RUSSIAN-ARMENIAN%20STATE%20UNIVERSITY%20PHYSICO-TECHNICAL%20DEPARTMENT%20Ovsep%20Emin%20Str.123,Yerevan,%20Armenia%20Prof.%20Stepan%20Petrosyan%20email:[e-mail]%20Dr.%20Vladimir%20Gevorkyan%20email:[e-mail]

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RUSSIAN-ARMENIAN STATE UNIVERSITYPHYSICO-TECHNICA
L DEPARTMENTOvsep Emin Str.123,Yerevan,
ArmeniaProf. Stepan Petrosyanemail
spetrosyan_at_rau.amDr. Vladimir Gevorkyan email
vgev_at_rau.am
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Field of Scientific Activities

• Growth and research of InAsSbP/InAs and Cu2O
  based heterostructures for photovoltaic and
  thermophotovoltaic applications
• Development of novel technological methods for
  the growth of III-V and ZnO nanowires for opto-
  and microelectronic device applications
• Theoretical and experimental study of high
  efficiency quantum dot solar cells
• Theory of nanoscale contacts and nanodevices
  (photodiodes, field-effect transistors,
  position-sensitive detector)

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Novel diode heterostructures on the base of InAs
alloys Fields of applications
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Thermophotovoltaic converters
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Relative spectral response of the n-InAs /
n0-InAs / p- InAs0.27Sb0.23P0.5 TPV diode
heterostructure grown by non-equilibrium MOVPE
growth technique
Sl,max 1.4 - 1.6 A/W h 0.4 - 0.5
Flexibility of the heat source, which includes
solar and other thermal sources of energy Compact
in size Light weight Low Noise TPV converters
can provide 24 hours of electricity due to
combining solar energy and thermal energy
(combustion flame, etc.).
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Mid-Infrared photodiodes
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Quantum Dot Solar Cell Structure

1. Schematic diagram of QDSC
2. Corresponding energy band structure

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Quantum Dot Solar Cell Results

1. Photocurrent density versus number of stacked
   layers compared with the photocurrent without
   QDs.
2. Comparison of external quantum efficiency of the
   solar cells with different stacked layers and
   without dots

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2D p-n JUNCTION

• l V
• QW thickness dependent built-in potential
• Small capacitance with log dependence on voltage
• Very large breakdown voltage
• High 2D electron mobility

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2D Shchottky contact
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2D electron gas field efect transistor
2DEG

• High channel conductivity
• Very high transconductance.

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Laser Synthesis of the Colloidal Nanoparticles
Laser ablation of materials in liquids
Technique Applied

• Semiconductor Nanoparticles (Quantum Dots)
• Metal Nanoparticles
• Carbon Nanoparticles
• Polymer Nanoparticles

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Quantum Dots

• Blue -Ultraviolet Luminescence
• Ultrafine Sizes 2-3nm

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Ultrafine nanoparticles in biological imaging

• In a frog embryo has been imaged using
• organic-dye techniques (b) Quantum Dots

An important aspect of QD labels is their
extremely high photostability, which allows
monitoring of intra-cellular processes over long
periods of time
The capillary structure, is revealed with
fluorescence microscopy as nanocrystal quantum
dots circulate through the bloodstream.
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Cancer TherapyDiagnostics

• Specific labeling of live cells with Quantum
  Dots

Breast cancer cells (A) and mouse mammary tumor
tissue section (B) were stained with QDs
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Magnetic Liquids

• Magnetic nanoparticles with particle sizes
  small enough
• to pass through the capillary systems of organs
  and tissues

• Their movement in the blood can be controlled
• with a magnetic field

Nanostructures
The ability to engineer nanoassemblies promise
for a new generation of electronics, and
optoelectronics
Carbon Micro/Nanofibers
Nanofibers

• plasmonic subwavelength waveguiding
• Plasmonic
• optoelectronics

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Actually, as it follows from Fig. 1, NMR response
precipitately changes upon the variation of the
binders content. These data speak about the of
the coppers valence state increase from 2 to
2?. Presumably, this is the underlying reason of
Ts increase by 1 to 3 degrees.
Fig.1. Cu2(I) of the super conducting
Y1Ba2Cu3O6.97 ceramics (curve 1) and composites
with HMPE. Curve 2 1 Curve 3 3
Curve 4 5 Curve 5 10 Curve 6 20 .
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Superconducting polymer-ceramic nanocomposites
are obtained with various binders
(superhighmolecular polyethylene, SHMPE ramified
polyethyelene, RPE copolymerfluorine with
polyethyelene, F-40 polyvinylidene fluoride,
PVIF, etc.). From the data in table it follows
that the critical transition temperature (Ts) is
higher by 13 degrees vs. the initial ceramic
(93 K).
SC properties of polymer-ceramic nanocomposites
based on Y1Ba2Cu3O6,97 ceramic ( ?pressing140
?C, ?pressing30 min.).
Composition Weight ratio of ceramic and binder Ts,K Tf,K
SHMPE Y1Ba2Cu3O6,97 80 20 85 15 85 15 96 96 96 84 84 84
RPE Y1Ba2Cu3O6,97 80 20 94 80
F-40 Y1Ba2Cu3O6,97 75 25 96 77
PB Y1Ba2Cu3O6,97 80 20 96 83
PVIF Y1Ba2Cu3O6,97 85 15 90 75
PF Y1Ba2Cu3O6,97 80 20 88 76
HMPEirgonaks Y1Ba2Cu3O6,97 80 20 96 89
RPE irgonaks Y1Ba2Cu3O6,97 80 20 94 85
PVA irganoks Y1Ba2Cu3O6,97 85 15 90 80
Intercalation of the macromolecules or their
fragments into the ceramic grains interstitial
layer is confirmed by NMR tool method (Fig. 1),
as well as by studying the dynamical-mechanical
properties (Fig. 2) and the morphology of the
obtained nanocomposites (Fig. 3). Actually, as
it follows from Fig. 1, NMR response
precipitately changes upon the variation of the
binders content. These data speak about the of
the coppers valence state increase from 2 to
2?. Presumably, this is the underlying reason of
Ts increase by 1 to 3 degrees.
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Temperature-to- mechanical-losses-dissipation-fac
tor interrelation is affected by the presence of
Y1Ba2Cu3O6,97 ceramic. This is another
confirmation of intercalation that holds true.
From Fig. 2 it follows that both the
low-temperature (T is ca 130 0C -100 0C) and
high-temperature transition (T is ca 130 0C 140
0C)
Fig2. Temperature dependence of tg? for the pure
HMPE and for the HMPE ceramic composite. Ceramic
content (weight ) curve 1- 0 2 15.
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Intercalation of the macromolecules or their
fragments into the ceramic grains interstitial
layer, obviously, must have an impact on the
binders morphological structure. Indeed, as it
could be seen in Fig. 3, fibrillar structures are
formed in the ceramic-binder interface. This is
unlike to polyolefin binders.
Fig3. Microphotography of polymer-ceramic nano
composites at different polymer to ceramic
ratio Y1Ba2Cu3O 6,97 HMPE 5050 (a), 7030
(b) 8515 (?) 9010(d).
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One wanders if it is possible to obtain
polymer-ceramic nanocomposites with Meissner
effect permitting high load of currents to pass?
Addition of nanosized aluminum (30 nm) or silver
(40 nm) into the polymer-ceramic composite
produces nanocomposites with zero value
resistance (Fig. 4).
Fig4. Resistance change of the SC polymer
ceramic nano composite Y1Ba2Cu3O6,97 with nano
aluminum depended on HMPE content
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Upon the change of binders content one could
obtain nanaocomposites with 1.6103 A cm2
current density loads. Deagglomeration and
uniform spatial distribution of nanoparticles
increases current density up to 3103 A cm2.
Fig.5. Dependence of the current density on the
binders content.
It is to be stressed that current-carrying
polymer-ceramic nanocomposites have rather good
physical-mechanical properties. For example, the
following characteristics (ultimate strength is
0.73 kg cm2 modulus of elasticity is 7.5
kg cm2 elongation is 23) exhibited a
nanocomposite of the formula Y1Ba2Cu3O
6,97  binder  nano aluminium  95  3.5  1.5.
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Periodically polled lithium niobate crystals
A new technique for creation of periodically
polled domain structure in lithium niobate (PPLN)
crystals directly during the growth process was
developed by the group of Dr.E.Kokanyan at the
IPR NASA. The mentioned method was successfully
used for the growth of pure as well as doped with
various transitional metal and rare-earth
impurity ions PPLN crystals. The controlled
formation of 4-50?m wide domains along the a-axis
of the crystals in lengths of 20mm without
interruptions or modulations in domain size and
with more than 3mm of the domain inversion depth
was possible.
Scanning election microscope (SEM) micrograph of
an etched surface of as-grown hafnium doped
lithium niobate crystal.

• E.Kokanyan, V.Babajanyan, G.Demirkhanyan,
  J.Gruber, S.Erdei. J. of Appl. Phys., 92, 1544
  (2002).
• E.P.Kokanyan, L.Razzari, I.Cristiani, V.Degiorgio
  and J.B.Gruber. Appl. Phys. Lett., 84, 1880
  (2004)

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Wavelength converters based on PPLN

• Another aspect is a strong limitation to the
  industrial utilization of wavelength converters
  based on PPLN crystals, which comes from the so
  called photorefractive effect, which induces
  semi-permanent changes in the refractive index
  under the light illumination. To redress this
  problem, at present 5mol magnesium oxide should
  be incorporated into lithium niobate. But because
  of the required very high concentration it makes
  very difficult to grow good optical quality
  crystal.
• The data obtained by Dr.Kokanyan with co-authors
  show that tetravalent hafnium ions can be
  successfully utilized to reduce the
  photorefractive effect in lithium niobate
  crystals. Hafnium doping is effective at
  concentrations much lower than those used with
  Mg-doping (more than 2 times), potentially
  allowing crystals with good optical quality and
  more reproducibly. The micro-Raman results allow
  assessing a good crystalline quality and a
  remarkable homogeneity of the Hf-doped lithium
  niobate crystals.

• L.Razzari, P.Minzioni, I.Cristiani, V.Degiorgio,
  E.P.Kokanyan. Appl. Phys. Lett., 86, 131914
  (2005)
• E.P.Kokanyan. Ferroelectrics, 341, 119 (2006).
• P. Minzioni, I. Cristiani, V. Degiorgio, and E.P.
  Kokanyan, J. of Appl. Phys., 101, 116105 (2007).

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Laser systems and applications in quantum
technologies based on periodically-polled
nonlinear crystals

• Periodically-polled nonlinear crystals
  are very promising for designing of many-line
  laser systems as well as in areas of applied
  quantum technologies, including Communication,
  and Quantum Computation. New laser systems for
  these goals were theoretically elaborated at Lab.
  of Quantum Informatics IPR NASA (Prof.
  Kryuchkyan).
• This activity also includes
  investigations of new quasi-periodic structures
  of nonlinear crystals that realize simultaneous
  frequency-conversion processes within the same
  crystal.

• H.H. Adamyan, G.Yu. Kryuchkyan, Physical Review
  A69, 053814 (2004) ibid. A74, 023810 (2006).
• N.H. Adamyan, H.H. Adamyan, G.Yu. Kryuchkyan,
  Physical Review A73, 033810, (2006) ibid A 77,
  023820 (2008).

• International projects Principal Investigator
  E.Kokanyan
• INTAS - 94-1080 (1995-1997), 96- 0599
  (1998-2000) NFSAT/CRDF- BGP-7431 (2000-2002),
  AR2-3235 (2006-2008) CRDF-CGP- AP2-2556
  (2004-2006) ISTC A-1033 (2005-2007)
• Principal Investigator-
  G..Kryuchkyan
• INTAS- 97-1672 (1997-1999), 04-77-7289
  (2005-2007) ISTC A-823 (2002-2005), A-1451
  (2007-2009), (Submanager) NFSAT PH 098-02 / CRDF
  12052 (2002-2004) NFSAT-UCEP 02/07 (2007-2009)