1. Dipartimento di Fisica “A. Volta” DFAV
University of Pavia
Dipartimento di Fisica “A. Volta” DFAV
Our activities on ABO3 oxides
Some information about DFAV
Brief summary on the activities of other groups or DFAV

2. Survey on activities on ABO3 oxides
University of Pavia Dipartimento di Fisica “A. Volta”
Survey on activities on ABO3 oxides
Staff and experimental facilities
Materials and Collaborations
Basic physical problems of interest
Examples
KTO/KLTN/BCT
Charge transport and trapping in KTO
Doping in KTO
LiNbO3  Characterization of LN substrates
Characterization of structural and photoinduced defects
Microstructures in LN by means of fs laser pulses
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

3. Staff members: Giorgio Samoggia Full Professor
Carlo Bruno Azzoni Associate Professor H. of D.
Pietro Galinetto Researcher
Enrico Giulotto Researcher
Daniela Grando * Researcher
Maria Cristina Mozzati Contract Researcher
Francesco Rossella Ph.D. Student
Dorino Maghini Technician
Massimo Marinone Graduate Student
Virginia Stasi Graduate Student
Massimiliano Rossi Graduate Student (USA LBL)
*Electronics Department
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

4. Experimental 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 spectroscopy
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

5. Materials LiNbO3 BaTiO3 LiTaO3 K1-xLixTa1-yNbyO3 Ba0.77Ca0.23TiO3Fe Cr Mg Cu Hf V …
LiNbO3
LiTaO3
K1-xLixTa1-yNbyO3
Ba0.77Ca0.23TiO3
LiNbO3/LiTaO3
BaTiO3
SrTiO3
KNbO3
KTaO3
Single crystals
thin films
Nano-particles diluted in silica glass
Nanosized grains ceramics
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

6. Collaborations Saes Getter S.p.a. Avanex 2 Co.
UniCatt. Physics Dept- Brescia
INOA Firenze
C.n.r. IMM Bologna
Dip. Fisica - Padova
C.n.r. Ist. di Cibernetica Napoli
Saes Getter S.p.a.
Avanex 2 Co.
Materials physics department – UA Madrid - E
Dept of Mat. Science, Ukrainian Acad.of Sciences, Kiev, Uk
Institute of Physics, AS CR, Prague RC
Fachbereich Physik, University of Osnabrueck - DE
A.F. Ioffe Physical & Technical Institute – S.Petersburg – RU
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

7. Main 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

8. Doped KTO, KLT, KLTN Phase transitions in mixed oxides…..
Study of self-ordering and of new phase transitions in soft matrices containing interacting degrees of freedom of impurities and Jahn-Teller polarons
Prof. Blinc, Opening talk EMF Cambridge 2003
Doped KTO, KLT, KLTN
PT temperature ranging from LT to RT and more
complex 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.
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

9. Investigations of PT in KLTN combining Raman and dielectric spectroscopy
KLTN 0.6/ Cu, V
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

10. Isovalent substitution Ba2+  Ca2+
Ca has smaller ionic radius (Ba= 1.35Å vs Ca= 0.99Å)
Influence on Curie temperature
Source 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

11. FWHM, integrated intensity and energy for the mode at 300 cm-1
Lowering the temperature...
The E-mode softens
FWHM, integrated intensity and energy for the mode at 300 cm-1
FWHM, integrated intensity and energy for the mode at 40 cm-1
The A-mode hardens

12. 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

13. Photo-induced transport phenomena and charge localization of ABO3 compounds
(PC + PL) vs T TL
TSC
+ EPR + photo-EPR
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

14. Cu centres in KTO ……impurities defects in ABO3 EPR+PhotoEPR +Abs
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
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

15. Keypoints of activities on LiNbO3
Characterization of structural, optical and electronic properties of LiNbO3 crystals and substrates in connection with different growth processes and different doping
Crystalline quality 1
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
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
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

16. How we study crystalline 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

17. coupling and mutual influence of intrinsic and extrinsic defects
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)
coupling and mutual influence of intrinsic and extrinsic defects
decrease of the intrinsic defect concentration
strong increase of the spectrum resolution due to line narrowing
changes of some LN properties
appearance of new impurity centers  
EPR
Raman
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
Lattice of ideal,
defect-free LN crystal
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

18. Fe3+ EPR lines (BIc) in CLN (LN:Fe 0.1%)
EPR spectroscopy :
Control of the material quality:
check of purity of growth processes
detection 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%)
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

19. Raman in LiNbO3 Porto notation: ki(ei,ed)kd
In 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
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

20. RS is strongly sensitive to orientation
Elight | c
Elight // c
m-Raman to check disorientation, multidomains…
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

21. 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.
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

22. 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.
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 ( mRaman), allows a 3D determination of the sample stoichiometry.
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

23. good homogeneity of Li/Nb ratio (changes less than 0.3 cm-1)
Scan at 10 microns depth in a 10 mm long plate
Depth profile
Li/Nb changes ˜ 0.08 %
good homogeneity of Li/Nb ratio (changes less than 0.3 cm-1)

24. mRaman for surface quality analysis after wafering process:
Non-destructive structural tool
Micron-scale spatial resolution
Presence of a structurally disordered layer
Effectiveness of damage removal method
Control on optical surface finishing
mRaman for surface quality analysis after wafering process:
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

25. Photo-EPR vs %, doping, l, T
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
Photovoltaic current, photoconductivity,
Photo-EPR
vs %, doping, l, T
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
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

26. 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.

27. 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.
Experimental RT l
Raman scattering, optical absorption, EPR
Photovoltaic and Photocurrent l
Charge transport and trapping phenomena
VIS-UV l
Foto-EPR UV

28. Raman spectroscopy

29. Optical absorption Shift in the ”optical edge”
Absorption Band at ~ 2.6 eV,
 Fe2+
antisites NbLi
Absorption Band at ~ 1.5 eV  polarons
Mg doping: decrease in the polaron induced abs band

30. EPR
B  c-axis
Fe3+: presente in tracce anche nei campioni nominalmente puri, non rilevato solo in CMg.
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
Cfe: righe più larghe e asimmetriche. BCFe è circa 3 volte BSFe (valori in accordo coi risultati di ΔB vs. xc di letteratura).
Appl. Phys. A 56, (1993)
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.

31. Photovoltaic current and Photoconductivity
VISIBLE UV

32. 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
0.02
3.6
-SFe – 514 nm
0.04
0.031
0.79
CFe - UV
0.036 L
H 3.02
-CFe 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).

33. Appl. Surf. Science in press
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

34. Femto-writing e femto-sculpture
Advantage of the method: 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:
Refraction index changes due to photorefractive/stresses/structural changes
Ablation – optical breakdown
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

35. Wave-guide laser writing in transverse and longitudinal geometry
Gratings written by means of ultrashort pulses (100fs) with interferential method in glasses
Applied Surface Science 197 (2002) 688, M. Hirano et al.
Wave-guide laser writing in transverse and longitudinal geometry

36. Experimental Set-up = 810 nm Ti:Sapphire oscillator
At the LaserLab of Electronics Dept
= 810 nm
Ti:Sapphire oscillator
25 nJ-130 fs-82 MHz
mirror
/2 sheet
isolatore
Ti:Sapphire amplifier
1 mJ-130 fs-1 kHz
shutter
/2 sheet
Dichroic mirror
Monitoring channel
objective
Commercial z-cut congruent LN substrates.
Sample on motor controlled xyz stage
filters
CCD camera
polarizer
in situ monitoring
mirror
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

37. 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 mm) triggered by the presence of crystal defects, surface scratches or accumulation centers.
Ti:Sapphire oscillator,
LE + HRR
The main effect of the irradiation in this regime was the formation of refractive index microstructures, visible at the polarizing microscope.

38. Raman shift (cm-1)
Oscillator ablation
Amplifier ablation

39. AFM
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

40. Grating diffraction spots
3μm-step grating
Efficiency:
10% - 1st order (red light)
10μm
Grating diffraction spots
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

42. Experimental set-up conventional Labram Dilor JYHoriba (mod. 010)
laser source (He-Ne):
20 mW , λ = 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
60 cm

43. EPR spectrometer
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

44. 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).

45. other research activities
Colossal Magnetoresistive Material
(La1-xAxMnO3 A = Ca, Na)
CaCu3Ti4O12 (CCTO): high-k material
Li3VO4:Cr,Mg  ionic transport, SHG
Ultrafast spin dynamics
in ferromagnetic thin films  transient MOKE
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

46. 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

47. Sources of budget (~)
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

48. Research activities of other groups
Physics education and physics history
Quantum information theory
Optical spectroscopy & laser-matter interaction in semiconductors
Magnetism and superconductivity
Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

49. QUANTUM INFORMATION THEORY GROUP
PHYSICS EDUCATION and PHYSICS HISTORY Group
Staff: 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 GROUP
Staff: 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

50. MAGNETISM AND SUPERCONDUCTIVITY
Dipartimento di Fisica “A. Volta”, Universita’ di Pavia and INFM, Via Bassi 6 , I 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. Aldrovandi
Post-doc : J. Lago
PhD 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

51. Motions and structure of flux lines lattice in superconductors
Diamagnetic fluctuations above TC in BCS superconductors (MgB2)
Quantum Phase transitions (Quantum Critical Point)
CeCu6-x Aux
Low-dimensional
quantum antiferromagnets (S=1/2)
La2CuO4
SrCu2O3
Sr2CuO3
Cu8

52. Molecular nanomagnets Quantum tunneling of the magnetization (QTM)
Negligible intermolecular interactions  molecular nanomagnets
Fe8 crystal
Quantum tunneling of the magnetization (QTM)
Easy-axis
(magnetization)
ground state
S=10 (giant spin)
Fe (3+) s=5/2

53. 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

54. Optical Techniques Linear: Nonlinear :
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 2

55. Optical Spectroscopy Laboratory Facilities
FFT-IR spectrometer, cm-1, with accessories for reflectance and transmittance measurements, cryostat for T= K, micro-reflectance apparatus and optical microscope for high spatial resolution
FT-Step Scan, with spectral extension up to the visible (20 – cm-1) for phase-sensitive detection and time-resolved spectroscopy (> 1 ms) in reflectance and transmittance.
Spectrophotometer nm, with cryostat for T = K, and accessories for transmittance and reflectance in the specular and diffuse configurations ( nm).
Spectroscopic ellipsometer ( 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 3

56. Laser Matter Interaction Laboratory Facilities
CW picosecond laser system 80 MHz, 40 ps, > 10 µm , ­ µm, THG and FHG
CW femtosecond laser system, ­130 fs, nm, 2 W
CW femtosecond OPO, 80 MHz, µm
Detection facilities from UV to IR, lock-in, average, photon counting
Nonlinear measurements, 2nd and 3rd harmonic generation 4

57. Research activities Metallic and semiconductingSi
SiO2
G – X ( = 0°)
Photonic crystals and waveguides
Metallic and semiconducting
nanoparticles in dielectric matrices
SiGe Q-dots for integrated optics Si-compatible
Q-dots InAs/InGaAs for 1.3 – 1.55 micron
III-V structures for photovoltaic applications

59. In any case…

60.                                                    
Thanks!