthesis and sintering. However, controllably engineering porosity in materials with laminated crystal structures without channels remains a challenge. Here, we demonstrate the realization of faceted and oriented nanopores in textured Ca 3 Co 4 O 9 a laminated ceramic with a misfit-layered structure of importance for thermoelectric applicationsfrom chemical reactions in CaO/Co 3 O 4 multilayers. We show that CaO conversion to Ca(OH) 2 and the cobalt oxide stoichiometry are key determinants of nanoporosity. Adjusting the unreacted CaO fraction alters the nanopore size and fraction and the thermoelectric properties of Ca 3 Co 4 O 9 . The preferred orientation of Ca 3 Co 4 O 9 is underpinned by the texture of the reactant multilayers and reactant−product crystallographic relationships and density difference. Oriented pore formation is attributed to basal plane removal driven by local densification of textured Ca 3 Co 4 O 9 nuclei through growth and impingement. These findings point to possibilities for controllably engineering nanoporosity and properties in a variety of inorganic materials with laminated crystal structures.

Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Engineering Faceted Nanoporosity by Reactions in Thin-Film Oxide Multilayers in Crystallographically Layered Calcium Cobaltate for Thermoelectrics

Xin

Febvrier

et al. 2021

ACS Appl. Nano Mater.

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“…High-entropy (TiZrTaMe)N 1−x (Me = Hf, Nb, Mo or Cr) films were deposited on Si(100) substrates using magnetron sputtering in an ultrahigh vacuum chamber 22 (base pressure <10 −7 Pa) with elemental targets (Ti, Zr, Ta, and Me; Me = Hf, Nb, Mo, or Cr) with a diameter of 50.8 mm. The distance between the targets and the substrate holder was approximately 140 mm.…”

Section: Methodsmentioning

confidence: 99%

Influence of Metal Substitution and Ion Energy on Microstructure Evolution of High-Entropy Nitride (TiZrTaMe)N_1–x (Me = Hf, Nb, Mo, or Cr) Films

ACS Appl. Electron. Mater.

Lundin

Xin

et al. 2021

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Multicomponent or high-entropy ceramics show unique combinations of mechanical, electrical, and chemical properties of importance in coating applications. However, generalizing controllable thin-film processes for these complex materials remains a challenge. Here, understoichiometric (TiZrTaMe)N 1−x (Me = Hf, Nb, Mo, or Cr, 0.12 ≤ x ≤ 0.30) films were deposited on Si(100) substrates at 400 °C by reactive magnetron sputtering using single elemental targets. The influence of ion energy during film growth was investigated by varying the negative substrate bias voltage from ∼10 V (floating potential) to 130 V. The nitrogen content for the samples determined by elastic recoil detection analysis varied from 34.9 to 43.8 at. % (0.12 ≤ x ≤ 0.30), and the metal components were near-equimolar and not affected by the bias voltage. On increasing the substrate bias, the phase structures of (TiZrTaMe)N 1−x (Me = Hf, Nb, or Mo) films evolved from a polycrystalline fcc phase to a (002) preferred orientation along with a change in surface morphology from faceted triangular features to a dense and smooth structure with nodular mounds. All the four series of (TiZrTaMe)N 1−x (Me = Hf, Nb, Mo, or Cr) films exhibited increasing intrinsic stress with increasing negative bias. The maximum compressive stress reached ∼3.1 GPa in Hf-and Cr-containing films deposited at −130 V. The hardness reached a maximum value of 28.0 ± 1.0 GPa at a negative bias ≥100 V for all the four series of films. The effect of bias on the mechanical properties of (TiNbZrMe)N 1−x films can thus guide the design of protective high-entropy nitride films.

“…The deposition system is described elsewhere. 22 Mg and Bi circular targets (50 mm in diameter) were used and driven by dc-power supplies with optimized (i.e., yielding approximately the desired 3:2 composition; see the supplementary material, Fig. S1) power of 90 and 15 W, respectively.…”

mentioning

confidence: 99%

Epitaxial growth and thermoelectric properties of Mg3Bi2 thin films deposited by magnetron sputtering

Sadowski

Zhu

Applied Physics Letters

et al. 2022

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Mg 3 Sb 2 -based thermoelectric materials attract attention for applications near room temperature. Here, Mg-Bi films were synthesized using magnetron sputtering at deposition temperatures from room temperature to 400 C. Single-phase Mg 3 Bi 2 thin films were grown on c-planeoriented sapphire and Si(100) substrates at a low deposition temperature of 200 C. The Mg 3 Bi 2 films grew epitaxially on c-sapphire and fiber-textured on Si(100). The orientation relationships for the Mg 3 Bi 2 film with respect to the c-sapphire substrate are (0001) Mg 3 Bi 2 k(0001) Al 2 O 3 and [1120] Mg 3 Bi 2 k[1120] Al 2 O 3 . The observed epitaxy is consistent with the relatively high work of separation, calculated by the density functional theory, of 6.92 J m À2 for the Mg 3 Bi 2 (0001)/Al 2 O 3 (0001) interface. Mg 3 Bi 2 films exhibited an in-plane electrical resistivity of 34 lX m and a Seebeck coefficient of þ82.5 lV K À1 , yielding a thermoelectric power factor of 200 lW m À1 K À2 near room temperature.