Abstract:Nanoscale superlattices represent a compelling platform for designed materials as the specific identity and spatial arrangement of constituent layers can lead to tunable properties. A number of kinetically stabilized, nonepitaxial superlattices with almost limitless structural tunability have been reported in telluride and selenide chemistries but have not yet been extended to sulfides. Here, we present SnS-TaS 2 nanoscale superlattices with tunable layer architecture. Layered amorphous precursors are prepared… Show more
“…Nucleation occurs at multiple sites within the precursors because any amorphous region formed during deposition onto the nominally room temperature substrates is supersaturated with respect to the crystalline constituents. Several recent reports discuss methods to control nucleation rates/sites, which could be used to reduce domain boundary and layer step defects. ,, Local variations in composition will always occur; therefore, controlling layer step defects would require controlling processing conditions and diffusion rates. , Our results also suggest that it should be possible to control the type and density of defects in these heterostructures by controlling the precursor structure and processing conditions to influence properties. Defects are desirable in some cases, such as reduced lattice thermal conductivity, which can be improved by increasing dislocation densities and decreasing grain size .…”
Section: Discussionmentioning
confidence: 70%
“…Several recent reports discuss methods to control nucleation rates/sites, which could be used to reduce domain boundary and layer step defects. 6,31,32 Local variations in composition will always occur; therefore, controlling layer step defects would require controlling processing conditions and diffusion rates. 18,33 Our results also suggest that it should be possible to control the type and density of defects in these heterostructures by controlling the precursor structure and processing conditions to influence properties.…”
Layered van der Waals heterostructures provide extraordinary opportunities for applications such as thermoelectrics and allow for tunability of optical and electronic properties. The performance of devices made from these heterostructures will depend on their properties, which are sensitive to the nanoarchitecture (constituent layer thicknesses, layer sequence, etc.). However, performance will also be impacted by defects, which will vary in concentration and identity with the nanoarchitecture and preparation conditions. Here, we identify several types of defects and propose mechanisms for their formation, focusing on compounds in the ([SnSe] 1+δ ) m (TiSe 2 ) n system prepared using the modulated elemental reactants method. The defects were observed by atomic resolution high-angle annular dark-field scanning transmission electron microscopy and can be broadly categorized into those that form domain boundaries as a result of rotational disorder from the self-assembly process and those that are layer-thickness-related and result from local or global deviations in the amount of material deposited. Defect type and density were found to depend on the nanoarchitecture of the heterostructure. Categorizing the defects provides insights into defect formation in these van der Waals layered heterostructures and suggests strategies for controlling their concentrations. Strategies for controlling defect type and concentration are proposed, which would have implications for transport properties for applications in thermoelectrics.
“…Nucleation occurs at multiple sites within the precursors because any amorphous region formed during deposition onto the nominally room temperature substrates is supersaturated with respect to the crystalline constituents. Several recent reports discuss methods to control nucleation rates/sites, which could be used to reduce domain boundary and layer step defects. ,, Local variations in composition will always occur; therefore, controlling layer step defects would require controlling processing conditions and diffusion rates. , Our results also suggest that it should be possible to control the type and density of defects in these heterostructures by controlling the precursor structure and processing conditions to influence properties. Defects are desirable in some cases, such as reduced lattice thermal conductivity, which can be improved by increasing dislocation densities and decreasing grain size .…”
Section: Discussionmentioning
confidence: 70%
“…Several recent reports discuss methods to control nucleation rates/sites, which could be used to reduce domain boundary and layer step defects. 6,31,32 Local variations in composition will always occur; therefore, controlling layer step defects would require controlling processing conditions and diffusion rates. 18,33 Our results also suggest that it should be possible to control the type and density of defects in these heterostructures by controlling the precursor structure and processing conditions to influence properties.…”
Layered van der Waals heterostructures provide extraordinary opportunities for applications such as thermoelectrics and allow for tunability of optical and electronic properties. The performance of devices made from these heterostructures will depend on their properties, which are sensitive to the nanoarchitecture (constituent layer thicknesses, layer sequence, etc.). However, performance will also be impacted by defects, which will vary in concentration and identity with the nanoarchitecture and preparation conditions. Here, we identify several types of defects and propose mechanisms for their formation, focusing on compounds in the ([SnSe] 1+δ ) m (TiSe 2 ) n system prepared using the modulated elemental reactants method. The defects were observed by atomic resolution high-angle annular dark-field scanning transmission electron microscopy and can be broadly categorized into those that form domain boundaries as a result of rotational disorder from the self-assembly process and those that are layer-thickness-related and result from local or global deviations in the amount of material deposited. Defect type and density were found to depend on the nanoarchitecture of the heterostructure. Categorizing the defects provides insights into defect formation in these van der Waals layered heterostructures and suggests strategies for controlling their concentrations. Strategies for controlling defect type and concentration are proposed, which would have implications for transport properties for applications in thermoelectrics.
“…This experimental workflow at NREL has been benchmarked against other laboratories. 14 , 15 Other publications demonstrate the range of materials chemistries (e.g., oxides, 16 nitrides, 17 chalcogenides, 18 Li-containing materials, 19 intermetallics) 20 and properties (e.g., optoelectronic, 21 electronic, 22 piezoelectric, 23 photoelectrochemical, 24 thermochemical) 25 to which these HTE methods have been applied. Figure 2 Experimental and data workflows for high-throughput materials research The workflow starts with (A) experiment design, then material samples are (B) produced, (C) treated, (D) measured, and (E) stored in archives.…”
Section: Resultsmentioning
confidence: 99%
“…This experimental workflow at NREL has been benchmarked against other laboratories. 14,15 Other publications demonstrate the range of materials chemistries (e.g., oxides, 16 nitrides, 17 chalcogenides, 18 Li-containing materials, 19 intermetallics) 20 and properties (e.g., optoelectronic, 21 electronic, 22 piezoelectric, 23 photoelectrochemical, 24 thermochemical) 25 to which these HTE methods have been applied.…”
Summary
The High-Throughput Experimental Materials Database (HTEM-DB,
htem.nrel.gov
) is a repository of inorganic thin-film materials data collected during combinatorial experiments at the National Renewable Energy Laboratory (NREL). This data asset is enabled by NREL's Research Data Infrastructure (RDI), a set of custom data tools that collect, process, and store experimental data and metadata. Here, we describe the experimental data flow from the RDI to the HTEM-DB to illustrate the strategies and best practices currently used for materials data at NREL. Integration of the data tools with experimental instruments establishes a data communication pipeline between experimental researchers and data scientists. This work motivates the creation of similar workflows at other institutions to aggregate valuable data and increase their usefulness for future machine learning studies. In turn, such data-driven studies can greatly accelerate the pace of discovery and design in the materials science domain.
“…However, although many known misfit compounds are in the sulfide space, the fabrication of kinetically controlled sulfide superlattices is still challenging due to the experimental challenges during sulfur deposition. Very recently, Roberts et al [116] demonstrated the preparation of nanoscale SnS-TaS 2 superlattices with independent sulfur source from designed amorphous precursors, which were deposited by using a radiofrequency (RF) co-sputtering technique. It is the first report of artificial sulfide misfit superlattices with kinetically controlled architectures (Figure 6B).…”
Two-dimensional transition metal dichalcogenides (2D-TMDs) have sparked immense interest, resulting from their unique structural, electronic, mechanical, and thermal properties. The band structures, effective mass, electron mobility, valley degeneracy, and the interactions between phonons and heat transport properties in 2D-TMDs can be efficiently tuned via various approaches. Moreover, the interdependent electrical and thermal conductivity can be modulated independently to facilitate the thermoelectric (TE)-based energy conversion process, which enables optimization of TE properties and promising TE applications. This article briefly reviews the recent development of TE properties in 2D-TMDs. First, the advantages of 2D-TMDs for TE applications are introduced. Then, the manipulations of electrical and thermal transport in 2D-TMDs are briefly discussed, including various influencing factors such as thickness effect, structural defects, and mechanical strain. Finally, the recent advances in the study of electrical, thermal transport, and TE properties of 2D-TMDs, TE-related applications, the challenges, and the future prospects in this field are reviewed.
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