V. B. Jayakrishnan, S. K. Mishra, A. B. Shinde, S. Wajhal, P. S. R. Krishna, P. U. Sastry, S. B. Phapale, Aditya Prasad Roy, Dipanshu Bansal
We have studied the dielectric, structural, and vibrational properties of 0.95NaNbO3–0.05(Na0.50Bi0.50)TiO3 (05NBT) solid solution belonging to the NN–NBT family that possess efficient power functionality and large electro-strain. We found that the magnitude of dielectric permittivity increases with temperature and shows diffuse peak anomalies at various temperatures. Detailed analyses of temperature-dependent neutron diffraction patterns revealed that the sample has the ideal cubic perovskite structure above 650 °C. On cooling, it undergoes a series of structural phase transitions from cubic to orthorhombic phases due to condensation of various lattice instabilities. The amplitude of antiferrodistortive distortion mode analysis showed that the value of primary distortive mode decreases on heating and, finally, diminishes at the phase transition temperatures. The displacement patterns corresponding to various lattice instabilities responsible for this structural phase transition are identified. Raman spectra exhibit noticeable changes in the relative intensities between the peaks as well as broadening, merging, and disappearance of certain peaks on heating. The symmetrical and asymmetrical stretching modes (ν1 and ν2) of BO6 octahedra exhibit opposite behavior with temperature while the bending modes merge into a single broad band. This provides clear evidence of local structural changes in the system.
我们研究了 0.95NaNbO3-0.05(Na0.50Bi0.50)TiO3（05NBT）固溶体的介电、结构和振动特性，该固溶体属于 NN-NBT 家族，具有高效的功率功能和较大的电应变。我们发现介电常数的大小随温度升高而增大，并在不同温度下显示出扩散峰异常。对随温度变化的中子衍射图样的详细分析显示，样品在 650 °C 以上具有理想的立方包晶结构。冷却时，由于各种晶格不稳定性的凝结，它经历了从立方到正方的一系列结构相变。反铁氧体畸变模振幅分析表明，主畸变模值在加热时减小，最后在相变温度时减小。与导致这种结构相变的各种晶格不稳定性相对应的位移模式也被确定下来。拉曼光谱显示了峰值之间相对强度的明显变化，以及加热时某些峰值的增宽、合并和消失。BO6 八面体的对称和不对称拉伸模式（ν1 和 ν2）随着温度的升高表现出相反的行为，而弯曲模式则合并成一个宽带。这清楚地证明了体系中局部结构的变化。
{"title":"Dielectric, structural, and vibrational properties of (Na0.975Bi0.025) (Nb0.95Ti0.05) O3 at elevated temperature","authors":"V. B. Jayakrishnan, S. K. Mishra, A. B. Shinde, S. Wajhal, P. S. R. Krishna, P. U. Sastry, S. B. Phapale, Aditya Prasad Roy, Dipanshu Bansal","doi":"10.1063/5.0207484","DOIUrl":"https://doi.org/10.1063/5.0207484","url":null,"abstract":"We have studied the dielectric, structural, and vibrational properties of 0.95NaNbO3–0.05(Na0.50Bi0.50)TiO3 (05NBT) solid solution belonging to the NN–NBT family that possess efficient power functionality and large electro-strain. We found that the magnitude of dielectric permittivity increases with temperature and shows diffuse peak anomalies at various temperatures. Detailed analyses of temperature-dependent neutron diffraction patterns revealed that the sample has the ideal cubic perovskite structure above 650 °C. On cooling, it undergoes a series of structural phase transitions from cubic to orthorhombic phases due to condensation of various lattice instabilities. The amplitude of antiferrodistortive distortion mode analysis showed that the value of primary distortive mode decreases on heating and, finally, diminishes at the phase transition temperatures. The displacement patterns corresponding to various lattice instabilities responsible for this structural phase transition are identified. Raman spectra exhibit noticeable changes in the relative intensities between the peaks as well as broadening, merging, and disappearance of certain peaks on heating. The symmetrical and asymmetrical stretching modes (ν1 and ν2) of BO6 octahedra exhibit opposite behavior with temperature while the bending modes merge into a single broad band. This provides clear evidence of local structural changes in the system.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"16 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Osbel Almora, Pilar López-Varo, Renán Escalante, John Mohanraj, Lluis F. Marsal, Selina Olthof, Juan A. Anta
Perovskite solar cells (PSCs) continue to be the “front runner” technology among emerging photovoltaic devices in terms of power conversion efficiency and versatility of applications. However, improving stability and understanding their relationship with their ionic–electronic transport mechanisms continue to be challenging. In this work, a case study of NiOx-based inverted PSCs and the effect of different interface passivating treatments on device performance is presented. Impedance spectroscopy (IS) measurements in short-circuit conditions were performed under different illumination intensities, as well as bias-stress operational stability tests under constant illumination intensity. Surface treatments that involved bulky Lewis bases resulted in better and more stable performance. In contrast, acidic anion donors could induce both an initial performance decrease with a characteristic three-arcs impedance Nyquist plot and a subsequent instability during light exposure. Drift–diffusion simulations suggest strong modifications of surface recombination at the interface with the hole transport material, and for the ion concentration and mobilities in the perovskite. Importantly, capacitance and resistance are shown to peak maximum and minimum values, respectively, around mobile ion concentration (Nion) of 1016 and 1017 cm−3. These features relate to the transition from a drift-, for low Nion below a threshold value, to a diffusion-dominated transport in the bulk of the perovskite, for high Nion beyond the threshold value. Our results introduce a general route for characterization of instability paths in PSCs via IS performed under short-circuit conditions.
{"title":"Instability analysis of perovskite solar cells via short-circuit impedance spectroscopy: A case study on NiOx passivation","authors":"Osbel Almora, Pilar López-Varo, Renán Escalante, John Mohanraj, Lluis F. Marsal, Selina Olthof, Juan A. Anta","doi":"10.1063/5.0216983","DOIUrl":"https://doi.org/10.1063/5.0216983","url":null,"abstract":"Perovskite solar cells (PSCs) continue to be the “front runner” technology among emerging photovoltaic devices in terms of power conversion efficiency and versatility of applications. However, improving stability and understanding their relationship with their ionic–electronic transport mechanisms continue to be challenging. In this work, a case study of NiOx-based inverted PSCs and the effect of different interface passivating treatments on device performance is presented. Impedance spectroscopy (IS) measurements in short-circuit conditions were performed under different illumination intensities, as well as bias-stress operational stability tests under constant illumination intensity. Surface treatments that involved bulky Lewis bases resulted in better and more stable performance. In contrast, acidic anion donors could induce both an initial performance decrease with a characteristic three-arcs impedance Nyquist plot and a subsequent instability during light exposure. Drift–diffusion simulations suggest strong modifications of surface recombination at the interface with the hole transport material, and for the ion concentration and mobilities in the perovskite. Importantly, capacitance and resistance are shown to peak maximum and minimum values, respectively, around mobile ion concentration (Nion) of 1016 and 1017 cm−3. These features relate to the transition from a drift-, for low Nion below a threshold value, to a diffusion-dominated transport in the bulk of the perovskite, for high Nion beyond the threshold value. Our results introduce a general route for characterization of instability paths in PSCs via IS performed under short-circuit conditions.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"179 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Lisong Zhang, Peng Zhang, Na Li, Xiaonan Zhang, Xianxiu Mei
Recently, high entropy alloy (HEA) has become a research hotspot as a new candidate structural material in nuclear reactors due to its good irradiation resistance in swelling and hardening. Focusing on the temperature effect of irradiation damage, this work investigated the influence of irradiation temperature on dislocation evolution and irradiation hardening of HEAs. CoCrFeMnNi HEA was irradiated by high-energy Fe ions at room temperature and 500 °C. It was found that dense small dislocations were produced in the damage attenuation region (i.e., the tail of the ion range) of HEAs after irradiation at room temperature, whereas the irradiation-induced dislocations could not be observed in the damage attenuation region when the irradiation temperature was increased to 500 °C. For the small-sized dislocations, dissociation may occur more easily than long-range migration in HEAs (such as CoCrFeNi systems) due to the inhibition of defect migration and the decrease in defect binding energy, and this order is reversed in pure metals (such as Ni, W). Therefore, at 500 °C irradiation, small dislocations in the damage attenuation region of CoCrFeMnNi HEAs were dissociated before migrating to deeper regions, thereby resulting in the depth of dislocation distribution smaller than the stopping and range of ions in matter-calculated damage stopping depth, unlike the phenomenon in pure metals where dislocations migrated to regions exceeding the calculated depth. In addition, the dislocation density of CoCrFeMnNi HEAs decreased significantly due to the promotion of dissociation and merging of dislocations by elevated temperatures, and the hardening after 500 °C irradiation was less than that after room temperature irradiation.
{"title":"Dislocation evolution and hardening of CoCrFeMnNi high entropy alloy under Fe ion irradiation at room temperature and 500 °C","authors":"Lisong Zhang, Peng Zhang, Na Li, Xiaonan Zhang, Xianxiu Mei","doi":"10.1063/5.0227228","DOIUrl":"https://doi.org/10.1063/5.0227228","url":null,"abstract":"Recently, high entropy alloy (HEA) has become a research hotspot as a new candidate structural material in nuclear reactors due to its good irradiation resistance in swelling and hardening. Focusing on the temperature effect of irradiation damage, this work investigated the influence of irradiation temperature on dislocation evolution and irradiation hardening of HEAs. CoCrFeMnNi HEA was irradiated by high-energy Fe ions at room temperature and 500 °C. It was found that dense small dislocations were produced in the damage attenuation region (i.e., the tail of the ion range) of HEAs after irradiation at room temperature, whereas the irradiation-induced dislocations could not be observed in the damage attenuation region when the irradiation temperature was increased to 500 °C. For the small-sized dislocations, dissociation may occur more easily than long-range migration in HEAs (such as CoCrFeNi systems) due to the inhibition of defect migration and the decrease in defect binding energy, and this order is reversed in pure metals (such as Ni, W). Therefore, at 500 °C irradiation, small dislocations in the damage attenuation region of CoCrFeMnNi HEAs were dissociated before migrating to deeper regions, thereby resulting in the depth of dislocation distribution smaller than the stopping and range of ions in matter-calculated damage stopping depth, unlike the phenomenon in pure metals where dislocations migrated to regions exceeding the calculated depth. In addition, the dislocation density of CoCrFeMnNi HEAs decreased significantly due to the promotion of dissociation and merging of dislocations by elevated temperatures, and the hardening after 500 °C irradiation was less than that after room temperature irradiation.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"66 2 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
We develop an analytical model for estimating the equilibrium quantities, such as electron temperature and number density, in an electron beam–plasma interaction system. This model provides a convenient way to calculate the effective electron temperature and density by considering the energy balance of the bulk cold electrons. Six energy sources/losses terms relevant to the cold electrons are accounted for, where quasi-linear theory is applied for estimating wave heating at equilibrium. We compare this calculation with the particle-in-cell (PIC) simulation results and find good agreement. Based on these results, we then consider two situations where we can simplify our model. The first is dominated by the balance between electron–electron Coulomb collisions and loss to the anode, which is mostly relevant to the conduction phase of plasma switches. The second is dominated by wave heating balanced by the anode loss, relevant to the electron beam–plasma discharge systems. We then couple our simplified energy balance model with the ion diffusion model and solve both the number density and the electron temperature as functions of the current density, electrode distance, pressure, and applied voltage, where a nice agreement is also obtained when comparing to PIC simulations.
{"title":"Analytical model for estimating the equilibrium plasma quantities in an electron beam–plasma system","authors":"Haomin Sun, Jian Chen, Guangyu Sun, Liang Xu","doi":"10.1063/5.0209651","DOIUrl":"https://doi.org/10.1063/5.0209651","url":null,"abstract":"We develop an analytical model for estimating the equilibrium quantities, such as electron temperature and number density, in an electron beam–plasma interaction system. This model provides a convenient way to calculate the effective electron temperature and density by considering the energy balance of the bulk cold electrons. Six energy sources/losses terms relevant to the cold electrons are accounted for, where quasi-linear theory is applied for estimating wave heating at equilibrium. We compare this calculation with the particle-in-cell (PIC) simulation results and find good agreement. Based on these results, we then consider two situations where we can simplify our model. The first is dominated by the balance between electron–electron Coulomb collisions and loss to the anode, which is mostly relevant to the conduction phase of plasma switches. The second is dominated by wave heating balanced by the anode loss, relevant to the electron beam–plasma discharge systems. We then couple our simplified energy balance model with the ion diffusion model and solve both the number density and the electron temperature as functions of the current density, electrode distance, pressure, and applied voltage, where a nice agreement is also obtained when comparing to PIC simulations.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"46 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Haonan Ju, Tianming Ye, Wenxiang Hu, Hengguang Shen
An ultrasonic nondestructive method for evaluating bonding interface properties using Stoneley waves was proposed. First, a theoretical model was established. In this model, the dispersion relationship of the Stoneley wave at the quartz–steel interface and the transient signals generated by a pulse were analyzed. Significant differences were observed in the dispersion characteristics of Stoneley waves under different weak bonding conditions. Laser ultrasonic experiments were conducted to confirm the theoretical predictions, in which different interfacial strengths were simulated through the bonding–curing times. Based on these results, the inversion method was implemented to reconstruct the interfacial stiffness by using the corresponding dispersion of the Stoneley wave at different quartz–steel bonding interfaces extracted by the spectral analysis method. The results showed a similar tendency to those shown by theoretical predictions. Finally, the reconstructed interfacial stiffnesses were used to calculate the transient waveforms of the interface waves at different bonding–curing times, and the results showed good consistency with the experimental results, thereby verifying the rationality of the inversion results.
{"title":"Ultrasonic characterization of bonding interfaces using Stoneley waves","authors":"Haonan Ju, Tianming Ye, Wenxiang Hu, Hengguang Shen","doi":"10.1063/5.0222221","DOIUrl":"https://doi.org/10.1063/5.0222221","url":null,"abstract":"An ultrasonic nondestructive method for evaluating bonding interface properties using Stoneley waves was proposed. First, a theoretical model was established. In this model, the dispersion relationship of the Stoneley wave at the quartz–steel interface and the transient signals generated by a pulse were analyzed. Significant differences were observed in the dispersion characteristics of Stoneley waves under different weak bonding conditions. Laser ultrasonic experiments were conducted to confirm the theoretical predictions, in which different interfacial strengths were simulated through the bonding–curing times. Based on these results, the inversion method was implemented to reconstruct the interfacial stiffness by using the corresponding dispersion of the Stoneley wave at different quartz–steel bonding interfaces extracted by the spectral analysis method. The results showed a similar tendency to those shown by theoretical predictions. Finally, the reconstructed interfacial stiffnesses were used to calculate the transient waveforms of the interface waves at different bonding–curing times, and the results showed good consistency with the experimental results, thereby verifying the rationality of the inversion results.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"12 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Two-dimensional spintronics has become a hot topic in recent years due to its advantages and potential in manipulating electron spins. In this paper, the electronic structures and magnetic properties of the Janus NbSSe monolayer are calculated using first-principles and Monte Carlo methods. Our study shows that the ground state of the material is a ferromagnetic metal. Under carrier doping, it undergoes a second-order phase transition from metal to half-metal, achieving 100% spin polarization, and enhancing or weakening ferromagnetic coupling. The value of the magnetocrystalline anisotropy energy is 570.96 μeV, and doping with an appropriate concentration of holes can transform the easy magnetization axis from in-plane to out-of-plane. Since the out-of-plane mirror symmetry is broken, we study the charge changes in the layer under the action of an external electric field. Due to the combined action of the external electric field and the built-in electric field, the layer exhibits a unique charge transfer mode. It is predicted that the Curie temperature of the material is about 156 K. When doped with 4.01 × 1013 cm−2 (0.04 holes per atom) concentration holes, the Curie temperature can reach about 350 K, indicating that the Curie temperature of the material can be reasonably controlled by regulating the carrier concentration. The coercive force calculated from the hysteresis loop is 0.01 T, and its hysteresis loss is low, showing its response to the external magnetic field. All of the above results indicate the application potential of this material in spin-electronic devices.
{"title":"Electronic structures and magnetic properties of Janus NbSSe monolayer controlled by carrier doping","authors":"Yan-Ling Wu, Zhao-Yi Zeng, Hua-Yun Geng, Xiang-Rong Chen","doi":"10.1063/5.0231503","DOIUrl":"https://doi.org/10.1063/5.0231503","url":null,"abstract":"Two-dimensional spintronics has become a hot topic in recent years due to its advantages and potential in manipulating electron spins. In this paper, the electronic structures and magnetic properties of the Janus NbSSe monolayer are calculated using first-principles and Monte Carlo methods. Our study shows that the ground state of the material is a ferromagnetic metal. Under carrier doping, it undergoes a second-order phase transition from metal to half-metal, achieving 100% spin polarization, and enhancing or weakening ferromagnetic coupling. The value of the magnetocrystalline anisotropy energy is 570.96 μeV, and doping with an appropriate concentration of holes can transform the easy magnetization axis from in-plane to out-of-plane. Since the out-of-plane mirror symmetry is broken, we study the charge changes in the layer under the action of an external electric field. Due to the combined action of the external electric field and the built-in electric field, the layer exhibits a unique charge transfer mode. It is predicted that the Curie temperature of the material is about 156 K. When doped with 4.01 × 1013 cm−2 (0.04 holes per atom) concentration holes, the Curie temperature can reach about 350 K, indicating that the Curie temperature of the material can be reasonably controlled by regulating the carrier concentration. The coercive force calculated from the hysteresis loop is 0.01 T, and its hysteresis loss is low, showing its response to the external magnetic field. All of the above results indicate the application potential of this material in spin-electronic devices.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"6 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
We investigate the stability of the polar surface of ZnO films grown homoepitaxially on atomically flat ZnO (0001¯) O-face substrates by neodymium yttrium aluminum garnet (Nd:YAG) pulsed laser deposition (PLD). For films grown in the temperature range from 500 to 700 °C, ion scattering spectroscopy showed that the film surface termination was the same as the ZnO substrate. Even for a Mg0.2Zn0.8O/ZnO superlattice, no polarity reversal occurred, indicating that the ZnO (0001¯) O-face is highly stable, despite the film surface sputtering caused by the high kinetic energy of the PLD plume generated by the Nd:YAG laser.
我们研究了通过钕钇铝石榴石（Nd:YAG）脉冲激光沉积（PLD）技术在原子平的氧化锌（0001¯）O 面基底上同序长成的氧化锌薄膜极性表面的稳定性。对于在 500 至 700 °C 温度范围内生长的薄膜，离子散射光谱显示薄膜的表面终止与氧化锌基底相同。即使是 Mg0.2Zn0.8O/ZnO 超晶格，也没有发生极性反转，这表明 ZnO (0001¯) O 面高度稳定，尽管 Nd:YAG 激光产生的高动能脉冲激光沉积羽流会导致薄膜表面溅射。
{"title":"Polarity of homoepitaxial ZnO films grown by Nd:YAG pulsed laser deposition","authors":"Tatsuya Masuda, Toshihiro Sato, Mikk Lippmaa, Takuro Dazai, Norihiko Sekine, Iwao Hosako, Hideomi Koinuma, Ryota Takahashi","doi":"10.1063/5.0223495","DOIUrl":"https://doi.org/10.1063/5.0223495","url":null,"abstract":"We investigate the stability of the polar surface of ZnO films grown homoepitaxially on atomically flat ZnO (0001¯) O-face substrates by neodymium yttrium aluminum garnet (Nd:YAG) pulsed laser deposition (PLD). For films grown in the temperature range from 500 to 700 °C, ion scattering spectroscopy showed that the film surface termination was the same as the ZnO substrate. Even for a Mg0.2Zn0.8O/ZnO superlattice, no polarity reversal occurred, indicating that the ZnO (0001¯) O-face is highly stable, despite the film surface sputtering caused by the high kinetic energy of the PLD plume generated by the Nd:YAG laser.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"64 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
In the present work, we have investigated the structural response of transition metal double perovskite oxide Nd2CoFeO6 under pressure by XRD and Raman spectroscopic measurements. From XRD data, we have observed a pressure-induced structural transition from the orthorhombic phase to the monoclinic phase at about 14.8 GPa. An anomalous increase in compressibility at a much lower pressure (∼1.1 GPa) is seen where no structural transition occurs. At about the same pressure, a sudden drop in the slope of the Raman shift is observed. Further investigation at low temperatures reveals that the B1g Raman mode is strongly affected by magnetic interactions. Additional high-pressure Raman experiments with the application of a magnetic field have indicated that the mentioned anomaly around 1.1 GPa can be explained by a high-spin to low-spin transition of Co3+.
{"title":"Pressure-induced softening in bulk modulus due to magnetoelastic coupling in Nd2CoFeO6 double perovskite","authors":"Bidisha Mukherjee, Mrinmay Sahu, Debabrata Samanta, Bishnupada Ghosh, Boby Joseph, Goutam Dev Mukherjee","doi":"10.1063/5.0216316","DOIUrl":"https://doi.org/10.1063/5.0216316","url":null,"abstract":"In the present work, we have investigated the structural response of transition metal double perovskite oxide Nd2CoFeO6 under pressure by XRD and Raman spectroscopic measurements. From XRD data, we have observed a pressure-induced structural transition from the orthorhombic phase to the monoclinic phase at about 14.8 GPa. An anomalous increase in compressibility at a much lower pressure (∼1.1 GPa) is seen where no structural transition occurs. At about the same pressure, a sudden drop in the slope of the Raman shift is observed. Further investigation at low temperatures reveals that the B1g Raman mode is strongly affected by magnetic interactions. Additional high-pressure Raman experiments with the application of a magnetic field have indicated that the mentioned anomaly around 1.1 GPa can be explained by a high-spin to low-spin transition of Co3+.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"14 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
A Python package to evaluate Wannier, Wannier–Stark, and EZ (both energy and location Z resolved) levels for quantum cascade lasers is presented. We provide the underlying theory in detail with a focus on the orthonormality and periodicity of the generated states.
本文介绍了一个 Python 软件包，用于评估量子级联激光器的 Wannier、Wannier-Stark 和 EZ（能量和位置 Z 解析）电平。我们详细介绍了基础理论，重点是生成状态的正交性和周期性。
{"title":"Orthonormal and periodic levels for quantum cascade laser simulation","authors":"Zakaria Mohamed, D. Ekin Önder, Andreas Wacker","doi":"10.1063/5.0228751","DOIUrl":"https://doi.org/10.1063/5.0228751","url":null,"abstract":"A Python package to evaluate Wannier, Wannier–Stark, and EZ (both energy and location Z resolved) levels for quantum cascade lasers is presented. We provide the underlying theory in detail with a focus on the orthonormality and periodicity of the generated states.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"46 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
Yankun Huo, Wenyuan Liu, Yajiao He, Hongjie Wang, Jun Cheng, Changfeng Ke
In this study, a fluorocarbon chain was grafted on the surface of the alumina insulator through the molecule self-assembly of perfluorododecyl trichlorosilane to enhance the vacuum surface flashover voltage. A hydrocarbon chain with the same molecular structure, devoid of fluorine element, was also grafted through the self-assembly of dodecyl trichlorosilane to enable comparison. The surface state examination of the self-assembled alumina insulators shows that both the molecules are attached to the alumina surface. The arrangement of the molecules on the surface is regular. Surface property tests reveal that the fluorocarbon chain endows the surface of alumina with a lower secondary electron emission yield and a lower gas adsorption volume than the hydrocarbon chain. Correspondingly, the surface flashover voltage of the fluorocarbon chain grafted insulator is higher than that of the hydrocarbon chain. This implies that the surface flashover voltage can be improved through surface fluorination, which converts hydrocarbon bonds to fluorocarbon bonds. The study demonstrates this possibility at the molecule level.
{"title":"Enhancing vacuum surface flashover voltage of alumina insulator by self-assembly of fluorine-containing molecule","authors":"Yankun Huo, Wenyuan Liu, Yajiao He, Hongjie Wang, Jun Cheng, Changfeng Ke","doi":"10.1063/5.0219587","DOIUrl":"https://doi.org/10.1063/5.0219587","url":null,"abstract":"In this study, a fluorocarbon chain was grafted on the surface of the alumina insulator through the molecule self-assembly of perfluorododecyl trichlorosilane to enhance the vacuum surface flashover voltage. A hydrocarbon chain with the same molecular structure, devoid of fluorine element, was also grafted through the self-assembly of dodecyl trichlorosilane to enable comparison. The surface state examination of the self-assembled alumina insulators shows that both the molecules are attached to the alumina surface. The arrangement of the molecules on the surface is regular. Surface property tests reveal that the fluorocarbon chain endows the surface of alumina with a lower secondary electron emission yield and a lower gas adsorption volume than the hydrocarbon chain. Correspondingly, the surface flashover voltage of the fluorocarbon chain grafted insulator is higher than that of the hydrocarbon chain. This implies that the surface flashover voltage can be improved through surface fluorination, which converts hydrocarbon bonds to fluorocarbon bonds. The study demonstrates this possibility at the molecule level.","PeriodicalId":15088,"journal":{"name":"Journal of Applied Physics","volume":"43 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
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