About
78
Publications
10,131
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
859
Citations
Introduction
Skills and Expertise
Publications
Publications (78)
Thermal sulfurization of ultra-thin Mo-based films represents a promising approach for large-area growth of MoS2. In this paper, we demonstrated that the crystalline quality (domains size and defects density), strain, doping, and light emission properties of monolayer (1L) MoS2 obtained from sputter deposited MoOx films on a c-sapphire substrate ca...
The combination of the unique physical properties of molybdenum disulfide (MoS2) with those of gallium nitride (GaN) and related group-III nitride semiconductors have recently attracted increasing scientific interest for the realization of innovative electronic and optoelectronic devices. A deep understanding of MoS2/GaN interface properties repres...
Metal-oxide-semiconductor (MOS) capacitors with Al2O3 as a gate insulator are fabricated on cubic silicon carbide (3C-SiC). Al2O3 is deposited both by thermal and plasma-enhanced Atomic Layer Deposition (ALD) on a thermally grown 5 nm SiO2 interlayer to improve the ALD nucleation and guarantee a better band offset with the SiC. The deposited Al2O3/...
The interface structure and electronic properties of monolayer (1L) MoS 2 domains grown by chemical vapor deposition on 4H–SiC(0001) are investigated by microscopic/spectroscopic analyses combined with ab initio calculations. The triangular domains are epitaxially oriented on the (0001) basal plane, with the presence of a van der Waals (vdW) gap be...
Here we investigate the interface properties of gold (Au) decorated graphenized surfaces of 4H-SiC intended for
electrochemical electrodes. These are fabricated using a two-step process: discontinuous Au layers with a nominal
thickness of 2 nm are sputter-deposited onto 4H-SiC substrates with different graphenization extent—zerolayer
graphene (ZLG)...
The integration of two-dimensional $MoS_{2}$ with $GaN$ recently attracted significant interest for future electronic/optoelectronic applications. However, the reported studies have been mainly carried out using heteroepitaxial $GaN$ templates on sapphire substrates, whereas the growth of $MoS_{2}$ on low-dislocation-density bulk GaN can be strateg...
In this paper, the Ni Schottky barrier on GaN epilayer grown on free standing substrates has been characterized. First, transmission electrical microscopy (TEM) images and nanoscale electrical analysis by conductive atomic force microscopy (C-AFM) of the bare material allowed visualizing structural defects in the crystal, as well as local inhomogen...
[Formula: see text]/AlGaN metal-oxide-semiconductor capacitors show a hysteretic behavior in their capacitance vs voltage characteristics, often attributed to near-interface traps deriving from defects within the oxide layer. The origin as well as the structural/electronic properties of such defects are still strongly debated in the literature. Her...
In this paper, 2D/3D heterojunction diodes have been fabricated by pulsed laser deposition (PLD) of MoS2 on 4H‐SiC(0001) surfaces with different doping levels, i.e., n− epitaxial doping (≈1016 cm−3) and n+ ion implantation doping (>1019 cm−3). After assessing the excellent thickness uniformity (≈3L‐MoS2) and conformal coverage of the PLD‐grown film...
The mechanical exfoliation assisted by gold has been applied to obtain good quality large lateral size single layer MoS2. The effects of 2.5 MeV electron irradiation have been investigated at room temperature on structural and electronic features by Raman and Microluminescence spectroscopy. The exciton recombination emission in the direct bandgap o...
The heterogeneous integration with 2D materials enables new functionalities and novel devices in state‐of‐the‐art bulk (3D) semiconductors. In this work, highly uniform MoS2 heterostructures with silicon carbide (4H‐SiC) are obtained by a facile synthesis method, highly compatible with semiconductor fab processing, i.e., the sulfurization of predep...
This paper presents a macro-and nanoscale electrical investigation of Schottky and metal-oxide junctions with hetero-epitaxial 3C-SiC layers grown on Si. Statistical current-density-voltage (J-V) characterization of Pt/3C-SiC Schottky diodes showed an increase of the reverse leakage current with increasing the devices diameters. Furthermore, C-V an...
High-κ dielectrics are insulating materials with higher permittivity than silicon dioxide. These materials have already found application in microelectronics, mainly as gate insulators or passivating layers for silicon (Si) technology. However, since the last decade, the post-Si era began with the pervasive introduction of wide band gap (WBG) semic...
In this paper, we report a multiscale investigation of the compositional, morphological, structural, electrical, and optical emission properties of 2H-MoS2 obtained by sulfurization at 800 °C of very thin MoO3 films (with thickness ranging from ~2.8 nm to ~4.2 nm) on a SiO2/Si substrate. XPS analyses confirmed that the sulfurization was very effect...
This paper reports an investigation of the structural, chemical and electrical properties of ultra-thin (5 nm) aluminum nitride (AlN) films grown by plasma enhanced atomic layer deposition (PE-ALD) on gallium nitride (GaN). A uniform and conformal coverage of the GaN substrate was demonstrated by morphological analyses of as-deposited AlN films. Tr...
In this article, the charge trapping phenomena in Al2O3 thin films grown by atomic layer deposition (ALD) on AlGaN/GaN heterostructures have been studied by time-dependent capacitance-voltage (C-V) measurements as a function of temperature. In particular, monitoring the transient of the capacitance enabled us to estimate the maximum depth of the in...
Atomic layer deposition (ALD) of high-κ dielectrics on two-dimensional (2D) materials (including graphene and transition metal dichalcogenides) still represents a challenge due to the lack of out-of-plane bonds on the pristine surfaces of 2D materials, thus making the nucleation process highly disadvantaged. The typical methods to promote the nucle...
In this paper, the authors demonstrate the atomic layer deposition (ALD) of highly homogeneous and ultrathin (≈3.6 nm) Al2O3 films with very good insulating properties (breakdown field of ≈10–12 MV cm−1) directly onto monolayer (1L) MoS2 exfoliated on gold. Differently than in the case of 1L MoS2 supported by a common insulating substrate (Al2O3/Si...
The gold-assisted exfoliation is a very effective method to produce large-area (cm²-scale) membranes of molybdenum disulfide (MoS2) for electronics. However, the strong MoS2/Au interaction, beneficial for the exfoliation process, has a strong impact on the vibrational and light emission properties of MoS2. Here, we report an atomic force microscopy...
In this paper we demonstrated the thermal Atomic Layer Deposition (ALD) growth at 250 {\deg}C of highly homogeneous and ultra-thin ($\approx$ 3.6 nm) $Al_2O_3$ films with excellent insulating properties directly onto a monolayer (1L) $MoS_2$ membrane exfoliated on gold. Differently than in the case of 1L $MoS_2$ supported by a common insulating sub...
The gold-assisted exfoliation is a very effective method to produce large-area ($cm^2$-scale) membranes of molybdenum disulfide ($MoS_2$) for electronics. However, the strong $MoS_2/Au$ interaction, beneficial for the exfoliation process, has a strong impact on the vibrational and light emission properties of $MoS_2$. Here, we report an atomic forc...
Gold-assisted mechanical exfoliation currently represents a promising method to separate ultra-large (cm-scale) transition metal dichalcogenides (TMDs) monolayers (1L) with excellent electronic and optical properties from the parent van der Waals (vdW) crystals. The strong interaction between $Au$ and chalcogen atoms is the key to achieve this near...
In this article, electron trapping in aluminum oxide (Al2O3) thin films grown by plasma enhanced atomic layer deposition on AlGaN/GaN heterostructures has been studied and a correlation with the presence of oxygen defects in the film has been provided. Capacitance–voltage measurements revealed the occurrence of a negative charge trapping effect upo...
The integration of graphene (Gr) with nitride semiconductors is highly interesting for applications in high-power/high-frequency electronics and optoelectronics. In this work, we demonstrated the direct growth of Gr on Al0.5Ga0.5N/sapphire templates by propane (C3H8) chemical vapor deposition at a temperature of 1350 °C. After optimization of the C...
The integration of graphene (Gr) with nitride semiconductors is highly interesting for applications in high-power/high-frequency electronics and optoelectronics. In this work, we demonstrated the direct growth of Gr on Al0.5Ga0.5N/sapphire templates by propane (C3H8) chemical vapor deposition (CVD) at temperature of 1350{\deg}C. After optimization...
The nucleation and growth mechanism of aluminum oxide (Al2O3) in the early stages of atomic layer deposition (ALD) on monolayer epitaxial graphene (EG) on silicon carbide (4H-SiC) has been investigated by atomic force microscopy (AFM), conductive-atomic force microscopy (C-AFM) and Raman spectroscopy. Differently than for other types of graphene, a...
This chapter presents an overview of recent developments in the integration of 2D materials, specifically graphene and MoS2, with nitride semiconductors for electronics and optoelectronics. The state‐of‐the‐art approaches for the fabrication of heterojunctions between these two classes of materials are discussed, considering advantages and limitati...
In this work, the nucleation and growth mechanism of aluminum oxide (Al2O3) in the early stages of the direct atomic layer deposition (ALD) on monolayer epitaxial graphene (EG) on silicon carbide (4H-SiC) has been investigated by atomic force microscopy (AFM) and Raman spectroscopy. Contrary to what is typically observed for other types of graphene...
The dielectric breakdown (BD) of thermal oxide (SiO2) grown on cubic silicon carbide (3C-SiC) was investigated comparing the electrical behavior of macroscopic metal-oxidesemiconductor (MOS) capacitors with nanoscale current and capacitance mapping using conductive atomic force (C-AFM) and scanning capacitance microscopy (SCM). Spatially resolved s...
Nanolaminated aluminum oxide (Al2O3)/hafnium oxide (HfO2) thin films as well as single Al2O3 and HfO2 layers have been grown as gate dielectrics by the plasma enhanced atomic layer deposition technique on silicon carbide (4H-SiC) substrates. All the three dielectric films have been deposited at a temperature as low as 250 °C, with a total thickness...
The dielectric breakdown (BD) of thermal oxide (SiO2) grown on cubic silicon carbide (3C-SiC) was investigated comparing the electrical behavior of macroscopic metal-oxide-semiconductor (MOS) capacitors with nanoscale current and capacitance mapping using conductive atomic force (C-AFM) and scanning capacitance microscopy (SCM). Spatially resolved...
Nanolaminated Al2O3/HfO2 thin films as well as single Al2O3 and HfO2 layers have been grown as gate dielectrics by Plasma Enhanced Atomic Layer Deposition (PEALD) technique on silicon carbide (4H-SiC) substrates. All the three dielectric films have been deposited at temperature as low as 250{\deg}C, with a total thickness of about 30 nm and in part...
Semiconducting transition metal dichalcogenides (TMDs) are promising materials for future electronic and optoelectronic applications. However, their electronic properties are strongly affected by peculiar nanoscale defects/inhomogeneities (point or complex defects, thickness fluctuations, grain boundaries, etc.), which are intrinsic of these materi...
Due to its excellent physical properties and availability directly on a semiconductor substrate, epitaxial graphene (EG) grown on the (0001) face of hexagonal silicon carbide is a material of choice for advanced applications in electronics, metrology and sensing. The deposition of ultrathin high-k insulators on its surface is a key requirement for...
Graphene (Gr)—a single layer of two-dimensional sp2 carbon atoms—and Carbon Dots (CDs)—a novel class of carbon nanoparticles—are two outstanding nanomaterials, renowned for their peculiar properties: Gr for its excellent charge-transport, and CDs for their impressive emission properties. Such features, coupled with a strong sensitivity to the envir...
In this work, hafnium oxide (HfO2) thin films have been grown on (001)Si substrates by two different Atomic Layer Deposition (ALD) methods, namely thermal and plasma-enhanced modes. Films have been deposited using tetrakis-dimethylamino hafnium as metal precursor, while water vapor was used as an oxygen reactant in the case of the thermal ALD (T-AL...
The electronic properties of the graphene (Gr) Schottky junction with an Al0.22Ga0.78N/GaN heterostructure on silicon have been investigated, both experimentally and using ab-initio DFT calculations. A peculiar high n-type doping (1.1×10¹³ cm⁻²), observed for Gr in contact with AlGaN, was explained by the combined effect of Fermi level pinning by A...
Graphene (Gr) with its distinctive features is the most studied two-dimensional (2D) material for the new generation of high frequency and optoelectronic devices. In this context, the Atomic Layer Deposition (ALD) of ultra-thin high-k insulators on Gr is essential for the implementation of many electronic devices. However, the lack of out-of-plane...
Grain boundaries (GBs) of transition metal dichalcogenide monolayers (ML) play an important role in many charge transport phenomena observed in these 2D materials. In this paper, nanoscale resolution current mapping by conductive atomic force microscopy (CAFM) has been employed for direct probing of the resistance associated to grain boundaries GBs...
In this paper, micro-Raman mapping and conductive atomic force microscopy (C-AFM) were jointly applied to investigate the structural and electrical homogeneity of quasi-free-standing monolayer
raphene (QFMLG), obtained by high temperature decomposition of 4H-SiC(0001) followed by hydrogen intercalation at 900 °C. Strain and doping maps, obtained by...
Atomic layer deposition (ALD) is the method of choice to obtain uniform insulating films on graphene for device applications. Owing to the lack of out‐of‐plane bonds in the sp² lattice of graphene, nucleation of ALD layers is typically promoted by functionalization treatments or predeposition of a seed layer, which, in turn, can adversely affect gr...
In this work, we report on the metal-organic-chemical-vapour-deposition (MOCVD) and characterization of Al-rich thin layers of AlGaN on conductive GaN, to be used as emitter-base barriers for graphene hot electron transistors. After preliminary experiments, aimed to assess the impact of unintentional Ga contaminations on the AlGaN composition, 4.7...
The structural and the electronic properties of monolayer graphene made by chemical vapor deposition and transferred on various oxide substrates (SiO 2 , Al 2 O 3 , and HfO 2 )are investigated by Raman Spectroscopy and Atomic Force Microscopy in order to highlight the influence of the substrate on the features of p-doping obtained by O 2 thermal tr...
Aluminum nitride (AlN) thin films have been deposited by Plasma Enhanced Atomic Layer Deposition (PE-ALD)
onto GaN-Sapphire substrates. The morphological, structural and electrical properties of AlN films with different
thickness (from 5 to 15 nm) have been investigated. They uniformly cover the underlying GaN substrate without
pinholes and cracks....
An overview of the interaction between monolayer graphene and SiO2 dielectric substrate is reported focusing on the effect this latter has on doping and strain induced by thermal treatments in controlled atmosphere. The disentanglement of strain and doping is highlighted and the comparison with another dielectric substrate of Al2O3 evidences the cr...
Low‐dimensional carbon materials occupy a relevant role in the field of nanotechnology. Herein, the authors report a study conducted by atomic force microscopy and Raman spectroscopy on the deposition of carbon dots onto graphene surfaces. The study aims at understanding if and how the morphology and the microstructure of chemical vapor deposited g...
The emission in solid phase of Carbon Dots (CDs) deposited by drop-casting technique is investigated by means of micro-photoluminescence. Graphene and SiO2 are used as substrates, and the influence of their different nature – conductive or insulating – on the emission of CDs is highlighed. In particular, a systematic loss of efficiency in the emiss...
Two-dimensional (2D) materials are currently object of many interests both from a basic and a technological standpoint. In particular, graphene (Gr) and the semiconducting transition metal dichalcogenides (including MoS2, WS2, MoSe2, WSe2) have been widely investigated for transistors applications. As a matter of fact, 2D materials present peculiar...
This letter presents time-dependent gate-capacitance transient measurements (C–t) to determine the oxide trapped charges (Not) in Al2O3 films deposited on recessed AlGaN/GaN heterostructures. The C–t transients acquired at different temperatures under strong accumulation allowed to accurately monitor the gradual electron trapping, while hindering t...
The hot electron transistor (HET) is an unipolar majority carrier vertical device with great potential for high frequency (THz) applications. Recently, graphene (Gr) heterostructures with Nitrides have been considered as a promising material system to implement this device concept, with GaN/AlGaN (or GaN/AlN) working as emitter/emitter-base barrier...
Time dynamics of doping and strain induced in single layer graphene by thermal treatments up to 300°C in vacuum, nitrogen, carbon dioxide and oxygen controlled atmosphere are deeply studied by Raman spectroscopy and they are compared with its morphological evolution investigated by Atomic Force Microscopy. The reaction dynamics in oxygen treatments...
Graphene (Gr) is currently one of the most appealing materials as conductive transparent electrode for flexible electronics, thanks to its bendability/stretchability accompanied by small variations of the electrical properties after mechanical deformations. In addition, the field-effect tunable carrier density combined to a high mobility and satura...
Graphene is an ideal candidate for next generation applications as a transparent electrode for electronics on plastic due to its flexibility and the conservation of electrical properties upon deformation. More importantly, its field-effect tunable carrier density, high mobility and saturation velocity make it an appealing choice as a channel materi...
High quality thin insulating films on graphene (Gr) are essential for field effect transistors (FETs) and other electronics applications of this material. Atomic Layer Deposition (ALD) is the method of choice to deposit high-κ dielectrics with excellent thickness uniformity and conformal coverage. However, to start the growth on the sp(2) Gr surfac...
Al2O3thin films were deposited by plasma enhanced atomic layer deposition (PEALD) from trimethylaluminum precursor and oxygen plasma at 250 °C on AlGaN/GaN heterostructures. Before deposition, the sample surfaces were treated with the following solutions: (A) H2O2:H2SO4 (piranha), (B) fluoride acid (HF) + HCl, and (C) piranha + HF for 10 min each....
Al2O3 films were grown by plasma enhanced-atomic layer deposition (PE-ALD) on 4H-SiC substrates, with and without the presence of a thin SiO2 layer. The collected data indicated the formation of amorphous, adherent, and uniform Al2O3 thin films with a thickness of about 30 nm. The electrical characterization has been performed on metal–oxide–semico...
This letter reports on the negative charge trapping in Al 2O3 thin films grown by atomic layer deposition onto oxidized silicon carbide (4H-SiC). The films exhibited a permittivity of 8.4, a breakdown field of 9.2 MV/cm and small hysteresis under moderate bias cycles. However, severe electron trapping inside the Al 2O3 film (1 × 1012 cm−2) occurs u...
This work reports on the growth and characterization of Al2O3 films on 4H-SiC, by Plasma Enhanced-Atomic Layer Deposition (PE-ALD). Different techniques were used to investigate the morphological, structural and electrical features of the Al2O3 films, both with and without the presence of a thin SiO2 layer, thermally grown on the 4H-SiC before ALD....
This paper presents a study of the vertical current transport in a graphene (Gr) heterostructure with AlxGa1-xN/GaN, which represent the main building block of a novel high frequency device, the hot electron transistor (HET) with Gr base. The morphological and electrical properties of this heterostructures have been investigated at nanoscale by ato...
A systematic study was performed on the effects of surface treatments before Atomic Layer Deposition (ALD) growth of Al2O3 thin films on (0001)AlGaN/GaN substrate. The AlGaN/GaN surface was treated either with: H2O2:H2SO4 (A treatment) and H2O2:H2SO4 + H2O:HF (B treatment). After surface wet-treatments, Al2O3 was immediately deposited at 250 °C by...
Nanolaminated Al2O3-HfO2 and Al2O3/HfO2 bilayer thin films have been grown by plasma enhanced atomic layer deposition on silicon substrates. The nanolaminated system consists of alternating layers of Al2O3 and HfO2, while the bilayer system by contrast has been fabricated as a HfO2 about 15nm thick film deposited on a Al2O3 15nm thick film directly...
Pr1–xCaxMnO3 thin films have been deposited through an in situ metal organic chemical vapor deposition (MOCVD) process using a molten multi-metal source, consisting of the Pr(hfa)3·diglyme, Ca(hfa)2·tetraglyme, and Mn(tmhd)3 precursor mixture on single crystal substrates such as LaAlO3 (001) and MgO (001). Optimization of processing parameters has...
In this work, we present a systematic study on the effects of surface nature of two different substrates such as Si(100) and AlGaN/GaN (0001) before atomic layer deposition (ALD) growth of Al2O3 thin films. The Si and AlGaN/GaN surfaces were treated either with: H2O2:H2SO4 (1:3 piranha solution) for 10 minutes and H2O:HF (10:1) for 5 minutes. After...
Calcium-doped praseodymium manganite films (Pr0.7Ca0.3MnO3, PCMO) were prepared by metal-organic chemical vapor deposition (MOCVD) on SrTiO3 (001) and SrTiO3 (110) single-crystal substrates. Structural characterization through X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) analyses confirmed the formation of epitaxi...
Hafnium oxide thin films have been deposited on Si(001) substrates by atomic layer deposition from the tetrakis-dimethylamino hafnium precursor using both conventional thermal and plasma-enhanced methods. The structural, compositional and morphological film characterization has been carried out by transmission electron microscopy, X-ray photoelectr...
