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Achievements 2003 - 2013
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0D, 1D and 2D Nitride Structures grown by MOCVD for LED Applications 

We have AIXTRON MOCVD equipment for growing of 0D, 1D and 2D Nitride structures. This equipment can be used for growing other materials as well (e.g., graphene, silicon nanowires, etc.). High quality LED can be grown in the MOCVD reactor. For example, we produced 382 nm InGaN/AlGaN LED having quantum well structure on saphire wafer [1]. AlGaN based structures can be used for producing of UV or VUV light emitters. Nitride nanowires are perspective materials for creation of new generation LED, for examples nanowire arrays based LED. Currently we are working in this field [2].

Nanowires and Nanocrystals: Syntesis and Investigation

Nanocrystal based solar cells is a new research area in photovoltaics. Main advantage of nanocrystal based solar cell is a possibility to deposit nanocrystal layers from solution at ambient condition. It is possible to combine nanocrystals with photoactive polimers and use flexible organic materials as substrates. Whole solar spectrum can be effectively used by choosing proper nanocrystal material and tuning nanocrystal diameter (due to quantum confinement effect, when band gap width depends on nanoparticle size). We are working on different nanocrystal syntesis (for example, lead sulphide, cadmium silphide, bismuth sulfide, zinc oxide, etc.) and nanocrystal based solar cell investigation [3].

Metallic nanoparticles and nanowires (gold, silver) have numerous applications in new generation solar cells. Nanowires can be solution processed. Metallic nanowire coating can be used as transparent conductive electrods, which are necessary part of solar cells. Low annealing temperature allows to combine nanowires with organic polimers and flexible organic substrates. We are studing mechanical and electrical properties of silver nanowires in collaboration with Institute of Physics, Tartu University [4].

Research and Development of Silicon Thin Film Solar Cells

Manufacturing of amorhous silicon thin film solar cells can be very perspective if methods to improve soalr cell efficiency can be found. It is well known that efficiency of amorhous silicon solar cells decrease with time due to accumulation of methastable defects. It is possible to diminish this effect using laser crystalization procedure. Main positive effects of laser crystalization are dopant impurity activation and increase of charge carriers mobility [5]. Commonly used excimer laser processing depth is only 100 nm, while thickness of amorhous silicon solar cell ranges from 500 to 1000 nm. We are using lasers of visible range, which allows to process simultaneously whole p-i-n structure of solar cell. It is worth to mention surface textiring after laser processing, which decrease light reflection and correspondingly increase solar cell efficiency [6].

Optical spectroscopy of fusion plasma and fusion reactor wall materials

In framework of EURATOM project Laser Ablation Spectroscopy for Impurity Depth Profiling and Concentration Imaging in Plasma we elaborated laser ablation spectroscopy method rapid qualitative and quantative characterization of fusion reactor wall material [7]. The important problems of fusion reactor operation are carbon layer deposition, migration of wolfram and oxigen, and hydrogen isotope diffusion inside reactor wall materials. Two beam laser ablation spectroscopy allows to probe impurities concentration, distribution profile and characterize erosion of ITER wall materials.


[1] L. Dimitrocenko, J. Grube, P. Kulis, G. Marcins, B. Polyakov, A. Sarakovskis, M. Springis, I. Tale. AlGaN–InGaN–GaN Near Ultraviolet Light Emitting Diode, Latvian Journal of Physics and Technical Sciences, 45, 25–32, (2008)

[2] L. Dimitrocenko, K. Kundzins, A. Mishnev, I. Tale, A. Voitkans, P. Kulis. Growth temperature influence on the GaN nanowires grown by MOVPE technique, IOP Conference Series: Materials Science and Engineering, 23, Article number 012026, (2011)

[3] P. Kulis, J. Butikova, B. Polyakov, G. Marcins, J. Pervenecka, K. Pudzs, I. Tale. Work function of colloidal semiconducting nanocrystals measured by Kelvin probe, IOP Conf. Ser.: Materials Science and Engineering, 38, 012048, (2012)

[4] S. Vlassov, B. Polyakov, L.Dorogin, M. Antsov, I. Kink, M. Mets, M.Umalas, R. Saar, R. Lõhmus. Elasticity and yield strength of pentagonal silver nanowires: in situ bending tests. Submitted.

[5] G. Marcins, J. Butikova, I. Tale, B. Polyakov , R. Kalendarjov, A. Muhin. Crystallization processes of amorphous Si by thermal annealing and pulsed laser processing, IOP Conf. Ser.: Materials Science and Engineering, 23, 012035, (2011)

[6] J. Butikova , G. Marcins, B. Polyakov, A. Muhins, A. Voitkans, I. Tale. Processing of amorphous Si by pulsed laser irradiation at different wavelengths, IOP Conf. Ser.: Materials Science and Engineering, 38, 012009, (2012)

[7] J. Butikova, A. Sarakovskis, I. Tale. Laser-induced plasma spectroscopy of plasma facing materials. 35th EPS Conference on Plasma Physics, ECA, 32, P-2.011, (2008).