Papers by Rosanna Larciprete
Thin Solid Films, 2001
In this paper, the XPS study of SnO thin films deposited by the L-CVD technique are presented. Th... more In this paper, the XPS study of SnO thin films deposited by the L-CVD technique are presented. The influence of exposition 2 of the as-deposited samples to oxygen O and hydrogen H on their stoichiometry was determined. Moreover, on the basis of 2 2 detailed shape analysis of the Sn3d and O1s XPS peaks, the chemical shift of binding energy corresponding to the change of 5r2 sample stoichiometry was separated from a shift of the binding energy corresponding to the change of interface Fermi level position E ᎐E in the band gap, using a new procedure of deconvolution of the core level XPS peaks. The shift of the Sn3d
Applied Optics, 1996
Ellipsometry is a sensitive and noninvasive technique for the characterization of thin films. A r... more Ellipsometry is a sensitive and noninvasive technique for the characterization of thin films. A recently developed ellipsometer, based on the four-detector photopolarimeter, was arranged outside a UHV chemical vapor deposition chamber for the in situ monitoring of film growth processes. The instrument showed a sensitivity in the submonolayer range when used to follow the growth of germanium thin films deposited on silicon substrates. As the main instrument drawback is represented by the need to have precise alignment, an effective positioning procedure was developed to obtain a positioning error smaller than 0.1°.
Applied Surface Science, 1993
Tin oxide films were deposited by ArF excimer laser induced photolysis of Sn(CH 3) 4/O 2 mixtures... more Tin oxide films were deposited by ArF excimer laser induced photolysis of Sn(CH 3) 4/O 2 mixtures. The "in situ" Auger analysis was used to determine the effect of the gas-phase oxygen concentration on the film composition. The surface properties of the films were investigated by synchrotron radiation UV photoemission spectroscopy. To this aim samples were transferred to a synchrotron radiation facility, without any exposure to air and kept in dynamical high vacuum. The results obtained showed that the valence-band spectrum was characteristic for SnO 2 and that the Sn 4d core peak did not have any contribution due to metallic tin. Furthermore, by tuning the synchrotron radiation photon energy, in order to vary the photoelectron escape depth, we got the indication that the oxygen vacancies responsible for the weak emission in the band-gap region were localized at the sample surface.
Journal of Vacuum Science & Technology A, 1993
ABSTRACT
Applied Surface Science, 1996
An integrated laser assisted process has been applied to prepare heteroepitaxial SixGe(1-x) alloy... more An integrated laser assisted process has been applied to prepare heteroepitaxial SixGe(1-x) alloys on Si(100) using the combination of laser induced chemical vapour deposition (LCVD) and pulsed laser induced epitaxy (PLIE). Both processes have been carried out with 193 nm radiation of an ArF excimer laser leading first to high quality amorphous hydrogenated germanium (a-Ge:H) thin films by LCVD and then to unstrained epitaxial SixGe 0 -x) alloys by PLIE. The optimization for depositing homogeneous, low impurity a-Ge:H films has been followed by profilometry, Raman spectroscopy and X-ray diffraction (XRD). Subsequent melting and recrystallization by PLIE was studied by X-ray photoelectron spectroscopy (XPS) for analysing the distribution tail of the graded SixGe 0 -x) alloys and conventional XRD analysis to determine the epitaxy of the relaxed, Ge-rich, SixGe(l_x) phase. The analyses evidenced the formation of thin unstrained epitaxial SixGe(1-x) layers, which can be used as buffer layers for the growth of symmetrically strained superlattices.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1998
ABSTRACT
Journal of Vacuum Science & Technology A, 1997
ABSTRACT
Physical Review B, 2002
Using photoemission microscopy at submicron lateral resolution, we measured the occupied density ... more Using photoemission microscopy at submicron lateral resolution, we measured the occupied density of states in MgB 2 single crystalline grains from commercial MgB 2 powder. This experiment provided a reliable measurement of the integrated density of states in MgB 2 ...
Physical Review B, 2007
The combination of the two-dimensional layered structure and the semimetallic character of graphi... more The combination of the two-dimensional layered structure and the semimetallic character of graphite is expected to produce a C1s photoemission spectrum of the (0001) surface with only one highly symmetric component. This simple view has been challenged by a recent study, performed on highly oriented pyrolytic graphite (HOPG), in which the existence of two components separated by 120meV has been
Journal of Electron Spectroscopy and Related Phenomena, 2005
... At variance with graphite and in agreement with very recent results on SWCNT mats [14], three... more ... At variance with graphite and in agreement with very recent results on SWCNT mats [14], three photoemission peaks corresponding to van Hove singularities (VHS) of the semiconducting and metallic SWCNTs are observed, at binding energies of about 0.4, 0.7 and 1 eV. ...
Surface Science, 2006
Here we demonstrate that a molecular dye film composed by a single layer of C 70 and a single lay... more Here we demonstrate that a molecular dye film composed by a single layer of C 70 and a single layer of Zn-Tetraphenyl-porhyrin (ZnTPP) adsorbed atop can be grown on large substrates using molecular beam epitaxy. The electrostatic interactions between the constituent molecules drive the formation of this ordered donor-acceptor layer. The overlapping between the !* orbitals of ZnTPP and C 70 allows the delocalisation of the excited electrons from the excited molecule on a timescale of ~ 6 fs. Generally, the ZnTPP/C 70 film, acting as a p-n junction, delocalise more efficiently the excited electrons as compared to pure ZnTPP films on a timescale that competes effectively against loss processes, suggesting its application for a more efficient solar energy conversion in organicbased devices.
Chemical Physics Letters, 2003
The effect of thermal processing at 1050°C of a dispersed film of carbon nanoparticles deposited ... more The effect of thermal processing at 1050°C of a dispersed film of carbon nanoparticles deposited on a Si substrate with a native SiO 2 layer has been studied by scanning electron microscopy and scanning photoelectron spectromicroscopy. It has been found that the thermal processing results in formation of pyramidal-shaped defects of 2-7 lm with strongly reduced SiO 2 content with silicon wires of diameter ranging between 30 and 50 nm decorating the pyramid walls. The nucleation of the Si nanowires occurs via reduction of the native oxide layer by the nanosized carbon particles, without the need of metal catalysts and at temperatures relatively lower than that used in similar techniques.
Chemical Physics, 2003
We have investigated the resonant charge transfer from an adsorbed Ar atom in an electronically e... more We have investigated the resonant charge transfer from an adsorbed Ar atom in an electronically excited 2p3/254s1 state into different metal substrates, i.e., Ag(111), Ni(111) and Cu(111). Using the so-called core hole clock method we have been able to determine the resonant charge transfer times for the three systems. They differ roughly by a factor of two with the fastest transfer time being observed for Ni(111) and the slowest for Ag(111). Furthermore we observe strong energy dependences of the charge transfer times across the resonances which are opposite to the expectations from a simple tunneling model, or from a detuning induced shortening of the interaction time. Possible reasons for the observed behavior are discussed.
Physical Review B, 2004
The charge transfer from Gd ions to C cage in endohedral Gd@C82 is probed by resonant photoemissi... more The charge transfer from Gd ions to C cage in endohedral Gd@C82 is probed by resonant photoemission spectroscopy. A careful data analysis shows that only one feature, ascribed to the 4f electron emission resonates across the Gd4d-->4f edge. The lack of the resonating spectral weight from the Gd6s2 or 5d6s states, which in turn are detected in the resonant photoemission
Physical Review B, 2005
The electronic properties of Li doped single-wall carbon nanotubes were studied by high-resolutio... more The electronic properties of Li doped single-wall carbon nanotubes were studied by high-resolution photoemission spectroscopy. Upon Li intercalation, the limited displacement of the Fermi level agrees with a partial charge transfer of the Li2s electron to the C2p- pi* states. The increase of the density of states near the Fermi level with Li concentration suggests a transition from the one-dimensional
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2003
The interaction of molecular oxygen with single wall nanotubes in the form of a commercial bucky ... more The interaction of molecular oxygen with single wall nanotubes in the form of a commercial bucky paper was investigated by high resolution photoemission spectroscopy. Sodium contamination was found in the sample, which was completely removed only after prolonged heating at 1250 K. The C1s core level spectrum measured on the sample annealed to 1020 K dramatically changed upon exposure to molecular oxygen. On the contrary, when exposing the Na-free SWNTs to several KL of O2, the sample remained oxygen free and no modification in the C1s core level was observed. Therefore the observed sensitivity of the sample to O2 was due to a Na mediated oxidation, determining a charge transfer from the C tubes to the Na–O complex.
Physical Review B, 2002
The structural reorganization of carbon nanoparticles into single-wall nanotubes via high tempera... more The structural reorganization of carbon nanoparticles into single-wall nanotubes via high temperature annealing in absence of metal catalysts, was monitored by photoemission and x-ray absorption spectroscopy. It has been found that for this system an advanced graphitization process is made possible by the peculiar nanoparticle internal structure containing extended sp2 coordinated domains with a sizable degree of ordering. Possible mechanisms for the formation of nanotubes via self-assembling of carbon aggregates are discussed.
Physical Review B, 2000
We present a method for evaluating the spatial inhomogeneity of adsorbate-induced band bending on... more We present a method for evaluating the spatial inhomogeneity of adsorbate-induced band bending on semiconductors from the substrate core-level lineshape. As a case study we consider the first stages of accumulation layer formation due to K adsorption on the H:Si(111) surface at 300 K. The observed Si 2p core-level lineshape variation is accounted for considering each randomly distributed adatom as
Journal of The American Chemical Society, 2003
Here, we show that residual contaminants in purified single-wall carbon nanotube bundles may be r... more Here, we show that residual contaminants in purified single-wall carbon nanotube bundles may be responsible for the reported sensitivity of the electronic and transport properties to oxygen. Removal of these contaminants makes the electronic spectra insensitive to O(2), CO, H(2)O, and N(2), while a strong sensitivity to NO(2), SO(2), and NH(3) is observed, confirming the possible application of single-wall nanotubes as powerful sensors capable of measuring environmentally significant levels of toxic gases.
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Papers by Rosanna Larciprete