Pub Date : 2020-08-03DOI: 10.3952/physics.v60i3.4306
U. Makhmanov, A. Kokhkharov, S. Bakhramov, D. Erts
The results of experiments on the self-aggregation of C60 fullerene molecules both inside a two-component solvent (xylene/tetrahydrofuran) and in the volume of an evaporating drop of C60 colloidal solution on a flat substrate surface are presented. The investigations of C60 solutions using dynamic light scattering, transmission electron microscopy and UV–Vis absorption spectroscopy methods revealed the possibility of synthesis of fractal nanoaggregates with a diameter of up to ~135 nm at low concentrations of C60 in the solutions. The final geometric dimensions of C60 nanoaggregates were determined by the initial concentration of fullerene in the solvent medium. Using the scanning electron microscopy method, we have shown that in an open dissipative system – in the volume of an evaporating droplet of the colloidal solution of fullerene C60 sessile on the surface of a flat glass substrate, large quasispherical nanoaggregates with an average diameter of ~380–800 nm are formed. The physical features and regularities that characterize the processes of self-aggregation of fullerene particles in the volume of a drying drop were determined.
{"title":"The formation of self-assembled structures of C60 in solution and in the volume of an evaporating drop of a colloidal solution","authors":"U. Makhmanov, A. Kokhkharov, S. Bakhramov, D. Erts","doi":"10.3952/physics.v60i3.4306","DOIUrl":"https://doi.org/10.3952/physics.v60i3.4306","url":null,"abstract":"The results of experiments on the self-aggregation of C60 fullerene molecules both inside a two-component solvent (xylene/tetrahydrofuran) and in the volume of an evaporating drop of C60 colloidal solution on a flat substrate surface are presented. The investigations of C60 solutions using dynamic light scattering, transmission electron microscopy and UV–Vis absorption spectroscopy methods revealed the possibility of synthesis of fractal nanoaggregates with a diameter of up to ~135 nm at low concentrations of C60 in the solutions. The final geometric dimensions of C60 nanoaggregates were determined by the initial concentration of fullerene in the solvent medium. Using the scanning electron microscopy method, we have shown that in an open dissipative system – in the volume of an evaporating droplet of the colloidal solution of fullerene C60 sessile on the surface of a flat glass substrate, large quasispherical nanoaggregates with an average diameter of ~380–800 nm are formed. The physical features and regularities that characterize the processes of self-aggregation of fullerene particles in the volume of a drying drop were determined.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44215715","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 : 2020-08-03DOI: 10.3952/physics.v60i3.4304
A. Cerskus, S. Ašmontas, K. Petrauskas, A. Sužiedėlis, J. Gradauskas, A. Opanasyuk, B. Vengalis
This paper presents a study of the photoluminescence properties of hybrid perovskite films deposited on titanium and magnesium zinc oxide films, as electron transport layers, using the spin-coating technique. The subject of the investigation was continuous wave photoluminescence versus temperature, excitation power and transient photoluminescence. Moreover, the paper discusses possible carrier recombination mechanisms. Complex temporal decay was approximated through the use of several models, but only the four-exponent model and the model using the sum of two hyperbolic functions provided a good agreement with the experimental data. The first attempt to replace titanium dioxide with magnesium zinc oxide in conjunction with the perovskite layer showed improved optical properties such as a weaker non-radiative recombination process and a longer decay time constant. PACS: 81.10.Dn, 84.60.Jt, 78.55.-m, 78.47.D
{"title":"Photoluminescence properties of hybrid perovskites in solar cells with TiO2 and Mg0.2Zn0.8O electron transport layers","authors":"A. Cerskus, S. Ašmontas, K. Petrauskas, A. Sužiedėlis, J. Gradauskas, A. Opanasyuk, B. Vengalis","doi":"10.3952/physics.v60i3.4304","DOIUrl":"https://doi.org/10.3952/physics.v60i3.4304","url":null,"abstract":"This paper presents a study of the photoluminescence properties of hybrid perovskite films deposited on titanium and magnesium zinc oxide films, as electron transport layers, using the spin-coating technique. The subject of the investigation was continuous wave photoluminescence versus temperature, excitation power and transient photoluminescence. Moreover, the paper discusses possible carrier recombination mechanisms. Complex temporal decay was approximated through the use of several models, but only the four-exponent model and the model using the sum of two hyperbolic functions provided a good agreement with the experimental data. The first attempt to replace titanium dioxide with magnesium zinc oxide in conjunction with the perovskite layer showed improved optical properties such as a weaker non-radiative recombination process and a longer decay time constant. PACS: 81.10.Dn, 84.60.Jt, 78.55.-m, 78.47.D","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46346697","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 : 2020-04-28DOI: 10.3952/physics.v60i2.4225
A. Poškus, Rokas Dobužinskas, M. Viliunas, K. Arlauskas
A simple theoretical model explaining the increase of X-ray sensitivity caused by adding tungsten nanoparticles into thin layers of organic materials is proposed. The mentioned increase of sensitivity is caused by quenched electron multiplication due to secondary electron emission from tungsten particles. After some simplifying assumptions, an expression of the electron multiplication factor K is derived for the case when tungsten atoms are uniformly mixed with the matrix material. The main assumption of the model is the existence of a threshold energy Emin of the order of 0.1 eV, below which the recombination of charge carriers prevents them from being accelerated by the electric field to energies sufficient for impact ionization. It is shown that this assumption makes the increase of K and photocurrent with increasing electric field much slower than the exponential increase commonly associated with an electron avalanche, and K may even start to decrease when the electric field strength exceeds a certain value. Another factor, which has an adverse effect on the X-ray sensitivity, is the ionization energy loss of photoelectrons inside metallic nanoparticles. The results of Monte Carlo simulations show that in the case of spherical tungsten particles with 0.8 μm diameter, the latter phenomenon may cause an additional decrease of the sensitivity by as much as 75%. In order to reduce this effect, the size of nanoparticles should be reduced, or, alternatively, most of the photoelectrons should be generated in the organic matrix rather than inside the nanoparticles.
{"title":"A physical mechanism of sensitivity enhancement of organic X-ray detectors with tungsten nanoparticles","authors":"A. Poškus, Rokas Dobužinskas, M. Viliunas, K. Arlauskas","doi":"10.3952/physics.v60i2.4225","DOIUrl":"https://doi.org/10.3952/physics.v60i2.4225","url":null,"abstract":"A simple theoretical model explaining the increase of X-ray sensitivity caused by adding tungsten nanoparticles into thin layers of organic materials is proposed. The mentioned increase of sensitivity is caused by quenched electron multiplication due to secondary electron emission from tungsten particles. After some simplifying assumptions, an expression of the electron multiplication factor K is derived for the case when tungsten atoms are uniformly mixed with the matrix material. The main assumption of the model is the existence of a threshold energy Emin of the order of 0.1 eV, below which the recombination of charge carriers prevents them from being accelerated by the electric field to energies sufficient for impact ionization. It is shown that this assumption makes the increase of K and photocurrent with increasing electric field much slower than the exponential increase commonly associated with an electron avalanche, and K may even start to decrease when the electric field strength exceeds a certain value. Another factor, which has an adverse effect on the X-ray sensitivity, is the ionization energy loss of photoelectrons inside metallic nanoparticles. The results of Monte Carlo simulations show that in the case of spherical tungsten particles with 0.8 μm diameter, the latter phenomenon may cause an additional decrease of the sensitivity by as much as 75%. In order to reduce this effect, the size of nanoparticles should be reduced, or, alternatively, most of the photoelectrons should be generated in the organic matrix rather than inside the nanoparticles.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46725483","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 : 2020-04-28DOI: 10.3952/physics.v60i2.4224
M. Misevicius, L. Dagys, A. Marsalka, Kristina Kristinaityte, V. Balevičius
The Eu2+-doped strontium aluminate SrAl4O7 samples have shown the blue-green persistent luminescence at 490 nm while the co-doping with Dy3+ shifts the maximum of emission to 475 nm. Undoped, 3% Eu-doped and 6% Dy-co-doped SrAl4O7 samples were prepared by the solid state-reaction method and studied by the solid-state 27Al MAS NMR applying the single pulse-acquire and Hahn-echo pulse sequences. It was shown that the Eu2+ with Dy3+ ion doping did not affect the bulk structure as well as the local Al environment in SrAl4O7. This means that large shifts of the emission maximum cannot be caused by changes in the local environment upon the co-doping of SrAl4O7:Eu2+ with Dy3+. However, the spectral features observed in the range between the signals of 4- and 6-coordinated Al (20–40 ppm) indicate that certain phase imperfections are present in all studied samples, and most probably amorphous/glassy domains were formed. Note that such amount of phase impurities was not detected by standard XRD or FTIR methods. This has revealed the 27Al MAS NMR technique to be a very effective tool monitoring the phase perfectness in series of strontium aluminate samples.
Eu2+掺杂的铝酸锶SrAl4O7在490 nm处呈现出蓝绿色的持续发光，而Dy3+共掺杂的SrAl4O7在475 nm处最大发光。采用固相反应法制备了未掺杂、3% eu掺杂和6% dy共掺杂的SrAl4O7样品，并采用单脉冲采集和哈恩回波脉冲序列对固态27Al MAS NMR进行了研究。结果表明，Eu2+与Dy3+离子的掺杂对SrAl4O7的体结构和局部Al环境没有影响。这意味着SrAl4O7:Eu2+与Dy3+共掺杂时，局部环境的变化不会引起发射最大值的大位移。然而，在4-和6-配位铝(20-40 ppm)信号范围内观察到的光谱特征表明，在所研究的样品中都存在一定的相缺陷，并且很可能形成了非晶/玻璃畴。值得注意的是，这样的相杂质量是无法通过标准的XRD或FTIR方法检测到的。这表明27Al MAS NMR技术是一种非常有效的监测一系列铝酸锶样品相完整性的工具。
{"title":"27Al MAS NMR spectroscopy study of Eu2+-doped and Dy3+-co-doped SrAl4O7","authors":"M. Misevicius, L. Dagys, A. Marsalka, Kristina Kristinaityte, V. Balevičius","doi":"10.3952/physics.v60i2.4224","DOIUrl":"https://doi.org/10.3952/physics.v60i2.4224","url":null,"abstract":"The Eu2+-doped strontium aluminate SrAl4O7 samples have shown the blue-green persistent luminescence at 490 nm while the co-doping with Dy3+ shifts the maximum of emission to 475 nm. Undoped, 3% Eu-doped and 6% Dy-co-doped SrAl4O7 samples were prepared by the solid state-reaction method and studied by the solid-state 27Al MAS NMR applying the single pulse-acquire and Hahn-echo pulse sequences. It was shown that the Eu2+ with Dy3+ ion doping did not affect the bulk structure as well as the local Al environment in SrAl4O7. This means that large shifts of the emission maximum cannot be caused by changes in the local environment upon the co-doping of SrAl4O7:Eu2+ with Dy3+. However, the spectral features observed in the range between the signals of 4- and 6-coordinated Al (20–40 ppm) indicate that certain phase imperfections are present in all studied samples, and most probably amorphous/glassy domains were formed. Note that such amount of phase impurities was not detected by standard XRD or FTIR methods. This has revealed the 27Al MAS NMR technique to be a very effective tool monitoring the phase perfectness in series of strontium aluminate samples.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44499735","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 : 2020-04-28DOI: 10.3952/physics.v60i2.4228
Olga Chabarova, R. Kačianauskas, V. Alekna
Insufficient exploration of the dependence between diseases of degenerative bones and the range of motion (ROM) during torsion, flexion and lateral bending limits further understanding about the lumbar biomechanics and treating of the lumbar related dysfunction. The objective of this study was to determine the effect of vertebral degradation on the instability of spine 2 motion L2–L4 segments during torsion, flexion and lateral bending by the finite element method (FEM). Three different 3D FE models comprising the healthy state and the degradation of trabecular bone and cortical bone were developed. Nonlinear numerical analyses of lumbar spine stability discovered that osteoporotic degradation can lead to critical segmental ROM and intervertebral shearing values, which results in the loss of spine stability for the case of flexion loading. Instability is caused by microscopic changes in the thickness of cortical shell. This analysis of the intervertebral shearing and ROM may be further used to diagnose such translation abnormalities like hypomobility or hypermobility.
{"title":"Effect of vertebral degeneration on the instability of spine","authors":"Olga Chabarova, R. Kačianauskas, V. Alekna","doi":"10.3952/physics.v60i2.4228","DOIUrl":"https://doi.org/10.3952/physics.v60i2.4228","url":null,"abstract":"Insufficient exploration of the dependence between diseases of degenerative bones and the range of motion (ROM) during torsion, flexion and lateral bending limits further understanding about the lumbar biomechanics and treating of the lumbar related dysfunction. The objective of this study was to determine the effect of vertebral degradation on the instability of spine 2 motion L2–L4 segments during torsion, flexion and lateral bending by the finite element method (FEM). Three different 3D FE models comprising the healthy state and the degradation of trabecular bone and cortical bone were developed. Nonlinear numerical analyses of lumbar spine stability discovered that osteoporotic degradation can lead to critical segmental ROM and intervertebral shearing values, which results in the loss of spine stability for the case of flexion loading. Instability is caused by microscopic changes in the thickness of cortical shell. This analysis of the intervertebral shearing and ROM may be further used to diagnose such translation abnormalities like hypomobility or hypermobility.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48101010","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 : 2020-04-28DOI: 10.3952/physics.v60i2.4226
M. Karaliūnas, A. Udal, G. Valušis
Parabolic quantum wells (PQWs) are known as a promising candidate for a compact terahertz (THz) source. PQWs have equidistant subbands that can be designed to be separated by few meV to meet the THz frequency range. To enhance the efficiency and power of THz emission from PQWs, a new approach is proposed by employing depopulation of the lowest subbands of PQW. In this work, the theoretical analysis of an incoherent THz torch device is presented. The findings suggest that the introduction of narrower band-gap GaAsBi/GaAs rectangular quantum well within the GaAs/AlGaAs PQW can alter subbands arrangement to enable a faster depopulation mechanism exploiting LO phonon scattering. The calculated radiative power spectra show the increase of oscillator strength between the rearranged subbands of PQW due to the added GaAsBi rectangular potential. The increased intersubband radiative transition probability can lead to an efficient compact incoherent THz source – THz torch.
{"title":"Depopulation mechanism for incoherent terahertz source – THz torch – based on GaAsBi/GaAs quantum well in GaAs/AlGaAs parabolic quantum well","authors":"M. Karaliūnas, A. Udal, G. Valušis","doi":"10.3952/physics.v60i2.4226","DOIUrl":"https://doi.org/10.3952/physics.v60i2.4226","url":null,"abstract":"Parabolic quantum wells (PQWs) are known as a promising candidate for a compact terahertz (THz) source. PQWs have equidistant subbands that can be designed to be separated by few meV to meet the THz frequency range. To enhance the efficiency and power of THz emission from PQWs, a new approach is proposed by employing depopulation of the lowest subbands of PQW. In this work, the theoretical analysis of an incoherent THz torch device is presented. The findings suggest that the introduction of narrower band-gap GaAsBi/GaAs rectangular quantum well within the GaAs/AlGaAs PQW can alter subbands arrangement to enable a faster depopulation mechanism exploiting LO phonon scattering. The calculated radiative power spectra show the increase of oscillator strength between the rearranged subbands of PQW due to the added GaAsBi rectangular potential. The increased intersubband radiative transition probability can lead to an efficient compact incoherent THz source – THz torch.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49455846","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 : 2020-04-28DOI: 10.3952/physics.v60i2.4227
I. Zamaraite, A. Dziaugys, Y. Vysochanskii, J. Banys
In this paper we report a dielectric study on four single crystals Pb2P2S6, (Pb0.98Ge0.02)2P2S6, (Pb0.7Sn0.3)2P2S6 + 5% Ge and (Pb0.7Sn0.3)2P2Se6 + 5% Ge down to 20 K. A new quantum paraelectric state was reported in the Ge-doped samples at low temperatures. In all of these materials the non-classical T2 temperature dependences of inverse dielectric permittivity were observed. The dielectric constants of Pb2P2S6-based single crystals were measured between 20 and 300 K. The temperature dependences of dielectric permittivity were analysed on the basis of Barrett’s model as a signature of quantum paraelectricity.
{"title":"Quantum paraelectricity and induced ferroelectricity by germanium doping of (PbySn1–y)2P2S(Se)6 single crystals","authors":"I. Zamaraite, A. Dziaugys, Y. Vysochanskii, J. Banys","doi":"10.3952/physics.v60i2.4227","DOIUrl":"https://doi.org/10.3952/physics.v60i2.4227","url":null,"abstract":"In this paper we report a dielectric study on four single crystals Pb2P2S6, (Pb0.98Ge0.02)2P2S6, (Pb0.7Sn0.3)2P2S6 + 5% Ge and (Pb0.7Sn0.3)2P2Se6 + 5% Ge down to 20 K. A new quantum paraelectric state was reported in the Ge-doped samples at low temperatures. In all of these materials the non-classical T2 temperature dependences of inverse dielectric permittivity were observed. The dielectric constants of Pb2P2S6-based single crystals were measured between 20 and 300 K. The temperature dependences of dielectric permittivity were analysed on the basis of Barrett’s model as a signature of quantum paraelectricity.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46715872","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 : 2020-02-05DOI: 10.3952/physics.v60i1.4161
S. Breidokaite, G. Stankūnas, A. Tidikas
Nuclear safety assessment in nuclear fusion devices relies on the Monte Carlo method based neutron transport calculations. This paper presents information about the calculation results of the activities and dose rates caused by neuron irradiation for the structural materials of the high flux test module sample holder of IFMIF-DONES. The neutron induced activities and dose rates at shutdown were calculated by means of the FISPACT-2010 code with data from the EAF-2010 nuclear data library. Neutron fluxes and spectra were obtained with MCNP neutron transport calculations. The activities and dose rates were calculated at the end of irradiation of the assumed device operation scenario for cooling times of 0 s – 1000 year. In addition, radionuclides with contribution of at least 0.5% to the total value of activation characteristics at the previously mentioned cooling times were identified. After the operation, the most active radionuclide is 55Fe, with an activity share ranging from 30% (M200) to 63% (M8), and at the end of the prediction it accounts for 86% of the total activity. The highest dose rates at the end of irradiation are attributed to 56Mn radionuclide. 54Mn and 60Co are the most dominant radionuclides during intermediate and long cool-down periods.
{"title":"Activation of high flux test module sample holder after IFMIF-DONES operation","authors":"S. Breidokaite, G. Stankūnas, A. Tidikas","doi":"10.3952/physics.v60i1.4161","DOIUrl":"https://doi.org/10.3952/physics.v60i1.4161","url":null,"abstract":"Nuclear safety assessment in nuclear fusion devices relies on the Monte Carlo method based neutron transport calculations. This paper presents information about the calculation results of the activities and dose rates caused by neuron irradiation for the structural materials of the high flux test module sample holder of IFMIF-DONES. The neutron induced activities and dose rates at shutdown were calculated by means of the FISPACT-2010 code with data from the EAF-2010 nuclear data library. Neutron fluxes and spectra were obtained with MCNP neutron transport calculations. The activities and dose rates were calculated at the end of irradiation of the assumed device operation scenario for cooling times of 0 s – 1000 year. In addition, radionuclides with contribution of at least 0.5% to the total value of activation characteristics at the previously mentioned cooling times were identified. After the operation, the most active radionuclide is 55Fe, with an activity share ranging from 30% (M200) to 63% (M8), and at the end of the prediction it accounts for 86% of the total activity. The highest dose rates at the end of irradiation are attributed to 56Mn radionuclide. 54Mn and 60Co are the most dominant radionuclides during intermediate and long cool-down periods.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49374045","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 : 2020-02-05DOI: 10.3952/physics.v60i1.4164
M. Kamarauskas, M. Treideris, V. Agafonov, A. Mironas, V. Strazdienė, A. Rėza, A. Šetkus
Here we present a study of the nickel-assisted etching applied to form uniform black silicon layers on crystalline silicon substrates. We related the parameters used for technological process control (etchant, nickel thickness) to parameters of the obtained surface and explain the correlation using the etching model responsible for etching of the silicon covered by a thin nickel film. The increase in the thickness of the metal catalyst did not suppress the etching completely but allowed one to tune the roughness of the silicon surface. The rate of the electrochemical etching was additionally changed by adaptation of the proportion of components in the complex etchant. Depending on the intentionally selected conditions, the duration of the optimized process was from 3 to 10 min. The lowest optical reflection commonly accepted as the black silicon surface was obtained for the mixture with a low amount of the active etchant component. It was demonstrated that the method is acceptable to improve the characteristics of a photovoltaic cell.
{"title":"Black silicon quality control by conditions of nickel-assisted etching of crystalline silicon surfaces in photovoltaic devices","authors":"M. Kamarauskas, M. Treideris, V. Agafonov, A. Mironas, V. Strazdienė, A. Rėza, A. Šetkus","doi":"10.3952/physics.v60i1.4164","DOIUrl":"https://doi.org/10.3952/physics.v60i1.4164","url":null,"abstract":"Here we present a study of the nickel-assisted etching applied to form uniform black silicon layers on crystalline silicon substrates. We related the parameters used for technological process control (etchant, nickel thickness) to parameters of the obtained surface and explain the correlation using the etching model responsible for etching of the silicon covered by a thin nickel film. The increase in the thickness of the metal catalyst did not suppress the etching completely but allowed one to tune the roughness of the silicon surface. The rate of the electrochemical etching was additionally changed by adaptation of the proportion of components in the complex etchant. Depending on the intentionally selected conditions, the duration of the optimized process was from 3 to 10 min. The lowest optical reflection commonly accepted as the black silicon surface was obtained for the mixture with a low amount of the active etchant component. It was demonstrated that the method is acceptable to improve the characteristics of a photovoltaic cell.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2020-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47848466","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 : 2020-02-05DOI: 10.3952/physics.v60i1.4162
A. Srivastava, S. Saxena
We have reported here the detailed investigation of the effect of methyl group substitution on the meta-position of the 2-hydroxypyridine molecule. Resonance enhanced multiphoton ionization (REMPI), FT-IR and Raman spectroscopic techniques have been used for the experimental study of the molecules. Ab initio calculations were used for theoretical investigations of the molecules. The origin band of the molecules 3-methyl-2-hydroxypyridine (3M2HP) and 5-methyl-2-hydroxypyridine (5M2HP) was observed at 33830 and 34105 cm–1 in their REMPI spectroscopy, and the bands assigned as a ππ* transition state. The vibronic coupling of nπ* and ππ* transition states took place in 3M2HP, thus some low intense bands near the origin band of the molecule were observed in the REMPI spectrum. However, there was no such kind of bands in 5M2HP. The π*–σ* hyperconjugation is responsible for the conformational change of the methyl group in 3M2HP upon excitation (S0 → S1).
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