our activities on abo 3 oxides our activities on abo 3 oxides some information about dfav some...
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• Our activities on ABOOur activities on ABO33 oxides oxides
• Some information about DFAVSome information about DFAV• Brief summary on the activities of other groups Brief summary on the activities of other groups or DFAVor DFAV
University of Pavia
Dipartimento di Fisica “A. Volta”Dipartimento di Fisica “A. Volta” DFAV DFAV
Survey on activities on ABOSurvey on activities on ABO33 oxides oxides
University of Pavia University of Pavia Dipartimento di Fisica “A. Volta”Dipartimento di Fisica “A. Volta”
LiNbO3 Characterization of LN substrates
Characterization of structural and photoinduced defects
Microstructures in LN by means of fs laser pulses
Staff and experimental facilities
Materials and Collaborations
Basic physical problems of interest
•KTO/KLTN/BCT
•Charge transport and trapping in KTO
•Doping in KTO
Examples
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Staff members:
Giorgio Samoggia Full Professor Carlo Bruno Azzoni Associate Professor
H. of D.Pietro Galinetto ResearcherEnrico Giulotto ResearcherDaniela Grando * ResearcherMaria Cristina Mozzati Contract
ResearcherFrancesco Rossella Ph.D. StudentDorino Maghini TechnicianMassimo Marinone Graduate StudentVirginia Stasi Graduate StudentMassimiliano Rossi Graduate Student (USA
LBL)*Electronics Departmente-mail : [email protected]
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Experimental facilitiesExperimental facilities
•Raman and micro-Raman spectroscopy
•Optical absorption, PL, TL, PC, TSC
•Hall, Photo-Hall and magneto-optical spectroscopy
•EPR spectroscopy and Photo-EPR
•Static magnetization measurements
•Electro-optical characterization
•Femto-second laser sources
•Dielectric permittivity spectroscopyKiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Materials
LiNbO3
K1-xLixTa1-yNbyO3
Ba0.77Ca0.23TiO3
LiNbO3/LiTaO3KTaO3
BaTiO3
KNbO3
SrTiO3
LiTaO3
FeCrMgCuHfV…
Single crystals
thin films
Nano-particles diluted in silica glass
Nanosized grains ceramicsKiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Kiev 2005, February 2nd – P. Galinetto DFAV University of
Pavia
UniCatt. Physics Dept- Brescia
INOA Firenze
C.n.r. IMM Bologna
Dip. Fisica - Padova
C.n.r. Ist. di Cibernetica Napoli
Collaborations
Saes Getter S.p.a.
Avanex 2 Co.
A.F. Ioffe Physical & Technical Institute – S.Petersburg – RU
Materials physics department – UA Madrid - E
Fachbereich Physik, University of Osnabrueck - DE
Institute of Physics, AS CR, Prague RC
Dept of Mat. Science, Ukrainian Acad.of Sciences, Kiev, Uk
Main Basic Physical PhenomenaMain Basic Physical Phenomena
•Phase transitions (PT) in pure and mixed oxides based on ABO3 (KTO, STO, BTO, etc) compounds
•Structural, electronic and optical properties of intrinsic and impurities defects in ABO3 related materials
•Study of the transport phenomena and charge localization due to optical irradiation in ABO3 compounds
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Study of self-ordering and of new phase transitions in soft matrices containing interacting degrees of freedom of impurities and Jahn-Teller polarons
Doped KTO, KLT, KLTN
PT temperature ranging from LT to RT and morecomplex interplay between Li-dipoles and Nb-dipoles character of soft-mode and relaxation order-disorder PT, magnitude of dielectric susceptibility, and very interesting new matrix and impurity mode coupling effects,new PT and related phenomena.
Phase transitions in mixed oxides…..
Prof. Blinc, Opening talk EMF Cambridge 2003
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
KLTN 0.14/1.2KLTN 0.14/1.2
KLTN 0.4/3.1KLTN 0.4/3.1
0 20 40 60 80 100 120 140 160 180 200 220 2400
500
1000
1500
2000
2500
3000
3500
Inte
nsi
ty (
arb
.un
its)
Raman Shift (cm-1)
17 K 30 K 60 K 100 K 130 K 150 K 180 K
KLTN 0.6/17.3 + Cu, VKLTN 0.6/17.3 + Cu, V
Investigations of PT in KLTN combining Raman and dielectric spectroscopy
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Isovalent substitution Isovalent substitution BaBa2+2+ Ca Ca2+2+
Ca has smaller ionic radius (Ba= 1.35Ca has smaller ionic radius (Ba= 1.35Å vsÅ vs Ca= Ca= 0.990.99ÅÅ) )
Influence on Curie temperatureInfluence on Curie temperature
Source of structural disorderSource of structural disorder
Congruently grown barium calcium titanate,
Ba0.77Ca0.23TiO3 (BCT77/23) can be fabricated as high
optical quality single crystals, possess large electro-optic coefficients. Another great advantage of BCT is that the tetragonal-ortorhombic phase transition, which is destructive in BaTiO3, is depressed in BCT 77/23 holographic sensitivity making it excellent candidate for various photorefraction based applications
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
0 50 100 150 200 250 300
30
40
50
60
70
80
(cm
-1)
T (K)
2
3
4
5
6
inte
grat
ed in
tens
ity (a
.u.)
260
270
280
290
300
310
(cm
-1)
FWHM, integrated intensity and energy for the mode at 300 cm-1
The A-mode hardens
0 50 100 150 200 250 30020
40
60
(c
m-1
)
T (K)
1
2
3
4
Inte
grat
ed in
tens
ity (a
.u.)
42
44
46
48
(c
m-1
)
FWHM, integrated intensity and energy for the mode at 40 cm-1
The E-mode softens
Lowering the temperature...
•PHOTO-INDUCED EFFECTS ON PT IN KTO, STO
•?Nano-materials?: effect of nanometric scaling on the occurrence and the nature of phase transition in BTO, KTO and STO
Photo-induced transport phenomena and charge localization of ABO3 compounds
0 40 80 120 1600
50
100
150
5 10 15 20 25
1
10
100
Inte
grat
ed in
tens
ity (
arb.
un.
)
Temperature (K)
#3 "as grown" #3 after oxidation #542
E=0.16 eV
E=0.08 eV
Inte
grat
ed in
tens
ity (
arb.
un.
)
1/T (K-1)
10-2
10-1
100
101
102
1x103 B
PC
(A
)
(PC + PL) vs T
TL
TSC
+ EPR + photo-EPR
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Cu centres in KTO……impurities defects in ABO3
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Characterization of Cu centres in KTO
Other dopants like Be, Co, Ni
Absorption due to polarons in KTO:Be
LT Absorption, EPR, PhotoEPR, Phototransport, PL, TL, TSC
300 400 500 600 700 800
0.2
0.4
0.6
0.8
KTBe456t Be (transparent) KTBe456b Be (blue) KTPC340 pure (pale yellow) KTPC340c CuO (pale green/blue) KTGRN yellow KTCO2 Co (green)
Op
tica
l Den
sity
Wavelenght (nm)
400 500 600 700 8000.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
KTBe456t Be (transparent) KTBe456b Be (blue) KTPC340 pure (pale yellow) KTPC340c CuO (pale green/blue) KTGRN yellow KTCO2 Co (green)
Op
tica
l den
sity
Wavelenght (nm)
EPR+PhotoEPR +Abs
Characterization of structural, optical and electronic properties of LiNbO3 crystals and substrates in connection with different growth processes and different doping
Study of the transport phenomena and charge localization due to optical irradiation of LiNbO3 (or other ABO3 compounds, eventually doped) and of the irradiation effects on the linear and nonlinear optical properties
Study of the feasibility of 1D, 2D and 3D periodical structures, waveguides and microstructures on LiNbO3 (or other ferroelectric oxides) crystalline substrates by means of femtosecond laser irradiation in the transparent spectral region
Keypoints of activities on LiNbO3
Crystalline quality1
2
3
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
How we study crystalline How we study crystalline quality?quality?
•Raman and micro-Raman spectroscopy
•Optical absorption, PL, TL, PC, TSC
•Hall, Photo-Hall and magneto-optical spectroscopy
•Ellipsometry
•Electron Paramagnetic Resonance (EPR) and Photo-EPR
•Static magnetization measurements
•Electro-optical characterization
•Femto-second laser sources *Kiev 2005, February 2nd – P. Galinetto DFAV University of
Pavia
Lattice of ideal, defect-free LN crystal
coupling and mutual influence of intrinsic and extrinsic defects
decrease of the intrinsic defect concentration
Due to the Li-deficiency the conventional congruent crystals have high concentration of intrinsic (non-stoichiometric) defects, which can easily compensate a high concentration of extrinsic defects (for instance, optically or acoustically active impurities)
Possibility to vary both the [Li]/[Nb] ratio and [O] contents (in addition to the modification by dopants!) is a very powerful tool for the optimisation of crystal parameters
•strong increase of the spectrum resolution due to line narrowing
•changes of some LN properties
•appearance of new impurity centers
EPR
Raman
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
EPR spectroscopy :•Control of the material quality:
check of purity of growth processesdetection of defects and/or unwanted EPR active magnetic
impurities information about structural disorder
•Evaluation of the oxidation state of the transition ions•Information about site symmetry from the EPR signal angular dependence
Fe3+ EPR lines (BIc) in CLN (LN:Fe 0.1%)
…in quasi-st LN(LN:Fe 0.1%) 500 1000 1500 2000 2500
Der
ivat
ive
EP
R S
ign
als
(arb
. un
.)
B (G)
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Raman in LiNbO3In crystals, Raman spectrum depends on the direction and
polarization state of the incident and scattered light with respect to the cristallographic axes
Porto notation: ki(ei,ed)kd
The crystal structure of pure LiNbO3 has Rc3 space group symmetry and 4A1+ 9E Raman-active modes are predicted by factor-group analysis
b
a
a
zA
00
00
00
:)(1
00
00
0
:)(
d
c
dc
xE
00
0
00
:)(
d
dc
c
yE
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
0 200 400 600 800 1000 12000.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
In
tens
ity (
arb.
units
)
Raman Shift (cm-1)
z(x,x)z x(z,z)x
RS is strongly sensitive to orientation
Elight | c
Elight // c
-Raman to check disorientation, multidomains…
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
RS is sensitive to the deformation of the lattice and to the presence of point defects, becoming a powerful tool to deal with the problem of stoichiometry
The mode at 880 cm-1 is the vibration, parallel to the c axis, of the oxygen ions which consists basically in the stretching of the Nb–O and Li–O bonds.
800 820 840 860 880 900 920 940
0
1
2
3
4
5
6
7
Inte
sity
(ar
b.un
its)
Raman Shift (cm-1)
When a Nb ion sits at a Li site its oxygen first neighbors increase their bonding forces respective to the perfect crystal situation because of the stronger electrostatic interaction.
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Can be used to check the stoichiometry (Li/Nb ratio)
monitoring the changes of linewidth of some Raman modes. FWHM changes are greater than
peak shift.
100 120 140 160 1800.0
0.5
1.0
1.5
CL1
CL2
q-SLCL3
Inte
nsit
y (a
rb.u
nits
)
Raman Shift (cm-1)
800 820 840 860 880 900 920 9400
1
2
3
4
5
6
7
8
q-SLCL1
Inte
sity
(ar
b.un
its)
Raman Shift (cm-1)
48.0 48.5 49.0 49.5 50.05
10
20
25
30
FWHM @ 152 cm-1
FWHM @ 870 cm-1
(c
m-1)
Li content (mol%)
The fact that the linewidth of some Raman modes scale with the composition xc =
[Li]/([Li] + [Nb]) of LN crystals, together with the use of a confocal microscope (
Raman), allows a 3D determination of the sample stoichiometry.
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
0 20 40 60 80 1009
10
11
12
= 1 cm-1
FWH
M (
cm-1)
depth ()0 2000 4000 6000 8000 10000
9.0
9.5
10.0
10.5
11.0
11.5
12.0
FWH
M (
cm-1)
spot position at 10 m depth (m)
Scan at 10 microns depth in a 10 mm
long plateDepth profile
Li/Nb changes ˜ 0.08 %
good homogeneity of Li/Nb ratio (changes less than 0.3 cm-1)
Non-destructive structural toolNon-destructive structural tool
Micron-scale spatial resolutionMicron-scale spatial resolution
Presence of a structurally disordered layerPresence of a structurally disordered layer
Effectiveness of damage removal methodEffectiveness of damage removal method
Control on optical surface finishingControl on optical surface finishing
Raman for surface quality analysis after wafering process:Raman for surface quality analysis after wafering process:
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Important complete characterization of: stoichiometry, nature and content of impurities, degree of structural disorder before starting with investigation of charge trapping mechanisms and phenomena related to photo-induced defects
Study of the transport phenomena and charge localization due to optical irradiation of LiNbO3 (or other ABO3 compounds, eventually doped) and of the irradiation effects on the linear and nonlinear optical properties
2
• Photovoltaic current, photoconductivity,
• Photo-EPR
vs %, doping, T
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
complementary techniques (Raman microscopy, Electron Paramagnetic Resonance, optical absorption, photo-voltaic current and photo-conductivity measurements) were used to detect intrinsic and extrinsic defects, charge trapping and recombination processes, and the related photo-refractive behaviour in lithium niobate single crystals, with congruent and stoichiometric composition, containing Fe and Mg dopant. The role of UV and visible irradiation was investigated.
Comprehension and control of the photocarrier localization mechanisms in connection with preparation methods and treatment of the materials.
Characterization of structural and photoinduced defects in pure and doped lithium niobate
The properties of LN crystals are not simply ruled by the stoichiometry (Li/Nb ratio) and by intentional or accidental impurities: interrelations of intrinsic and extrinsic defects ever exist, leading to different phenomena in samples with apparent similar composition. In this frame it is important to perform experiments in crystals well characterized in terms of stoichiometry, impurity content and degree of structural disorder.ExperimentalExperimental
VIS-UV
UV
Charge transport and trapping phenomena
Photovoltaic and Photocurrent
Raman scattering, optical absorption, EPR
Foto-EPR
130 140 150 160 170 180
1
2
3
E mode at about 150 cm-1
Inte
nsi
ty (
arb
. un
.)
Raman Shift (cm-1)
Sp SFe CFe Cp CFM
825 850 875 900 925
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
A mode at about 870 cm-1
Raman Shift (cm-1)
In
ten
sity
(ar
b.u
nit
s) Sp CFe Cp CMg SFe CFM
Raman spectroscopy Raman spectroscopy
1 2 3 4
0.5
1.0
1.5
SFeCMF
CpCFe
CFe5%
Opt
ical
den
sity
energy (eV)
Optical absorptionOptical absorption
Shift in the ”optical edge”
Absorption Band at ~ 2.6 eV,
Fe2+Mg doping: decrease in the polaron induced abs band
antisites NbLi
Absorption Band at ~ 1.5 eV polarons
0 2000 4000 6000 8000
x0.2
x10
x20
CMg
CFM
Cp
CFe
Sp
SFe
Der
ivat
ive
EP
R S
ign
als
(arb
. un
.)
B (G)
EPR EPR B c-axisB c-axis
Sfe: componenti a 380 G e 1440 G, più intense, con la minore larghezza di riga (ΔB) e forma quasi simmetrica, in accordo con stechiometria nominale
SFe e CFe hanno stechiometria in accordo con quella nominale, paragonabile quantità di Fe3+ e, in particolare SFe, buona
qualità del cristallo
SFe e CFe hanno stechiometria in accordo con quella nominale, paragonabile quantità di Fe3+ e, in particolare SFe, buona
qualità del cristallo
CMF: transizione –½ +½, indipendente dalla simmetria puntuale, è la più intensa alto grado di disordine nei siti reticolari di Fe, indotto dal drogaggio di Mg, porta allo “spread” e quindi all’allargamento e alla scomparsa delle componenti a bassi campi di risonanza.
Appl. Phys. A 56, 103-108 (1993)
Fe3+: presente in tracce anche nei campioni nominalmente puri, non rilevato solo in CMg.
Cfe: righe più larghe e asimmetriche. BCFe è circa 3 volte BSFe (valori in accordo coi risultati di ΔB vs. xc di letteratura).
0 100 200 300 400 500-10
-8
-6
-4
-2
0
2
4
6Ar-ion laser source: 514nm, 15mW
J (1
0-6A
/m2 )
CFe SFe CFM
time (s)
Photovoltaic current and Photoconductivity Photovoltaic current and Photoconductivity
VISIBLE
UV
0 100 200 300 400-50
-40
-30
-20
-10
0
10
20
30
40
Xe-lamp, broad-band UV light, 70 mW
J (1
0-6A
/m2 )
time (s)
CFe SFe CFM
0 100 200
-3
-2
-1
0
J (1
0-6A
/m2 ))
time (s)
2.725 0.1 0.17 CFM - UV
2.37 0.13 0.044 -CFM – 514 nm
0.58 1.55 3.4 SFe - UV
0.16 0.023.6 -SFe – 514 nm
0.04 0.031 0.79 CFe - UV
0.036 L 0.054 H 3.02 -CFe - 514 nm
JDARK (10-6A/m2) JPHC (10-6A/m2) JPHV (10-6A/m2)
Jphv is proportional to the number of Fe2+, while Jphc is proportional to the [Fe2+]/[Fe3+] ratio
This one-center model was refined, adding to the scheme the intrinsic defects NbLi, which can take part in the charge transport as shallow electron traps, lowering the n-type Jphc
Campo applicato: 60kV/m. Contatti normali all’asse ottico (asse c).
Study of the feasibility of 1D, 2D and 3D periodical structures, waveguides and microstructures on LiNbO3 (or other ferroelectric oxides) crystalline substrates by means of femtosecond laser irradiation in the transparent spectral region
3
“MICROSTRUCTURAL MODIFICATION OF LINBO3 CRYSTALS INDUCED BY
FEMTOSECOND LASER IRRADIATION”Appl. Surf. Science in press
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Femto-writing e femto-sculptureFemto-writing e femto-sculptureAdvantage of the method: Advantage of the method: i irradiation in the transparence region
higher penetration length
very high peak intensity multiphoton absorption cascade ionization
the energy transfer is confined in the focal volume
Possible effects: Possible effects:
•Refraction index changes due to photorefractive/stresses/structural changes
•Ablation – optical breakdown
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Gratings written by means of ultrashort pulses (100fs) with interferential method in glassesApplied Surface Science 197
(2002) 688, M. Hirano et al.
Wave-guide laser writing in transverse and longitudinal geometry
Experimental Set-up
Ti:Sapphire oscillator
25 nJ-130 fs-82 MHz
Ti:Sapphire amplifier
1 mJ-130 fs-1 kHz
Dichroic mirror
CCD camera
in situ monitoring
Sample on motor controlled xyz stage
mirror
shutter
/2 sheet
isolatore
polarizer
objectiveMonitoring channel
filters
mirror
= 810 nm
/2 sheet
Commercial z-cut congruent LN substrates.
At the LaserLab of Electronics Dept
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
The main effect of the irradiation in this regime was the formation of refractive index microstructures, visible at the polarizing microscope.
Ti:Sapphire oscillator, LE + HRR
At the focus region either refractive index changes or material removal were observed at variance of irradiation conditions.
Formation of large ablated regions (>10 m) triggered by the presence of crystal defects, surface scratches or accumulation centers.
200 400 600 800 1000
Raman Shift (cm-1)
Ram
an
In
ten
sity
(arb
.un
its)
Oscillator ablationAmplifier ablation
200 400 600 800 10000
2000
4000
6000
8000
10000
Y A
xis
Titl
e
X Axis Title
B D F
Raman shift (cm-1)
AFM
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
3μm-step grating
Efficiency:
10% - 1st order (red light)
Grating diffraction spots
10μm
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
laser source (He-Ne): 20 mW , λ = 632.8 nm
Integrated Optical microscope Olimpus Spot diameter 10 µm ÷ 1 µm depending on the objectives (10X, 50X, 100X), autofocus by means of piezoelectric driver Back-scattering geometry
Spectrometer focal length = 300 mm , 2 holographic gratings (1800 gg/mm or 600 gg/mm). Resolution 0.2 cm-1
Holographic notch filter
CCD 256 X 1024 pixels (pixel = 27 µn, 16 bit dinamical range), Peltier cooled system
Experimental set-upconventional Labram Dilor JYHoriba (mod. 010)
60 cm
EPR spectrometer
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Apparato di misura: MAGNETOMETRO SQUID
Cosa misura:
momento magnetico“m” di un campione,
da cui si determinano suscettività magnetica e magnetizzazione
Unità di misura: emu (erg/G)
Range di misura di “m”: 10-8 2
emu (condizioni standard)
Errore di misura: in genere < 2%
Come misura:
Sonda bobina superconduttrice connessa
a uno SQUID che rileva la variazione del flusso
magnetico provocata dal movimento del
campione attraverso la bobina stessa (tecnica a
estrazione).
other research activities
Colossal Magnetoresistive Material (La1-xAxMnO3 A = Ca, Na)
CaCu3Ti4O12 (CCTO): high-k material
Li3VO4:Cr,Mg ionic transport, SHG
Ultrafast spin dynamicsin ferromagnetic thin films transient MOKE
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Dipartimento di Fisica “A. Volta”Dipartimento di Fisica “A. Volta”
12 full professors
18 associate professors
10 researchers
15 technicians
30 post graduate, PhD and fellowship students
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Sources of budget (~)
1990
20%
0%45%
10%25%
National Grant Eu-Int Grant UniPV Private companies INFM
2004
0%7%
8%
35%
50%
National Grant Eu-Int Grant UniPV Private companies INFM
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
•Physics education and physics history
•Quantum information theory
•Optical spectroscopy & laser-matter interaction in semiconductors
•Magnetism and superconductivity Magnetism and superconductivity
Research activities of other groups
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
PHYSICS EDUCATION and PHYSICS HISTORY GroupStaff: G. Bonera, L. Borghi, A. De Ambrosis, L. Falomo, L. Mascheretti, M.C. Garbarino, L. Cardinali
*Identification of tools and strategies to support the Physics teaching/learning process
*Historical comprehension of the developments of different physical branches, taking into account not only the technical aspects but also the global cultural and social context.
QUANTUM INFORMATION THEORY GROUPStaff: GM D’Ariano, C. Macchiavello, M. Sacchi, P. Lo Presti, R. Buscemi, E. Chiribella, P. Perinotti
•Quantum Measuring Devices for Photonics and Quantum Information •Entanglement Assisted High Precision Measurements •Quantum Teleportation and Quantum Cloning by the optical parametric squeezing process •Quantum Properties of Distributed Systems
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
MAGNETISM AND SUPERCONDUCTIVITYMAGNETISM AND SUPERCONDUCTIVITYDipartimento di Fisica “A. Volta”, Universita’ di Pavia and INFM, Via Bassi 6 , I-27100 Pavia (Italy)
Techniques : Nuclear Magnetic Resonance (NMR, mainly in Solids)Muon Spin Rotation (MUSR) Susceptibility and magnetization (SQUID)Specific heat Magnetic Resonance Imaging (collaborations)
Team : Prof. A. Rigamonti, Prof. F. Borsa, Prof. P. Carretta, Prof. M. Corti, Dr. A. Lascialfari, p.i. S. AldrovandiPost-doc : J. LagoPhD and graduate students : I. Zucca, L. Spanu, E. Micotti, N. Papinutto, M. Filibian, M. Mariani
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Motions and structure of flux lines lattice in Motions and structure of flux lines lattice in superconductorssuperconductors
Diamagnetic fluctuations above TDiamagnetic fluctuations above TCC in BCS superconductors (MgB in BCS superconductors (MgB22))
Quantum Phase transitions (Quantum Critical Point)Quantum Phase transitions (Quantum Critical Point)
CeCuCeCu6-x6-x Au Auxx
Low-dimensional Low-dimensional quantum antiferromagnets (S=1/2) quantum antiferromagnets (S=1/2)
La2CuO
4
SrCu2
O3
Sr2CuO
3
Cu8
Negligible intermolecular interactions molecular nanomagnets
Molecular nanomagnetsMolecular nanomagnets
Fe8 crystal
Easy-axis (magnetization)
Fe (3+) s=5/2 ground state S=10 (giant spin)
Quantum tunneling of the magnetization (QTM)Quantum tunneling of the magnetization (QTM)
Optical Spectroscopy & Laser-Matter Interaction
Optical Spectroscopy Laboratory
M. Galli, D. Bajoni, M. Patrini, M. Belotti, G. Guizzetti, F. Marabelli
Nonlinear Optics Laboratory
A.M. Malvezzi, M. Patrini, G. Vecchi, C. Comaschi
Electronic and photonic nanostructures: theory
D. Gerace, M. Liscidini, M. Agio, A. Balestrieri, L.C. Andreani
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Optical Techniques
Linear:•angle-resolved reflectance & transmittance
•spectroscopic ellipsometry
•modulation spectroscopies (photo-, electro- and thermo-reflectance).
Nonlinear : •Raman scattering •luminescence and •second-harmonic generation•time-resolved spectroscopy
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia
Optical Spectroscopy Laboratory Facilities
•FFT-IR spectrometer, 20-5000 cm-1, with accessories for reflectance and transmittance measurements, cryostat for T= 4-300 K, micro-reflectance apparatus and optical microscope for high spatial resolution
•FT-Step Scan, with spectral extension up to the visible (20 – 50000 cm-1) for phase-sensitive detection and time-resolved spectroscopy (> 1 s) in reflectance and transmittance.
•Spectrophotometer 200-3300 nm, with cryostat for T = 12 - 300 K, and accessories for transmittance and reflectance in the specular and diffuse configurations (250-2500 nm).
•Spectroscopic ellipsometer (250 - 900 nm), with macro- and micro- probe (minimum spot size 100 microns) .
•Micro - Raman apparatus with He-Ne laser source, microprobe (down to 1 micron) and stage for mapping, CCD camera detector.
•Atomic Force microscope
Laser Matter Interaction Laboratory Facilities
• CW picosecond laser system 80 MHz, 40 ps, > 10 W @1.053 µm , 1.5 W @ 0.53 µm, THG and FHG
• CW femtosecond laser system, 130 fs, 760 - 840 nm, 2 W
• CW femtosecond OPO, 80 MHz, 1.4 - 2 µm
• Detection facilities from UV to IR, lock-in, average, photon counting
• Nonlinear measurements, 2nd and 3rd harmonic generation
• Photonic crystals and waveguides
•Metallic and semiconducting nanoparticles in dielectric matrices
•SiGe Q-dots for integrated optics Si-compatible
• Q-dots InAs/InGaAs for laser @ 1.3 – 1.55 micron
• III-V structures for photovoltaic applications
Research activities
Si
SiO2
– X ( = 0°)
In any case…