Международные конференции в 2010 году

Международные конференции ИПЛИТ РАН в 2010 году.

5 – 8 августа 2010 года в Санкт-Петербурге (Пушкин) проходила конференция - International Conference “Fundamentals of Laser Assisted Micro- and Nanotechnologies” (FLAMN-10). Сотрудниками ИПЛИТ РАН были представлены следующие доклады:

Khaydukov E.V., Novodvorsky O.A., Lotin A.A., Rocheva V.V., Panchenko V.Ya. The deposited particles energy spectrum control in the PLD method.

In the present work it is informed on engineering of the modified crossed-beam pulsed laser deposition method (CBPLD) which allows operating deposited particles energy in a wide range. Laser ablation was performed for the Si, Fe, Cr, Mn and Sn materials by the radiation of the first and second harmonics of the solid-state laser (1,06 µm and 0,53 µm) at the different power density on the targets. By the Langmuir probe technique ions time-of-flight curves (TFC) for the plasma beam formed by the intersecting plumes from two targets and the erosion plume from one target are received. The ions time-of-flight curves (TFC) are received at the probe-to-target distances in the 25-120 mm range. It is shown that ions TFC of the erosion plume approximate by the sum of one-dimensional Maxwell velocity distributions. It is demonstrated that the ions expansion velocity is in inverse proportion to root of ions mass. Ions concentration changing in initial plumes as a result of interaction is measured. For the first time the possibility of the ions energy spectrum control in a wide range at the crossed plumes method by means of angle changing between initial plumes axes is shown. It is shown that the modified CBPLD method allows creating the Si-based multilayer periodical spin-tunnel nanostructures with atomic-smooth interfaces even to first laser harmonics using for ablation.

Khaydukov E.V., Khramova O.D., Zuev D.A., Novodvorsky O.A., Lotin A.A., Rocheva V.V., Parshina L.S., Poroykov A. Yu., Timofeev M.A., Untila G.G., Panchenko V.Ya. Laser-induced silicon surface structuring for solar cell application.

Creation of laser-induced morphology features of the crystalline and multicrystalline silicon at the influence of the 532 nm wavelength Nd:YAG laser and also at the influence of the 248 nm wavelength KrF eximer laser (LPX 200) nanosecond pulses in air and vacuum atmosphere was investigated at different power density and radiation dose. Distinctive feature of this work is application of the sufficient power lasers to the increasing of the spot size minimum on two orders than the characteristic sizes of the formed laser-induced structures. It allows to at carrying out of the structure analysis completely exclude nonuniformity effects of the intensity distribution at the spot edges and that is even more important, nonuniformity of the temperature distribution within the spot – factors which in practice cannot be considered completely in case of tightly-focused laser beams usually used in similar researches. The structured plate samples of the multicrystalline silicon of the 20х20 mm2 size that sufficient for creation of the solar cells and studying of their photo-electric characteristics are received. The effect of laser influence modes on the morphological properties of the received by the laser method structures is investigated. The insensitivity to the borders presence between grains with various crystallographic orientations of the formed by the laser method structures has been shown and possibility of the uniform microtexturing of the multicrystalline silicon surface for high-performance solar cells creation is confirmed.

Lotin A. A., Parshina L. S., Novodvorsky O. A., Khramova O. D., Cherebilo Ye. A., Khaydukov E.V., Panchenko V. Ya. Electroluminescence from n-ZnO/p-GaN/c-Al2O3 and n-ZnO/i-ZnO/p-GaN/c-Al2O3 heterojunctions light-emitting diodes grown by pulsed laser deposition.

ZnO is one of the most promising materials for shortwavelength light-emitting diode (LED) and laser diode applications. However, the application of ZnO to homojunction diodes has been limited due to the difficulties of highquality ZnO fabrication and p-doping on ZnO. As an alternative approach to utilize ZnO for optoelectronic applications, a ZnO film/GaN film heterojunction structure has been suggested. These GaN/ZnO LEDs exhibit the improved carriers confinement compared to homojunction, which leads to higher recombination and improved device efficiency. However, due to relatively lower carrier concentration and mobility of p-GaN compared with those of n-ZnO, the blue-violet electroluminescence (EL) of those reported GaN/ZnO heterojunctions usually originates from GaN layer, while UV EL related to ZnO exciton recombination is not observed. In our work, a thin semi-insulating ZnO (i-ZnO) layer with high resistivity was inserted between the p-GaN and n-ZnO layer, to form p-i-n heterojunction, which confined parts of carriers to recombine in i-ZnO region.

In this work, we report on the fabrication and characteristics of light-emitting diodes based on p-GaN/n-ZnO and p-GaN/i-ZnO/n-ZnO heterojunctions. The hybrid heterojunctions were grown on c-Al2O3 substrates. The p-GaN films were produced by MOCVD and the n-ZnO and i-ZnO films were grown by PLD. We present the materials characterization of this structure using x-ray diffraction, scanning electron microscopy and atomic force microscopy. In the p-GaN/n-ZnO heterojunction case was suggested that the high materials and interface quality obtained using pulsed laser deposition for the n-ZnO and growth and metal–organic chemical vapor deposition for the p-GaN were key factors enabling the injection of holes and the radiative near band edge recombination in the ZnO. The p-GaN/n-ZnO LEDs showed I-V characteristics confirming a rectifying diode behavior and a RT electroluminescence peaked at about 380 nm was observed. A good correlation between the wavelength maxima for the EL and PL suggests that recombination occurs in the ZnO layer and that it may be excitonic in origin. This also indicates that there is significant hole injection from the GaN into the ZnO layer. The I-V characteristics of n-ZnO/i-ZnO/p-GaN LEDs showed a rectifying diode behavior and a RT width electroluminescence (360 – 700 nm) with peak maximum at about 490 nm. The comparison of the film photoluminescence and diode EL are indicated that emitted recombination occurs as in the ZnO layer thus in the p-GaN layer.

С 4 по 8 октября 2010 года в г.Звенигород (Ершово) Московской области проходила XIV Международная научная конференция физико-химические процессы при селекции атомов и молекул. Младшим научным сотрудником ИПЛИТ РАН на конференции был сделан следующий доклад: «Численное моделирование кинетики плавления микрочастиц при селективном лазерном спекании» (Гришаев Р.В, Мирзаде Ф.Х., Хоменко М.Д.).

Разработан вычислительный алгоритм и создана программа, позволяющая за время, зависящее от требуемой точности, рассчитывать параметры плавления частиц различных радиусов при различных интенсивностях. Рассчитано температурное поле частицы с учетом температурных нелинейностей поглощательной способности и теплообмена с газом (воздухом), а так же теплового излучения с поверхности. Исследована динамика фронта плавления частиц различных размеров, и ее зависимость от интенсивности излучения. Оценены характерные времена начала плавления и полного проплавления частиц в зависимости от размеров частиц и от интенсивности излучения. Так же исследовано влияние кинетики плавления на температурные поля частицы различных размеров в зависимости от интенсивности облучения. Показано, что плавление микрочастиц происходит при значительном перегреве и имеет резко нелинейный характер. Выявлено, что процессы плавления могут протекать не одинаково на поверхности и в центре частицы в зависимости от интенсивности.