Surfaces and Interfaces of Nanoscale Silicon Materials

Abstract

Surfaces and interfaces play a critical role in determining properties and functions of nanomaterials, in many cases dominating bulk properties, owing to the large surface-and interface-area-to-volume ratio. Using Si nanomembranes, a well-controlled two-dimensional single-crystalline semiconductor, as a prototype system, we discuss how surfaces and interfaces influence electrical transport properties at the nanoscale. We show that electronic conduction in Si nanomembranes is not determined by bulk dopants but by the interplay of surface and interface electronic structures with the "bulk" band structure of the thin Si membrane. Additionally, we describe our recent experimental results on the control of highly ordered molecular structures on Si surfaces, which is of intense interest for the integration of ordered organic thin films in silicon-based electronics. This could also potentially lead to the rational design of Si nanostructures with controlled properties through regulation of the surface chemistry.

Nanometre-thick single-crystalline nanosheets grown at the water–air interface

“…Intentional p -type doping of ZnO has been a contentious topic, although few successful doping strategies have yielded fairly stable p -type conductivity 26 27 28 29 . Given the few nanometre thickness, it is reasonable to assume the surface adsorbed molecules might have had profound influence on the electrical properties 30 31 . To further understand the atomistic structures and electronic properties of the 2D ZnO, we theoretically investigate a ∼1-nm-thick ZnO(0001) slab through density functional theory calculations (see Supplementary Methods ) using Heyd–Scuseria–Ernzerhof functional.…”

Salt‐Assisted Synthesis of 2D Materials

“…It was assumed that the surface adsorbed molecules had profound influence on the electrical properties. [ 73–74 ] However, most TMOs have a nonlayered crystal structure and the lack of universal and mass production technology has hindered their practical application. [ 16 ] Salts with a large lateral size and numerous crystal structures can confine the synthesis of nanomaterials with 2D morphology and special crystal structures based on the hard template effect and lattice matching mechanism.…”

Growth of Metal Phthalocyanine on Deactivated Semiconducting Surfaces Steered by Selective Orbital Coupling

“…1(d)) of a highly ordered ZnPc domain to represent individual ZnPc molecules with tilted orientation. For CuPc, although it preserves the identical molecular orientation and packing motif as ZnPc [12][13][14], a notable degradation of the film quality is observed where a significant amount of gap defects and shifts in the molecular packing occur within the molecular domains ( Fig. 1(b) and (e)) [39].…”

“…Intriguingly, for the CoPc growth, we find that the molecules predominantly lie flat on the surface while the molecular patches with tilted con-figuration only emerge and are sparsely dispersed among the flat-lying molecules when the coverage is increased above a certain threshold, as illustrated in Fig This is further corroborated by the difference observed in the initial molecular adsorption on the Si(111)-B surface. For ZnPc molecules, once deposited they are able to diffuse rapidly across the Si terraces and nucleate at the energetically favorable Si step edge sites [12][13][14][15].…”

“…As a result, with increasing molecular coverage the energy gain from the intermolecular interaction can be fully achieved on a metallic surface due to its flat potential energy landscape, driving the formation of close-packed flat-lying MPc molecular structures on the surface [17,19,22]. However, the significant potential corrugation of Si (111) (Table I), it is energetically more beneficial to maximize the π-π intermolecular attraction at a cost of a portion of the surface adsorption energy, leading to a structural transition to a tilted molecular configuration [12][13][14][15]. However, for CoPc, the molecule-Si binding energy is significantly larger than the intermolecular binding energy (Table I), enabling the majority of the molecules to adopt the flat-lying orientation ( Fig.…”