Bulat Rameev | Gebze Institute Of Technology (original) (raw)

Papers by Bulat Rameev

Bulletin of the American Physical Society, 2016

available ITO thin films on fused silica substrates were implanted with 40 keV Ni + ions to fluen... more available ITO thin films on fused silica substrates were implanted with 40 keV Ni + ions to fluences of (0.5,1.0&1.5) ×10 17 ions/cm 2 at room temperature. XRR measurements show that the thickness of the implanted films (∼ 28.5 nm) does not change noticeably with the fluence, while the surface roughness increases essentially. SEM and EDX studies revealed a highly non-uniform distribution of Ni atoms. Room temperature ferromagnetism was observed in the samples with fluences of (1.0&1.5)×10 17 ions/cm 2. VSM hysteresis curves and FMR signal point to the formation of a ferromagnetic near-surface layer in the implanted films due to agglomeration of closely-spaced metal Ni nanoparticles. The filling factor of the Ni ferromagnetic phase in the granular magnetic layer was estimated from the FMR results. Super-and para-magnetic phases were observed in the temperature dependence of magnetization by VSM. Superparamagnetic phase is attributed to the Ni nanoparticles located in deeper regions near the film/substrate interface, while paramagnetic phase is related to the impurity centers. For the samples with fluences of (1.0&1.5) ×10 17 ions/cm 2 average sizes of the superparamagnetic nanoparticles were calculated from the blocking temperatures T B observed in thermo-magnetic dependences.

Chemical Physics, 2018

The T 1 and T 2 relaxation times of some nitrogen-containing liquids were measured by 14 N pulse ... more The T 1 and T 2 relaxation times of some nitrogen-containing liquids were measured by 14 N pulse nuclear magnetic resonance (NMR) in the magnetic field of 0.575 T. The liquids measured in this paper were energetic and toxic substances as well as some electrolytes. A method of the fast discrimination of dangerous liquids by the low field 14 N NMR relaxation parameters was proposed. It is shown that flammable and toxic nitrogen-based liquids have small values of T 1 and T 2 , therefore these liquids may be discriminated from the group of less dangerous liquids.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003

Iron granular films were synthesized in silicone polymers by implantation of 40 keV Fe þ ions wit... more Iron granular films were synthesized in silicone polymers by implantation of 40 keV Fe þ ions with a fluence of 1.25 • 10 17 ion/cm 2 into viscous polymer substrates with various viscosity of 20-1000 Pa s. After the implantation the iron-implanted silicone substrates have been cured in the solid rubber-like state on the expiration of 72 h. The influence of the substrate viscosity on the magnetic properties of the synthesized iron films was studied by ferromagnetic resonance (FMR) spectroscopy. It was shown that magnetic anisotropy and magnetization of the iron granular films is strongly and non-monotonically depended on the viscosity of silicone polymer under irradiation. Particularly, the maximal value of magnetization, 610 G, is observed for iron granular film synthesized at substrate viscosity on order of 70 Pa s. This value is higher than the magnetization of films obtained in silicone substrate implanted with iron ions in fully cured state.

Technical Physics, 2014

The application of the multipulse sequences in nuclear quadrupole resonance (NQR) detection of ex... more The application of the multipulse sequences in nuclear quadrupole resonance (NQR) detection of explosive and narcotic substances has been studied. Various approaches to increase the signal to noise ratio (SNR) of signal detection are considered. We discussed two modifications of the phase alternated multiple pulse sequence (PAMS): the 180° pulse sequence with a preparatory pulse and the 90° pulse sequence. The advantages of optimal filtering to detect NQR in the case of the coherent steady state precession have been analyzed. It has been shown that this technique is effective in filtering high frequency and low frequency noise and increasing the reliability of NQR detection. Our analysis also shows the PAMS with 180° pulses is more effective than PSL sequence from point of view of the application of optimal filtering procedure to the steady state NQR signal.

Journal of Magnetism and Magnetic Materials, 2015

Abstract The magnetic properties of Ni-implanted ITO thin films have been investigated by ferroma... more Abstract The magnetic properties of Ni-implanted ITO thin films have been investigated by ferromagnetic resonance (FMR) technique and vibrating sample magnetometry (VSM) techniques. Commercially available ITO thin films on fused silica substrates have been implanted with different fluences of Ni+ ions with energy of 40 keV and ion current density of 8 µA/cm2 at room temperature. The samples with three doses of 0.5×1017, 1.0×1017 and 1.5×1017 ions/cm2 have been studied. Room temperature ferromagnetism has been observed in the nickel-implanted ITO samples with fluences of 1.0×1017 and 1.5×1017 ions/cm2. The magnetic properties of the samples have been explained by the formation of Ni-nanoparticles in the implanted surface layer of the ITO films. Although the formation of a diluted magnetic oxide phase cannot be ruled out entirely, the analysis of our FMR and VSM data reveals that the metallic Ni nanoparticles, formed during high-dose implantation process, have major contribution to the magnetic properties of the Ni-implanted ITO thin films. The sizes of the Ni-nanoparticles have been calculated from the blocking temperatures obtained by the VSM measurements. The filling factor of the Ni ferromagnetic phase in the granular magnetic layer has also been estimated by the effective magnetization approach applied to the FMR results.

Vacuum, 2000

ABSTRACT Composite metal–polymer thin films were formed by implantation of 40KeV Fe+ and Co+ ions... more ABSTRACT Composite metal–polymer thin films were formed by implantation of 40KeV Fe+ and Co+ ions into viscous and solid silicone substrates in the dose range of (0.3–1.5)×1017 ions/cm2. Morphology and magnetic properties of the synthesized films were investigated. TEM investigations showed that the microstructure of metal granular layers synthesized in silicone polymers strongly depends on an initial relaxation state of the target. Magnetic resonance studies revealed essential differences in the magnetic properties of thin metal films synthesized at different initial states of silicone substrate and with respect to the type of implanted ions (Fe or Co). A shift and broadening of FMR signal with the samples cooling are observed both for perpendicular and parallel orientation of the films with respect to the magnetic field. These effects are associated with the increase of the inter-particle interactions and superparamagnetism blocking in the particles. It was found that the viscous initial state of the polymer is a favourable factor for the high anisotropy of FMR response in Fe-implanted samples in contrast to the Co-based ones. The reasons for this have been discussed with respect to the morphology of Fe and Co synthesized films.

Technical Physics, 2010

Nonuniform line broadening in quadrupole spin systems is analyzed. It is shown theoretically that... more Nonuniform line broadening in quadrupole spin systems is analyzed. It is shown theoretically that this broadening is of the tensor type. This forms the basis of the method for analyzing the distribution of local inhomogeneities in the crystal lattice, which is verified experimentally on a sodium nitride sample.

physica status solidi (b), 2003

ABSTRACT

Applied Magnetic Resonance, 2000

The two-frequency nuclear quadrupole resonance (NQR) of 14N nuclei is described for purposes of e... more The two-frequency nuclear quadrupole resonance (NQR) of 14N nuclei is described for purposes of explosives detection. Two applications are known: two-frequency NQR for increasing the signal intensity, two-frequency NQR for improved reliability of explosives detection. The two-frequency experiments were carried out in hexahydro-1,3,5-trinitro-s-triazine C 1 H6N606 and sodium nitrite NaNO2 as a substitute for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocycine C 4H,N,O,. The twofrequency sequences for NQR are proposed for increasing the amplitude of NQR signal and improvement of detection condition.

Research and reviews: journal of material sciences, Nov 8, 2018

2022 Photonics & Electromagnetics Research Symposium (PIERS)

Journal of Solid State Chemistry, 2019

Recently tetrahedrite compounds have attracted great attention due to their potential application... more Recently tetrahedrite compounds have attracted great attention due to their potential applications on the mid-temperature thermoelectric technologies. In this work, structural, Electron Paramagnetic Resonance (EPR) and the thermoelectric properties of tetrahedrite (Cu 12-x Fe x Sb 4 S 13 where x=0.0, 1.0, 1.5, 2.5) were investigated. The crystal structural, morphological properties and elemental compositions of the samples were investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS-EDX) tools respectively. Magnetic properties of the samples were performed by EPR techniques using electron spin resonance (ESR) spectrometer with the model of Bruker EMX series at X-band (9.5 GHz). The thermoelectric properties were assisted based on Seebeck coefficient, electrical resistivity, and thermal conductivity measurement between 300 and 600 K temperature range. PXRD patterns and SEM-EDX analysis confirmed the main phase of tetrahedrite structure for all compounds. The Seebeck coefficient sign indicated that holes were dominant carriers in all compounds. Electrical resistivity measurement showed an increment with increasing Fe concentration likely due to decreasing in carrier density. A typical behavior of intrinsic semiconductor was observed from temperature-dependent electrical resistivity measurements. The maximum ZT value of 0.6 was achieved for the sample Cu 11 Fe 1 Sb 4 S 13 at 550 K. Electron Paramagnetic Resonance (EPR) and thermoelectric measurements exhibited that the maximum Fe concentration might be ≤1.0 for achieving high ZT value in Cu 12-x Fe x Sb 4 S 13 compounds.

Solid State Communications, 2006

TlGaS 2 single crystal doped by paramagnetic Fe 3C ions has been studied by electron paramagnetic... more TlGaS 2 single crystal doped by paramagnetic Fe 3C ions has been studied by electron paramagnetic resonance (EPR) technique. The fine structure of EPR spectra of paramagnetic Fe 3C ions was observed. The spectra reveal a nearly orthorhombic symmetry of the crystal field (CF) on the Fe 3C ions. Two groups each consisting of four equivalent Fe 3C centers were observed in the EPR spectra. The local symmetry of the crystal field on the Fe 3C centers and CF parameters were determined. Experimental results indicate that the Fe ions substitute Ga at the center of the GaS 4 tetrahedrons. The rhombic distortion of the sulfur ligand CF is attributed to the effect of Tl ions located in the trigonal cavities between the tetrahedral complexes. The observed twinning of the resonance lines indicates a presence of two non-equivalent positions of Tl ions that confirms their zigzag alignment in the TlGaS 2 crystal structure.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000

40 keV Fe+ and Co+ ions were implanted in both viscous and solid silicone substrates at doses of ... more 40 keV Fe+ and Co+ ions were implanted in both viscous and solid silicone substrates at doses of (0.1–1.8)×1017 ions/cm2 and an ion current density of 4 μA/cm2. The microstructure and magnetic properties of the Fe- and Co-implanted silicone layers were then investigated as a function of the initial relaxation state (viscosity) of the polymer target. TEM investigations showed that

Journal of Physics: Conference Series, 2009

ABSTRACT Single crystals of manganese-implanted TiO2 rutile have been investigated by electron pa... more ABSTRACT Single crystals of manganese-implanted TiO2 rutile have been investigated by electron paramagnetic resonance (EPR) technique at room temperature. ESR spectra have been interpreted to correspond to the transitions among the spin multiplet (S=3/2) of the paramagnetic Mn4+ ion. Characteristic six-line hyper-fine splitting of the ESR spectra resulting from the spin I=5/2 of the Mn55 nucleus has been observed. Analysis of EPR spectra shows that manganese in TiO2 rutile host substitutes for Ti4+ ions. Two equivalent Mn4+ centers have been observed in the EPR spectra in correspondence with two equivalent octahedral positions of Ti ions in the rutile structure. Parameters of the crystal field of orthorhombic symmetry on the Mn4+ centers have been obtained as result of computer modelling.

Journal of Non-Crystalline Solids, 2004

ABSTRACT The structure and magnetic properties of composite films obtained by ion irradiation or ... more ABSTRACT The structure and magnetic properties of composite films obtained by ion irradiation or thermal treatment of triethoxysilane gels containing iron or nickel in solution are investigated by means of X-ray diffraction, electron microscopy and electron spin resonance. Ion irradiated gels are converted into silica glasses containing metallic nanoparticles with a narrow range of sizes. These particles exhibit a magnetic resonance with a preferential alignment of magnetic moments perpendicular to the surface. This unusual out of plane anisotropy seem to be ascribed to an interaction of the moments with radiation defects. The magnetization in irradiated film is comparable to that in films of same materials submitted to a thermal conversion at 1000 °C in vacuum. But the latter films are porous and contain particles of metal and silicide or silicate with a wider range of sizes.

Applied Physics A, 2011

Single-crystalline ZnO thin films have been grown on sapphire substrates and implanted by 40 keV ... more Single-crystalline ZnO thin films have been grown on sapphire substrates and implanted by 40 keV Ni + ions with a dose of 0.25-1.25 × 10 17 ions/cm 2. After implantation the samples have been annealed at T = 1000°C for 30 minutes in air. Both as-prepared and annealed nickelimplanted ZnO samples have been investigated by ferromagnetic resonance (FMR), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), and optical techniques. SEM studies reveal that the surface of non-implanted ZnO thin film is very smooth, while microcracks are present in the Ni-implanted ZnO samples. Annealing after implantation recovers the surface of the implanted ZnO. Energy dispersive X-ray spectroscopy shows that the Ni concentration increases with increasing the im

Microelectronic Engineering, 2011

Charging effect becomes a more serious issue when performing electron beam lithography using high... more Charging effect becomes a more serious issue when performing electron beam lithography using high beam current. Here we studied the charging effect using PMMA, PMGI and ZEP-520A resist to pattern 200 nm period hole array. It is found that charging effect can be reduced by simply rearranging the exposure sequence such that subsequent writing elements are farther apart. It can also be decreased by using a more conductive substrate. Among the three resists, the charging effect is the least for the insensitive PMGI resist, though at the cost of longer writing time when using the same beam current. The opposite is true for the more sensitive ZEP-520A resist.

We report the development and test of planar microwave Inverse Anapole Resonators (IARs) made of ... more We report the development and test of planar microwave Inverse Anapole Resonators (IARs) made of superconducting Yttrium Barium Copper Oxide (YBCO) for electron spin resonance spectroscopy on small samples. We first characterize our resonators in zero field and then by carrying out transmission spectroscopy on a diluted α, γ-bisdiphenylene-β-phenylally (BDPA) organic radical spin ensemble in an applied magnetic field. These IARs allow us to carry out electron spin resonance spectroscopy both in Continuous-Wave and Pulsed-Wave mode, and to estimate the spin memory time of BDPA. The comparison with the results obtained for the same sample on typical linear coplanar resonators shows an improvement by ≈ 2 - up to 3 - orders of magnitude in spin sensitivity, with effective sensing volumes below 1 nanoliter. The best sensitivity we achieved is S ≈ 107 spin/√Hz in the Pulsed-Wave regime. These results compare well with similar experiments reported in literature.