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Victor A Ermakov

Universidade Estadual de Campinas, Departamento de Física Aplicada, Post-Doc

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Phone: +55 19 981218446
Address: Departamento de Fisica Aplicada
Instituto de Física "Gleb Wataghin" - IFGW
Universidade Estadual de Campinas - Unicamp
Cidade Universitária Zeferino Vaz
Rua Sérgio Buarque de Holanda, 777
13083-859 - Campinas, SP, Brasil
Instituto de Física "Gleb Wataghin" - IFGW
Universidade Estadual de Campinas - Unicamp
Cidade Universitária Zeferino Vaz
Rua Sérgio Buarque de Holanda, 777
13083-859 - Campinas, SP, Brasil

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Papers by Victor A Ermakov

Perovskite Thin Film Synthesised from Sputtered Lead Sulphide

In the last few years, research on dye-sensitised devices has been focused on the development of ... more In the last few years, research on dye-sensitised devices has been focused on the development of solar cells, based on CH 3 NH 3 PbX 3 (X = I − , Br − , Cl −) composites with perovskite structure. The deposition of perovskite thin films is usually carried out by solution-based processes using spin-coating techniques that result in the production of high quality films. Solar cells made by this method exceed 20% efficiency, with the potential for use in large scale production through ink print or screen printing techniques. As an alternative route, perovskite thin films can be deposited through thermal evaporation. A new method is proposed to produce CH 3 NH 3 PbI 3 , based on a radio-frequency (rf)-sputtering technique that results in a high reproducibility of the films and is compatible with roll-to-roll processes. We deposited thin films of lead-sulphide (PbS) and converted them into perovskite by placing the films in an iodine atmosphere, followed by dipping in a solution of methylammonium iodide (CH 3 NH 3 I). The conversions to PbI 2 and CH 3 NH 3 PbI 3 were confirmed by elemental analyses, absorption, and photoluminescence spectroscopy. Structural properties were revealed by X-ray diffraction and infrared and Raman spectroscopy.

Size Control of Silver-Core/Silica-Shell Nanoparticles Fabricated by Laser-Ablation-Assisted Chemical Reduction

by Victor A Ermakov and Ernesto Jimenez-Villar

Aqueous colloidal silver nanoparticles have substantial potential in biological application as ma... more Aqueous colloidal silver nanoparticles have substantial potential in biological application as markers and antibacterial agents and in surface-enhanced Raman spectroscopy applications. A simple method of fabrication and encapsulation into an inert shell is of great importance today to make their use ubiquitous. Here we show that colloids of silver-core/silica-shell nanoparticles can be easily fabricated by a laser-ablation-assisted chemical reduction method and their sizes can be tuned in the range of 2.5 to 6.3 nm by simply choosing a proper water− ethanol proportion. The produced silver nanoparticles possess a porous amorphous silica shell that increases the inertness and stability of colloids, which decreases their toxicity compared with those without silica. The presence of a thin 2 to 3 nm silica shell was proved by EDX mapping. The small sizes of nanoparticles achieved by this method were analyzed using optical techniques, and they show typical photoluminescence in the UV−vis range that shifts toward higher energies with decreasing size.

ВЛИЯНИЕ ОТЖИГА НА ОПТИЧЕСКИЕ СВОЙСТВА, ХИМИЧЕСКИЙ И ФАЗОВЫЙ СОСТАВ ПЛЕНОК ОКСИДА ВОЛЬФРАМА

Приведены результаты исследования оптических свойств, химического состава и кристаллической струк... more Приведены результаты исследования оптических свойств, химического состава и кристаллической структуры пленок оксида вольфрама после отжига в вакууме и на воздухе при температуре 700°С. Пленки осаждены методом реактивного магнетронного распыления на постоянном токе. Исследо- вание выполнено на образцах, содержащих на кварцевом стекле одиночные пленки и гетерострук- туры с пленками оксидов вольфрама и титана. Установлено, что в разных образцах отжиг приводит к различным изменениям оптических свойств, химического состава и кристаллической структуры пленок.

Influence of Annealing on the Optical Properties and Chemical and Phase Compositions of Tungsten-Oxide Films

The results of investigating the optical properties, chemical composition, and crystal structure ... more The results of investigating the optical properties, chemical composition, and crystal structure of tungsten-oxide films annealed in vacuum and air at 700°C are presented. The films are deposited by means of reactive dc magnetron sputtering. The samples involving single films, as well as heterostructures with tungsten and titanium-oxide films, located on quartz glass substrates are examined. It is ascertained that, in different samples, annealing leads to different changes in the optical properties, chemical composition, and crystal structure of the films.

Особенности фазовых превращений в титаносодержащих цинковоалюмосиликатных стеклах, допированных оксидом кобальта

Показана эффективность метода спектроскопии KP в исследовании процесса формирования аморфной цинк... more Показана эффективность метода спектроскопии KP в исследовании процесса формирования аморфной цинковоалюмотитанатной (ЦАТ) фазы при фазовом распаде титаносодержащего цинковоалюмосиликатного стекла, допированного оксидом кобальта. Получены количественные зависимости изменения интенсивности полос KP, характерных для аморфной и кристаллических фаз, от температуры термообработки и содержания оксида кобальта. При низкотемпературных термообработках скорость фазового распада с выделением наноразмерных кристаллов алюмоцинковой шпинели (ганита) и ЦАТ фазы возрастает с увеличением содержания оксида кобальта. Добавки оксида кобальта увеличивают количество выделяющейся при фазовом распаде аморфной ЦАТ фазы и повышают ее термическую стабильность при высокотемпературных обработках. Показано, что ионы Со 2+ входят в возникающие при фазовом распаде кристаллы алюмоцинковой шпинели (ганита). Высказано предположение, что остаточное стекло по составу близко к кварцевому и содержит очень небольшое количество титанкислородных тетраэдров.

Технология получения одномерных фотонных кристаллов с помощью фотоэлектрохимического травления кремния

by Victor A Ermakov and T. S. Perova

Анализируются условия формирования глубоких периодических щелей в процессе фотоэлектрохимическо- ... more Анализируются условия формирования глубоких периодических щелей в процессе фотоэлектрохимическо- го травления n-Si ориентации (100) с линейными затравками на поверхности. Сформулированы критерии для выбора периода затравочных канавок и для плотности тока травления в зависимости от уровня легирования подложки. Характерной особенностью полученных структур является гофрировка их стенок, обусловленная следами слившихся макропор. С помощью атомно-силовой микроскопии исследована неровность стенок в зависимости от режима травления и найдена плотность тока, при которой можно получить наиболее гладкие стенки. Их шероховатость в структурах с периодом 7 и 9мкм на Si с удельным сопротивлением 15Ом · см составила ∼ 40 нм. Показано, что дополнительная обработка структур в щелочных растворах может уменьшить шероховатость стенок примерно в 2 раза.

Исследование Фазового Распада в Титаносодержащий Цинковоалюмосиликатных Наноструктурированных Стеклах, Легированных СоО, Методом Спектроскопии Комбинационного Рассеяния Света

Сообщается о результатах исследования фазового распада и кристаллизации фаз в цинковоалюмосили- к... more Сообщается о результатах исследования фазового распада и кристаллизации фаз в цинковоалюмосили- катных стеклах с добавками TiO2, легированных ионами Со2+.Определено влияние оксида кобальта СоО на процессы формирования прозрачных ситаллов, а также состав и структуру наноразмерных фаз, появляющихся при температурной обработке стекол, методом спектроскопии комбинационного рассеяния (КР) света.

Photoinduced electrical response in quantum dots/graphene hybrid structure

by A. Alaferdov and Victor A Ermakov

Journal of Applied Physics, 2015

Determining the exact number of dye molecules attached to colloidal CdSe/ZnS quantum dots in Förs... more

Study of the thermal contact between carbon nanotubes and a metal electrode

by M. Canesqui, Victor A Ermakov, and Stanislav Moshkalev

Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques, 2013

The thermal resistance of the contact between a metal and carbon nanotubes (CNTs) and between CNT... more The thermal resistance of the contact between a metal and carbon nanotubes (CNTs) and between CNT layers is estimated by the local heating of CNT arrays (films) of different thicknesses using a focused laser beam and measuring their local temperature via Raman spectroscopy. It is demonstrated that thermal contacts between nanotubes, and also between CNTs and an electrode, can be formed by means of laser annealing.

Formation of reliable electrical and thermal contacts between graphene and metal electrodes by laser annealing

by Stanislav Moshkalev, Raluca Savu, and Victor A Ermakov

Microelectronic Engineering, 2014

A new approach for electrical and thermal improvement of contacts between carbon nanostructures (... more A new approach for electrical and thermal improvement of contacts between carbon nanostructures (multi-wall carbon nanotubes -MWCNTs and multi-layer graphene -MLG) and metal electrodes by localized laser heating is presented. The nanostructures were deposited over electrodes using the dielectrophoresis (DEP) technique. A focused laser beam was used for direct heating the samples in ambient atmosphere. The Raman spectroscopy was used to determine the process temperature by observations of the graphitic G-line downshift. In the laser annealing experiments, the G-line position was found first to downshift linearly with laser power indicating gradual heating of the sample proportional to the absorbed power. However, with increasing power the shift was found to saturate at levels that depend on the metal and the contact area. This saturation was attributed to gradual increase of the contact area and improvement of the thermal contacts between the nanostructures and metal electrode that can occur during sample heating. The maximum sample temperature in the beginning of the annealing process was always higher for MLG samples, due to smaller area of contact established between rigid multi-layer graphene and initially rough metal surface. The final result is the increased heat losses to the electrodes and, subsequently, the reduction of the samples temperature.

Thermal contacts between multi-layer graphene and metals: Effect of laser annealing

28th Symposium on Microelectronics Technology and Devices (SBMicro 2013), 2013

The quality of thermal contacts between a graphene flake and metal electrodes was shown to improv... more The quality of thermal contacts between a graphene flake and metal electrodes was shown to improve strongly by laser annealing. The improvement of thermal contacts to initially rough metal electrodes is attributed to local melting of the metal surface under laser heating, and increased area of real metal-graphene contact. Improvement of the thermal contacts was observed also between multi-layer graphene and silicon oxide surface, with more efficient heat transfer from graphene as compared with the graphene-metal case.

Features of the phase transformations in titanium-containing zinc aluminosilicate glasses doped with cobalt oxide

by Victor A Ermakov and Dymshits Olga

Glass Physics and Chemistry, 2013

Диагностика плазмонного резонанса в спектрах оптического поглощения водных суспензий нанографита

by Alexander Baranov and Victor A Ermakov

ABSTRACT В спектрах оптического поглощения водных суспензий нанографита выявлена характерная особ... more ABSTRACT В спектрах оптического поглощения водных суспензий нанографита выявлена характерная особенность в области ~255 нм. Обнаруженный широкий пик поглощения связан с поверхностным плазмонным резонансом в частицах нанографита. Форма и интенсивность пика поглощения при ~255 нм зависят от структурного совершенства и агрегатного состояния частиц нанографита луковичного типа в суспензии.

Изучение Термического Контакта Между Углеродными Нанотрубками и Металлом

by Victor A Ermakov and Raluca Savu

Drop of Thermal Contacts Resistance between Multi-Layer Graphene and Metals caused by Laser

Significant drop of thermal contact resistance between a graphene flake and metal electrodes was ... more Significant drop of thermal contact resistance between a graphene flake and metal electrodes was shown as a result of laser annealing. The improvement of thermal contacts of initially rough metal electrodes is attributed to local melting of the metal surface caused by laser heating followed by increasing of real metal-graphene contact area.

Nanocarbons and quantum dots formation in new hybrid materials

by Victor A Ermakov, Stanislav Moshkalev, Alexander Baranov, and Anatoly Fedorov

Nanophotonics V, 2014

We present technique of obtaining complex hybrid structures combining the multi-walled carbon nan... more We present technique of obtaining complex hybrid structures combining the multi-walled carbon nanotubes or multi-layer graphene and luminescent hydrophobic semiconductor core/shell quantum dots CdSe/ZnS. As a result, a formation of quantum dot decorated carbon nanotubes and graphene films is evidenced by 2D microluminescence and micro-Raman mapping of quantum dots and nanocarbons, respectively, where a spatial correlation between the luminescence and Raman signals is found.

Quantum dots - graphene hybrid structures: interplay of optical and electrical properties

by Victor A Ermakov, Alexander Baranov, and Anatoly Fedorov

Nanophotonics V, 2014

We investigate electrical photoresponse of multilayer graphene decorated with CdSe/ZnS quantum do... more We investigate electrical photoresponse of multilayer graphene decorated with CdSe/ZnS quantum dots. It was found that photoresponse of these hybrid structures depends on quantum dot photoluminescence quantum yield. We demonstrate influence of external factors (light exposure and treatment with ammonia vapors) on photoluminescence quantum yield of quantum dots and electrical photoresponse of the hybrid structures. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/27/2014 Terms of Use: http://spiedl.org/terms Proc. of SPIE Vol. 9126 91262K-2 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/27/2014 Terms of Use: http://spiedl.org/terms Proc. of SPIE Vol. 9126 91262K-5 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/27/2014 Terms of Use: http://spiedl.org/terms

Study of the thermal contact between carbon nanotubes and a metal electrode

Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques, 2013

The thermal resistance of the contact between a metal and carbon nanotubes (CNTs) and between CNT... more The thermal resistance of the contact between a metal and carbon nanotubes (CNTs) and between CNT layers is estimated by the local heating of CNT arrays (films) of different thicknesses using a focused laser beam and measuring their local temperature via Raman spectroscopy. It is demonstrated that thermal contacts between nanotubes, and also between CNTs and an electrode, can be formed by means of laser annealing.

Fabrication of one-dimensional photonic crystals by photoelectrochemical etching of silicon

by Victor A Ermakov and T. S. Perova

Semiconductors, 2010

The conditions of formation of deep periodic trenches by photoelectrochemical etching of n Si (10... more The conditions of formation of deep periodic trenches by photoelectrochemical etching of n Si (100) with linear seeds on the surface are analyzed. Criteria for the proper choice of the period of seed grooves and the etching current density in relation to the doping level of the substrate are formulated. Corrugation of walls is a characteristic feature of the obtained structures; this corrugation is caused by traces of merged macropores. Atomic force microscopy is used to study roughness of the side walls in relation to the etching conditions; the current density at which one can obtain the smoothest side walls is determined. The rough ness of the side walls in structures with periods of 7 and 9 μm on Si with the resistivity of 15 Ω cm amounts tõ 40 nm. It is shown that additional treatment of the structures in alkaline solutions can decrease the side wall roughness by approximately a factor of 2.

Diagnostics of plasmon resonance in optical absorption spectra of nanographite aqueous suspensions

by Victor A Ermakov and Alexander Baranov

Optics and Spectroscopy, 2011

A characteristic feature near ~255 nm has been revealed in the optical absorption spectra of nano... more A characteristic feature near ~255 nm has been revealed in the optical absorption spectra of nano graphite aqueous suspensions. This is a broad absorption peak, which is due to the surface plasmon resonance in nanographite particles. The peak shape and intensity depend on the structural quality and aggregate state of onion like nanographite particles in suspension.