Silicon Nanomembranes: Fundamental Science and Applications

Book Preface

The origins of nanoscience and nanotechnology can be traced in large part, atleast  from the standpoint of material sciences, to seminal research on cadmium selenide nanocrystals [1] and spherical fullerenes [2]. Studies of these and other related zero-dimensional (0D) materials soon expanded to one-dimensional (1D) nanostructures, such as nanowires and nanotubes [3–5]. Although such 1D nanostructures are comparatively easy to manipulate and to interface with contact metallization, building general classes of semiconductor devices at interesting levels of integration with individual wires and tubes is challenging, perhaps prohibitively so, due to lack of means for uniform synthesis and assembly. More recent activities in electronic nanomaterials explore, as an alternative, ultrathin membranes or two-dimensional (2D) layers of semiconductors, sometimes referred to generically as semiconductor nanomembranes (NMs) [6–14]. The 2D, planar geometries facilitate integration into device systems with realistic pathways to manufacturing; they also afford easy formation of electrical contacts and natural compatibility with well-developed thin-film growth and processing technologies.

Many classes of advanced materials can be physically isolated or chemically synthesized in the form of NMs, including organics such as graphene and 2D polymers, and inorganics such as silicon, germanium, gallium arsenide (GaAs), gallium nitride, and transition-metal dichalcogenides [6–14]. Existing transfer printing approaches allow the manipulation of NMs with thicknesses down to the atomic level and with lateral dimensions of up to dozens of inches [7, 11–13]. Recent research efforts establish strategies for deforming NMs into complex, three dimensional (3D) configurations, conforming them onto tissue-like curvilinear surfaces, and deterministic assembly of them onto substrates of interest with high fidelity in positions and orientations [12, 13]. Many NM-based advanced functional device systems have been realized, demonstrating high operating performance, unique stretchability and flexibility, 3D layouts, physical disappearance at programmed rates, and many other attractive features, which are hardly achievable in their related bulk counterparts, or with 0D and 1D nanomaterials [12, 13].

Single-crystal silicon NMs are particularly appealing because of capabilities in high-quality synthesis over large areas and with precise thicknesses at relatively low cost in the nanometer regime; they are also naturally compatible with conventional fabrication techniques and can be fully exploited in unique, high-performance electronic, and optoelectronic systems [12, 13]. In addition, the nanoscale thicknesses of silicon NMs enable many attractive features, which are unavailable in their bulk counterparts, such as high flexibility due to the linear decrease of bending strains with thicknesses, fast dissolution in biofluids because of their nanoscale geometries, splitting of the conduction band valleys induced by electronic confinement effects, andmanipulation of heat flow allowed by phonon confinement effects [13]. The following sections describe recent research advancements in silicon NMs including synthesis, assembly, and device integration.