Presentation on theme: "RUSSIAN-ARMENIAN STATE UNIVERSITY PHYSICO-TECHNICAL DEPARTMENT Ovsep Emin Str.123,Yerevan, Armenia Prof. Stepan Petrosyan Dr."— Presentation transcript:
RUSSIAN-ARMENIAN STATE UNIVERSITY PHYSICO-TECHNICAL DEPARTMENT Ovsep Emin Str.123,Yerevan, Armenia Prof. Stepan Petrosyan Dr. Vladimir Gevorkyan
Field of Scientific Activities Growth and research of InAsSbP/InAs and Cu 2 O 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)
Novel diode heterostructures on the base of InAs alloys Fields of applications Methane Sensors: for methane leakage in houses, along gas communications, in mines Systems of optical fibres communication Free-space optical link Mid IR Photodiodes Medical Diagnostics: glucose and other substances in blood, in tissue Medical Diagnostics: Carbon Dioxide, Acetone and gases in breath Energy production and energy-saving applications Thermophotovol taic Water Sensors: water in paper, water in grain, water in oil products. Ecological monitoring of different industrial pollutants in air and water
Thermophotovoltaic converters Source of thermal or solar energy Heated body (emitter) О С Selective optical filter/refle ctor TPV cell (E g ) Backside reflector ħ ω
Relative spectral response of the n + -InAs / n 0 -InAs / p + - InAs 0.27 Sb 0.23 P 0.5 TPV diode heterostructure grown by non-equilibrium MOVPE growth technique S max = A/W = 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.).
Amplifi er Photo- diode Chip Sapphire Window Schematic view and photo of an engineering model of infrared photo-diode. Packaged Mid-IR photo-diode. Mid-Infrared photodiodes Epitaxial film ready for Mid- IR device manufacturing Pilot model of Mid-IR Photodetector with parabolic reflector and amplifier as a final product. Maximum sensitivity without reflector ~1 nWatt. E g2 ECEC EFEF ħω EVEV E g1 n- InAs Subst rate p-InAs 1-x- y P y Sb x emitter layer Band diagram of the n-InAs/p-InAs 1- x-y P x Sb y TPV diode heterostructure
Quantum Dot Solar Cell: Structure (a) Schematic diagram of QDSC (b) Corresponding energy band structure
Quantum Dot Solar Cell: Results Theoretical results Experimental 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
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
2D Shchottky contact x z 2ДЭГ 2Д Металл l VA=0VA=0 V А =-4 eV V А =4 eV ( x)
2D electron gas field efect transistor x y L 2a2a V(y)V(y) VGVG VGVG VSVS VDVD W(y)W(y) W(y)W(y) High channel conductivity Very high transconductance. 2DEG
Laser Synthesis of the Colloidal Nanoparticles Semiconductor Nanoparticles (Quantum Dots) Metal Nanoparticles Carbon Nanoparticles Polymer Nanoparticles Laser ablation of materials in liquids Technique Applied:
Blue -Ultraviolet Luminescence Ultrafine Sizes: 2-3nm Quantum Dots
In a frog embryo has been imaged using (a)organic-dye techniques (b) Quantum Dots The capillary structure, is revealed with fluorescence microscopy as nanocrystal quantum dots circulate through the bloodstream. Ultrafine nano[particles in biological imaging An important aspect of QD labels is their extremely high photostability, which allows monitoring of intra-cellular processes over long periods of time
Cancer Therapy&Diagnostics Specific labeling of live cells with Quantum Dots Breast cancer cells (A) and mouse mammary tumor tissue section (B) were stained with QDs
Magnetic Liquids M agnetic 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 The ability to engineer nanoassemblies promise for a new generation of electronics, and optoelectronics plasmonic subwavelength w aveguiding Plasmonic optoelectronics Nanofibers Carbon Micro/Nanofibers Nanostructures
Fig.1. Cu2+(I) of the super conducting Y 1 Ba 2 Cu 3 O 6.97 ceramics (curve 1); and composites with HMPE. Curve 2 – 1% ; Curve 3 – 3% ; Curve 4 – 5% ; Curve 5 – 10 % ; Curve 6 – 20 %. 2 4, 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+Δ. Presumably, this is the underlying reason of Ts increase by 1 to 3 degrees.
18 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 (T s ) is higher by 1–3 degrees vs. the initial ceramic (93 K). CompositionWeight ratio of ceramic and binderT s,KTf,KTf,K SHMPE + Y 1 Ba 2 Cu 3 O 6,97 80 : : RPE+ Y 1 Ba 2 Cu 3 O 6,97 80 : F-40+ Y 1 Ba 2 Cu 3 O 6,97 75 : PB+ Y 1 Ba 2 Cu 3 O 6,97 80 : PVIF+ Y 1 Ba 2 Cu 3 O 6,97 85 : PF+ Y 1 Ba 2 Cu 3 O 6,97 80 : HMPE+irgonaks+ Y 1 Ba 2 Cu 3 O 6,97 80 : RPE+ irgonaks + Y 1 Ba 2 Cu 3 O 6,97 80 : PVA+ irganoks + Y 1 Ba 2 Cu 3 O 6,97 85 : SC properties of polymer-ceramic nanocomposites based on Y 1 Ba 2 Cu 3 O 6,97 ceramic ( Т pressing=140 о C, pressing=30 min.). 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+Δ. Presumably, this is the underlying reason of Ts increase by 1 to 3 degrees.
19 Temperature-to- mechanical-losses-dissipation-factor interrelation is affected by the presence of Y 1 Ba 2 Cu 3 O 6,97 ceramic. This is another confirmation of intercalation that holds true. From Fig. 2 it follows that both the low-temperature (T is ca –130 0 C; C) and high-temperature transition (T is ca C; C) Fig2. Temperature dependence of tg for the pure HMPE and for the HMPE ceramic composite. Ceramic content (weight %): curve 1- 0%; 2 – 15%.
20 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: Y 1 Ba 2 Cu 3 O 6,97 : HMPE =50:50 (a), 70:30 (b) 85:15 (с) 90:10(d).
21 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 Y 1 Ba 2 Cu 3 O 6,97 with nano aluminum depended on HMPE content
22 Upon the change of binders content one could obtain nanaocomposites with 1.6·10 3 A cm –2 current density loads. Deagglomeration and uniform spatial distribution of nanoparticles increases current density up to 3·10 3 A cm –2. 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 cm –2 ; modulus of elasticity is 7.5 kg cm –2 ; elongation is 2–3%) exhibited a nanocomposite of the formula: Y 1 Ba 2 Cu 3 O 6,97 : binder : nano aluminium = 95 : 3.5 : 1.5.
Periodically polled lithium niobate crystals Scanning election microscope (SEM) micrograph of an etched surface of as-grown hafnium doped lithium niobate crystal. 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 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. 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)
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, (2005) E.P.Kokanyan. Ferroelectrics, 341, 119 (2006). P. Minzioni, I. Cristiani, V. Degiorgio, and E.P. Kokanyan, J. of Appl. Phys., 101, (2007).
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, (2004); ibid. A74, (2006). N.H. Adamyan, H.H. Adamyan, G.Yu. Kryuchkyan, Physical Review A73, , (2006); ibid A 77, (2008). International projects: Principal Investigator – E.Kokanyan INTAS ( ), ( ); NFSAT/CRDF- BGP-7431 ( ), AR ( ); CRDF-CGP- AP ( ); ISTC – A ( ) Principal Investigator- G..Kryuchkyan INTAS ( ), ( ); ISTC A-823 ( ), A-1451 ( ), (Submanager); NFSAT PH / CRDF ( ); NFSAT-UCEP 02/07 ( )