skip to main content

Title: Thick Film Ni0.5Mn0.5−xSnx Heusler Alloys by Multi-layer Electrochemical Deposition

The design of multifunctional alloys with multiple chemical components requires controllable synthesis approaches. Physical vapor deposition techniques, which result in thin films (<1 μm), have previously been demonstrated for micromechanical devices and metallic combinatorial libraries. However, this approach deviates from bulk-like properties due to the residual stress derived in thin films and is limited by total film thickness. Here, we report a route to obtain ternary Ni-Mn-Sn alloy thick films with controllable compositions and thicknesses by annealing electrochemically deposited multi-layer monatomic (Ni, Mn, Sn) films, deposited sequentially from separate aqueous deposition baths. We demonstrate (1) controllable compositions, with high degree of uniformity, (2) smooth films, and (3) high reproducibility between film transformation behavior. Our results demonstrate a positive correlation between alloy film thicknesses and grain sizes, as well as consistent bulk-like transformation behavior.

Award ID(s):
Publication Date:
Journal Name:
Scientific Reports
Nature Publishing Group
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Structural color printings have broad applications due to their advantages of long-term sustainability, eco-friendly manufacturing, and ultra-high resolution. However, most of them require costly and time-consuming fabrication processes from nanolithography to vacuum deposition and etching. Here, we demonstrate a new color printing technology based on polymer-assisted photochemical metal deposition (PPD), a room temperature, ambient, and additive manufacturing process without requiring heating, vacuum deposition or etching. The PPD-printed silver films comprise densely aggregated silver nanoparticles filled with a small amount (estimated <20% volume) of polymers, producing a smooth surface (roughness 2.5 nm) even better than vacuum-deposited silver films (roughness 2.8 nm) at ~4 nm thickness. Further, the printed composite films have a much larger effective refractive indexn(~1.90) and a smaller extinction coefficientk(~0.92) than PVD ones in the visible wavelength range (400 to 800 nm), therefore modulating the surface reflection and the phase accumulation. The capability of PPD in printing both ultra-thin (~5 nm) composite films and highly reflective thicker film greatly benefit the design and construction of multilayered Fabry–Perot (FP) cavity structures to exhibit vivid and saturated colors. We demonstrated programmed printing of complex pictures of different color schemes at a high spatial resolution of ~6.5 μm by three-dimensionally modulating the top composite film geometries andmore »dielectric spacer thicknesses (75 to 200 nm). Finally, PPD-based color picture printing is demonstrated on a wide range of substrates, including glass, PDMS, and plastic, proving its broad potential in future applications from security labeling to color displays.

    « less
  2. Multilayered thermoelectric Sn/Sn+SnO2 thin films were prepared using KJL DC/RF magnetron sputtering system under Ar gas plasma on the SiO2 substrates. The thicknesses of the fabricated thin films were found using Filmetrics UV thickness measurement system. The fabricated thin films were annealed at different temperatures for one hour to tailor the thermoelectric properties. In this study, unannealed, annealed at 150 and 300 °C samples were characterized using Thermo Fisher XPS system brought to the Alabama A&M University by the NSF-MRI support. X-ray Photoelectron Spectroscopy (XPS), also known as Electron Spectroscopy for Chemical Analysis (ESCA) is a type of analysis used for characterization of various surface materials. XPS is mostly known for the characterization of thin films - which are coatings that have been deposited onto a substrate and may be comprised of many different materials to alter or enhance the substrate’s performance. XPS analysis provides information for composition, chemical states, depth profile, imaging and thickness of thin film. This paper focuses on the application of XPS techniques in thin film research for Sn/Sn+SnO2 multilayered thermoelectric system and SiO2 substrates annealed at different temperatures. Since SiO2 substrates were used during the deposition of the multilayer thin films, we would like tomore »perform detailed XPS studies on the SiO2 substrates. SiO2 substrates is being used with many researchers, this manuscript will be good reference for the researchers using SiO2 substrates. Thermal treatment of the substrates and the multilayered thin films has caused some changes of the XPS characterization including binding energy, depth profile, peak value and FWHM. The treatment effects were discussed and compared to each other.« less
  3. Heterogeneous bonding between metals and ceramics is of significant relevance to a wide range of applications in the fields of industry, defense, and aerospace. Metal/ceramic bonding can be used in various specific part applications such as vacuum tubes, automotive use of ceramic rotors, and rocket igniter bodies. However, the bonding of ceramic to metal has been challenging mainly due to (1) the low wettability of ceramics, on which the adhesion of molten adhesive bonders is limited and (2) the large difference between the coefficients of thermal expansion (CTE) of the two dissimilar bonded materials, which develops significant mechanical stresses at the interface and potentially leads to mechanical failures. Vapor-phase deposition is a widely used thin film processing technique in both academic research laboratories and manufacturing industries. Since vapor phase coatings do not require wettability or hydrophobicity, a uniform and strongly adherent layer is deposited over virtually any substrate, including ceramics. In this presentation, we report on the effect of vapor phase-deposited interfacial metal layers on the mechanical properties of bonding between stainless steel and Zerodur (lithium aluminosilicate-based glass ceramic). Direct-current magnetron sputtering was utilized to deposit various thin interfacial layers containing Ti, Cu, or Sn. In addition, to minimize themore »unfavorable stress at the bonded interface due to the large CTE difference, a low temperature allow solder, that can be chemically and mechanically activated at temperatures of approximately 200 °C, was used. The solder is made from a composite of Ti-Sn-Ce-In. A custom-built fixture and universal testing machine were used to evaluate the bonding strength in shear, which was monitored in-situ with LabView throughout the measurement. The shear strength of the bonding between stainless steel and Zerodur was systematically characterized as a function of interfacial metal and metal processing temperature during sputter depositions. Maximum shear strength of the bonding of 4.36 MPa was obtained with Cu interfacial layers, compared to 3.53 MPa from Sn and 3.42 MPa from Ti adhesion promoting layers. These bonding strengths are significantly higher than those (~0.05 MPa) of contacts without interfacial reactive thin metals. The fracture surface microstructures are presented as well. It was found that the point of failure, when Cu interfacial layers were used, was between the coated Cu film and alloy bonder. This varied from the Sn and Ti interfacial layers where the main point of failure was between the interfacial film and Zerodur interface. The findings of the effect of thin adhesion promoting metal layers and failure behaviors may be of importance to some metal/ceramic heterogeneous bonding studies that require high bonding strength and low residual stresses at the bonding interface. The authors gratefully acknowledge the financial support of the Improvement of Measurement Standards and Technology for Mechanical Metrology (Grant No. 20011028) by KRISS.« less
  4. Bi 3 MoM T O 9 (BMoM T O; M T , transition metals of Mn, Fe, Co and Ni) thin films with a layered supercell structure have been deposited on LaAlO 3 (001) substrates by pulsed laser deposition. Microstructural analysis suggests that pillar-like domains with higher transition metal concentration ( e.g. , Mn, Fe, Co and Ni) are embedded in the Mo-rich matrix with layered supercell structures. The layered supercell structure of the BMoM T O thin films accounts for the anisotropic multifunctionalities such as the magnetic easy axis along the in-plane direction, and the anisotropic optical properties. Ferroelectricity and ferromagnetism have been demonstrated in the thin films at room temperature, which confirms the multiferroic nature of the system. By varying the transition metal M T in the film, the band gaps of the BMoM T O films can be effectively tuned from 2.44 eV to 2.82 eV, while the out-of-plane dielectric constant of the thin films also varies. The newly discovered layered nanocomposite systems present their potential in ferroelectrics, multiferroics and non-linear optics.
  5. Spin-to-charge conversion and the reverse process are now critically important physical processes for a wide range of fundamental and applied studies in spintronics. Here, we experimentally demonstrate effective spin-to-charge conversion in thermally evaporated chromium thin films using the longitudinal spin Seebeck effect (LSSE). We present LSSE results measured near room temperature for Cr films with thicknesses from 2 to 11 nm, deposited at room temperature on bulk polycrystalline yttrium-iron-garnet (YIG) substrates. Comparison of the measured LSSE voltage, [Formula: see text], in Cr to a sputtered Pt film at the same nominal thickness grown on a matched YIG substrate shows that both films show comparably large spin-to-charge conversion. As previously shown for other forms of Cr, the LSSE signal for evaporated Cr/YIG shows the opposite sign compared to Pt, indicating that Cr has a negative spin Hall angle, [Formula: see text]. We also present measured charge resistivity, [Formula: see text], of the same evaporated Cr films on YIG. These values are large compared to Pt and comparable to [Formula: see text]-W at a similar thickness. Non-monotonic behavior of both [Formula: see text] and [Formula: see text] with film thickness suggests that spin-to-charge conversion in evaporated Cr, which we expect has a differentmore »strain state than previously investigated sputtered films, could be modified by spin density wave antiferromagnetism in Cr.

    « less