Mohamed Abdellah Lemine | Al-Imam University (original) (raw)

Papers by Mohamed Abdellah Lemine

Optics Express, Vol. 22, Issue 10, pp. 11680-11689 (2014)

We report room-temperature Raman scattering studies of nominally undoped (100) GaAs1−xBix epitaxi... more We report room-temperature Raman scattering studies of nominally undoped (100) GaAs1−xBix epitaxial layers exhibiting Bi-induced (p-type) longitudinal-optical-plasmon-coupled (LOPC) modes for 0.018 ≤ x ≤ 0.048. Redshifts in the GaAs-like optical modes due to alloying are evaluated and are paralleled by strong damping of the LOPC. The relative integrated Raman intensities of LO(Γ) and LOPC ALO/ALOPC are characteristic of heavily doped p-GaAs, with a remarkable near total screening of the LO(Γ) phonon (ALO/ALOPC → 0) for larger Bi concentrations. A method of spectral analysis is set out which yields estimates of hole concentrations in excess of 5 × 1017cm−3 and correlates with the Bi molar fraction. These findings are in general agreement with recent electrical transport measurements performed on the alloy, and while the absolute size of the hole concentrations differ, likely origins for the discrepancy are discussed. We conclude that the damped LO-phonon-hole-plasmon coupling phenomena plays a dominant role in Raman scattering from unpassivated nominally undoped GaAsBi.

Biomaterials and Medical Tribology, 2013, Pages 1-132- A volume in Woodhead Publishing Series in Biomaterials

Journal of Alloys and Compounds, http://dx.doi.org/10.1016/j.jallcom.2014.04.002

Iron oxides nanoparticles with different sizes are successfully synthesized using sol-gel method... more Iron oxides nanoparticles with different sizes are successfully synthesized using sol-gel
method. X-ray diffraction (XRD) and Mössbauer spectroscopy show that the obtained
nanoparticles are mainly composed of maghemite phase (-Fe2O3). XRD and transmission
electron microscopy (TEM) results suggest that the nanoparticles have sizes ranging from 14
to 30 nm, which are indeed confirmed by large magnetic saturation and high blocking
temperature. At room temperature, the observation of a non-negligible coercive field suggests
2
that the particles are ferro/ferrimagnetic. The specific absorption rate (SAR) under an
alternating magnetic field is investigated as a function of size, frequency and amplitude of the
applied magnetic field. A mean heating efficiency of 30 W/g is obtained for the smallest
particles at 110 kHz and 190 Oe, whereas further increase of particle size does not improve
significantly the heating efficiency.

PhysicaE56(2014)107–112

Mn-doped ZnOnanocrystalsweresuccessfullypreparedusinganovelsol–gel methodfollowedbydrying in aut... more Mn-doped ZnOnanocrystalsweresuccessfullypreparedusinganovelsol–gel methodfollowedbydrying
in autoclaveundersupercriticalconditions.Theestimatedcrystallitesizeisintherangeof30–50 nm,in
agreement withTEManalysis.Rietveldrefinements confirm theformationofpureMn-dopedZnOfor
lowerMnconcentration.i.e.lessthan5%.ThelatticeparametersincreasewithincreasingMncontent
according toVegard'slawduetothelargerionicradiusofMn2þ compared tothatofZn2þ. Magnetic
analysisrevealsthatincreasingthedopinglevelofMnabove2%isnothelpingthelongrange
ferromagnetic orderinthesamplebutonlyenhancingtheparamagneticcomponent.Theparamagnetic
susceptibility isfoundtoincreaselinearlywithincreasingMnconcentrationwhichsuggeststhe
formation ofuncoupledmagneticmoment.TheestimatedvaluesforthemagneticmomentperMn
atom arefoundtobeintherangeof2–3.5 mB/Mn. Ab-initiocalculationsalsohavebeenperformedwhich
showedthatdopingdiamagneticbulkZnOwithMninducesferromagneticatroomtemperature,the
totalmagneticmomentumincreaseswithincreasingMncontentwhereasthemagneticmomentofMnis
predictedtobeintherangeof3–3.5 μB/Mn atomwhichisconsistentwiththevaluesobtainedfrom
magnetic measurements.

Journal of Alloys and Compounds 588 (2014) 592–595

Nanocrystalline Ni doped Fe2O3 powders were prepared by high-energy ball-milling from powders mix... more Nanocrystalline Ni doped Fe2O3 powders were prepared by high-energy ball-milling from powders mixture
of Nickel metal (Ni) and hematite (a-Fe2O3) with balls to powders mass ratio of 10:1 and for different
concentration. X-ray diffraction and vibrating sample magnetometer (VSM) are used to characterize the
samples. Phase identification shows that the hematite remains and confirmed the formation of a secondary
phase identified as NiFe2O4. The lattice parameters (a and c) of hematite phase increase with increasing
Ni concentration indicating an isotropic lattice expansion. The obtained nanocrystalline powders
were tested for toxic metals removal from aqueous solutions. It was found that Ni-doped Fe2O3 is a highly
efficient sorbent for Cd, Co and Ni from aqueous solution, and the maximum quantities of the adsorbed
Cd, Co and Ni concentration per gram of Ni-doped Fe2O3 are 65.46 mg/g, 43.29 mg/g, and 42 mg/g respectively.
We showed that Ni-doped Fe2O3 with 15 wt% is a highly efficient sorbent for Cd, Co and Ni from
aqueous solution, and this nanomaterial is more efficient to remove Cd (II), Co (II) and Ni (II) than Cr (VI).

Journal of Mechanical Science and Technology ,28, number 1, 2014 (January 2014).

An artificial-neural-network (ANN) model was developed to estimate the crystalline size of ZnO na... more An artificial-neural-network (ANN) model was developed to estimate the crystalline size of ZnO nanopowder as a function on the
milling parameters such as milling times and balls to powder ratio. This nanopowder was synthesized by high energy mechanical milling
and the required data for training were collected from the experimental results. The synthesized ZnO nanoparticles are characterized by
X-ray diffraction (XRD) and scanning electron microcopy (SEM). It was found that artificial neural network was very effective providing
a perfect agreement between the outcomes of ANN modeling and experimental results with an error by far better than multiple linear
regressions. An optimization model and this experimental validation of the ball milling process for producing the nanopowder ZnO are
carried out.

PhysicaE54(2013)233–236

Photoluminescenceintensityenhancementhasbeenobservedforself-assembledInAsquantumdots (QDs) coate... more Photoluminescenceintensityenhancementhasbeenobservedforself-assembledInAsquantumdots
(QDs) coatedwithgoldnanoparticlesandassociatedtosurfaceplasmon(SP)couplingeffects.Thiseffect
wasinvestigatedfordifferenttemperatures,excitationenergy,laserpower,GaAscaplayerthickness,and
QD morphology.ItwasfoundthattheSP–QD couplingefficiency increaseswiththeincreaseofthe
temperature.ItwasalsoobservedthatthiseffectisenhancedforQDsgrownon(311)BGaAsoriented
substrates.

Superlattices and Microstructures 65 (2014) 48–55.

The effects of long time thermal annealing at 200 C on the optical and structural properties of... more The effects of long time thermal annealing at 200 C on the optical
and structural properties of GaAs1xBix alloys were investigated by
X-ray diffraction (XRD), field emission scanning electron microscopy
(FESEM), high resolution transmission electron microscopy
(HRTEM) and photoluminescence (PL). FESEM images show that
bismuth islands nucleate on the surface and their diameter
increases after annealing. It was observed a PL intensity enhancement
and a small blue shift in PL peak energy after thermal annealing
at 200 C for 3 h of GaAs1xBix alloys which was associated to
the reduction of the density of defects. However these defects are
not completed removed by thermal annealing although an important
PL intensity improvement is observed.

J. Phys. D: Appl. Phys. 47 (2014) 075103 (4pp)

We have investigated the effect of long thermal annealing (3 h) at 200 ◦C on the physical proper... more We have investigated the effect of long thermal annealing (3 h) at 200 ◦C on the physical
properties of GaBiAs layers with a Bi concentration of 3% by using photoluminescence (PL)
and polarized resolved PL under magnetic fields up to 14 T. The PL intensity and the
diamagnetic shift of the annealed samples increased substantially. This indicates a reduction of
carrier/exciton localization due to defects. In addition, it was found that the degree of the
electron spin polarization increases up 41% at 14 T after thermal annealing due to the
reduction of the density of defects.

JOURNAL OF APPLIED PHYSICS 114, 193516 (2013)

We report room-temperature Raman studies of strained (100) and (311)B GaAs1xBix epitaxial layer... more We report room-temperature Raman studies of strained (100) and (311)B GaAs1xBix epitaxial
layers for x0.039. The Raman spectra exhibit a two-mode behavior, as well as disorder-activated
GaAs-like phonons. The experimental results show that the GaAs-like LO(C) mode experiences a
strong composition-dependent redshift as a result of alloying. The peak frequency decreases
linearly from the value for pure GaAs (293 cm1) with the alloyed Bi fraction x and the
introduced in-plane lattice strain ek, by DxLO ¼ Dxalloy Dxstrain. X-ray diffraction measurements
are used to determine x and ek allowing Dxalloy to be decoupled and is estimated to be 12(64)
cm1/x for (100) GaAs1xBix. DxLO is measured to be roughly double for samples grown on
(311)B-oriented substrates to that of (100) GaAs. This large difference in redshift is accounted for
by examining the Bi induced strain, effects from alloying, and defects formed during high-index
(311)B crystal growth.

Superlattices and Microstructures 60 (2013) 139–147

Mn doped ZnO nanoparticles with different doping concentration (1, 2, 3, 4, 5 at.%) were prepare... more Mn doped ZnO nanoparticles with different doping concentration
(1, 2, 3, 4, 5 at.%) were prepared by sol–gel method using supercritical
drying conditions of ethyl alcohol. The structural, morphological,
optical and magnetic properties of the as-prepared
nanoparticles were investigated by X-ray diffraction (XRD), transmission
electron microscopy (TEM), UV measurements and superconducting
quantum interference device (SQUID). The structural
properties showed that the undoped and Mn doped ZnO nanoparticles
exhibit hexagonal wurtzite structure. From the optical studies,
the transmittance in UV region was decreased with the
increase of Mn concentration. For Mn doped ZnO nanoparticles
the optical band gap varies between 3.34 eV and 3.22 eV. It was
found that the doping Mn2+ ions have a significant influence on
the optical properties. The magnetic characterization of the samples
with 1% and 5% Mn concentrations reveal diamagnetic behavior
for the first one and the presence of both paramagnetic and
ferromagnetic behavior for the second. The room ferromagnetic
component is due to the presence of the secondary phase ZnOMn3
which is confirmed by XRD study.

Bull. Mater. Sci., Vol. 36, No. 1, February 2013, pp. 25–29.

Molybdenum-doped indium oxide nanopowders were synthesized via mechanical alloying with subsequen... more Molybdenum-doped indium oxide nanopowders were synthesized via mechanical alloying with subsequent
annealing at a relatively low temperature of 600 ◦C. Themorphologies and crystal structures of the synthesized
nanopowders were examined by using scanning electron microscopy (SEM) and X-ray diffraction patterns. X-ray
diffraction pattern of the milled mixture shows the presence of both In2O3 phase and Mo element. The presence of
broad peaks in the pattern confirms that the synthesized powders are nanosized. The X-ray diffraction of annealed
samples at 600 ◦C shows the absence of Mo peaks revealing that the Mo was incorporated into the crystal lattices of
In2O3. Interestingly, it was observed that the diffraction peaks were still broad in the annealed samples indicating
the single phase at the nanoscale. From the XRD pattern, the calculated crystallite sizes were in the range of
12–18 nm. Magnetic properties of the synthesized Mo-doped In2O3 nanopowders were examined and it was found
that the obtained nanopowders possess diamagnetic properties.

Superlattices and Microstructures 52 (2012) 793–799

Magnetite (Fe3O4) nanoparticles were successfully synthesized by a sol–gel method. The obtained ... more Magnetite (Fe3O4) nanoparticles were successfully synthesized by a
sol–gel method. The obtained nanoparticles were characterized by
X-ray diffraction (XRD), field emission scanning electron microscopy
(FE-SEM), energy dispersive analysis by X-ray (EDAX), transmission
electron microscopy (TEM), superconducting quantum
interference device (SQUID) and Mössbauer spectrometry. XRD
and Mössbauer measurements indicate that the obtained nanoparticles
are single phase. TEM analysis shows the presence of spherical
nanoparticles with homogeneous size distribution of about
8 nm. Room temperature ferromagnetics behavior was confirmed
by SQUID measurements. The mechanism of nanoparticles formation
and the comparison with recent results are discussed. Finally,
the synthesized nanoparticles present a potential candidate for
hyperthermia application given their saturation magnetization.

$Research paper thumbnail of Neutron diffraction study and ab-initio calculations of nanostructured doped ZnO,$

Journal of Alloys and Compounds 536 (2012) 66–72

Nanostructured doped-ZnO system with various elements (M = Cr, Mn, Fe, Co, Ni, and In) at 10 at.%... more Nanostructured doped-ZnO system with various elements (M = Cr, Mn, Fe, Co, Ni, and In) at 10 at.% doping
concentration, was investigated. Neutron diffraction refinements confirm the stability of the würztite
crystal structure of the parent compound ZnO, the localization of the doping elements within Zn sites,
and some residual impurities. Magnetic measurements show a ferromagnetic behavior at room temperature
where the magnetic parameters, saturation magnetization (Ms), remanence (Mr) and coercivity (Hc)
vary considerable according to the nature of the doping elements, its valence and its solubility level: Ms
has the highest value of 0.223 emu/g for Ni and lowest value of 0.011 emu/g for Cu. The ab-initio calculations
using DFT method confirm the ferromagnetism of doped-ZnO in agreement with magnetic measurements.
It is found that oxygen plays an important role to explain the magnetic properties observed in
diluted magnetic semiconductors (DMS) of the studied doped-ZnO system. The estimated Curie temperature
was found to vary considerably according to the nature of the doping element, with the lowest
value for In (105 K) and highest value for Co (737 K).

Physica B 406 (2011) 1989–1994

Nanocrystalline zinc ferrite (ZnFe2O4) is synthesized by high-energy ball-milling after 12 h from... more Nanocrystalline zinc ferrite (ZnFe2O4) is synthesized by high-energy ball-milling after 12 h from a
powders mixture of zinc oxide (ZnO) and hematite (a-Fe2O3) with balls to powders mass ratio of 20:1.
X-ray diffraction, vibrating sample magnetometer (VSM), the M¨ ossbauer spectrometry and photoluminescence
(PL) are used to characterize the samples. Rietveld analysis and VSM measurements show
that the powder has an average crystallites size of 10 nm and a ferrimagnetic behavior with a saturation
magnetization of 30 emu/g. After annealing at 700 1C, the lattice parameter reduces from 8.448 to
8.427 ˚A and the sample transforms into a superparamagnetic behavior, which was confirmed as well by
the room temperature M¨ossbauer spectrometry. Different mechanisms to explain the obtained results
and the correlation between magnetism and structure are discussed. Finally, the broadband visible
emission band is observed in the entire PL spectrum and the estimated energy band gap is about
2.13 eV.

Journal of Alloys and Compounds 502 (2010) 279–282

The effect of high energy ball milling on the hematite for milling periods of times ranging from ... more The effect of high energy ball milling on the hematite for milling periods of times ranging from 1 to 48 h
was investigated by Rietveld analysis based on XRD patterns and Mössbauer spectroscopy. An expansion
of the unit cell parameters was observed. Both Scherrer method and Rietveld analysis show an evident
decrease of the grain size with the increase of the milling time. Moreover, some dependence of the lattice
parameters on the grain size was observed. Mössbauer spectroscopy measurements reveal that there
are two kinds of particles which co-exist in the sample: nanostructured and micrometric hematite. The
magnetic hyperfine field is affected by the grain size.

Superlattices and Microstructures 45 (2009) 576-582

In this investigation, the structural characteristics of α-Fe2O3 nanoparticles synthesised by a ... more In this investigation, the structural characteristics of α-Fe2O3
nanoparticles synthesised by a mechanical milling have been
explored. The structure and morphology of samples were char-
acterized by X-ray powder diffraction, field-emission scanning
electron microscope (FE-SEM) and FT-IR measurements. The crys-
tallite size and internal strain were evaluated by XRD patterns
using Williamson-Hall and Scherrer methods. The results did not
reveal any phase change during the milling. The average particle
size decreases with a prolongation of milling times, while the lat-
tice parameters and internal strain increase. Itwas found that using
this method allowed the formation of hematite nanoparticles.

Physical Review Letters vol 86 (2001) 3883 – 3886.

In ferromagnetic thin ﬁlms, the Curie temperature variation with the thickness is always consider... more In ferromagnetic thin ﬁlms, the Curie temperature variation with the thickness is always considered as
continuous when the thickness is varied from n to n 1 1 atomic planes. We show that it is not the case
for Fe in FeIr superlattices. For an integer number of atomic planes, a unique magnetic transition is
observed by susceptibility measurements, whereas two magnetic transitions are observed for fractional
numbers of planes. This behavior is attributed to successive transitions of areas with n and n 1 1 atomic
planes, for which the Tc’s are not the same. Indeed, the magnetic correlation length is presumably shorter
han the average size of the terraces. Monte Carlo simulations are performed to support this explanation.

Journal of Magnetism and Magnetic Materials 165 (1997) 220-223

he magnetic properties of Fe grown in FeIr(100) superlattices are investigated by 57F... more he magnetic properties of Fe grown in FeIr(100) superlattices are investigated by 57Fe Miissbauer spectrometry. Series
of superlattices with 3 to 8 57Fe and/or 56Fe atomic planes and Ir thicknesses from 2 to 30 A were prepared by molecular
beam epitaxy. For the series with 4 Fe atomic planes with body-centered tetragonal (bet) structure, the occurrence of a
sizeable magnetic moment in the two central Fe layers above a critical volume threshold is evidenced, whilst the Fe in
contact with Ir keep weakly magnetic. For series with more than 4 Fe planes, the transition from the bet to the bee structure
results in new magnetic sites. The arrangement along the growth direction is detailed showing a magnetic dissymmetry
between the Ir/Fe and Fe/Ir interfaces. Moreover, magnetic relaxation effects and spin wave softening are observed, likely
due to small magnetic correlations from plane to plane.