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  • AIP Publishing  (37)
  • 1
    Online Resource
    Online Resource
    Investigation of p-type depletion doping for InGaN/GaN-based light-emitting diodes
    AIP Publishing ; 2017
    In:  Applied Physics Letters Vol. 110, No. 3 ( 2017-01-16)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 110, No. 3 ( 2017-01-16)
    Abstract: Due to the limitation of the hole injection, p-type doping is essential to improve the performance of InGaN/GaN multiple quantum well light-emitting diodes (LEDs). In this work, we propose and show a depletion-region Mg-doping method. Here we systematically analyze the effectiveness of different Mg-doping profiles ranging from the electron blocking layer to the active region. Numerical computations show that the Mg-doping decreases the valence band barrier for holes and thus enhances the hole transportation. The proposed depletion-region Mg-doping approach also increases the barrier height for electrons, which leads to a reduced electron overflow, while increasing the hole concentration in the p-GaN layer. Experimentally measured external quantum efficiency indicates that Mg-doping position is vitally important. The doping in or adjacent to the quantum well degrades the LED performance due to Mg diffusion, increasing the corresponding nonradiative recombination, which is well supported by the measured carrier lifetimes. The experimental results are well numerically reproduced by modifying the nonradiative recombination lifetimes, which further validate the effectiveness of our approach.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.4973743
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 2
    Online Resource
    Online Resource
    Pulsating modes of a Taylor cone under an unsteady electric field
    AIP Publishing ; 2022
    In:  Physics of Fluids Vol. 34, No. 1 ( 2022-01-01)
    Details
    In: Physics of Fluids, AIP Publishing, Vol. 34, No. 1 ( 2022-01-01)
    Abstract: Micro-thrusters based on the mechanism of electro-atomization are widely used in space engines and play an important role in spacecraft power supply and attitude adjustment. However, current research on the dynamic characteristics of electro-atomization is focused on a steady electric field, and the effect of an alternating electric field is helpful in order to realize the attitude adjustment of the micro-thruster pulse working mode and the self-neutralization of a plume by alternating polarity. For this reason, this work focuses on experimental investigation; the oscillation behavior of a Taylor cone under an alternating electric field excitation has also been systematically examined. Using a high-speed camera, the pulsating modes of a Taylor cone under the disturbance of a continuous sinusoidal waveform and a single pulse waveform were recorded, and the responses of different oscillation modes and geometric characteristics to different disturbance parameters analyzed and discussed. This research has shown that the oscillation of a Taylor cone under a continuous sinusoidal waveform disturbance can be divided into six different modes; the dynamic characteristics of each mode are discussed, and each mode has been assigned its own unique matching relationship for different disturbance parameters. The three-dimensional distribution phase diagrams of the six modes were drawn after the relevant parameters were made dimensionless. Under the disturbance of a single pulse waveform, the geometric oscillation of the Taylor cone displayed a specific law: the oscillation period of the diameter and cone angle was consistent and showed a strong correlation with the charge relaxation time of the liquid.
    Type of Medium: Online Resource
    ISSN: 1070-6631 , 1089-7666
    URL: Article
    DOI: 10.1063/5.0075250
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 1472743-2
    detail.hit.zdb_id: 241528-8
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  • 3
    Online Resource
    Online Resource
    Ferroelectric, elastic, piezoelectric, and dielectric properties of Ba(Ti0.7Zr0.3)O3- x (Ba0.82Ca0.18)TiO3 Pb-free ceramics
    AIP Publishing ; 2017
    In:  Journal of Applied Physics Vol. 122, No. 4 ( 2017-07-28)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 122, No. 4 ( 2017-07-28)
    Abstract: We designed and synthesized a pseudo-binary Pb-free system, Ba(Ti0.7Zr0.3)O3-x(Ba0.82Ca0.18)TiO3, by combining a rhombohedral end (with only cubic to rhombohedral ferroelectric phase transition) and a tetragonal end (with only cubic to tetragonal ferroelectric phase transition). The established composition-temperature phase diagram is characterized by a tricritical point type morphotropic phase boundary (MPB), and the MPB composition has better ferroelectric, piezoelectric, and dielectric properties than the compositions deviating from MPB. Moreover, a full set of material constants (including elastic stiffness constants, elastic compliance constants, piezoelectric constants, dielectric constants, and electromechanical coupling factors) of the MPB composition are determined using a resonance method. The good piezoelectric performance of the MPB composition can be ascribed to the high dielectric constants, elastic softening, and large electromechanical coupling factor.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.4996353
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 4
    Online Resource
    Online Resource
    Novel Bi2MoO6 Nanosheets/Vertical TiO2 Nanorods Arrays Heterojunction with Enhanced Photoelectrochemical Performance under Visible Light Irradiation
    AIP Publishing ; 2017
    In:  Chinese Journal of Chemical Physics Vol. 30, No. 5 ( 2017-10-27), p. 576-580
    Details
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 30, No. 5 ( 2017-10-27), p. 576-580
    Abstract: Novel Bi2MoO6/TiO2 heterojunction was fabricated by growing Bi2MoO6 nanosheets arrays on the vertically aligned TiO2 nanorods arrays via a two-step solvothermal method. The obtained Bi2MoO6/TiO2 hierarchical heterojunction showed excellent visible light photoelectrochemical performance. Compared with the pure TiO2 and Bi2MoO6, the photocurrent density of the heterojunction was increased 57 and 29 times, respectively. Furthermore, the hydrogen generation rate of the Bi2MoO6/TiO2 for photoelectrocatalytic water-splitting was about 6 times higher than that of the pure Bi2MoO6. The improved performance can be attributed to the synergistic effects of enhanced absorption of visible light, increase of migration rate and separation efficiency of photo-induced carriers.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    URL: Article
    DOI: 10.1063/1674-0068/30/cjcp1705095
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 2381472-X
    SSG: 6,25
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  • 5
    Online Resource
    Online Resource
    Cavity-induced coherence phenomena in a Josephson parametric amplifier
    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: By adjusting the frequency of the cavity, we perform a microwave reflection measurement and directly probe the coherence and interference effects in a phase-sensitive Josephson parametric amplifier. We demonstrate the shift in the peak and the dip in the reflection spectra of the amplifier, which operates in the phase-sensitive mode. The behavior of the shift can be precisely controlled by tuning the pump power, the frequency of the cavity, and the relative phase between the incident signal and pump field. Theoretical simulations are in good agreement with the experimental results. These results provide an alternative way of controlling the parametric process by adjusting the frequency of the cavity.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    URL: Article
    DOI: 10.1063/1.5128724
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 2583909-3
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  • 6
    Online Resource
    Online Resource
    A practical method to avoid bond crossing in two-dimensional dissipative particle dynamics simulations
    AIP Publishing ; 2008
    In:  The Journal of Chemical Physics Vol. 129, No. 2 ( 2008-07-14)
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 129, No. 2 ( 2008-07-14)
    Abstract: Dissipative particle dynamics (DPD) simulation technique is an effective method targeted on mesoscopic simulations in which the interactions between particles are soft. As a result, it inevitably causes bond crossing and interpenetration between particles. Here we develop a practical method based on the two-dimensional DPD model which can extremely reduce the possibility of bond crossing. A rigid core is added to each particle by modifying the form of the conservative force in DPD so that the particles cannot penetrate each other. Then by adjusting the spring constant of the bond, we can impose a simple geometry constraint so that the bond crossing can hardly take place. Furthermore, we take into account an analytic geometry constraint in the polymerization model of DPD by which we can successfully avoid the severe bond crossing problem during bond generation in two dimensions. A parabola fitting between the pressure and the particle number density shows that our modified DPD model with small rigid cores can still be mapped onto the Flory–Huggins model, and the mesoscopic length scale of our simulations does not change. By analyzing the mean-square displacement of the innermost monomer and the center of mass of the chains, we find a t8/15 power law of the polymer dynamics in our model instead of the Rouse prediction supporting the recent results in literature.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.2953694
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2008
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 7
    Online Resource
    Online Resource
    Two-dimensional monitoring of a laser–solid x-ray source spot via penumbral coded aperture imaging technique
    AIP Publishing ; 2022
    In:  Review of Scientific Instruments Vol. 93, No. 4 ( 2022-04-01)
    Details
    In: Review of Scientific Instruments, AIP Publishing, Vol. 93, No. 4 ( 2022-04-01)
    Abstract: The uncertainties of spot size and position need to be clarified for x-ray sources as they can affect the detecting precision of the x-ray probe beam in applications such as radiography. In particular, for laser-driven x-ray sources, they would be more significant as they influence the inevitable fluctuation of the driving laser pulses. Here, we have employed the penumberal coded aperture imaging technique to diagnose the two-dimensional spatial distribution of an x-ray emission source spot generated from a Cu solid target irradiated by an intense laser pulse. Taking advantage of the high detection efficiency and high spatial resolution of this technique, the x-ray source spot is characterized with a relative error of ∼5% in the full width at half maximum of the intensity profile in a single-shot mode for general laser parameters, which makes it possible to reveal the information of the unfixed spot size and position precisely. Our results show the necessity and feasibility of monitoring the spot of these novel laser-driven x-ray sources via the penumbral coded aperture imaging technique.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    URL: Article
    DOI: 10.1063/5.0082555
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 8
    Online Resource
    Online Resource
    History dependence of avalanche dynamics of ferroelectric phase transition in BaTiO3 under external bias field
    AIP Publishing ; 2023
    In:  Applied Physics Letters Vol. 122, No. 2 ( 2023-01-09)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 122, No. 2 ( 2023-01-09)
    Abstract: A ferroelectric phase transition under an external bias electric field after field cooling and zero field cooling in barium titanate single crystals shows scale invariant nucleation and growth of complex domain structures. The avalanche energy exponents vary with the external bias, depending on the cooling history of the sample under applied field or zero field cooling. After field cooling, resulting in a single domain sample, the energy exponent is near the integrated mean field value of 5/3, namely, 1.68 ± 0.022. The sample after field cooling shows the same exponent with an external bias electric field range of up to 4.5 kV/cm. The exponent of a multi-domain sample, after zero field cooling, decreases from ε = 1.85 to the fixed point of 1.66 under high fields. The different behavior is attributed to the greater complexity of domain patterns in the multi-domain sample, which reduces to a single domain state under strong applied fields. Compared with the single-domain state, the multi-domain state has more domain boundaries and the intersections formed by these domain boundaries. These domain boundaries and their intersections will hinder the movement of the phase boundary and act as a pinning effect on the front of the phase interface. The effect is to generate more small energy signals, making the critical exponent high. At the same time, the aftershock time distribution (Omori law) remains the same for all switching conditions with an Omori exponent near −1 and switching time correlations of −1 ± 0.05 for short times ( & lt;1 s) and −2 ± 0.10 for long times ( & gt;1 s).
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0133020
    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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  • 9
    Online Resource
    Online Resource
    Anisotropic avalanche dynamics during ferroelectric switching in BaTiO3 and 0.7Pb(Mg2/3Nb1/3)O3–0.3PbTiO3
    AIP Publishing ; 2020
    In:  Applied Physics Letters Vol. 117, No. 17 ( 2020-10-26)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 117, No. 17 ( 2020-10-26)
    Abstract: A ferroelectric hysteresis depends on the orientation of the applied field with respect to the spontaneous polarization. The ferroelectric switching occurs through correlated domain movements forming avalanches. We tested whether avalanches in single crystals of the prototypic ferroelectric BaTiO3 and the relaxor ferroelectric 0.7Pb(Mg2/3Nb1/3)O3–0.3PbTiO3 show anisotropic field dependences. The anisotropy of the energy exponent of avalanches is very small in BaTiO3 with exponents between 1.53 and 1.6, which is remarkably close to the prediction of mean field theory 5/3. The anisotropy is much stronger in 0.7Pb(Mg2/3Nb1/3)O3–0.3PbTiO3 with one exponent slightly above the typical range of mean field values (4/3–5/3): 1.43 ± 0.02, 1.64 ± 0.03, and 1.79 ± 0.03 for fields along [100], [110] , and [111], respectively. This anisotropy indicates a variation of the fractal dimensions of the transient domain patterns depending on the direction of the switching field.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0027752
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 10
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    Online Resource
    Surface forward and backward discharges and corresponding residual charge accumulation characteristics under positive impulse
    AIP Publishing ; 2022
    In:  Journal of Applied Physics Vol. 131, No. 3 ( 2022-01-21)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 131, No. 3 ( 2022-01-21)
    Abstract: The backward discharge induced by residual charge has attracted considerable attention, but the complex mechanism requires further investigation. This article analyzes the surface discharge and the residual surface charge accumulation characteristics in atmospheric air under a positive impulse. The photographic figure method, the dust figure method, and the electrostatic probe method are employed, allowing the residual charge distribution to be quantitatively determined. One main forward discharge is observed at the impulse front and several subsequent backward discharges are observed at the impulse tail. The propagation length of the forward streamer is closely related to the voltage at the moment of discharge. A model illustrating the evolution process of surface forward and backward discharges as well as the corresponding residual charge accumulation characteristics is established. The residual surface charge plays a significant role in the development of the streamer discharge. The backward discharge is incurred by the positive charge that is deposited by the previous forward discharge.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/5.0077542
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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