Novel Metal Silicide Thin Films by Design via Controlled Solid-State Diffusion

Abstract

: In the quest to accelerate the discovery and deployment of new materials with ideal and tailored properties, synthesis via solid-state diffusion holds particular promise as it allows the crystal structure and stoichiometry of thin films to be controlled independently of the deposition method. However, the kinetics and the quality of the resulting materials remain relatively unexplored. Here we demonstrate both source-limited and kinetically-limited solid-state diffusion as novel routes to tune the stoichiometry of platinum silicide (Pt x Si) thin films, representative of metal silicides which have attractive mechanical and electronic properties. Using in situ heating inside a transmission electron microscope (TEM) while performing electron diffraction, we show that both routes lead to stoichiometrically-controlled formation of Pt x Si (x = 1, 2, 3) thin films with high phase selectivity, revealing the crystal structure and formation sequence for each phase. The Pt x Si formation process from sequentially-deposited layers of platinum (Pt) and amorphous silicon (a-Si) significantly differs from the Pt/single-crystal silicon (sc-Si) case, allowing the formation of Pt 3 Si thin films for the first time.

Large-area synthesis of high-quality monolayer 1T’-WTe 2 flakes

“…Background subtraction was performed using the Shirley–Sherwood method. Examples of XPS analysis performed with this spectrometer can be found in references [49, 50]. The quantitative evaluation of the XPS data was based on integrating the intensity of the W 4 d 5/2 and Te 3 d 5/2 peaks by taking the atomic sensitivity factors for those signals into account.…”

Synthesis and thermal stability of Pt3Si, Pt2Si, and PtSi films grown by e-beam co-evaporation

“…As a result, there are few reports of synthesizing large regions of the Pt 3 Si phase and reports on its electronic properties are accordingly scarce. Streller et al [74,36] recently demonstrated that by replacing single crystalline (sc-) or polycrystalline (poly-) Si with a sputtered amorphous Si precursor film, solid-state silicide reaction of a bilayer of aSi/Pt yields mixed-phase, sub-50 nm thick films that predominantly consist of a Pt 3 Si phase. Si and Pt were sequentially sputtered in various Si:Pt thickness ratios onto PELCO 50 nm silicon nitride (Si 3 N 4 ) support TEM grids and annealed to form mixed films either primarily consisting of Pt 3 Si, Pt 2 Si, or PtSi via source-limited (i.e., Silimited) or kinetically limited (i.e., time/temperature-limited at fixed temperature/time) controlled solid-state diffusion.…”

Mechanisms of Contact, Adhesion, and Failure of Metallic Nanoasperities in the Presence of Adsorbates: Toward Conductive Contact Design

“…Electromechanical switches generically operate by mechanically pushing two surfaces into contact to close an electrical circuit and pulling the surfaces apart to open it. Such switches are of interest for scales ranging from the macro- to micro- ,− and, more recently, nanoscales. − ,− Since the opening and closing of such contacts occurs repeatedly, the effects of adsorbates are compounded and dynamic. Interestingly, the mechanical and/or electrical stressing of the system commonly enhances reactions between adsorbates, leading to the formation of cross-linked contaminant or “tribopolymer” films − and eventual failure by preventing the closing of the electrical circuit when in contact.…”