Pub Date : 2022-12-10DOI: 10.3952/physics.v62i4.4820
A. Ibenskas
A model, based on the pairwise intermolecular halogen–hydrogen (Br–H) and halogen–halogen (Br–Br) bonding, is proposed to describe the self-assembly of Br4Py molecules into two different planar structures (Phase I and Phase II). The pair bonding interactions are calculated by the density functional theory for the two-molecule and four-molecule clusters. It is shown that about 60% of bonding strength is due to the electrostatic Br(top)–Br(belt) interactions, while the remaining originates from Br–H interactions. The obtained values of pair interactions are further used for Monte Carlo calculations. The model for these calculations is proposed on a square lattice. The two main pair interactions are needed for the emergence of the Phase I ordering, while the Phase II ordering is obtained using a single interaction. The obtained results explain the emergence of both phases.
{"title":"Model for self-assembly of Br–H and Br–Br bonded Br4Py molecules","authors":"A. Ibenskas","doi":"10.3952/physics.v62i4.4820","DOIUrl":"https://doi.org/10.3952/physics.v62i4.4820","url":null,"abstract":"A model, based on the pairwise intermolecular halogen–hydrogen (Br–H) and halogen–halogen (Br–Br) bonding, is proposed to describe the self-assembly of Br4Py molecules into two different planar structures (Phase I and Phase II). The pair bonding interactions are calculated by the density functional theory for the two-molecule and four-molecule clusters. It is shown that about 60% of bonding strength is due to the electrostatic Br(top)–Br(belt) interactions, while the remaining originates from Br–H interactions. The obtained values of pair interactions are further used for Monte Carlo calculations. The model for these calculations is proposed on a square lattice. The two main pair interactions are needed for the emergence of the Phase I ordering, while the Phase II ordering is obtained using a single interaction. The obtained results explain the emergence of both phases.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44553299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-25DOI: 10.3952/physics.v62i3.4799
E. Şahi̇n
In this study, the traditional mixed oxide process was used to create ZnNb2O6-chopped strands composites. The single phase compound with the chemical formula ZnNb2O6 was generated after sintering at 1100°C for 4 h. For the structural investigation, various quantities of ZnNb2O6-chopped strands were generated. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were carried out for the structural analysis, which indicated that the second phase did not form in ZnNb2O6. Additionally, the ZnNb2O6-strands composites were manufactured by hot pressing using the compositions of ZnNb2O6-chopped strands in various proportions and epoxy. The ZnNb2O6-chopped strands compound formed in various weights, and epoxy resin were used to fabricate microwave shielding effectiveness composites. Utilizing a network analyzer, the microwave shielding effect of ZnNb2O6-chopped strands composites was investigated in a range of 6.5–18 GHz. At a thickness of 1.5 mm, a minimum of –51.32 dB shielding effectiveness value was achieved at 6.75 GHz. The ZnNb2O6-chopped strands compounds were produced as composite and their features were characterized for shielding effectivacy. The content of components in the samples may be managed for the larger and needed frequency bands to change the microwave shielding performance.
{"title":"Microwave electromagnetic shielding effectiveness of ZnNb2O6-chopped strands composites for radar and wideband (6.5–18 GHz) applications","authors":"E. Şahi̇n","doi":"10.3952/physics.v62i3.4799","DOIUrl":"https://doi.org/10.3952/physics.v62i3.4799","url":null,"abstract":"In this study, the traditional mixed oxide process was used to create ZnNb2O6-chopped strands composites. The single phase compound with the chemical formula ZnNb2O6 was generated after sintering at 1100°C for 4 h. For the structural investigation, various quantities of ZnNb2O6-chopped strands were generated. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were carried out for the structural analysis, which indicated that the second phase did not form in ZnNb2O6. Additionally, the ZnNb2O6-strands composites were manufactured by hot pressing using the compositions of ZnNb2O6-chopped strands in various proportions and epoxy. The ZnNb2O6-chopped strands compound formed in various weights, and epoxy resin were used to fabricate microwave shielding effectiveness composites. Utilizing a network analyzer, the microwave shielding effect of ZnNb2O6-chopped strands composites was investigated in a range of 6.5–18 GHz. At a thickness of 1.5 mm, a minimum of –51.32 dB shielding effectiveness value was achieved at 6.75 GHz. The ZnNb2O6-chopped strands compounds were produced as composite and their features were characterized for shielding effectivacy. The content of components in the samples may be managed for the larger and needed frequency bands to change the microwave shielding performance.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43227101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-25DOI: 10.3952/physics.v62i3.4798
V. Palenskis, J. Glemza, J. Matukas
The characteristics of the generation-recombination (g-r) process in silicon are investigated in a temperature range from 25 to 360 K. In the case of shallow donors, it is shown that the free electron density strongly depends on temperature: only 20% of donors are ionized at shallow donor densities of about 1017 cm–3 at liquid nitrogen temperature. The maximum of the variance of generation-recombination noise due to the free electron density fluctuations for a silicon sample with shallow donors strongly increases with donor density and shifts with temperature. It is demonstrated that the relative variance of free electron number fluctuations is always equal to 0.5 at low temperatures. The normalized generation-recombination noise spectra are depicted in a very wide frequency range. There is also a detailed investigation of the generation-recombination noise characteristics of an acceptor-partially compensated silicon sample with two donor levels. In this work, the main focus is on the characteristics of silicon doped by shallow donors as it is extremely widely used.
{"title":"Generation-recombination noise and other features of doped silicon in a wide temperature range","authors":"V. Palenskis, J. Glemza, J. Matukas","doi":"10.3952/physics.v62i3.4798","DOIUrl":"https://doi.org/10.3952/physics.v62i3.4798","url":null,"abstract":"The characteristics of the generation-recombination (g-r) process in silicon are investigated in a temperature range from 25 to 360 K. In the case of shallow donors, it is shown that the free electron density strongly depends on temperature: only 20% of donors are ionized at shallow donor densities of about 1017 cm–3 at liquid nitrogen temperature. The maximum of the variance of generation-recombination noise due to the free electron density fluctuations for a silicon sample with shallow donors strongly increases with donor density and shifts with temperature. It is demonstrated that the relative variance of free electron number fluctuations is always equal to 0.5 at low temperatures. The normalized generation-recombination noise spectra are depicted in a very wide frequency range. There is also a detailed investigation of the generation-recombination noise characteristics of an acceptor-partially compensated silicon sample with two donor levels. In this work, the main focus is on the characteristics of silicon doped by shallow donors as it is extremely widely used.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43973407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-25DOI: 10.3952/physics.v62i3.4796
A. Cesiul, K. Ikamas, D. B. But, I. Morkunaitė, T. Lisauskas, A. Lisauskas
This paper presents a fully-electronic wireless link operating at the 250 GHz frequency. The key elements of the developed system are the voltage-controlled harmonic oscillator implemented in 65 nm complementary metal-oxide-semiconductor technology (CMOS) and a quasi-optical detector with a resonantantenna- coupled field-effect transistor completed in 90 nm CMOS. The source is optimized for the third harmonic emission at 252 GHz with radiated power reaching up to –11 dBm (decibels with reference to one milliwatt) level. The detector has a resonance maximum of 254 GHz with a bandwidth of 25% and a minimal optical noise equivalent power of 22 pW/√−H−z . We employ an on-off keying technique for data coding and demonstrate digital signal transmission from 0.4 to 18 m distances. At 0.4 m distance and modulation frequency of 32 MHz, we achieve a 15.9 dB signal-to-noise ratio. The channel capacity of assembled communication link reaches 266 Mbit/s. However, it is limited by external electronic components – the amplifier and the modulator bandwidths. Implementing state-of-the-art high-frequency circuits should allow directly scaling the throughput to 10 Gbit/s.
{"title":"Towards wireless data transmission with compact all-electronic THz source and detector system","authors":"A. Cesiul, K. Ikamas, D. B. But, I. Morkunaitė, T. Lisauskas, A. Lisauskas","doi":"10.3952/physics.v62i3.4796","DOIUrl":"https://doi.org/10.3952/physics.v62i3.4796","url":null,"abstract":"This paper presents a fully-electronic wireless link operating at the 250 GHz frequency. The key elements of the developed system are the voltage-controlled harmonic oscillator implemented in 65 nm complementary metal-oxide-semiconductor technology (CMOS) and a quasi-optical detector with a resonantantenna- coupled field-effect transistor completed in 90 nm CMOS. The source is optimized for the third harmonic emission at 252 GHz with radiated power reaching up to –11 dBm (decibels with reference to one milliwatt) level. The detector has a resonance maximum of 254 GHz with a bandwidth of 25% and a minimal optical noise equivalent power of 22 pW/√−H−z . We employ an on-off keying technique for data coding and demonstrate digital signal transmission from 0.4 to 18 m distances. At 0.4 m distance and modulation frequency of 32 MHz, we achieve a 15.9 dB signal-to-noise ratio. The channel capacity of assembled communication link reaches 266 Mbit/s. However, it is limited by external electronic components – the amplifier and the modulator bandwidths. Implementing state-of-the-art high-frequency circuits should allow directly scaling the throughput to 10 Gbit/s.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42234407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-25DOI: 10.3952/physics.v62i3.4797
A. Aghajamali, S. K. Srivastava, C. Nayak
In this paper, optical reflectance properties of an annular photonic crystal (APC) composed of alternate layers of double negative (DNG) material and a non-magnetized plasma (NMP) layer, immersed in free space, have been theoretically investigated and studied. The reflectance spectra of the annular PC have been obtained by employing the transfer matrix method (TMM) for the cylindrical waves in the case of TEpolarized wave only. It has been found that the spectral position and width of the reflection bands of APC are greatly influenced by the variation in the thickness of DNG metamaterial and NMP layer, respectively. Interestingly, it is observed that the presence of NMP layer causes the increase in photonic band gap (PBG) whereas the DNG layer reduces the PBG. Further, the effect of azimuthal mode number (m) on the reflectance spectra shows that for m > 0, splitting in the reflection bands occurs at the frequency corresponding to the zero permeability value of DNG metamaterial layer. Moreover, with the increase in azimuthal mode number one PBG is red-shifted and the second one is blue-shifted. Finally, the effect of change in the starting radius parameter of curved surface and plasma electron density on the reflectance spectra of APC has also been studied and very interesting results have been observed.
{"title":"Investigation of reflection bands of 1D annular photonic crystal containing double negative index material and non-magnetized plasma","authors":"A. Aghajamali, S. K. Srivastava, C. Nayak","doi":"10.3952/physics.v62i3.4797","DOIUrl":"https://doi.org/10.3952/physics.v62i3.4797","url":null,"abstract":"In this paper, optical reflectance properties of an annular photonic crystal (APC) composed of alternate layers of double negative (DNG) material and a non-magnetized plasma (NMP) layer, immersed in free space, have been theoretically investigated and studied. The reflectance spectra of the annular PC have been obtained by employing the transfer matrix method (TMM) for the cylindrical waves in the case of TEpolarized wave only. It has been found that the spectral position and width of the reflection bands of APC are greatly influenced by the variation in the thickness of DNG metamaterial and NMP layer, respectively. Interestingly, it is observed that the presence of NMP layer causes the increase in photonic band gap (PBG) whereas the DNG layer reduces the PBG. Further, the effect of azimuthal mode number (m) on the reflectance spectra shows that for m > 0, splitting in the reflection bands occurs at the frequency corresponding to the zero permeability value of DNG metamaterial layer. Moreover, with the increase in azimuthal mode number one PBG is red-shifted and the second one is blue-shifted. Finally, the effect of change in the starting radius parameter of curved surface and plasma electron density on the reflectance spectra of APC has also been studied and very interesting results have been observed.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48952774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-10-25DOI: 10.3952/physics.v62i3.4800
J. Garankin, A. Plukis
The separation of ionizing radiation particles is an important and challenging task, especially regarding neutrons and gamma rays. The separation of neutron and gamma radiation is necessary for safeguard purposes and control of nuclear reactions. Standard mathematical models of pulse analysis work well in the presence of large energy transfer (>1 MeV) from the particle to the detector. However, the quality of the separation decreases as the amount of transferred energy lessens, making it impossible to determine the exact type of particle at a sufficiently low-energy level. In this work, an artificial neural network model was used to solve the problem of separation at low-energy levels. The supervised machine learning (ML) model was used to analyse pulses received from the polyethylene naphthalate (PEN) scintillation detector. Several data sets after the PEN exposure to neutron/gamma (combined 239PuBe and 238PuBe source), alpha (238Pu) and beta (90Sr/90Y) sources were used to train the models. The information obtained from the separation of neutrons and gamma particles was compared with the information obtained using standard pulses delayed fluorescence analysis methods. The obtained results showed that the model was able to separate particles in the fields of low- and high-energy transfer.
{"title":"Application of artificial neural network for the ionizing radiation particle identification by the plastic scintillation detector response","authors":"J. Garankin, A. Plukis","doi":"10.3952/physics.v62i3.4800","DOIUrl":"https://doi.org/10.3952/physics.v62i3.4800","url":null,"abstract":"The separation of ionizing radiation particles is an important and challenging task, especially regarding neutrons and gamma rays. The separation of neutron and gamma radiation is necessary for safeguard purposes and control of nuclear reactions. Standard mathematical models of pulse analysis work well in the presence of large energy transfer (>1 MeV) from the particle to the detector. However, the quality of the separation decreases as the amount of transferred energy lessens, making it impossible to determine the exact type of particle at a sufficiently low-energy level. In this work, an artificial neural network model was used to solve the problem of separation at low-energy levels. The supervised machine learning (ML) model was used to analyse pulses received from the polyethylene naphthalate (PEN) scintillation detector. Several data sets after the PEN exposure to neutron/gamma (combined 239PuBe and 238PuBe source), alpha (238Pu) and beta (90Sr/90Y) sources were used to train the models. The information obtained from the separation of neutrons and gamma particles was compared with the information obtained using standard pulses delayed fluorescence analysis methods. The obtained results showed that the model was able to separate particles in the fields of low- and high-energy transfer.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43145370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-12DOI: 10.3952/physics.v62i2.4744
V. Balevičius, K. Aidas, A. Marsalka, F. Kuliesius, V. Jakubkienė, S. Tumkevičius
O NMR spectra of pyridine N-oxide (PyO) complexes with the acids – acetic (AA), cyanoacetic (CyA), propiolic (PA), trichloroacetic (TCA), trifluoroacetic (TFA), hydrochloric (HCl) and methanesulfonic (MSA) – as well as some related molecules with intramolecular H-bonds (4-substituted picolinic acid N-oxides) were studied in an acetonitrile (ACN) solution. In order to evaluate the effect of proton positioning along the O–H…O bond on the measured chemical shifts the full geometry optimization was carried out, and 17O magnetic shielding tensors were calculated using density functional theory (DFT). The modified hybrid functional PBE1PBE with the 6-311++G** basis set and the gauge-including atomic orbital (GIAO) approach were applied. The solvent effect was taken into account by a polarized continuum model using the integral equation formalism (IEFPCM). Two stable structures were deduced for the PyO complexes with TCA and TFA that correspond to the H-bonds with and without proton transfer (PT). Two minima on the potential surface were separated by ca 0.2 Å. The experimental 17O NMR spectra have shown that the PyO-TCA complex in ACN can be considered as H-bonding with incipient PT, whereas it is known from neutron diffraction that in its crystalline state PT occurs. The proton location in PyO-TFA due to the thermally induced proton sharing was found at the middle point. The 17O NMR data for the acids with an intramolecular H-bond (nitroPANO, PANO and methoxyPANO) deviate from the general trend. The factors that can cause it, such as the substitution effect, persistence of nano-crystallites in a solution due to a low solubility, etc., have been discussed.
{"title":"O NMR and DFT study of hydrogen bonding: Proton sharing and incipient transfer","authors":"V. Balevičius, K. Aidas, A. Marsalka, F. Kuliesius, V. Jakubkienė, S. Tumkevičius","doi":"10.3952/physics.v62i2.4744","DOIUrl":"https://doi.org/10.3952/physics.v62i2.4744","url":null,"abstract":"O NMR spectra of pyridine N-oxide (PyO) complexes with the acids – acetic (AA), cyanoacetic (CyA), propiolic (PA), trichloroacetic (TCA), trifluoroacetic (TFA), hydrochloric (HCl) and methanesulfonic (MSA) – as well as some related molecules with intramolecular H-bonds (4-substituted picolinic acid N-oxides) were studied in an acetonitrile (ACN) solution. In order to evaluate the effect of proton positioning along the O–H…O bond on the measured chemical shifts the full geometry optimization was carried out, and 17O magnetic shielding tensors were calculated using density functional theory (DFT). The modified hybrid functional PBE1PBE with the 6-311++G** basis set and the gauge-including atomic orbital (GIAO) approach were applied. The solvent effect was taken into account by a polarized continuum model using the integral equation formalism (IEFPCM). Two stable structures were deduced for the PyO complexes with TCA and TFA that correspond to the H-bonds with and without proton transfer (PT). Two minima on the potential surface were separated by ca 0.2 Å. The experimental 17O NMR spectra have shown that the PyO-TCA complex in ACN can be considered as H-bonding with incipient PT, whereas it is known from neutron diffraction that in its crystalline state PT occurs. The proton location in PyO-TFA due to the thermally induced proton sharing was found at the middle point. The 17O NMR data for the acids with an intramolecular H-bond (nitroPANO, PANO and methoxyPANO) deviate from the general trend. The factors that can cause it, such as the substitution effect, persistence of nano-crystallites in a solution due to a low solubility, etc., have been discussed.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47423111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-12DOI: 10.3952/physics.v62i2.4741
D. Khveshchenko
This paper discusses the examples of 0 + 1-dimensional Liouvillean dynamics instigated by the various deformations of the Sachdev–Ye–Kitaev (SYK) model. In reference to such deformations the main focus is on the regions of parameter space where the competing SYK couplings are of a comparable strength and cannot be treated as each other’s perturbations in the vicinity of the conformal fixed points corresponding to the pure SYKq models with different values of q. Crossovers between such fixed points (‘SYK transits’) can be efficiently studied in the equivalent framework of single-particle quantum mechanics.
{"title":"The gloria mundi of SYK does not transit yet","authors":"D. Khveshchenko","doi":"10.3952/physics.v62i2.4741","DOIUrl":"https://doi.org/10.3952/physics.v62i2.4741","url":null,"abstract":"This paper discusses the examples of 0 + 1-dimensional Liouvillean dynamics instigated by the various deformations of the Sachdev–Ye–Kitaev (SYK) model. In reference to such deformations the main focus is on the regions of parameter space where the competing SYK couplings are of a comparable strength and cannot be treated as each other’s perturbations in the vicinity of the conformal fixed points corresponding to the pure SYKq models with different values of q. Crossovers between such fixed points (‘SYK transits’) can be efficiently studied in the equivalent framework of single-particle quantum mechanics.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47886838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-12DOI: 10.3952/physics.v62i2.4742
S. Pūkienė, A. Jasinskas, A. Zelioli, S. Stanionytė, V. Bukauskas, B. Čechavičius, E. Dudutienė, R. Butkutė
A series of 100 nm-thick pseudomorphic GaAsBi layers with the Bi content varying from 0.97 to 11.2% have been grown by molecular beam epitaxy (MBE) on the semi-insulating GaAs(100) substrates buffered with an ultra-thin up to 20 nm thick GaAs layer. The main attention in this work was focused on the investigation of relaxation in the Bi induced compressively-strained GaAsBi layers containing a various content of Bi. The lattice parameters of GaAs- Bi compound and the Bi concentration have been evaluated from high resolution X-ray diffraction measurements. The relaxation values of GaAsBi layers ranging from 0.4 to 3.5% were obtained analyzing the symmetric and asymmetric reciprocal space maps of (004) and (115) planes, respectively. Also, the complex study was performed to clarify the relaxation effect on structural, morphological and optical properties of bismide layers. Optical measurements revealed a significant reduction of the energy band gap from 1.34 to 0.92 eV for the layers containing 0.97–8.6% of Bi in the GaAs lattice.
{"title":"Influence of an ultra-thin buffer layer on the growth and properties of pseudomorphic GaAsBi layers","authors":"S. Pūkienė, A. Jasinskas, A. Zelioli, S. Stanionytė, V. Bukauskas, B. Čechavičius, E. Dudutienė, R. Butkutė","doi":"10.3952/physics.v62i2.4742","DOIUrl":"https://doi.org/10.3952/physics.v62i2.4742","url":null,"abstract":"A series of 100 nm-thick pseudomorphic GaAsBi layers with the Bi content varying from 0.97 to 11.2% have been grown by molecular beam epitaxy (MBE) on the semi-insulating GaAs(100) substrates buffered with an ultra-thin up to 20 nm thick GaAs layer. The main attention in this work was focused on the investigation of relaxation in the Bi induced compressively-strained GaAsBi layers containing a various content of Bi. The lattice parameters of GaAs- Bi compound and the Bi concentration have been evaluated from high resolution X-ray diffraction measurements. The relaxation values of GaAsBi layers ranging from 0.4 to 3.5% were obtained analyzing the symmetric and asymmetric reciprocal space maps of (004) and (115) planes, respectively. Also, the complex study was performed to clarify the relaxation effect on structural, morphological and optical properties of bismide layers. Optical measurements revealed a significant reduction of the energy band gap from 1.34 to 0.92 eV for the layers containing 0.97–8.6% of Bi in the GaAs lattice.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46151643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-12DOI: 10.3952/physics.v62i2.4743
K. Kandrotaitė, V. Dudoitis, I. Uogintė, P. Strizak, F. Pope, K. Plauškaitė, S. Byčenkienė
The global spread of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) proved to be a challenge for public health. The high demand of medical masks worldwide during the pandemic has led to a critical situation for decision-makers regarding high-quality mask supply. For this period, the World Health Organization has suggested the use of non-medical face masks (also known as ‘community’ masks) in public places to reduce the airborne spread of SARS-CoV-2. In this study, the filtration efficiency of various fabrics widely used in community masks was determined based on two main mask filtering properties: filtration efficiency (FE) and pressure drop (ΔP) according to the recommendations of the CEN Workshop Agreement (CWA) 17553:2020. The combination of FE and ΔP parameters must be considered in order to select suitable materials for public masks. The filtration efficiencies for various fabrics ranged from 6 to 100%. It was found that the composite materials have the highest FE equivalent to the requirements of a medical mask (FE > 95%), that is confirmed by high-quality parameters 16–30 kPa–1. The study found that fabrics of natural fibres (100% cotton) have a higher FE with Ag coating (18–40% before and 29–40% after coating) in the 0.54–1.50 μm particle size range.
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