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  • AIP Publishing  (13)
  • 2020-2024  (13)
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  • AIP Publishing  (13)
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  • 2020-2024  (13)
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Subjects(RVK)
  • 1
    Online Resource
    Online Resource
    A two-buncher high-efficiency transit-time oscillator with a low guiding magnetic field
    AIP Publishing ; 2021
    In:  AIP Advances Vol. 11, No. 6 ( 2021-06-01)
    Details
    In: AIP Advances, AIP Publishing, Vol. 11, No. 6 ( 2021-06-01)
    Abstract: The energy consumption of high-power microwave sources has attracted much attention in the research field of high-power microwaves. One way of decreasing the energy consumption is to reduce the guiding magnetic field. In this work, a high-efficiency transit-time oscillator is proposed with a low guiding magnetic field. In order to enhance the modulation depth of electrons and increase the conversion efficiency under a low guiding magnetic field, two bunchers are adopted to modulate the electron beam. 2.5D simulation results show that the proposed device generates microwaves with a power of 3.6 GW and a frequency of 4.31 GHz. The power conversion efficiency is 40% and the modulation depth is 125% when the guiding magnetic field is only 0.5 T. In addition, a 3D simulation verifies the results.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    URL: Article
    DOI: 10.1063/5.0048265
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 2583909-3
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  • 2
    Online Resource
    Online Resource
    Demonstration of infrared nBn photodetectors based on the AlInAsSb digital alloy materials system
    AIP Publishing ; 2021
    In:  Applied Physics Letters Vol. 119, No. 3 ( 2021-07-19)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 119, No. 3 ( 2021-07-19)
    Abstract: We report an nBn photodetector based on the AlInAsSb digital alloy materials system, which has the advantage of a near-zero valence band offset. These photodetectors have achieved 28% external quantum efficiency, dark current densities of 2.6 × 10−3 A/cm2 at 300 K and 1.8 × 10−9 A/cm2 at 100 K with −0.5 V bias, and detectivity of 1.7 × 1010 Jones at room temperature under 2 μm wavelength illumination.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0058462
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 3
    Online Resource
    Online Resource
    Band convergence and phonon engineering to optimize the thermoelectric performance of CaCd2Sb2
    AIP Publishing ; 2022
    In:  Applied Physics Letters Vol. 120, No. 4 ( 2022-01-24)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 120, No. 4 ( 2022-01-24)
    Abstract: Alignment of valence bands has been demonstrated to be effective in promoting the thermoelectric performance of p-type AB2X2 zintl phases. In this work, the degeneracy of the valence bands is manipulated by alloying CaCd2Sb2 with CaMg2Sb2. It is found that the Γ(pxy) band and the Γ(pz) band were effectively converged in CaCd1.5Mg0.5Sb2. By further doping Ag at the Cd site, the carrier concentration can be maintained when the alloying concentration varies. The room-temperature Seebeck coefficient increased from ∼150 μV K−1 in CaCd2Sb2 to ∼190 μV K−1 in CaCd1.5Mg0.5Sb2 when the carrier concentration was maintained at ∼2.5 × 1019 cm−3. In addition, Cd/Mg substitutional point defects with substantial atomic mass difference induced significant phonon scattering; thus, a lattice thermal conductivity as low as ∼0.5 W m−1 K−1 was achieved at 750 K. Eventually, a peak zT value of ∼1.3 was realized in CaCd1.494Ag0.006Mg0.5Sb2.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0076087
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 4
    Online Resource
    Online Resource
    Simulation study of alleviating the communication blackout using high-power microwave irradiating plasma sheaths
    AIP Publishing ; 2022
    In:  Physics of Plasmas Vol. 29, No. 12 ( 2022-12-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 29, No. 12 ( 2022-12-01)
    Abstract: During hypersonic vehicle flight at high speed, plasma sheath on the vehicle surface will attenuate or even interrupt the communication signal, leading to the “communication blackout” problem. The vehicle probably moves a long distance during the communication blackout due to its high speed, which is a serious threat to the safety of the vehicle. This paper proposes a method to solve the communication blackout problem using high-power microwave (HPM) irradiation. The multicomponent compressible model, finite difference time domain algorithm, and multi-fluid model are used to simulate the interaction between HPM and plasma sheath. The results show that after HPM irradiation, the electromagnetic (EM) wave transmissivity of the plasma sheath will change, and the electric field (E-field) amplitude and irradiation time of HPM significantly influence the change of transmissivity. Thereafter, analyses of the changes of the collision and plasma frequencies of the plasma sheath after HPM irradiation showed the transmissivity of the plasma sheath to low-frequency EM waves is improved by optimizing E-field amplitude and irradiation time of HPM. Therefore, HPM irradiation can be performed to enhance the transmissivity of the plasma sheath to the communication signal, thus alleviating the communication blackout problem.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/5.0105947
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 1472746-8
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  • 5
    Online Resource
    Online Resource
    Preliminary experimental research of a Ka-band radial transit time oscillator
    AIP Publishing ; 2020
    In:  Review of Scientific Instruments Vol. 91, No. 10 ( 2020-10-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 91, No. 10 ( 2020-10-01)
    Abstract: Radial transit time oscillator (RTTO) can be relied on to generate effective coherent electromagnetic radiation in the millimeter wave domain. In this paper, the preliminary experimental research on a Ka-band RTTO is reported for the first time. In experiments, the radial electron beam emitted from the knife edge of the disk cathode is guided by the radial magnetic field. The bombardment trace on the nylon target verifies the emission and transportation uniformity of the radial e-beam. When the diode voltage is 410 kV, the beam current is 7.8 kA, and the magnetic field is 0.6 T, the RTTO can output microwaves with the power of 320 MW and the frequency of 31.35 GHz. As the diode voltage increases from 350 kV to 430 kV, the output microwave power will grow accordingly. Taking the ohmic loss into consideration, the experimental results are in agreement with the simulation ones.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/5.0012233
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 6
    Online Resource
    Online Resource
    Realization of independent contacts in barrier-separated InAs/GaSb quantum wells
    AIP Publishing ; 2023
    In:  Applied Physics Letters Vol. 122, No. 12 ( 2023-03-20)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 122, No. 12 ( 2023-03-20)
    Abstract: InAs/GaSb double quantum wells separated by a 100 Å AlSb middle barrier are grown by molecular beam epitaxy. We report a nanofabrication technique that utilizes the surface Fermi level pinning position in InAs [Efs(InAs)] for realizing independent electric contacts to each well. In particular, separate Ohmic contacts to the upper InAs quantum well are achieved by selectively etching down to the InAs, while contacts to the lower GaSb quantum well are obtained by the depletion method. For the latter, the upper InAs quantum well is locally pinched off by top etched trenches capped with a remaining 2–3 nm InAs layer. As a result of a relatively low Efs(InAs), applying a negative bias gate potential will create a conducting hole channel in GaSb and, hence, a separate Ohmic contact to the lower quantum well. This method is demonstrated with experiment and the support of a self-consistent band bending calculation. A number of experiments on separately probing Coulomb and tunnel-coupled InAs/GaSb systems now become accessible.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0133795
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 7
    Online Resource
    Online Resource
    Infrared camouflage based on the crystalline and amorphous GST multilayer films
    AIP Publishing ; 2022
    In:  Applied Physics Letters Vol. 121, No. 25 ( 2022-12-19)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 121, No. 25 ( 2022-12-19)
    Abstract: Infrared camouflage technology has received considerable attention for escaping the tracking by an infrared detector. The phase-changing material Ge2Sb2Te5 (GST) has widely been utilized to design dynamic spectral regulation. Herein, we propose a planar selective emitter based on the GST with different phases to simultaneously realize infrared camouflage and radiative heat dissipation. The fabricated emitter demonstrates a low emissivity of 32.6% inside the atmospheric windows and a high emissivity of 67.8% outside the atmospheric windows due to the formed quasi-optical cavity of the GST and the metal Ni layer in the structure. Moreover, it also has the potential to be used in different conditions by controlling the emission peak position. The facile process technique allows scalable production and large-scale deployment of the proposed emitter.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0134673
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 8
    Online Resource
    Online Resource
    Study on vehicle drag reduction simulation based on Suzen–Huang model
    AIP Publishing ; 2021
    In:  Physics of Plasmas Vol. 28, No. 6 ( 2021-06-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 28, No. 6 ( 2021-06-01)
    Abstract: In the past numerical simulation of plasma and fluid coupling, the usually used Suzen numerical simulation model has the defect that the error increases with the increase in excitation voltage. The static test of the ionic wind is used to modify the parameters of the Suzen simulation model, and it applied the modified Suzen model to the flow control of the automobile external flow field, which shows good consistency with the wind tunnel test results. Results show that the Suzen model modified by the static test results of the ionic wind is suitable for different excitation voltage conditions. The corrected body force and charge density distribution conform to the change trend of plasma discharge, and the error between the maximum ionic wind velocity obtained by simulation and the test result is within 4%; the modified Suzen model is successfully applied to the plasma flow control of automobile aerodynamic drag reduction. The results show that the exciter suppresses the generation of periodic separation vortices in the tail of the model, which makes the vorticity in the wake significantly decrease, thereby reducing the energy dissipation and the aerodynamic drag of the model. Through the research in this paper, the modified Suzen model reduces the simulation error. Plasma flow control technology is applied to the field of automobile aerodynamic drag reduction, which has accumulated important experience methods and data foundation for the engineering application of this technology. It also provides new methods for improving vehicle aerodynamic performance and fuel economy.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/5.0050374
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 1472746-8
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  • 9
    Online Resource
    Online Resource
    Reduced thermal conductivity of epitaxial GaAsSb on InP due to lattice mismatch induced biaxial strain
    AIP Publishing ; 2021
    In:  Journal of Applied Physics Vol. 130, No. 1 ( 2021-07-07)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 130, No. 1 ( 2021-07-07)
    Abstract: High-quality lattice-matched and mismatched strained GaAs1−xSbx (0.37  & lt; x  & lt; 0.57) sub-micrometer epilayers are grown on InP by molecular beam epitaxy. Based on a heat conduction model regarding the heat transfer process between the thin GaAsSb films and thick InP substrates, the corresponding thermal conductivity of GaAsSb epilayers was accurately extracted from the power and temperature micro-Raman measurement. Combined with time-domain thermoreflectance measurements, we found that in comparison to the lattice-matched sample with Sb = 47.7%, a significant reduction in thermal conductivity of the lattice-mismatched sample with Sb = 37.9% and Sb = 56.2% is observed. With the help of diffraction reciprocal space maps and temperature-dependent photoluminescence results, the reduction in thermal conductivity is attributed to lattice-mismatch-induced biaxial tensile and compressive strain that can cause the breakage of the cubic crystal symmetry and provoke more defects.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/5.0049136
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 10
    Online Resource
    Online Resource
    A high power capacity Ka-band radial transit time oscillator with one-gap extraction cavity
    AIP Publishing ; 2020
    In:  AIP Advances Vol. 10, No. 2 ( 2020-02-01)
    Details
    In: AIP Advances, AIP Publishing, Vol. 10, No. 2 ( 2020-02-01)
    Abstract: The radial transit time oscillator (RTTO) is promising to realize high power output of millimeter-waves. Although the radial structure can enhance the power capacity, less cavities and small radial dimension make it difficult to improve the power capacity in RTTOs, especially in the extraction cavity. A one-gap extraction cavity in the Ka-band RTTO is proposed in this paper to improve the power capacity. Without electrons, taking the TM011 cavity as an example, the radial reversal resonant electric field can intersect with radial electrons. By choosing the sizes of the cavity, the synchronization of the electrons and the electric field can be realized to achieve effective energy exchange. In particle-in-cell simulation, the RTTO with the TM011 extraction cavity can output 1.0 GW high power microwaves (HPMs) at 31.2 GHz, and the beam-wave conversion efficiency is 31.6%. The maximum electric field in the TM011 cavity is only 800 kV/cm, which is less than one third that in the TM010 extraction cavities. In addition, the TM012 extraction cavity is employed to improve the efficiency to 35.4%. At the same time, because of the increase in the output power, the maximum radial electric field in the TM012 cavity increases to 850 kV/cm. Therefore, the one-gap extraction cavity can realize multiple energy exchanges to get high beam-wave conversion efficiency and enhance the power capacity in the extraction cavity significantly.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    URL: Article
    DOI: 10.1063/1.5131239
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 2583909-3
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