sandra landi - Academia.edu (original) (raw)

Papers by sandra landi

Journal of the Brazilian Chemical Society, 2023

AIP Conference Proceedings, 2005

It is experimentally observed that the introduction of an nipi delta doping superlattice in the m... more It is experimentally observed that the introduction of an nipi delta doping superlattice in the multiple quantum well (MQW) region of an amplitude modulator improves the device performance in terms of contrast ratio.

Summary form only given. Laser-assisted scanning tunneling microscopy (STM) has been used in rece... more Summary form only given. Laser-assisted scanning tunneling microscopy (STM) has been used in recent years to obtain new information about surfaces properties in atomic scale. Frequency mixing at the STM junction with infrared radiation, photoassisted spectroscopy in semiconductors materials, and images with atomic resolution of graphite recording rectification signal have been reported. We have performed an experiment using a tungsten tip and highly oriented pyrolytic graphite (HOPG) as the sample. The tip-sample interface was illuminated with an He-Ne laser polarized in the s and p directions.

RSC Advances, 2015

SHINERS and SHINEF from Ag@SiO2and Au@SiO2excited in the near-infrared are presented, with high e... more SHINERS and SHINEF from Ag@SiO2and Au@SiO2excited in the near-infrared are presented, with high enhancement factors, together to TEM/EDX evidences of silica coverage over Au and Au nanoparticles.

AIP Conference Proceedings, 2007

Photoluminescent Properties of InAs Quantum Dots Grown by MOVPE on an InAlGaAs Layer and their De... more Photoluminescent Properties of InAs Quantum Dots Grown by MOVPE on an InAlGaAs Layer and their Dependence on the Layer Stoichiometry. [AIP Conference Proceedings 893, 943 (2007)]. Julio G. Mendoza‐Alvarez, Mauricio ...

31st European Conference on Optical Communications (ECOC 2005), 2005

ABSTRACT An enhancement by a factor of two of the Stark shift in amplitude modulators containing ... more ABSTRACT An enhancement by a factor of two of the Stark shift in amplitude modulators containing an nipi delta-doping superlattice in the multiple quantum well region is observed. This enhancement substantially reduces the device operation voltage. (2 pages)

Ultramicroscopy, 1999

Thermal expansion produced by laser irradiation of the tunneling junction is analyzed, as a neces... more Thermal expansion produced by laser irradiation of the tunneling junction is analyzed, as a necessary step towards detection and identification of other laser induced currents in scanning tunneling microscopy (STM). Solving a tridimensional heat diffusion model, the amplitude of thermal expansion as a function of the modulation frequency (ω) of the light power, rolls off as 1/ω while the in-phase

physica status solidi c, 2007

Photocurrent measurements were carried out on doped and undoped InAs/InGaAs/InP quantum dot struc... more Photocurrent measurements were carried out on doped and undoped InAs/InGaAs/InP quantum dot structures. A photocurrent peak is observed at 5 μm for the undoped sample, which is identified as a bound to bound transition. Additional peaks are detected for the doped structure, which, with the help of a simple 1D model, are tentatively identified as transitions from a dot bound state to a quantum well state. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

physica status solidi (c), 2005

Self-assembled InAs quantum dots (QDs) over an InGaAs layer on InP substrates were grown by metal... more Self-assembled InAs quantum dots (QDs) over an InGaAs layer on InP substrates were grown by metalorganic chemical vapor deposition. Their structural and optical properties were investigated by atomic force microscopy and photoluminescence. Optimised stacks of structures were grown for a QD infrared photodetector and their absorption was measured. Magnetotransport measurements on the stacked QD structures revealed tunneling between quantum dot states with an applied magnetic field parallel to the current.

Physica E: Low-dimensional Systems and Nanostructures, 2006

ABSTRACT We report photoluminescence (PL) spectra of InP/InxGa1-xAs/InAs/InP dot-in-a-well struct... more ABSTRACT We report photoluminescence (PL) spectra of InP/InxGa1-xAs/InAs/InP dot-in-a-well structures grown by MOVPE, with different compositions of the ternary layer. Measurements with atomic force microscopy showed that the largest quantum dot (QD) height is obtained when the InAs QDs are grown on the InxGa1-xAs layer with a mismatch of 1000ppm, and the height decreases as the mismatch departs from this value. PL spectra of the QDs showed an asymmetric band, which involves transitions between dot energy levels and can be deconvoluted into two peaks. The highest energy PL peak of this band was observed for the sample with the QDs grown on top of the lattice-matched InxGa1-xAs layer and it shifted to lower energies for strained samples as the degree of mismatch increased. Theoretical calculations of the energy levels of the entire structure were used to interpret the obtained PL spectra and determine the possible detection tunability range.

Journal of Materials Science: Materials in Medicine, 2014

Journal of Crystal Growth, 2004

... Quantum-well (QW) IR photodetectors based on intersubband transitions have demonstrated great... more ... Quantum-well (QW) IR photodetectors based on intersubband transitions have demonstrated great capability to produce devices with good detectivity and multicolor detection [1]. In the past few years, there has been intense research to fabricate mid-IR (MIR) and far-IR (FIR ...

Journal of Crystal Growth, 2003

Journal of Applied Physics, 1997

Thermal expansion of the sample or tip in a laser-assisted scanning tunneling microscope (STM) ju... more Thermal expansion of the sample or tip in a laser-assisted scanning tunneling microscope (STM) junction can obstruct the study of other phenomena related with STM–light interactions, when photoinduced currents are analyzed. In this article, we show that the thermal contribution is proportional to the average tunneling current and that this can be used to distinguish it from other contributions. Simultaneous tunneling current–voltage and photoinduced current–voltage curves are recorded for highly oriented pyrolitic graphite and gold samples with a Pt tip. We have done the measurements for two different polarizations of the incident beam. We show that the I–V curves can be used to discriminate between different mechanisms that appear, producing photoinduced currents.

IEEE Photonics Technology Letters, 2005

Amplitude modulators based on the quantum confined Stark effect, whose active multiple quantum-we... more Amplitude modulators based on the quantum confined Stark effect, whose active multiple quantum-well region contains an nipi delta doping superlattice were investigated. An enhacement by a factor of two of the Stark shift is observed. This observation was made possible by a thorough doping level calibration procedure. As a result, a larger contrast ratio for the devices based on these novel structures was detected, substantially reducing their operation voltage.

Brazilian Journal of Physics, 2002

Applied Thermal Engineering, 2012

Applied Physics Letters, 2005

Transmission measurements as a function of applied reverse voltage, together with a fit procedure... more Transmission measurements as a function of applied reverse voltage, together with a fit procedure, demonstrate that the introduction of a nipi delta-doping superlattice in a GaAs∕AlGaAs multiple-quantum-well structure, for application in amplitude modulation, enhances the change in absorption with applied electric field, leading to an improvement of the device performance.