Aleksandra Krajewska

Polish Academy of Sciences

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Iwona Pasternak

Vigo System (Poland)

Włodek Strupiński

Vigo System (Poland)

Aleksandra Przewłoka

Institute of High Pressure Physics

G. Cywiński

Institute of High Pressure Physics

Sergey Rumyantsev

Institute of High Pressure Physics

Pavlo Sai

Institute of High Pressure Physics

Grzegorz Soboń

Wrocław University of Science and Technology

Jarosław Sotor

Wrocław University of Science and Technology

A. Wysmołek

University of Warsaw

Tymoteusz Ciuk

Łukasiewicz Research Network

Cooperative Institutions

Polish Academy of Sciences

Warsaw University of Technology

University of Warsaw

Institute of High Pressure Physics

Centre National de la Recherche Scientifique

Institute of Electronic Materials Technology

Institute of Physics

Consejo Superior de Investigaciones Científicas

Military University of Technology in Warsaw

Łukasiewicz Research Network

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Electrostatically-induced strain of graphene on GaN nanorods

arXiv (Cornell University) (2023)

Jakub Kierdaszuk R. Bożek Tomasz Stefaniuk Ewelina B. Możdżyńska Karolina Piętak

Few-layer graphene deposited on semiconductor nanorods separated by undoped spacers has been studied in perspective for the fabrication of stable nanoresonators. We show that an applied bias between the graphene layer and the nanorod substrate affects the graphene electrode in two ways: 1) by a change of the carrier concentration in graphene and 2) by inducing strain, as demonstrated by the Raman spectroscopy. The capacitance of the investigated structures scales with the area of graphene in contact with the nanorods. Due to the reduced contact surface, the efficiency of graphene gating is one order of magnitude lower than for a comparable structure without nanorods. The shift of graphene Raman modes observed under bias clearly shows the presence of electrostatically-induced strain and only a weak modification of carrier concentration, both independent of number of graphene layers. A higher impact of bias on strain was observed for samples with a larger contact area between the graphene and the nanorods which shows perspective for the construction of sensors and nanoresonator devices.

Nanorod

10.48550/arxiv.2307.02940

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Pressure tuning of HgCdTe epitaxial layers -- the role of the highly disordered buffer layer

arXiv (Cornell University) (2024)

D. Yavorskiy Yurii Ivonyak Dmytro B. But K. Karpierz Aleksandra Krajewska

HgCdTe alloys are unique because by increasing the Cd content x, one modifies the band structure from inverted to normal, which fundamentally modifies the dispersion of bulk and surface or edge (in the case of quantum wells) energy states. Using alloys with x close to the concentration x_c at which the band inversion transition is observed and with additional application of hydrostatic pressure (p), one creates a favorable playground for studying the evolution of Dirac matter and its topological properties. In this work, cryogenic magnetospectroscopy in quantizing magnetic fields (B) at the far-infrared is used to study inter-Landau-level transitions in high-quality HgCdTe MBE-grown epitaxial layers with x ~ x_c as a function of p up to 4.2 kbar. Special attention is paid to elucidate the role of the substrate and buffer layers, which usually modify the pressure coefficients of epitaxial layers. For this purpose, comparative measurements were carried out on as-grown epilayers with a GaAs substrate and on free-standing layers obtained by etching off the substrate. Spectra registered as a function of B (at given p) were analyzed with the help of the Kane model modified to include magnetic field. The pressure coefficient as well as the difference between conduction and valence band deformation potentials of the free-standing layer were determined at 2 K. Surprisingly, the deformation potentials and pressure coefficients of the epitaxial layer and those of the free-standing layer differed by no more than 10 % in the pressure range up to 4.2 kbar. This finding questions the common belief of a dominant influence of the substrate on the pressure coefficients of epitaxial layers...

Buffer (optical fiber)

10.48550/arxiv.2406.16122

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Conductivity inversion of methyl viologen-modified random networks of single-walled carbon nanotubes

Carbon (2022)

Aleksandra Przewłoka Adil Rehman Serguei Smirnov Ewelina Karpierz-Marczewska Aleksandra Krajewska

Surface Modification

Ultraviolet photoelectron spectroscopy

10.1016/j.carbon.2022.10.071

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Electron scattering in graphene with adsorbed NaCl nanoparticles

Journal of Applied Physics (2015)

Aneta Drabińska P. Kaźmierczak R. Bożek Ewelina Karpierz Agnieszka Wołoś

In this work, the results of contactless magnetoconductance and Raman spectroscopy measurements performed for a graphene sample after its immersion in NaCl solution were presented. The properties of the immersed sample were compared with those of a non-immersed reference sample. Atomic force microscopy and electron spin resonance experiments confirmed the deposition of NaCl nanoparticles on the graphene surface. A weak localization signal observed using contactless magnetoconductance showed the reduction of the coherence length after NaCl treatment of graphene. Temperature dependence of the coherence length indicated a change from ballistic to diffusive regime in electron transport after NaCl treatment. The main inelastic scattering process was of the electron-electron type but the major reason for the reduction of the coherence length at low temperatures was additional, temperature independent, inelastic scattering. We associate it with spin flip scattering, caused by NaCl nanoparticles present on the graphene surface. Raman spectroscopy showed an increase in the D and D′ bands intensities for graphene after its immersion in NaCl solution. An analysis of the D, D′, and G bands intensities proved that this additional scattering is related to the decoration of vacancies and grain boundaries with NaCl nanoparticles, as well as generation of new on-site defects as a result of the decoration of the graphene surface with NaCl nanoparticles. The observed energy shifts of 2D and G bands indicated that NaCl deposition on the graphene surface did not change carrier concentration, but reduced compressive biaxial strain in the graphene layer.

10.1063/1.4905418

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Strain control in graphene on GaN nanowires: Towards pseudomagnetic field engineering

Carbon (2021)

Jakub Kierdaszuk P. Dąbrowski Maciej Rogala Paweł Krukowski Aleksandra Przewłoka

Gallium nitride nanowire and nanorod substrates are prospective platforms allowing to control the local strain distribution in graphene films on top of them, resulting in an induction of pseudomagnetic fields. AFM measurements performed in a HybriD mode complemented by SEM allow for a detailed visualization of the strain distribution on graphene surface. Graphene in direct contact with supporting regions is tensile strained, while graphene located in-between is characterized by lower strain. Characteristic tensile strained wrinkles also appear in the areas between the supporting regions. A positive correlation between strain gradient and distances between borders of supporting regions is observed. These results are confirmed by analysis of the Raman D' band intensity, which is affected by an enhancement of intravalley scattering. Furthermore, scanning tunneling spectroscopy shows a local modification of the density of states near the graphene wrinkle and weak localization measurements indicate the enhancement of pseudomagnetic field-induced scattering. Therefore, we show that nanowire and nanorod substrates provide strain engineering and induction of pseudomagnetic fields in graphene. The control of graphene morphology by modification of distances between supporting regions is promising for both further fundamental research and the exploration of innovative ways to fabricate pseudomagnetic field-based devices like sensors or filters.

Nanorod

Strain engineering

Strain (injury)

10.1016/j.carbon.2021.10.012

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Optimum Choice of Randomly Oriented Carbon Nanotube Networks for UV-Assisted Gas Sensing Applications

ACS Sensors (2023)

Katarzyna Drozdowska Adil Rehman Janusz Smulko Aleksandra Krajewska Bartłomiej Stonio

We investigated the noise and photoresponse characteristics of various optical transparencies of nanotube networks to identify an optimal randomly oriented network of carbon nanotube (CNT)-based devices for UV-assisted gas sensing applications. Our investigation reveals that all of the studied devices demonstrate negative photoconductivity upon exposure to UV light. Our studies confirm the effect of UV irradiation on the electrical properties of CNT networks and the increased photoresponse with decreasing UV light wavelength. We also extend our analysis to explore the low-frequency noise properties of different nanotube network transparencies. Our findings indicate that devices with higher nanotube network transparencies exhibit lower noise levels. We conduct additional measurements of noise and resistance in an ethanol and acetone gas environment, demonstrating the high sensitivity of higher-transparent (lower-density) nanotube networks. Overall, our results indicate that lower-density nanotube networks hold significant promise as a viable choice for UV-assisted gas sensing applications.

Photoconductivity

10.1021/acssensors.3c01185

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Dual-wavelength fiber mode-locked laser based on graphene saturable absorber

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2014)

Jarosław Sotor Grzegorz Soboń Iwona Pasternak Karol Krzempek Grzegorz Dudzik

In this paper we present a dual-wavelength fiber mode-locked laser based on CVD-graphene saturable absorber (SA). The laser setup is based on two ring cavities connected by a common branch with a graphene SA. As a gain media erbium (Er) and thulium (Tm) doped active fiber were used. The laser generate optical pulses centered at 1558.5 nm and 1937 nm. The repetition rates and pulse durations were of 23.2 MHz, 16.42 MHz and 0.95 ps, 1.03 ps for the solitons generated in Er- and Tm-doped cavities, respectively.

Saturable absorption

Erbium

Thulium

Mode-Locking

10.1117/12.2041041

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Low Frequency Noise of Carbon Nanotubes THz detectors

2022 47th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz) (2021)

Adil Rehman Aleksandra Krajewska Serguei Smirnov Bartłomiej Stonio Dmytro B. But

We report studies of noise properties of carbon nanotube (CNT) networks-based devices used for the terahertz detectors. Low-frequency noise characteristics of CNTs as a function of temperature, UV illumination, and back-gate voltages were examined. Our results demonstrated the existence of at least two important resistance components of nanotubes rather than generally accepted dominant tube-to-tube junction resistance. We showed that noise spectroscopy can be employed to probe the structural quality of nanotube networks. Measurements as a function of back gate voltages revealed the existence of generation-recombination noise, related to deep tarps, which play a significant role in the performances of CNT networks-based terahertz detectors.

10.1109/irmmw-thz50926.2021.9567425

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Negative Kerr Nonlinearity of Graphene as seen via Chirped-Pulse-Pumped Self-Phase Modulation

Physical Review Applied (2016)

Nathalie Vermeulen David Castelló‐Lurbe Jinluo Cheng Iwona Pasternak Aleksandra Krajewska

The optical Kerr effect is the variation of a material's refractive index in response to high-intensity light, and as such causes the spectrum of the light to change. The authors measure the spectral broadening of chirped laser pulses in graphene-covered silicon waveguides, and determine the sign of graphene's Kerr index to be $n\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}g\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}v\phantom{\rule{0}{0ex}}e$, contrary to common assumption. This finding suggests greatly extended applicability of graphene in nonlinear photonic devices.

10.1103/physrevapplied.6.044006

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Citations (90)

Multilayer graphene-based saturable absorbers with scalable modulation depth for mode-locked Er- and Tm-doped fiber lasers

Optical Materials Express (2015)

Grzegorz Soboń Jarosław Sotor Iwona Pasternak Aleksandra Krajewska Włodek Strupiński

We demonstrate an experimental study on the influence of the parameters of a graphene-based saturable absorber (SA) on the performance of mode-locked Er- and Tm-doped fiber lasers. We have fabricated a set of saturable absorbers with different number of graphene layers: 9, 12, 24, 37 and 48. Each SA was characterized in terms of nonlinear optical parameters (modulation depth, saturation intensity, saturation fluence) and tested in two state-of-the-art, low-power Er- and Tm-doped fiber lasers. Our results show, that in the Er-laser the broadest output spectrum (11 nm) and shortest pulses (345 fs) are generated using 37 layers of graphene in the SA. In case of a Tm-laser, the best performance (737 fs pulses with 5.82 nm bandwidth) was achieved with 24 layers. Additionally, we show that the modulation depth of a 9-layer SA is insufficient to initiate mode-locking in both lasers. This is the first reported comprehensive study on controlling of the parameters of a SA by scaling the number of graphene layers.

Saturable absorption

Mode-Locking

10.1364/ome.5.002884

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Citations (94)