Abstract
The unique features of dynamic shadowing growth (DSG) in structural and compositional design of nanomaterials are discussed. Their recent applications in energy storage, fuel cell, and solar energy conversion have been reviewed briefly. Future directions for applying DSG nanostructures in renewable energy applications are presented.
Highlights
Dynamic shadowing growth (DSG) or glancing angle deposition (GLAD) is a versatile nanofabrication technique based on the self-shadowing effect during a thin-film deposition process (Young and Kowal, 1959; Motohiro and Taga, 1989; Robbie and Brett, 1997; Robbie et al, 1998; Messier et al, 2000; He and Zhao, 2011)
For a conventional physical vapor or chemical vapor thinfilm deposition process, as long as the incident vapor possesses certain directionality and there are protrusions on the substrate, as shown in Figure 1A, a self-shadowing effect will occur, i.e., there will be an area around the protrusion opposite to the incident vapor direction that cannot receive vapor to grow further
Many physical vapor deposition methods working in high vacuum or ultrahigh vacuum, such as thermal evaporation (Beydaghyan et al, 2008), electron beam evaporation (Zhao et al, 2002a,b), and molecular beam epitaxy (Robbie et al, 2004), can be used to generate pronounced self-shadowing effects due to the intrinsic directionality occurring at long vapor striking distances
Summary
Any conventional thin-film deposition technique could naturally exhibit the self-shadowing effect due to the uneven surface features formed thermodynamically during deposition and the directionality of the local incident vapor. Once the self-shadowing effect becomes the dominant growth mechanism, by combining substrate rotation together with different thin-film growth configurations, such as multilayer deposition and co-deposition, one can alter the direction of the incident vapor with respect to the shadowing centers to generate nanostructures with different morphology and composition.
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