Papers by Faramarz Sahra Gard
Applied Physics A, 2013
In the present study, shards from Roman wall paintings (from the end of the first century to the ... more In the present study, shards from Roman wall paintings (from the end of the first century to the fourth century A.D.) decorating the domus below the Basilica of SS. John and Paul on the Caelian Hill (Rome), were analyzed in order to identify the pigments used. The analytical techniques employed for the characterization of the pigments were the scanning electron microscope coupled with an energy dispersive spectrometer (SEM-EDS) and infrared spectroscopy (ATR and micro ATR). While SEM-EDS allowed to perform a qualitative analysis of the material, by FT-IR chemical species have been identified. The pigments identified were those mentioned in the literature for the Imperial Roman fresco painting: different types of ochre (yellow and red), mixtures containing lead, green earths and precious pigments such as cinnabar and Egyptian blue. They were often used as mixtures and the use of the most valuable pigments (cinnabar and Egyptian blue) were found in the most ancient rooms.
Microscopy and Microanalysis, 2020
Applied Physics A, 2020
X-ray photoemission spectroscopy and Raman spectroscopy were used to identify pigments on an Egyp... more X-ray photoemission spectroscopy and Raman spectroscopy were used to identify pigments on an Egyptian cartonnage from the Ptolemaic period (305–30 BC). While XPS allowed us to perform a qualitative chemical analysis and establish the chemical composition of each pigment, Raman spectroscopy was employed to identify the associated minerals. High-resolution (HR) XPS spectra revealed the existence of Hg and S in the red region of the sample; Raman spectroscopy confirmed the presence of cinnabar (α-HgS), as the red pigment. Sulfur and arsenic were detected by HR XPS in the yellow part of the fragment, which is confirmed to be orpiment mineral (As 2 S 3 ) by Raman spectroscopy. Raman spectra from blue/green dark-colored regions of the samples corresponds to Egyptian blue pigment (CaCuSi 4 O 10 ). Detection of Cu and Cl by XPS, from the same region, is a strong indication of a degradation product of the Egyptian blue, namely a polymorph of trihydroxychloride Cu 2 (OH) 3 Cl.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2002
ABSTRACT A method which allows the erosion rate to be established from the earliest stages of an ... more ABSTRACT A method which allows the erosion rate to be established from the earliest stages of an ultralow energy secondary ion mass spectrometry (ule-SIMS) profile is described. Using the technique of medium energy ion scattering (MEIS), this method provides data which enables an accurate depth scale to be established from a depth of a few nanometers onwards. The method is applicable for a thin amorphous layer at the surface or a heavy element marker in the near-surface region, and enables the erosion rate as a function of SIMS ion dose to be established for particular bombardment conditions. The erosion rate obtained is used to calibrate the depth and intensity scales of implant profile measured using ule-SIMS and to interpret the near-surface distribution. In this article we demonstrate this methodology using a Ge preamorphized Si(001) surface with a 1 keV boron implant. The altered layer formed by the primary SIMS O incorporation and the redistribution of Ge in the samples used, are also described. Based on the Ge redistribution results, the possibility of adapting this method for determining erosion rates in crystalline silicon and silicon surface recession measurements, is also discussed.
Physical Review B, 2002
A method to accurately determine the sputter yield of the matrix from the earliest stages of a sp... more A method to accurately determine the sputter yield of the matrix from the earliest stages of a sputter profile is described. Using the technique of medium-energy ion-scattering spectroscopy, this method provides data that enable a depth scale to be established from subnanometer depths onward. It may be adapted to samples containing a thin amorphous surface layer ͑e.g., a preamorphized shallow implant͒ or to crystalline surfaces containing a heavy-element marker layer. In this Brief Report we have used this method to interpret the near-surface profile using erosion-rate data obtained from a 1-keV boron implant into a germanium preamorphized silicon ͑001͒ surface.
Applied Surface Science, 2003
The near-surface erosion rate in SIMS depth pro®ling is signi®cantly different from that in the b... more The near-surface erosion rate in SIMS depth pro®ling is signi®cantly different from that in the bulk, and varies with primary ion dose across the transient region in a currently unknown manner. Here, we describe a new method using medium energy ion scattering to measure the transient matrix sputter yield, and hence determine the erosion rate. We demonstrate its use in converting the raw dose and yield scales in a shallow depth pro®le to depth and concentration. We show that the surface erosion rate may be more than 10 times that in the bulk, and that the ion yield for boron in silicon apparently stabilizes before the sputter yield.
Surface and Interface Analysis, 2019
A wide range of analytical techniques has been used to study an Egyptian funerary mask of the Pto... more A wide range of analytical techniques has been used to study an Egyptian funerary mask of the Ptolemaic period (305-30 bc). Secondary electron (SE) and back-scattering (BS) images, recorded by a scanning electron microscope (SEM), provided a detailed representation of the metallurgical techniques used to construct the gilded mask. It is confirmed, that the golden leaf used to cover the mask is the product of an antique refinery practice, so called, cementation process of naturally occurring alloy of gold and silver, namely electrum. Complementary results of SEM-electron dispersion spectroscopy (EDS) and electron probe microanalysis (EPMA)–wavelength dispersion spectroscopy (WDS) provided chemical compositions of the golden leaf as well as in the plaster base of the mask. X-ray photoemission spectroscopy (XPS) revealed the presence of Au, Ag, Si, S, Cl, Ca, and N, in addition to O and C. Relative concentration of Au/Ag at the surface has been measured by XPS to be 70% to 30%. XPS depth profiling verified silver-enrichment at the surface, as ratio of gold to silver is measured to be 80% to 20% at the depth of 15 nm. XPS chemical mapping images of gold and silver confirmed a rather inhomogeneous character of Au/Ag relative concentration at the surface. The main diffraction peaks in the X-ray diffraction (XRD) spectrum coincide with diffraction peaks of pure gold, silver metals, and magnesium calcite Mg0.03Ca0.97CO3. Whereas, Raman spectroscopy results implied the existence of Ag2S, a tarnishing compound, on the golden area of the mask.Fil: Gard, Faramarz Sahra. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); ArgentinaFil: Daizo, María Belén. Universidad de Buenos Aires. Facultad de Filosofía y Letras; Argentina. Universidad Pedagógica Nacional. Departamento de Humanidades y Artes; ArgentinaFil: Santos, Diego Maximiliano. Universidad Pedagogica Nacional. Departamento de Humanidades y Artes.; ArgentinaFil: Halac, Emilia Betty. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Freire Espeleta, Eleonora. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Reinoso, Maria Elba. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bozzano, Patricia Beatriz. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Dominguez, Silvia Adriana. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Montero, Ricardo Jesús. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentin
Se desarrolla un sistema de espectroscopia de reflectancia difusa (DRS) para medir la temperatura... more Se desarrolla un sistema de espectroscopia de reflectancia difusa (DRS) para medir la temperatura de materiales semiconductores en vacío ultra alto cámara. DRS es un método óptico para monitorear la temperatura de materiales semiconductores con la temperatura dependiente band gap. El sistema está calibrado y probado para sustratos de n-GaAs y GaAs. En la comunicación actual, se informa sobre el desarrollo de hardware, software y la calibración del sistema.
Relative concentrations of nickel and copper at the surface of the ring and centre parts of 1-pes... more Relative concentrations of nickel and copper at the surface of the ring and centre parts of 1-peso and 2-pesos Argentine coins have been studied by means of X-ray photoemission spectroscopy (XPS). It has been observed Ni-enrichment at the surface of the ring (silvery) part of a 1-peso, minted in 1994, whereas the XPS data reveals lack of nickel at the surface of the centre (silvery) part of a 2-pesos, minted in 2016. This discrepancy is explained by analyzing the XPS peaks of oxygen and carbon, and is suggested to be related to the contamination layer on the surface of the coins. The XPS analysis of the golden parts of the coins, namely the centre part of the 1-peso and the ring part of the 2-pesos coins were inconclusive, due to the small amount of the Ni (nominally %2) used in those parts. The possible oxidations states of the metals at the surface of the untreated and treated coins with the artificial human sweat were also identified.
Surface and Interface Analysis
The European Physical Journal Applied Physics
Single crystals α-Al2O3 (0001) were exposed to the energetic Ar+-ions for two periods of 4 min wi... more Single crystals α-Al2O3 (0001) were exposed to the energetic Ar+-ions for two periods of 4 min with kinetic energy of 2 keV and 4 min of 5 keV at an incident angle of 45°. The samples were studied by X-ray photoemission spectroscopy (XPS) before and after Ar+-ion beam exposure. The average values of the bandgap energy before and after Ar+-ion beam treatment were measured to be (7.8 ± 0.2) eV and (6.3 ± 0.2) eV, respectively. The dynamic change in the XPS spectra of the valence band (VB) region before and after Ar+-ion beam treatment were explained using the theoretical calculation of the density of state (DOS) and the molecular orbital (MO) theory. This change is attributed to the transformation of α-phase to γ-Al2O3 phase at the surface. The surface morphology of the samples before and after Ar+-ion bombardment was also examined using scanning electron microscopy (SEM). Creation of circular well-shaped nanoholes with diameters in the range of (20–550) nm was observed at the surface...
A UHV atomic hydrogen-cracking cell has been constructed to produce atomic hydrogen in order to p... more A UHV atomic hydrogen-cracking cell has been constructed to produce atomic hydrogen in order to perform in-situ cleaning of semiconductor samples. The cell was calibrated and tested with the objective of cleaning the III-V semiconductor samples such as GaAs. Mass spectroscopy studies during the atomic hydrogen cleaning of the GaAs samples revealed the chemical process of the hydrogen cleaning. X-ray Photoemission Spectroscopy (XPS) was also carried out on the samples at different stages of cleaning. Desorption of the native oxide from GaAs samples resulted in a smooth surface, which was confirmed by Reflection High Energy Electron Diffraction (RHEED).
1998 Conference on Optoelectronic and Microelectronic Materials and Devices. Proceedings (Cat. No.98EX140), 1999
The studies reported here present data obtained from ZnSe epilayers grown on GaAs substrates by M... more The studies reported here present data obtained from ZnSe epilayers grown on GaAs substrates by MBE. The native oxide and carbon were removed from the substrate surface in two different ways, by thermally cleaning up to around 600°C and by exposing substrates at 450°C to atomic hydrogen. As passivated GaAs epilayers have also been used as substrates to grow ZnSe
COMMAD 2000 Proceedings. Conference on Optoelectronic and Microelectronic Materials and Devices, 2000
ZnSe epilayers were grown on GaAs using MBE. The native contamination (oxide and carbon) was remo... more ZnSe epilayers were grown on GaAs using MBE. The native contamination (oxide and carbon) was removed from the substrate surfaces by conventional thermal cleaning and by exposure to atomic hydrogen. A maximum substrate temperature of 600°C was required for the thermal cleaning process, while a substrate temperature of 450°C was sufficient to clean the substrate using the hydrogen. ZnSe epilayers
2009 International Semiconductor Device Research Symposium, 2009
Poly ethylene terephthalate (PET) is a favorite polymer for applications in flexible electronics ... more Poly ethylene terephthalate (PET) is a favorite polymer for applications in flexible electronics such as flexible displays and solar cells. Also it has extensive applications in food and packaging industries. A considerable decrease in permeability of polyethylene terephthalate (PET) films by means of surface plasma treatment in a reactive ion etching system is reported. The effects of hydrogen, oxygen and
Uploads
Papers by Faramarz Sahra Gard