Filippo Giannazzo

MoS2 thin films were synthesized via pulsed laser deposition (PLD) onto AlN/Si(111) templates, where the AlN buffer layers (110 and 200 nm thick) were grown by molecular beam epitaxy. We achieved excellent MoS2 thickness uniformity (≈3 monolayers) and confirmed the conformal coverage of the PLD-grown films by Raman mapping. Transmission electron microscopy analysis confirmed the epitaxial character of the AlN film and the presence of an ultrathin aluminum oxynitride layer on its surface. Following X-ray photoelectron spectroscopy analysis, oxygen impurities were confirmed in the bulk AlN film as well. Heterojunctions between the ultrathin MoS2 film and AlN, investigated by current–voltage characterization of vertical diode structures, exhibit Esaki-diode-like behavior with a negative-resistance zone. A diagram of the energy bands and Fermi levels in the heterostructure composed of the thick oxygen-doped AlN film sandwiched between the MoS2 and Si electrodes was proposed, and the observed Esaki-diode-like current–voltage characteristic was attributed to electron tunneling from the oxygen impurity band in the AlN film into the valence band of the degenerate p-MoS2 film.

Semi‐transparent perovskite solar cells offer a route to agrivoltaics, combining electricity generation with controlled light transmission for crop cultivation. However, conventional perovskite films preferentially absorb blue photons, producing redshifted transmitted spectra that can affect plant photophysiology. This work presents quasi‐neutral‐color semi‐transparent perovskite films based on AVA‐MAPbI ₃ islands rooted in mesoporous TiO ₂ (mp‐TiO ₂ ). This architecture localizes absorption within the islands while ensuring spectrally balanced, visually neutral transmitted light and efficient charge extraction via the extended perovskite/mp‐TiO ₂ interface. Films are fabricated through a one‐step, antisolvent‐free process where controlled de‐wetting and crystallization form islands anchored to the mp‐TiO ₂ scaffold. Island coverage and size are tuned via spin‐coating speed and annealing temperature. Using HTL‐free carbon‐based architecture as a testbed, perovskite coverage is identified as the main factor governing the transmittance‐efficiency trade‐off. Photocurrent scaling with coverage and conductive AFM measurements suggest that each island behaves as an independent photogeneration unit. Year‐long outdoor simulations at 37.3°N project that a device with an ideal transparent cathode can reach 4.50% efficiency and generate 116.38 kWh m ⁻² year ⁻¹ , sufficient to power energy‐intensive greenhouses. Lettuce grown under an LED‐simulated perovskite spectrum showed uncompromised biomass, pigments, leaf nitrogen‐carbon content, and carbon/nitrogen ratio, supporting perovskite island‐based photovoltaics for agrivoltaic applications.

The electrical behavior of SiO ₂ /4H‐SiC interfaces is a central challenge for the development of high‐efficiency MOSFETs, where trap states and interfacial structural distortions can affect carrier mobility and device reliability. In this work, we investigate thermally grown SiO ₂ on n‐type 4H‐SiC epilayers, analyzing the effects of different post‐oxidation annealings (POAs) in N ₂ and Ar on both the electrical response and the interfacial strain. MOS capacitors subjected to POA in N ₂ exhibit a marked reduction of interface states density (D _it ) near the conduction band edge, together with an increase of the electron Fowler–Nordheim barrier height. These electrical signatures occur simultaneously with negative flat‐band voltage shifts, suggesting the presence of an interfacial dipole rather than the presence of fixed charges only. Raman spectroscopy reveals that N ₂ ‐based POA induces an increase of biaxial tensile strain at the SiO ₂ /SiC interface, which is less pronounced in the case of POA in Ar. The observation of strain evolution and electrical properties demonstrates that nitrogen incorporation not only passivates dangling bonds but also modifies the interfacial stress state, thereby influencing barrier properties and charge distribution. These findings provide new insights to be considered in the optimization of SiO ₂ /SiC gate stacks in 4H‐SiC MOSFETs.

An Al₂O₃/AlN stack deposited via Atomic Layer Deposition (ALD) methods as a gate insulator for silicon carbide (4H-SiC) has been investigated, focusing on the effects of different Al₂O₃ deposition processes on the nitride layer. In particular, dielectric stacks, consisting of a 10 nm AlN interface (001)-oriented layer directly grown on a 4H–SiC substrate and in 20 nm of additional amorphous Al₂O₃ layers were synthesized in sequential deposition runs by thermal ALD (T-ALD) or plasma-enhanced ALD (PEALD) methods. The evolution of the phenomena occurring at the Al₂O₃/AlN interfaces has been established by in situ ellipsometry measurements. Strong effects of the oxygen plasma because of the O-Al-N bond formation have been clearly observed and corroborated by ex situ structural and electrical characterizations, especially in the case of the plasma-enhanced Al₂O₃ process. In particular, the Al₂O₃/AlN bilayer grown by the Al₂O₃ T-ALD method exhibited good insulating behavior and an 8.7-high dielectric constant was measured. By contrast, the Al₂O₃/AlN bilayer grown by the Al₂O₃ PEALD method demonstrated poor insulating properties.

In this work, the atomic layer deposition (ALD) of an ultra-thin AlN film on the surface of monolayer EG grown on-axis 4H-SiC(0001) substrates has been investigated as a function of the number of ALD cycles. The formation of a homogeneous film with a 10 nm thickness and crystalline wurtzite structure was obtained after 320 cycles, as demonstrated by atomic force microscopy (AFM) mapping, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. Raman mapping revealed a significant reduction in the native compressive strain of as-grown EG (ε ≈ −0.36%) with increasing ALD cycles, down to a value of −0.16% after full coverage. Finally, Kelvin Probe Force Microscopy (KPFM) surface potential mapping allowed the evaluation of energy band alignment of the AlN/EG heterojunction, with a conduction band offset of ~2.6 eV between the crystalline AlN film and the underlying EG. Such a large offset confirms AlN as a promising gate dielectric for EG-based devices.

In this work, the electrical properties of Mo ₂ C/4H-SiC Schottky contacts were studied at different annealing temperatures. In particular, the Schottky barrier height was derived by current-voltage measurements on as-deposited and 400 °C and 700 °C-annealed contacts. The Schottky barrier height was comparable for the as-deposited and 400°C-annealed Mo ₂ C/4H-SiC contact (0.94 and 0.96 eV, respectively), while it increased (1.07 eV) for the 700 °C-annealed Mo ₂ C/4H-SiC one. For the sample annealed at 700°C, the electrical characterization of the diodes was combined with the study of the surface and interface electrical properties, by Kelvin-probe force microscopy (KPFM) and frequency dependent capacitance-voltage measurements (C-f-V) and discussed assuming a Mo/4H-SiC Schottky contact (F _B =1.39 eV) as a reference. The KPFM measurements revealed a similar value of the surface potential, thus suggesting that the work function of the metal is the same in both cases. On the other hand, a higher density of interface state was obtained by C-f-V for the Mo ₂ C/4H-SiC system. This latter can explain the reduction of the Schottky barrier height observed for this system.

Silicon carbide (SiC) has emerged as a leading material for high-power applications. However, the high density of interface states (D _it ) at the SiO ₂ /SiC interface still constrains the performance and reliability of MOSFET devices. In this work, lateral 4H-SiC MOSFETs subjected to post-deposition annealing (PDA) in nitric oxide (NO) of different durations were investigated through capacitance-voltage measurements, supported by an analytical model and an iterative MATLAB-based D _it extraction algorithm. The results demonstrate that NO PDA effectively reduces D _it not only near the conduction band edge but also towards the valence band, yielding improved channel mobility (µ _FE ) and enhanced threshold voltage stability.

The integration of 2D molybdenum disulfide (MoS ₂ ) with gallium nitride (GaN) enables many interesting (opto)electronic applications, such as heterojunction diodes and UV/visible photodetectors, whose performances crucially depend on the thickness uniformity, strain and doping of MoS ₂ films and on the energy band alignment at the interface. This work reports a multiscale electro‐optical characterization of large size (∼100 µm) monolayer (1L) MoS ₂ flakes directly grown on n‐GaN and, for comparison, on a SiO ₂ /Si substrate by liquid‐precursors‐intermediated chemical vapor deposition. XPS and micro‐Raman mapping revealed a superior crystalline quality, lower average strain ε ≈ −0.06% and higher n‐type doping n ≈ 0.7 × 10 ¹³ cm ⁻² for 1L‐MoS ₂ grown on GaN, as compared to MoS ₂ grown under identical conditions on the amorphous SiO ₂ surface. Nanoscale current‐voltage mapping by C‐AFM showed a significantly reduced Schottky barrier (Φ _B = 0.57 ± 0.06 eV) at 1L‐MoS ₂ /GaN interface as compared to the bare GaN surface. This result, combined with a MoS ₂ /n‐GaN work function difference W _MoS2 ‐W _GaN ≈ 360 meV evaluated by KPFM mapping, revealed a type‐I band alignment at the heterojunction. Finally, photocurrent measurements on macroscopic Ni/n‐GaN, Ni/MoS ₂ /n‐GaN and Ni/MoS ₂ /SiO ₂ lateral devices under illumination with photon energies from ∼2 to ∼5 eV showed superior electro‐optical performances of Ni/MoS ₂ /n‐GaN heterojunctions both in the visible and UV range.