Daniela Cavalcoli | AICCON - Associazione Italiana per la Promozione della Cultura della Cooperazione e del Non Profit (original) (raw)
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Papers by Daniela Cavalcoli
Scripta Materialia, 2011
Here we report on the study of nano-crack formation in Ali_ x In x N/AlN/GaN heterostructures, on... more Here we report on the study of nano-crack formation in Ali_ x In x N/AlN/GaN heterostructures, on its association with composition fluctuation and on its local electrical properties. It is shown here that indium segregation at nano-cracks and threading dislocations originating from the non-pseudomorphic AIN interlayer could be the cause of the high reverse-bias gate leakage current of Ni/Au Schottky contacts on Ali_ x In x N/AlN/GaN heterostructures and significantly affects the contact rectifying behavior. Segregation of indium around crack tips in Ali_ x In x N acting as conductive paths was assessed with conductive atomic force microscopy.
Hydrogenated nanocrystalline silicon films were prepared by hot-wire method at low substrate temp... more Hydrogenated nanocrystalline silicon films were prepared by hot-wire method at low substrate temperature (200∘C) without hydrogen dilution of silane (SiH4). A variety of techniques, including Raman spectroscopy, low angle X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and UV-visible (UV-Vis) spectroscopy, were used to characterize these films for structural and optical properties. Films are grown at reasonably high deposition rates (>15 Å/s), which are very much appreciated for the fabrication of cost effective devices. Different crystalline fractions (from 2.5% to 63%) and crystallite size (3.6–6.0 nm) can be achieved by controlling the process pressure. It is observed that with increase in process pressure, the hydrogen bonding in the films shifts from Si–H to Si–H2and(Si–H2)ncomplexes. The band gaps of the films are found in the range 1.83–2.11 eV, whereas the hydrogen content remains <9 at.% over the entire range of process pressure studied. The ease of depositing films with tunable band gap is useful for fabrication of tandem solar cells. A correlation between structural and optical properties has been found and discussed in detail.
Solid State Phenomena, Sep 30, 2003
... Similar non standard SPV behaviors in cast mc Si was observed by Hwang and Schroder [7] and a... more ... Similar non standard SPV behaviors in cast mc Si was observed by Hwang and Schroder [7] and attributed to inaccurate values of α used to obtain the SPV -1 vs α -1 plots. These authors used the α(λ) data of ref. ... Mat. [7] IG Hwang and K. Schroder: Sol State Electronics Vol. ...
Applied Physics Letters, 2012
Page 1. On the Interaction of Dislocations with Impurities in Silicon Daniela Cavalcoli a and Ann... more Page 1. On the Interaction of Dislocations with Impurities in Silicon Daniela Cavalcoli a and Anna Cavallini b ... Lett. Vol. 84, (2004) p.2106. [6] W Schröter, and H. Cerva, in Defect Interaction and Clustering, (Trans Tech, Zürich, 2001). [7] N Lehto, Phys. Rev.B, 55, 15601 (1997). ...
ACS Applied Materials & Interfaces, 2015
In the present article we report enhanced light absorption, tunable size-dependent blue shift, an... more In the present article we report enhanced light absorption, tunable size-dependent blue shift, and efficient electron-hole pairs generation in Ge nanoporous films (np-Ge) grown on Si. The Ge films are grown by sputtering and molecular beam epitaxy; subsequently, the nanoporous structure is obtained by Ge+ self-implantation. We show, by surface photovoltage spectroscopy measurements, blue shift of the optical energy gap and strong signal enhancement effects in the np-Ge films. The blue shift is related to quantum confinement effects at the wall separating the pore in the structure, the signal enhancement to multiple light-scattering events, which result in enhanced absorption. All these characteristics are highly stable with time. These findings demonstrate that nanoporous Ge films can be very promising for photovoltaic applications.
Physical Review B, 1997
The electronic properties of deformed n-type silicon have been investigated via deep-level transi... more The electronic properties of deformed n-type silicon have been investigated via deep-level transient spectroscopy (DLTS). The four deformation-induced levels usually labeled in the literature as A, B, C, and D have been found. Their analysis as a function of the deformation parameters and the study of their thermal stability have allowed us to conclude that only the C line, located
Physical Review B, 1997
The frequently observed variation of the deep-level-transient-spectroscopy ͑DLTS͒ peak amplitude ... more The frequently observed variation of the deep-level-transient-spectroscopy ͑DLTS͒ peak amplitude with emission rate is often attributed to peculiar characteristics of the investigated traps: ͑i͒ broadening of the trap activation energy resulting in nonexponential capacitance transients, ͑ii͒ amphoteric behavior of the deep level, and ͑iii͒ temperature dependence of the capture cross section. Otherwise it could be attributed to factors related to the technique itself such as contribution of the volume and effect of the leakage current. In this work we demonstrate that the DLTS peak amplitude variation effect is sometime due to the presence of a Coulombic repulsive barrier associated with the defect investigated.
Solid State Phenomena, 2002
Scripta Materialia, 2011
Here we report on the study of nano-crack formation in Ali_ x In x N/AlN/GaN heterostructures, on... more Here we report on the study of nano-crack formation in Ali_ x In x N/AlN/GaN heterostructures, on its association with composition fluctuation and on its local electrical properties. It is shown here that indium segregation at nano-cracks and threading dislocations originating from the non-pseudomorphic AIN interlayer could be the cause of the high reverse-bias gate leakage current of Ni/Au Schottky contacts on Ali_ x In x N/AlN/GaN heterostructures and significantly affects the contact rectifying behavior. Segregation of indium around crack tips in Ali_ x In x N acting as conductive paths was assessed with conductive atomic force microscopy.
Hydrogenated nanocrystalline silicon films were prepared by hot-wire method at low substrate temp... more Hydrogenated nanocrystalline silicon films were prepared by hot-wire method at low substrate temperature (200∘C) without hydrogen dilution of silane (SiH4). A variety of techniques, including Raman spectroscopy, low angle X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and UV-visible (UV-Vis) spectroscopy, were used to characterize these films for structural and optical properties. Films are grown at reasonably high deposition rates (>15 Å/s), which are very much appreciated for the fabrication of cost effective devices. Different crystalline fractions (from 2.5% to 63%) and crystallite size (3.6–6.0 nm) can be achieved by controlling the process pressure. It is observed that with increase in process pressure, the hydrogen bonding in the films shifts from Si–H to Si–H2and(Si–H2)ncomplexes. The band gaps of the films are found in the range 1.83–2.11 eV, whereas the hydrogen content remains <9 at.% over the entire range of process pressure studied. The ease of depositing films with tunable band gap is useful for fabrication of tandem solar cells. A correlation between structural and optical properties has been found and discussed in detail.
Solid State Phenomena, Sep 30, 2003
... Similar non standard SPV behaviors in cast mc Si was observed by Hwang and Schroder [7] and a... more ... Similar non standard SPV behaviors in cast mc Si was observed by Hwang and Schroder [7] and attributed to inaccurate values of α used to obtain the SPV -1 vs α -1 plots. These authors used the α(λ) data of ref. ... Mat. [7] IG Hwang and K. Schroder: Sol State Electronics Vol. ...
Applied Physics Letters, 2012
Page 1. On the Interaction of Dislocations with Impurities in Silicon Daniela Cavalcoli a and Ann... more Page 1. On the Interaction of Dislocations with Impurities in Silicon Daniela Cavalcoli a and Anna Cavallini b ... Lett. Vol. 84, (2004) p.2106. [6] W Schröter, and H. Cerva, in Defect Interaction and Clustering, (Trans Tech, Zürich, 2001). [7] N Lehto, Phys. Rev.B, 55, 15601 (1997). ...
ACS Applied Materials & Interfaces, 2015
In the present article we report enhanced light absorption, tunable size-dependent blue shift, an... more In the present article we report enhanced light absorption, tunable size-dependent blue shift, and efficient electron-hole pairs generation in Ge nanoporous films (np-Ge) grown on Si. The Ge films are grown by sputtering and molecular beam epitaxy; subsequently, the nanoporous structure is obtained by Ge+ self-implantation. We show, by surface photovoltage spectroscopy measurements, blue shift of the optical energy gap and strong signal enhancement effects in the np-Ge films. The blue shift is related to quantum confinement effects at the wall separating the pore in the structure, the signal enhancement to multiple light-scattering events, which result in enhanced absorption. All these characteristics are highly stable with time. These findings demonstrate that nanoporous Ge films can be very promising for photovoltaic applications.
Physical Review B, 1997
The electronic properties of deformed n-type silicon have been investigated via deep-level transi... more The electronic properties of deformed n-type silicon have been investigated via deep-level transient spectroscopy (DLTS). The four deformation-induced levels usually labeled in the literature as A, B, C, and D have been found. Their analysis as a function of the deformation parameters and the study of their thermal stability have allowed us to conclude that only the C line, located
Physical Review B, 1997
The frequently observed variation of the deep-level-transient-spectroscopy ͑DLTS͒ peak amplitude ... more The frequently observed variation of the deep-level-transient-spectroscopy ͑DLTS͒ peak amplitude with emission rate is often attributed to peculiar characteristics of the investigated traps: ͑i͒ broadening of the trap activation energy resulting in nonexponential capacitance transients, ͑ii͒ amphoteric behavior of the deep level, and ͑iii͒ temperature dependence of the capture cross section. Otherwise it could be attributed to factors related to the technique itself such as contribution of the volume and effect of the leakage current. In this work we demonstrate that the DLTS peak amplitude variation effect is sometime due to the presence of a Coulombic repulsive barrier associated with the defect investigated.
Solid State Phenomena, 2002