Luigi Colombo

Luigi Colombo
University of Texas at Dallas | UTD · Department of Materials Science & Engineering

Doctor of Philosophy

About

220
Publications
78,244
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
41,939
Citations

Publications

Publications (220)
Article
Full-text available
Ferroelectric domain walls naturally form at nanoscale interfaces of polar order leading to electronic properties distinct from the bulk that can also be electrically programmed. These nanoscale features currently are being actively explored for the development of agile, low‐energy electronics for applications in memory, logic, and brain‐inspired n...
Book
Defects in Two-Dimensional Materials addresses the fundamental physics and chemistry of defects in 2D materials and their effects on physical, electrical and optical properties. The book explores 2D materials such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMD). This knowledge will enable scientists and engine...
Article
This article proposes a novel design approach for the fabrication of lateral Schottky barrier diodes (SBD) using a wide bandgap oxide semiconductor on silicon. Structural and electrical properties of the fabricated device are reported and compared with published data. The metal–insulator–semiconductor (MIS) Schottky barrier is realized between the...
Article
There is a constant need for Hall-effect magnetic sensors with lower noise and lower offset for the high accuracy analog applications driven primarily by industrial and automotive markets, for example, high dynamic range current sensing for battery management in electric vehicles. Graphene-based Hall sensors (GHSs) demonstrate low thermal noise due...
Article
We review recent developments on the synthesis and properties of two-dimensional materials which, although being mainly of an sp2 bonding character, exhibit highly disordered, non-uniform and structurally random morphologies. The emergence of such class of amorphous materials, including amorphous graphene and boron nitride, have shown superior prop...
Article
Corrosion of metals in atmospheric environments is a worldwide problem in industry and daily life. Traditional anticorrosion methods including sacrificial anodes or protective coatings have performance limitations. Here, we report atomically thin, polycrystalline few-layer graphene (FLG) grown by chemical vapor deposition as a long-term protective...
Article
Hexagonal boron nitride (h-BN) has been considered a promising dielectric for two-dimensional (2D) material-based electronics due to its atomically smooth and charge-free interface with an in-plane lattice constant similar to that of graphene. Here, we report atomic layer deposition of boron nitride (ALD-BN) using BCl3 and NH3 precursors directly o...
Article
Full-text available
We present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures. We adopt a 'hands-on' approach, providing practical details and procedures as derived from literature as well as from the authors' experience, in order to enable the reader to reproduc...
Article
Full-text available
Resistive switching (RS) induced by electrical bias is observed in numerous materials, including 2D hexagonal boron nitride (hBN), which has been used in resistive random access memories (RRAMs) in recent years. For practical high‐density, cross‐point memory arrays, compared with bipolar memories, nonpolar (or unipolar) devices are preferable in te...
Article
The ferroelectric (FE) properties of 10-nm-thick Hf0.5Zr0.5O2 (HZO) films deposited by an atomic layer deposition technique were improved by adopting O3 as an oxygen source instead of H2O. All HZO films were annealed at 400 °C for 1 min in an N2 atmosphere after TiN top electrode deposition. Regardless of the oxygen source, the HZO films exhibited...
Article
Full-text available
The pervasiveness of information technologies is generating an impressive amount of data, which need to be accessed very quickly. Nonvolatile memories (NVMs) are making inroads into high‐capacity storage to replace hard disk drives, fuelling the expansion of the global storage memory market. As silicon‐based flash memories are approaching their fun...
Article
Increasing interest in the development of alternative energy storage technologies has led to efforts to improve the energy density of dielectric capacitors with high power density. However, dielectric polymer materials still have low energy densities due to their low dielectric constant, while Pb-based materials are limited by environmental issues...
Article
Chemical vapor deposition of 2D materials has been an active area of research in recent years because it is a scalable process for obtaining thin films that can be used to fabricate devices. The growth mechanism for hexagonal boron nitride (h-BN) on metal catalyst substrates has been described to be either surface energy driven or diffusion driven....
Article
In this letter, the ferroelectric (FE) properties of 5-nm-thick Hf0.5Zr0.5O2 (HZO) films deposited by atomic layer deposition have been investigated. By reducing the HZO film thickness to 5 nm, low-voltage operation (1.0 V) of the HZO-based capacitor was achieved while maintaining a remnant polarization (Pr) of about 10 μC/cm² (i.e., 2Pr of 20 μC/c...
Article
Mass production of large, high-quality single-crystalline graphene is dependent on a complex coupling of factors including substrate material, temperature, pressure, gas flow, and the concentration of carbon and hydrogen species. Recent studies have shown that the oxidation of the substrate surface such as Cu before the introduction of the C precur...
Article
Two-dimensional materials have shown great promise for implementation in next-generation devices, however, controlling the film thickness during epitaxial growth remains elusive and must be fully understood before wide scale industrial application. Currently, uncontrolled multilayer growth is frequently observed, and not only does this growth mode...
Article
Full-text available
In the version of this Perspective originally published, in the email address for the author Giuseppe Iannaccone, the surname was incorrectly given as "innaconne"; this has now been corrected in all versions of the Perspective. Also, an error in the production process led to Figs. 1, 2 and 3 being of low resolution; these have now been replaced wit...
Article
Full-text available
We report on the effect of the Hf0.5Zr0.5O2 (HZO) film thickness on the ferroelectric and dielectric properties using pulse write/read measurements. HZO films of thicknesses ranging from 5 to 20 nm were annealed at 400 °C for 1 min in a nitrogen ambient to be compatible with the back-end of the line thermal budget. As the HZO film thickness decreas...
Article
Full-text available
Quantum engineering entails atom-by-atom design and fabrication of electronic devices. This innovative technology that unifies materials science and device engineering has been fostered by the recent progress in the fabrication of vertical and lateral heterostructures of two-dimensional materials and by the assessment of the technology potential vi...
Article
Full-text available
We report on atomic layer deposited Hf0.5Zr0.5O2 (HZO)-based capacitors which exhibit excellent ferroelectric (FE) characteristics featuring a large switching polarization (45 μC/cm²) and a low FE saturation voltage (∼1.5 V) as extracted from pulse write/read measurements. The large FE polarization in HZO is achieved by the formation of a non-centr...
Article
Full-text available
The limited grain size (<200 nm) for transition metal dichalcogenides (TMDs) grown by molecular beam epitaxy (MBE) reported in the literature thus far is unsuitable for high-performance device applications. In this work, the fundamental nucleation and growth behavior of WSe2 is investigated through a detailed experimental design combined with on-la...
Article
Full-text available
Controlled growth of crystalline solids is critical for device applications, and atomistic modeling methods have been developed for bulk crystalline solids. Kinetic Monte Carlo (KMC) simulation method provides detailed atomic scale processes during a solid growth over realistic time scales, but its application to the growth modeling of van der Waal...
Article
Chemical vapor deposition (CVD) of two-dimensional (2D) hexagonal boron nitride (h-BN) is at the center of numerous studies for its applications in novel electronic devices. However, a clear understanding of the growth mechanism is lacking for its wider industrial adoption on technologically relevant substrates such as SiO2. Here, we demonstrate a...
Article
Full-text available
We show that in a low-pressure chemical vapor deposition (CVD) system, the residual oxygen and/ or air play a crucial role in the mechanism of the growth of hexagonal boron nitride (h-BN) films on Ni foil ‘enclosures’. Hexagonal-BN films grow on the Ni foil surface via the formation of an intermediate boric-oxide (BOx) phase followed by a thermal r...
Article
Chemical vapor deposition (CVD) of two-dimensional (2D) hexagonal boron nitride (h-BN) is at the center of numerous studies for its applications in novel electronic devices. However, a clear understanding of the growth mechanism is lacking for its wider industrial adoption on technologically relevant substrates such as SiO2. Here, we demonstrate a...
Article
Full-text available
The growth of WTe2 thin films by molecular beam epitaxy is demonstrated for the first time on a variety of 2D substrates including MoS2, Bi2Te3, and graphite. We demonstrate that beam interruption of the metal source enables the growth of crystalline WTe2 films in the distorted octahedral (1T') phase. As a result of the van der Waals nature of this...
Article
Full-text available
We present an overview of the electrical, mechanical, and thermal properties of polycrystalline graphene. Most global properties of this material, such as the charge mobility, thermal conductivity, or Young's modulus, are sensitive to its microstructure, for instance the grain size and the presence of line or point defects. Both the local and globa...
Article
Two-dimensional transition metal dichalcogenides (TMDs) are promising low-dimensional materials which can produce diverse electronic properties and band alignment in van der Waals heterostructures. Systematic density functional theory (DFT) calculations are performed for 24 different TMD monolayers and their bilayer heterostacks. DFT calculations s...
Article
The thickness and interfacial geometry of hexagonal boron nitride (hBN) films grown by chemical vapor deposition on polycrystalline nickel foils is studied using low-energy electron microscopy (LEEM). The reflectivity of the electrons, measured over an energy range of 0 - 20 eV, reveals distinct minima and maxima. The measured data is compared with...
Article
Three-dimensional (3D) graphene-based structures combine the unique physical properties of graphene with the opportunity to get high electrochemically available surface area per unit of geometric surface area. Several preparation techniques have been reported to fabricate 3D graphene-based macroscopic structures for energy storage applications such...
Article
Synthesis of graphene films on copper foils is discussed by X. Li, L. Colombo, and R. S. Ruoff on page 6247. Graphene can grow on metal substrates by chemical vapor deposition of hydrocarbons. Hydrocarbons crack on a metal surface, nucleate, grow, and finally merge to form a continuous graphene film. Copper is one of the best candidates for graphen...
Article
The control of domain morphology and defect level of synthesized transition metal dichalcogenides (TMDs) is of crucial importance for their device applications. However, current TMDs synthesis by chemical vapor deposition and molecular beam epitaxy is in an early stage of development, where much of the understanding of the process-property relation...
Article
Over the past decade, graphene has advanced rapidly as one of the most promising materials changing human life. Development of production-worthy synthetic methodologies for the preparation of various types of graphene forms the basis for its investigation and applications. Graphene can be used in the forms of either microflake powders or large-area...
Article
Full-text available
Bernal (AB)-stacked bilayer graphene (BLG) is a semiconductor whose bandgap can be tuned by a transverse electric field, making it a unique material for a number of electronic and photonic devices. A scalable approach to synthesize high-quality BLG is therefore critical, which requires minimal crystalline defects in both graphene layers and maximal...
Article
Despite of the number of existing studies that showcase the promising application of fluorinated graphene in nanoelectronics, the impact of the fluorine bonding nature on the relevant electrical behaviors of graphene devices, especially at low fluorine content, remains to be experimentally explored. Using CF4 as the fluorinating agent, we studied t...
Article
Heterostructures coupling transition metal dichalcogenides (TMDs) and insulating hexagonal boron nitride (h-BN) were grown by molecular beam epitaxy (MBE) demonstrating the unique opportunities for fabricating all 2D heterostructures with the desired band alignments for novel nanoelectronic devices. Structural and chemical characterization of the T...
Article
Full-text available
A resonance Raman study of graphene samples with different [superscript 13]C isotopic concentrations and using different laser excitation energies is presented. The main Raman peaks (D, G, G[superscript *], and 2D) of graphene were measured and the dependence of their frequencies on the isotope atomic mass follows a simple harmonic oscillator relat...
Article
Room temperature X-ray photoelectron spectroscopy (XPS), inductively-coupled plasma mass spectrometry (ICPMS), high resolution Rutherford backscattering spectrometry (HR-RBS), Kelvin probe method, and scanning tunneling microscopy (STM) are employed to study the properties of freshly exfoliated surface of geological MoS2 crystals. Our findings reve...
Article
Transition metal dichalcogenides (TMDs) are being considered for making a variety of electronic and optoelectronic devices such as beyond complementary metal-oxide-semiconductor (CMOS) switches, light-emitting diodes, solar cells, as well as sensors among others. Molybdenum disulfide (MoS2) is the most studied of the TMDs in part because of the ava...
Article
Full-text available
Controlled synthesis of graphite at low temperatures is a desirable process for a number of applications. Here, we present a study on the growth of thin graphite films on polycrystalline Ni films at low temperatures, about 380 °C, using inductively coupled plasma enhanced chemical vapor deposition. Raman analysis shows that the grown graphite films...
Article
Full-text available
We present the room temperature operation of a vertical tunneling field-effect transistor using a stacked double bilayer graphene (BLG) and hexagonal boron nitride heterostructure. The device shows two tunneling resonances with negative differential resistance (NDR). An analysis of the electrostatic potential drop across the heterostructure indicat...
Article
Full-text available
Graphene and related two-dimensional crystals and hybrid systems showcase several key properties that can address emerging energy needs, in particular for the ever growing market of portable and wearable energy conversion and storage devices. Graphene's flexibility, large surface area, and chemical stability, combined with its excellent electrical...
Article
In this work, we demonstrate the growth of HfSe2 thin films using molecular beam epitaxy. The relaxed growth criteria has allowed us to demonstrate layered, crystalline growth without misfit dislocations on other 2D substrates such as highly ordered pyrolytic graphite (HOPG) and MoS2. The HfSe2 thin films exhibit an atomically sharp interface with...
Article
The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option...
Article
Full-text available
We present the science and technology roadmap (STR) for graphene, related two-dimensional (2d) crystals, and hybrid systems, targeting an evolution in technology, with impacts and benefits reaching into most areas of society. The roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research...
Patent
Full-text available
An article of manufacture includes a semiconductor die (110) having an integrated circuit (105) on a first side of the die (110), a diffusion barrier (125) on a second side of the die (110) opposite the first side, a mat of carbon nanotubes (112) rooted to the diffusion barrier (125), a die attach adhesive (115) forming an integral mass with the ma...
Article
Full-text available
We have studied angle dependent magnetoresistance of Bi2Te3 thin film with field up to 9 T over 2–20 K temperatures. The perpendicular field magnetoresistance has been explained by the Hikami-Larkin-Nagaoka theory alone in a system with strong spin-orbit coupling, from which we have estimated the mean free path, the phase coherence length, and the...
Article
Density functional theory calculations are performed to unravel the nature of the contact between metal electrodes and monolayer MoS2. Schottky barriers are shown to be present for a variety of metals with the work functions spanning over 4.2 - 6.1 eV. Except for the p-type Schottky contact with platinum, the Fermi levels in all of the studied meta...
Article
The deposition of ultra-thin metal oxides on graphene is challenging due to the inert nature of the sp2 bonded graphene lattice. The feasibility of e-beam deposition of hafnium and hafnium oxide layers as seeds for further growth by atomic layer deposition on graphene CVD graphene is presented here. It is shown that metallic hafnium deposited in an...
Article
We use a triangular-pulse measurement technique to obtain the hysteretic electrical characteristics of flexible graphene field-effect transistors (GFETs). To minimize charge trapping, the gate-voltage scanning rate was controlled (up to 2 ${rm V}/mu{rm s}$) by varying the triangular-pulse rise and fall times. This method makes it possible to measur...
Article
The presence of grain boundary affects the mechanical strength, thermal dissipation, and charge transport of polycrystalline graphene flakes. There is still a debate on whether the electronic transmission is severely degraded by the grain boundary, especially between simulations and experiments. To address this issue, we performed electrical transp...
Patent
The invention provides a method for manufacturing a semiconductor device that comprises placing a metallic gate layer over a gate dielectric layer where the metallic gate layer has a crystallographic orientation, and re-orienting the crystallographic orientation of the metallic gate layer by subjecting the metallic gate layer to a hydrogen anneal.
Article
The growth of high-quality single crystals of graphene by chemical vapor deposition on copper (Cu) has not always achieved control over domain size and morphology, and the results vary from lab to lab under presumably similar growth conditions. We discovered that oxygen (O) on the Cu surface substantially decreased the graphene nucleation density b...
Article
During chemical-vapor-deposited graphene transfer onto target substrates, a polymer film coating is necessary to provide a mechanical support. However, the remaining polymer residues after organic solvent rinsing cannot be effectively removed by the empirical thermal annealing in vacuum or forming gas. Little progress has been achieved in the past...
Article
Full-text available
Tunnel field effect transistors (TFETs) based on vertical stacking of two dimensional materials are of interest for low-power logic devices. The monolayer transition metal dichalcogenides (TMDs) with sizable band gaps show promise in building p-n junctions (couples) for TFET applications. Band alignment information is essential for realizing broken...
Article
Graphene has been introduced to the electronics community as a potentially useful material for scaling electronic devices to meet low-power and high-performance targets set by the semiconductor industry international roadmap, radio-frequency (RF) devices, and many more applications. Growth and integration of graphene for any device is challenging a...