Low-Temperature Growth of Bismuth Thin Films with (111) Facet on Highly Oriented Pyrolytic Graphite

Abstract

The epitaxial growth of artificial two-dimensional metals at interfaces plays a key role in fabricating heterostructures for nanoelectronics. Here, we present the growth of bismuth nanostructures on highly oriented pyrolytic graphite (HOPG) under ultrahigh vacuum (UHV) conditions, which was investigated thoroughly by a combination of scanning tunneling microscopy (STM), ultraviolet photoemission spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED). It was found that (111)-oriented bilayers are formed on as-cleaved high-quality HOPG at 140 K, which opens the possibility of making Bi(111) thin films on a semimetal, and this is a notable step forward from the earlier studies, which show that only Bi(110) facets could be formed at ultrathin thickness at room temperature. XPS investigation of both C 1s and Bi 4f reflects the rather weak bonding between the Bi film and the HOPG substrate and suggests a quasi layer-by-layer growth mode of Bi nanostructures on HOPG at low temperature. Moreover, the evolution of the valence band of the interface is recorded by UPS, and a transition from quantum well states to bulk-like features is observed at varying film thickness. Unlike semimetallic bulk bismuth, ultrathin Bi(111) films are expected to be topological insulators. Our study may therefore pave the way for the generation of high quality Bi nanostructures to be used in spin electronics.

Exploring the Adsorption Mechanism of Tetracene on Ag(110) by STM and Dispersion-Corrected DFT

“…In short, the formation of patterned molecular nanostructures by the adsorption of π-conjugated tetracene molecules on Ag(110) shows a delicate balance between the inter-molecular and moleculesubstrate interaction, and the key role of vdW dispersion force within intermolecular interaction in mediating the tetracene molecular network on Ag(110), in good agreement with literature reports of aromatic molecules adsorbed on coinage metal surfaces [30][31][32]. While the periodical brightness variation of molecular feature in STM experiments has been satisfactorily explained with the longrange vdW dispersion interaction properly considered, this study demonstrates that the adsorption site is considerably important at describing the self-assembled tetracene on Ag(110) and shed further insights onto previous reports of molecular self-assembly [16,[46][47][48]. More importantly, herein, the fabrication of periodical molecular pattern on solid substrate could be utilized as a constructive approach to prepare functional template or platform for engineering nanostructures towards molecular electronics and nanodevices.…”

Controlling the growth of Bi(110) and Bi(111) films on an insulating substrate

“…Especially the spin-momentum locked surface states of topological insulating Bi films [13][14][15][16], make them very attractive candidates for spintronic devices. To develop and optimize topological insulators (TIs) towards applications, thin films of high quality are a necessity, as otherwise the exotic electronic properties are hampered by bulk conduction [7,17,18].…”

“…This choice of substrate is also very beneficial for practical applications, as the interface between film and insulating substrate, expected to reveal topological states, will also be protected from influencing oxidation effects arising from ambient exposure in technological applications [19]. The growth of Bi has been extensively studied on Si(111) [20][21][22][23][24][25][26][27][28][29] and HOPG [13,[30][31][32] as well as other surfaces [3,4,12,[33][34][35][36][37][38], resulting in fabrication of films with a range of different morphologies, orientations, and strain. The fabrication of Bi films has attracted considerable interest in recent years, as their controlled growth, with focus on morphology and crystallographic orientation, on semiconductor and oxide surfaces is not a trivial task.…”

Computational scanning tunneling microscope image database

“…We simulate computational STM images of 716 exfoliable materials (E f < 200 meV/atom) using the Tersoff-Hamann approach. We compare computational STM images with those from experiments for graphene 16 , 2H-MoS 2 17 , 2H-NbSe 2 18 , 2H-WSe 2 19 , 1T'-WTe 2 20 , FeSe 21 , black-P 22,23 , SnSe 24 , Bismuth 64,65 . We chose these systems because we could find well-characterized experimental images in the literature.…”