Amorphous sulfide heterostructure precursors prepared by radio frequency sputtering

Abstract

Two-dimensional sulfides and their heterostructures have emerged as potentially useful materials for technological applications. Controllable self-assembly of interleaved crystalline heterostructures from designed thin-film precursors has been demonstrated in selenide and telluride chemical systems, but not yet in sulfide chemistries. Preparing such amorphous sulfide heterostructure precursors is a necessary first step toward this goal. Here, deposition of thin-film amorphous precursors for layered sulfide heterostructures by RF sputtering is presented on the example of SnS-MoS2. A calibration process specific to the mechanisms of RF sputtering from sulfide and disulfide compound targets is established. Precursor film structure and composition are confirmed via x-ray reflectivity and Rutherford backscattering measurements. Local nanostructure and composition are also examined by electron microscopy and electron energy loss spectroscopy.

Synthesis of Tunable SnS-TaS2 Nanoscale Superlattices

“…The shutters above each sputter plume are sequentially activated such that layered precursors locally contain the precise number of atoms to nucleate monolayers, similar to our previous protocol. 24 Further experimental details can be found in the Methods section. Signals from quartz crystal microbalances placed above each cation source during preparation of a [(SnS) 1+δ ] 3 (TaS 2 ) 1 precursor film are shown alongside a schematic of the final heterostructure in Figure 1d.…”

“…39−42 As described in our previous work, precursor films can be prepared such that thickness gradients of SnS and Ta are orthogonal to one another on a sample surface. 24 Compositional and structural characterization of a sample prepared in this way is shown in Figure 4, showing systematic changes across the sample surface. Relative XRF signal intensities from Sn and Ta are plotted in Figure 4a, showing an increasing fraction of Sn, and thus SnS, moving up the rows of the sample.…”

“…Precursor films are deposited in an RF sputter chamber using a calibration procedure described in our previous work, with some modification. 24 An elemental Ta and compound SnS target are used as a source of cations in the film. Supplemental sulfur is provided by an RF solids cracker from Oxford Applied Research.…”

“…We previously reported a framework for the preparation of sulfide films with controlled layer thicknesses and compositions using radio frequency (RF) co-sputtering, a technique which mitigates issues in sulfide-based depositions. 24 While an important first step, the layered precursor films reported there lacked independent control of sulfur content and thus were unable to self-assemble into crystalline products.…”

COMBIgor: Data-Analysis Package for Combinatorial Materials Science

“…This newer version has already been used for data analysis and preparation of figures in several recent manuscripts. [49][50][51][52][53][54] Based on this history, COMBIgor brings the experience of almost 20 years of software development at NREL for handling and processing combinatorial data. Additionally, it has been integrated with public data repositories to enable cutting-edge data transparency and openness.…”