Elena Obraztsova | Prokhorov General Physics Institute (original) (raw)

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Papers by Elena Obraztsova

Research paper thumbnail of Crystallization of Copper Films on Sapphire Substrate for Large-Area Single-Crystal Graphene Growth

Nanomaterials

Chemical vapor deposition synthesis of graphene on polycrystalline copper substrates from methane... more Chemical vapor deposition synthesis of graphene on polycrystalline copper substrates from methane is a promising technique for industrial production and application. However, the quality of grown graphene can be improved by using single-crystal copper (111). In this paper, we propose to synthesize graphene on epitaxial single-crystal Cu film deposited and recrystallized on a basal-plane sapphire substrate. The effect of film thickness, temperature, and time of annealing on the size of copper grains and their orientation is demonstrated. Under optimized conditions, the copper grains with the (111) orientation and a record size of several millimeters are obtained, and the single-crystal graphene is grown over their entire area. The high quality of synthesized graphene has been confirmed by Raman spectroscopy, scanning electron microscopy, and the sheet resistance measurements by the four point probe method.

Research paper thumbnail of Vapor-phase epitaxial re-growth of large diameter single-walled carbon nanotubes

Applied Physics Letters

Long single-wall carbon nanotubes (SWCNTs) with a controlled conductivity type or chirality are i... more Long single-wall carbon nanotubes (SWCNTs) with a controlled conductivity type or chirality are interesting for fundamental study and are promising in many different technological applications, such as nanoelectronics, optoelectronics, and also upon utilizing them as nanoscale reactors to produce nanomaterials. In this study, the long aligned large diameter SWCNTs and the large diameter nanotube dense networks were synthesized via a vapor-phase epitaxial re-growth method. The nanotubes were re-grown on ST (stable temperature)-cut quartz substrates from short SWCNT seeds using the mixture of ethanol and acetylene as a precursor. The efficient nanotube re-growth was achieved using unsorted SWCNTs with diameters of 1.2–2.0 nm and semiconducting SWCNTs, sorted by an aqueous two-phase extraction method, as seeds. According to our study, the re-grown nanotubes in an array have an average length of 5.5 μm, while the individual re-grown nanotubes can reach up to 20–30 μm. The extensive optical study confirms the preservation of SWCNTs diameter during the re-growth and signifies the high quality of produced nanotubes. We demonstrate the SWCNT chirality selective efficiency of the re-growth, which leads to predominance of the metallic nanotubes.

Research paper thumbnail of Laser‐induced heating of porous Ge layers implanted with Ag+ and Cu+ ions

Journal of Raman Spectroscopy, 2022

Porous Ge layers consisting of nanowires were formed by low‐energy high‐dose implantation of mono... more Porous Ge layers consisting of nanowires were formed by low‐energy high‐dose implantation of monocrystalline c‐Ge substrate with Ag+ and Cu+ ions. The obtained layers were studied by Raman spectroscopy using solid‐state and He‐Ne exciting lasers with wavelength of 532 and 633 nm, respectively. The crystalline volume fraction and local temperature of porous layers at the surface sites of laser probing were determined. To interpret the change in the shape of the spectra under the action of laser radiation, deconvolution into amorphous and nanocrystalline components was carried out. Analysis of the spectral line shape made it possible to estimate the crystalline and amorphous volume fractions. The quantum confinement model for Ge nanocrystallites was taken into account for accurate estimations of volume fractions. These estimates showed that the implanted amorphous layers of all samples were locally crystallized with a solid‐state laser. He‐Ne laser excitation resulted in partial cryst...

Research paper thumbnail of C-4-17 Dispersion Management in Mode-locked Fiber Lasers at 2μm using CNT

Research paper thumbnail of Hybrid source of subnanosecond pulses in the spectral range 532-600 nm

Applied Physics Express, 2021

The source of subnanosecond pulses in the spectral range of 532–600 nm due to the second harmonic... more The source of subnanosecond pulses in the spectral range of 532–600 nm due to the second harmonic generation in nonlinear lithium niobate and potassium dihydrogen phosphate crystals is presented. Pulses for second harmonic generation are obtained by amplifying the signal of the ytterbium-doped fiber laser with hybrid mode-locking. The hybrid mode provided self-triggering and reproducibility of the fiber system with stable temporal and spectral characteristics. The pulse repetition rate was 1 MHz with a duration of 210 ps and an energy of 0.7 nJ before amplification and 420 ps with an energy of 0.9 μJ after.

Research paper thumbnail of Controlled Graphene Synthesis from Solid Carbon Sources

physica status solidi (b), 2019

Here the authors present the investigation of controllable growth of large area high quality grap... more Here the authors present the investigation of controllable growth of large area high quality graphene from different solid carbon sources. A home‐made cold‐wall chamber is used for chemical vapor deposition realization to grow graphene on copper foils. It is supplied with tools for in situ monitoring the temperature along the entire sample. Monolayer graphene films are synthesized using solid poly(methyl methacrylate) (PMMA) and paraffin precursors at a growth temperature of about 850 °C and under low pressure conditions. The area of 1 × 1 cm2 appears to be covered by graphene. Raman spectroscopy and scanning electron microscopy are used to estimate the quality of graphene films fabricated and the graphene layer number.

Research paper thumbnail of Optical Features of Vapor‐Phase Epitaxial Re‐Grown Long Semiconducting Single‐Walled Carbon Nanotubes

physica status solidi (b), 2019

The monodispersed long single‐wall carbon nanotubes (SWCNTs) with controlled morphology are promi... more The monodispersed long single‐wall carbon nanotubes (SWCNTs) with controlled morphology are promising in various research fields and many applications, such as optoelectronics, nanoelectronics and recently upon utilizing them as nanoreactors. In this work the long aligned semiconducting single‐walled carbon nanotubes as well as the extended semiconducting nanotube networks are synthesized via a vapor‐phase epitaxial (VPE) cloning growth method. The semiconducting nanotubes are grown on ST‐cut quartz substrates using acetylene and ethanol as a precursors from the seeds of sorted SWCNTs. According to the conducted study the length of the grown nanotubes can reach up to 70 μm. The extensive optical study confirms the preservation of SWCNTs chirality during re‐growth from nanotube seeds and the high quality of the obtained long semiconducting nanotubes. Polarization dependent Raman demonstrates the high alignment degree of the re‐grown SWCNTs. In dense growth regime SWCNTs demonstrate s...

Research paper thumbnail of Fe–Mo and Co–Mo Catalysts with Varying Composition for Multi‐Walled Carbon Nanotube Growth

physica status solidi (b), 2017

The formation of active component of Fe–Mo and Co–Mo catalysts for carbon nanotube growth with va... more The formation of active component of Fe–Mo and Co–Mo catalysts for carbon nanotube growth with variable Mo content is studied with in situ XRD, XPS, and STEM&EDX. The activation of bimetallic Fe–Mo catalysts under the growth conditions leads to the formation of Fe–Mo alloy particles in contrast to Co‐containing catalysts in which active alloy incorporates only a small portion of Mo (<2–3 at.%). The stable carbide formation for these systems is not detected. The effect of Mo content in Fe–Mo and Co–Mo catalysts on the properties of MWCNTs is additionally investigated using the Raman spectroscopy in combination with measurements of the temperature dependence of conductivity. It is shown that MWCNT defectiveness depends on the active component composition for both Fe–Mo and Co–Mo catalysts. The current carrier concentration for the MWCNTs grown on Fe–Mo catalysts slightly increases with the Mo content. The opposite effect is observed for the tubes grown on Co–Mo catalysts, showing a...

Research paper thumbnail of Gyroscopic effect detection in the colliding-pulse hybridly mode-locked erbium-doped all-fiber ring soliton laser

Research paper thumbnail of Band structure calculation of GaSe-based nanostructures using empirical pseudopotential method

Journal of Physics: Conference Series, 2016

Research paper thumbnail of Saturation parameters studies of carbon nanotube-based thin-film saturable absorbers for erbium fiber laser mode-locking

2016 International Conference Laser Optics (LO), 2016

We have experimentally studied saturation behavior of Single-Walled Carbon Nanotube-based saturab... more We have experimentally studied saturation behavior of Single-Walled Carbon Nanotube-based saturable absorbers at different temperatures and SWCNT concentrations in the carboxymetylcellulose polymer matrix and related it to the mode-locked erbium-doped fiber laser performance.

Research paper thumbnail of Generation regimes of bidirectional hybridly mode-locked ultrashort pulse erbium-doped all-fiber ring laser with a distributed polarizer

Applied optics, Jan 20, 2016

We report on the stable picosecond and femtosecond pulse generation from the bidirectional erbium... more We report on the stable picosecond and femtosecond pulse generation from the bidirectional erbium-doped all-fiber ring laser hybridly mode-locked with a coaction of a single-walled carbon nanotube-based saturable absorber and nonlinear polarization evolution that was introduced through the insertion of the short-segment polarizing fiber. Depending on the total intracavity dispersion value, the laser emits conservative solitons, transform-limited Gaussian pulses, or highly chirped stretched pulses with almost 20 nm wide parabolic spectrum in both clockwise (CW) and counterclockwise (CCW) directions of the ring. Owing to the polarizing action in the cavity, we have demonstrated for the first time, to the best of our knowledge, an efficient tuning of soliton pulse characteristics for both CW and CCW channels via an appropriate polarization control. We believe that the bidirectional laser presented may be highly promising for gyroscopic and other dual-channel applications.

Research paper thumbnail of 特別記事 エレーナ・オブラスツォワ、大いに語る

Research paper thumbnail of Performance peculiarities of carbon-nanotube-based thin-film saturable absorbers for erbium fiber laser mode-locking

Journal of the Optical Society of America B, 2016

Research paper thumbnail of Application of scanning tunneling-field emission microscopy for investigations of field electron emission from nanoscale diamond films

Ultramicroscopy, 1999

A special scanning tunneling-field emission microscope (STFEM) has been used for studying field e... more A special scanning tunneling-field emission microscope (STFEM) has been used for studying field electron emission from thin nanocrystalline diamond films grown by a DC plasma CVD. These are characterized by turn-on electric fields as low as 3.5 V/μm and by long-term stability of the emission current. Comparing different surface properties (topography, field electron emission intensity, surface potential and local electroconductivity

Research paper thumbnail of Stable similariton generation in hybrid mode-locked erbium-doped all-fiber ring laser for application in optical frequency standard

Photonics, Devices, and Systems VI, 2015

Research paper thumbnail of Femtosecond laser ablation of single-wall carbon nanotube-based material

Laser Physics Letters, 2014

ABSTRACT Single- and multi-shot femtosecond laser surface ablation of a single-wall carbon nanotu... more ABSTRACT Single- and multi-shot femtosecond laser surface ablation of a single-wall carbon nanotube-based substrate at 515- and 1030 nm wavelengths was studied by scanning electron microscopy and micro-Raman spectroscopy. The laser ablation proceeds in two ways: as the low-fluence mesoscopic shallow disintegration of the surface nanotube packing, preserving the individual integrity and the semiconducting character of the nanotubes or as the high-fluence deep material removal apparently triggered by the strong intrinsic or impurity-mediated ablation of the individual carbon nanotubes on the substrate surface.

Research paper thumbnail of Simulation and Modeling

Research paper thumbnail of Single-shot and single-spot measurement of laser ablation threshold for carbon nanotubes

Journal of Physics D: Applied Physics, 2013

Research paper thumbnail of Optical Studies of Single Walled Nanotubes Synthesized from C:BN:B4C Catalytic Mixture

Journal of Nanoelectronics and Optoelectronics, 2009

ABSTRACT Single-walled nanotubes have been synthesized by arc discharge technique from C:BN:B4C c... more ABSTRACT Single-walled nanotubes have been synthesized by arc discharge technique from C:BN:B4C catalytic mixture with an admixture of a typical Ni:Y2O3 catalyst. Nitrogen and helium have been used as ambient gases. The arc current and voltage were varied in the process. The synthesized materials have been characterized by a Raman spectroscopy. The arc current value increase induced a frequency shift of the dominating Raman radial breathing mode toward higher frequencies. This trend was opposite to that observed for the pure carbon nanotubes. A probability of doping and other mechanisms being able to result in such shift are discussed in this article.

Research paper thumbnail of Crystallization of Copper Films on Sapphire Substrate for Large-Area Single-Crystal Graphene Growth

Nanomaterials

Chemical vapor deposition synthesis of graphene on polycrystalline copper substrates from methane... more Chemical vapor deposition synthesis of graphene on polycrystalline copper substrates from methane is a promising technique for industrial production and application. However, the quality of grown graphene can be improved by using single-crystal copper (111). In this paper, we propose to synthesize graphene on epitaxial single-crystal Cu film deposited and recrystallized on a basal-plane sapphire substrate. The effect of film thickness, temperature, and time of annealing on the size of copper grains and their orientation is demonstrated. Under optimized conditions, the copper grains with the (111) orientation and a record size of several millimeters are obtained, and the single-crystal graphene is grown over their entire area. The high quality of synthesized graphene has been confirmed by Raman spectroscopy, scanning electron microscopy, and the sheet resistance measurements by the four point probe method.

Research paper thumbnail of Vapor-phase epitaxial re-growth of large diameter single-walled carbon nanotubes

Applied Physics Letters

Long single-wall carbon nanotubes (SWCNTs) with a controlled conductivity type or chirality are i... more Long single-wall carbon nanotubes (SWCNTs) with a controlled conductivity type or chirality are interesting for fundamental study and are promising in many different technological applications, such as nanoelectronics, optoelectronics, and also upon utilizing them as nanoscale reactors to produce nanomaterials. In this study, the long aligned large diameter SWCNTs and the large diameter nanotube dense networks were synthesized via a vapor-phase epitaxial re-growth method. The nanotubes were re-grown on ST (stable temperature)-cut quartz substrates from short SWCNT seeds using the mixture of ethanol and acetylene as a precursor. The efficient nanotube re-growth was achieved using unsorted SWCNTs with diameters of 1.2–2.0 nm and semiconducting SWCNTs, sorted by an aqueous two-phase extraction method, as seeds. According to our study, the re-grown nanotubes in an array have an average length of 5.5 μm, while the individual re-grown nanotubes can reach up to 20–30 μm. The extensive optical study confirms the preservation of SWCNTs diameter during the re-growth and signifies the high quality of produced nanotubes. We demonstrate the SWCNT chirality selective efficiency of the re-growth, which leads to predominance of the metallic nanotubes.

Research paper thumbnail of Laser‐induced heating of porous Ge layers implanted with Ag+ and Cu+ ions

Journal of Raman Spectroscopy, 2022

Porous Ge layers consisting of nanowires were formed by low‐energy high‐dose implantation of mono... more Porous Ge layers consisting of nanowires were formed by low‐energy high‐dose implantation of monocrystalline c‐Ge substrate with Ag+ and Cu+ ions. The obtained layers were studied by Raman spectroscopy using solid‐state and He‐Ne exciting lasers with wavelength of 532 and 633 nm, respectively. The crystalline volume fraction and local temperature of porous layers at the surface sites of laser probing were determined. To interpret the change in the shape of the spectra under the action of laser radiation, deconvolution into amorphous and nanocrystalline components was carried out. Analysis of the spectral line shape made it possible to estimate the crystalline and amorphous volume fractions. The quantum confinement model for Ge nanocrystallites was taken into account for accurate estimations of volume fractions. These estimates showed that the implanted amorphous layers of all samples were locally crystallized with a solid‐state laser. He‐Ne laser excitation resulted in partial cryst...

Research paper thumbnail of C-4-17 Dispersion Management in Mode-locked Fiber Lasers at 2μm using CNT

Research paper thumbnail of Hybrid source of subnanosecond pulses in the spectral range 532-600 nm

Applied Physics Express, 2021

The source of subnanosecond pulses in the spectral range of 532–600 nm due to the second harmonic... more The source of subnanosecond pulses in the spectral range of 532–600 nm due to the second harmonic generation in nonlinear lithium niobate and potassium dihydrogen phosphate crystals is presented. Pulses for second harmonic generation are obtained by amplifying the signal of the ytterbium-doped fiber laser with hybrid mode-locking. The hybrid mode provided self-triggering and reproducibility of the fiber system with stable temporal and spectral characteristics. The pulse repetition rate was 1 MHz with a duration of 210 ps and an energy of 0.7 nJ before amplification and 420 ps with an energy of 0.9 μJ after.

Research paper thumbnail of Controlled Graphene Synthesis from Solid Carbon Sources

physica status solidi (b), 2019

Here the authors present the investigation of controllable growth of large area high quality grap... more Here the authors present the investigation of controllable growth of large area high quality graphene from different solid carbon sources. A home‐made cold‐wall chamber is used for chemical vapor deposition realization to grow graphene on copper foils. It is supplied with tools for in situ monitoring the temperature along the entire sample. Monolayer graphene films are synthesized using solid poly(methyl methacrylate) (PMMA) and paraffin precursors at a growth temperature of about 850 °C and under low pressure conditions. The area of 1 × 1 cm2 appears to be covered by graphene. Raman spectroscopy and scanning electron microscopy are used to estimate the quality of graphene films fabricated and the graphene layer number.

Research paper thumbnail of Optical Features of Vapor‐Phase Epitaxial Re‐Grown Long Semiconducting Single‐Walled Carbon Nanotubes

physica status solidi (b), 2019

The monodispersed long single‐wall carbon nanotubes (SWCNTs) with controlled morphology are promi... more The monodispersed long single‐wall carbon nanotubes (SWCNTs) with controlled morphology are promising in various research fields and many applications, such as optoelectronics, nanoelectronics and recently upon utilizing them as nanoreactors. In this work the long aligned semiconducting single‐walled carbon nanotubes as well as the extended semiconducting nanotube networks are synthesized via a vapor‐phase epitaxial (VPE) cloning growth method. The semiconducting nanotubes are grown on ST‐cut quartz substrates using acetylene and ethanol as a precursors from the seeds of sorted SWCNTs. According to the conducted study the length of the grown nanotubes can reach up to 70 μm. The extensive optical study confirms the preservation of SWCNTs chirality during re‐growth from nanotube seeds and the high quality of the obtained long semiconducting nanotubes. Polarization dependent Raman demonstrates the high alignment degree of the re‐grown SWCNTs. In dense growth regime SWCNTs demonstrate s...

Research paper thumbnail of Fe–Mo and Co–Mo Catalysts with Varying Composition for Multi‐Walled Carbon Nanotube Growth

physica status solidi (b), 2017

The formation of active component of Fe–Mo and Co–Mo catalysts for carbon nanotube growth with va... more The formation of active component of Fe–Mo and Co–Mo catalysts for carbon nanotube growth with variable Mo content is studied with in situ XRD, XPS, and STEM&EDX. The activation of bimetallic Fe–Mo catalysts under the growth conditions leads to the formation of Fe–Mo alloy particles in contrast to Co‐containing catalysts in which active alloy incorporates only a small portion of Mo (<2–3 at.%). The stable carbide formation for these systems is not detected. The effect of Mo content in Fe–Mo and Co–Mo catalysts on the properties of MWCNTs is additionally investigated using the Raman spectroscopy in combination with measurements of the temperature dependence of conductivity. It is shown that MWCNT defectiveness depends on the active component composition for both Fe–Mo and Co–Mo catalysts. The current carrier concentration for the MWCNTs grown on Fe–Mo catalysts slightly increases with the Mo content. The opposite effect is observed for the tubes grown on Co–Mo catalysts, showing a...

Research paper thumbnail of Gyroscopic effect detection in the colliding-pulse hybridly mode-locked erbium-doped all-fiber ring soliton laser

Research paper thumbnail of Band structure calculation of GaSe-based nanostructures using empirical pseudopotential method

Journal of Physics: Conference Series, 2016

Research paper thumbnail of Saturation parameters studies of carbon nanotube-based thin-film saturable absorbers for erbium fiber laser mode-locking

2016 International Conference Laser Optics (LO), 2016

We have experimentally studied saturation behavior of Single-Walled Carbon Nanotube-based saturab... more We have experimentally studied saturation behavior of Single-Walled Carbon Nanotube-based saturable absorbers at different temperatures and SWCNT concentrations in the carboxymetylcellulose polymer matrix and related it to the mode-locked erbium-doped fiber laser performance.

Research paper thumbnail of Generation regimes of bidirectional hybridly mode-locked ultrashort pulse erbium-doped all-fiber ring laser with a distributed polarizer

Applied optics, Jan 20, 2016

We report on the stable picosecond and femtosecond pulse generation from the bidirectional erbium... more We report on the stable picosecond and femtosecond pulse generation from the bidirectional erbium-doped all-fiber ring laser hybridly mode-locked with a coaction of a single-walled carbon nanotube-based saturable absorber and nonlinear polarization evolution that was introduced through the insertion of the short-segment polarizing fiber. Depending on the total intracavity dispersion value, the laser emits conservative solitons, transform-limited Gaussian pulses, or highly chirped stretched pulses with almost 20 nm wide parabolic spectrum in both clockwise (CW) and counterclockwise (CCW) directions of the ring. Owing to the polarizing action in the cavity, we have demonstrated for the first time, to the best of our knowledge, an efficient tuning of soliton pulse characteristics for both CW and CCW channels via an appropriate polarization control. We believe that the bidirectional laser presented may be highly promising for gyroscopic and other dual-channel applications.

Research paper thumbnail of 特別記事 エレーナ・オブラスツォワ、大いに語る

Research paper thumbnail of Performance peculiarities of carbon-nanotube-based thin-film saturable absorbers for erbium fiber laser mode-locking

Journal of the Optical Society of America B, 2016

Research paper thumbnail of Application of scanning tunneling-field emission microscopy for investigations of field electron emission from nanoscale diamond films

Ultramicroscopy, 1999

A special scanning tunneling-field emission microscope (STFEM) has been used for studying field e... more A special scanning tunneling-field emission microscope (STFEM) has been used for studying field electron emission from thin nanocrystalline diamond films grown by a DC plasma CVD. These are characterized by turn-on electric fields as low as 3.5 V/μm and by long-term stability of the emission current. Comparing different surface properties (topography, field electron emission intensity, surface potential and local electroconductivity

Research paper thumbnail of Stable similariton generation in hybrid mode-locked erbium-doped all-fiber ring laser for application in optical frequency standard

Photonics, Devices, and Systems VI, 2015

Research paper thumbnail of Femtosecond laser ablation of single-wall carbon nanotube-based material

Laser Physics Letters, 2014

ABSTRACT Single- and multi-shot femtosecond laser surface ablation of a single-wall carbon nanotu... more ABSTRACT Single- and multi-shot femtosecond laser surface ablation of a single-wall carbon nanotube-based substrate at 515- and 1030 nm wavelengths was studied by scanning electron microscopy and micro-Raman spectroscopy. The laser ablation proceeds in two ways: as the low-fluence mesoscopic shallow disintegration of the surface nanotube packing, preserving the individual integrity and the semiconducting character of the nanotubes or as the high-fluence deep material removal apparently triggered by the strong intrinsic or impurity-mediated ablation of the individual carbon nanotubes on the substrate surface.

Research paper thumbnail of Simulation and Modeling

Research paper thumbnail of Single-shot and single-spot measurement of laser ablation threshold for carbon nanotubes

Journal of Physics D: Applied Physics, 2013

Research paper thumbnail of Optical Studies of Single Walled Nanotubes Synthesized from C:BN:B4C Catalytic Mixture

Journal of Nanoelectronics and Optoelectronics, 2009

ABSTRACT Single-walled nanotubes have been synthesized by arc discharge technique from C:BN:B4C c... more ABSTRACT Single-walled nanotubes have been synthesized by arc discharge technique from C:BN:B4C catalytic mixture with an admixture of a typical Ni:Y2O3 catalyst. Nitrogen and helium have been used as ambient gases. The arc current and voltage were varied in the process. The synthesized materials have been characterized by a Raman spectroscopy. The arc current value increase induced a frequency shift of the dominating Raman radial breathing mode toward higher frequencies. This trend was opposite to that observed for the pure carbon nanotubes. A probability of doping and other mechanisms being able to result in such shift are discussed in this article.