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  • AIP Publishing  (11)
  • Physics  (11)
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  • Physics  (11)
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  • 1
    Online Resource
    Online Resource
    Zn vacancy induced room-temperature ferromagnetism in Mn-doped ZnO
    AIP Publishing ; 2007
    In:  Applied Physics Letters Vol. 91, No. 6 ( 2007-08-06)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 91, No. 6 ( 2007-08-06)
    Abstract: X-ray absorption fine structure (XAFS) and first-principles calculations were employed to study the structure and ferromagnetism origin of Zn0.97Mn0.03O thin film grown by metal organic chemical vapor deposition. The magnetization measurements indicate that this sample is ferromagnetic at room temperature. The Mn ions are located at the substitutional Zn sites as revealed by the Mn K-edge XAFS spectroscopy. Moreover, the O K-edge XAFS analysis indicated the existence of numerous Zn vacancies. Based on first-principles calculations, the authors propose that the Zn vacancy can induce the room-temperature ferromagnetism in Mn-doped ZnO.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.2769391
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2007
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 2
    Online Resource
    Online Resource
    Microscopic formation mechanism of Si/Tl5Al1/TiN ohmic contact on non-recessed i-InAlN/GaN heterostructures with ultra-low resistance
    AIP Publishing ; 2022
    In:  Applied Physics Letters Vol. 121, No. 21 ( 2022-11-21)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 121, No. 21 ( 2022-11-21)
    Abstract: In this work, we use Si/Tl5Al1/TiN for a source/drain ohmic contact to demonstrate an ultra-low contact resistance of 0.11 Ω mm (ρc = 2.62 × 10−7 Ω cm2) on non-recessed i-InAlN/GaN heterostructures. The Ti5Al1 alloy was used to suppress the out-diffusion of Al and extract N from the InAlN layer, which aided the formation of ohmic contact by improving the tunneling efficiency of electrons, as we have reported in the past work. A thin Si inter-layer combined with the Ti5Al1 alloy is proposed to further reduce contact resistance. A heavy n-type InAlN layer was obtained through doping with Si atoms to improve the tunneling transport of electrons. Furthermore, the TiN inclusions penetrated into the GaN channel because the in-diffused Si promoted the decomposition of GaN at a high annealing temperature and the in-diffused Ti reacted with GaN. These TiN inclusions provided direct contact with two-dimensional electron gas, offering an additional path for the injection of electrons into the channel. The tunneling and spike mechanism worked alternately to lower the contact resistance at different annealing temperatures (dividing at 900 °C), implying that the joint effect of tunneling and the spike mechanism was initially promoted in the formation of ohmic contact. The mechanism of this Si/Ti5Al1/TiN ohmic contact was fully understood through microscopic and thermodynamic analyses. These results shed light on the mechanism for the formation of ohmic contact in a gold-free metal stack for GaN-based HEMTs.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0117205
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 211245-0
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  • 3
    Online Resource
    Online Resource
    Baking and plasma pretreatment of sapphire surfaces as a way to facilitate the epitaxial plasma-enhanced atomic layer deposition of GaN thin films
    AIP Publishing ; 2020
    In:  Applied Physics Letters Vol. 116, No. 21 ( 2020-05-26)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 116, No. 21 ( 2020-05-26)
    Abstract: The growth of high-quality epitaxial gallium nitride (GaN) thin films is achieved by using a baking and plasma pretreatment of the substrate prior to the GaN plasma-enhanced atomic layer deposition (PE-ALD). It is found that such pretreatment makes the GaN films grow coherently on sapphire substrates, following a layer-by-layer growth mechanism. The deposited GaN film shows high crystalline quality, a sharp GaN/sapphire interface, and a flat surface. The possibility of growing high-quality GaN epilayers in this way broadens the range of applications for PE-ALD in GaN-based devices.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0003021
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
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  • 4
    Online Resource
    Online Resource
    Ballistic transport in sub-10 nm monolayer planar GaN transistors for high-performance and low-power applications
    AIP Publishing ; 2021
    In:  Applied Physics Letters Vol. 119, No. 16 ( 2021-10-18)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 119, No. 16 ( 2021-10-18)
    Abstract: With the constant scaling down of transistors, “More Moore” has put forward requirements for channel materials. Two-dimensional materials are considered as potential next-generation channel materials due to their unique physical properties. Herein, we study the ballistic transport characteristics of sub-10 nm monolayer (ML) planar GaN metal–oxide–semiconductor field-effect transistors (MOSFETs) based on density functional theory and the non-equilibrium Green's function method. The calculation results indicate that n-type ML planar GaN MOSFETs with gate lengths not less than 5 nm exhibit excellent subthreshold characteristics, fast switching speeds, and low switching energies, and the corresponding parameters (off-current, on-current, delay time, and power-delay product) can simultaneously meet the requirements of the International Roadmap for Devices and Systems for the 2028 horizon for high-performance and low-power applications. Therefore, ML planar GaN is predicted to be a reliable next-generation channel material to extend Moore's law.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0070904
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2021
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  • 5
    Online Resource
    Online Resource
    Size and kink effects on thermal conductivity in nickel nanowires
    AIP Publishing ; 2023
    In:  Applied Physics Letters Vol. 123, No. 8 ( 2023-08-21)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 123, No. 8 ( 2023-08-21)
    Abstract: The potential applications of nanowires in thermal management and thermoelectric energy conversion have sparked extensive research on thermal transport in various nanowires. Nickel nanowires, with their unique properties and promising applications, have been extensively studied. However, the influence of size, particularly the impact of kink structures, on the thermal transport behavior in nickel nanowires remains unclear. In this paper, we employed electron-beam lithography and liftoff techniques to fabricate suspended nickel nanowires with varying sizes and kinks to experimentally investigate the size and kink effect on the thermal conductivity. The experimental results revealed that the thermal transport behavior of nickel nanowires is significantly influenced by both size and kink effects. Notably, as the nanowire size decreases, the thermal conductivity also decreases. Furthermore, we discovered that the thermal conductivity can be adjusted by altering the number and angle of kinks. Increasing the number of kinks from 18 to 36 resulted in a significant decrease in thermal conductivity. In contrast, as the kink angle decreased from 157° to 90°, the thermal conductivity also decreased. However, intriguingly, when the kink angle was further decreased from 90° to 43°, the thermal conductivity increases. This non-monotonic change in thermal conductivity with the kink angle provides an interesting insight into the intricate behavior of heat carriers in kinked nickel nanowires. Additionally, we found that varying the alloy elements can profoundly alter the thermal conductivity of nanowires with kinks. These results offer valuable insights into the behaviors of heat carriers, including electrons and phonons, during heat transfer in nickel nanowires.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0159583
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
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  • 6
    Online Resource
    Online Resource
    Comparative study on high-voltage safety performance of LiNixMnyCozO2 cathode with different nickel contents
    AIP Publishing ; 2022
    In:  Applied Physics Letters Vol. 121, No. 20 ( 2022-11-14)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 121, No. 20 ( 2022-11-14)
    Abstract: In this article, systematic comparison of the safety performance of LiNixMnyCozO2 is made to find a balance among nickel content, energy density, and thermal stability. Three kinds of LiNixMnyCozO2 cathodes with different nickel contents are charged to different cut-off voltages from 4.2 to 4.6 V (vs Li+/Li) to obtain different energy densities, and their safety is evaluated through differential scanning calorimetry. Different characteristic temperatures are proposed to describe the cathode safety comprehensively and a relationship between energy density and thermal stability is established. It is found that cathode with lower nickel content (LiNi0.5Mn0.3Co0.2O2 and LiNi0.6 Mn0.2Co0.2O2) charging to high voltage exhibits better thermal stability compared to high nickel cathode (LiNi0.8Mn0.1Co0.1O2) at a conventional voltage. Numerical simulation based on a lumped thermal model is also performed to predict the real thermal behaviors of batteries using different cathodes. The discussion of the impact of the cut-off voltage for NMC cathodes provides a new dimension to further improve the comprehensiveness of battery material safety database and a new viewpoint on the trade-off between cathode energy density and safety.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0123625
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
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  • 7
    Online Resource
    Online Resource
    Probing the dipole–dipole interaction in single 0D/2D heterostructures by tightly focused cylindrical vector beams
    AIP Publishing ; 2023
    In:  Applied Physics Letters Vol. 122, No. 10 ( 2023-03-06)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 122, No. 10 ( 2023-03-06)
    Abstract: Energy transfer from zero-dimensional (0D) quantum dots (QDs) to two-dimensional (2D) materials has attracted much attention for both the manipulation of fundamental material properties and their potential device applications. An understanding of the effect of dipole interactions on energy transfer rate in the hybrid dimensional system is essential for improving optoelectronic device performance. Here, we report the dipole-orientation-dependent energy transfer from individual core–shell CdSe/ZnS QDs to bilayer molybdenum disulfide (MoS2) by utilizing tightly focused azimuthally and radially polarized cylindrical vector beams. With second-order photon correlation measurements [g2(τ)], we show the single-photon emission behavior from QDs in 0D/2D heterostructures, indicating that the investigated heterostructure is constructed from single QDs. By polarization resolved photoluminescence (PL) imaging and PL lifetime measurements, we observe a fast energy transfer rate of the system excited with azimuthally polarized beams and interpret it based on dipole–dipole interactions with Förster energy transfer theory. Our work provides an in-depth understanding of the dipole-orientation-dependent energy transfer mechanism in 0D/2D systems, which could offer guidance for designing the related optoelectronic device applications.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0133325
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
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  • 8
    Online Resource
    Online Resource
    Electro-activation to achieve entropy increase of organic cathode for potassium-ion batteries
    AIP Publishing ; 2023
    In:  Applied Physics Letters Vol. 122, No. 26 ( 2023-06-26)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 122, No. 26 ( 2023-06-26)
    Abstract: Developing highly stable cathode materials is the key to achieving long-life K-ion batteries (KIBs). Considering that cathode with higher entropy can promote the ion adsorption process, we developed a method with heat treatment and synergistic electro-activation of 3,4,9,10-perylene-tetracarboxylic dianhydride (EA-PTCDA) to realize entropy increase in PTCDA, which achieves a stable K-ion storage. From our characterization results, the molecular stacking structure of EA-PTCDA and the C–O and C–H bending vibration at the edge position of PTCDA molecules decreased after electro-activation, indicating the achievement of entropy increase in the EA-PTCDA cathode. After treatment, our EA-PTCDA exhibits a high discharge capacity of 92 mA h g−1 after 100 cycles at 20 mA g−1 for KIBs. Even at a high current density of 200 mA g−1, our EA-PTCDA also maintains a discharge specific capacity of 66 mA h g−1 after 1000 cycles, showing shallow capacity decay. We believe that our method of achieving entropy increase in cathode materials based on electro-activation provides a reference for achieving high-performance KIBs.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0156072
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
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  • 9
    Online Resource
    Online Resource
    Modeling the conduction mechanisms of intrinsic multi-level states in HfOx-based resistive random access memory
    AIP Publishing ; 2023
    In:  Applied Physics Letters Vol. 123, No. 4 ( 2023-07-24)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 123, No. 4 ( 2023-07-24)
    Abstract: Multi-level cell storage technology based on resistive random access memory (RRAM) with multi-level state characteristics is more attractive in achieving low-cost ultra-high-density nonvolatile memory. Although a large number of literatures have reported the multi-level state characteristics of RRAM, so far there is no unified model that can well explain the intrinsic reasons for the existence of intermediate resistance state (IRS) and the switching mechanism between different resistance states. Multi-level state characteristics are observed by I–V characteristic measurements on RRAM with TiN/HfOx/barrier layer/TiN stacks fabricated using a commercialized 28 nm CMOS process. Compared to other published resistive switching models, the proposed model based on trap-assisted tunneling is more consistent with the measured. The model can reproduce the multi-level state characteristics based on the mechanism that interaction between defects and oxygen vacancies at the interface of HfOx and TiN electrode, resulting in the formation of multiple weak conductive filaments. Furthermore, the wide spread of high resistance state (HRS) and the switching between HRS and IRS are determined by the distance of tunneling gap. As HfOx-based RRAM will soon be commercialized, it is becoming very urgent to clarify the switching mechanisms of multi-level state characteristics and propose a universal model. Consequently, this work satisfied the current demand and significantly advanced the understanding and development of commercialized, cost-effective, high-density multi-bit HfOx-based RRAM technology.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/5.0160109
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 211245-0
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  • 10
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    Online Resource
    Nanopillars assisted multilayer antireflection coating for photovoltaics with multiple bandgaps
    AIP Publishing ; 2019
    In:  Applied Physics Letters Vol. 115, No. 13 ( 2019-09-23)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 115, No. 13 ( 2019-09-23)
    Abstract: A nanopillar assisted multilayer antireflection (AR) coating that combines the Ta2O5/SiO2 multilayer with SiO2 nanopillars was investigated to improve the light absorption of quadruple-bandgap photovoltaics. After clarifying that the performance of the traditional multilayer AR coating is restricted by the available refractive index of the top layer, periodic SiO2 rhombic nanopillars that work in the subwavelength regime were used to vary its effective index from 1 to 1.46. Then, the effective index and thickness of SiO2 nanopillars were optimized together with the Ta2O5/SiO2 stack using the global optimization algorithm to further reduce the reflection loss. When the SiO2 nanopillars have an effective index of 1.15 and a thickness of 108 nm, the best AR performance was achieved with a reflectance of 3.9% in the target spectral range of 300–1700 nm. Using laser interference lithography and ion assisted deposition technologies, the nanopillar assisted AR coating was realized with a reflectance of 4.5%. Compared to the traditional multilayer AR coating, this hybrid approach can not only achieve better AR performance but also reduce the disparities of the reflection loss among different bandgaps, which helps us to effectively improve the current matching and enhance the overall efficiency of quadruple-bandgap photovoltaics.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.5111363
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2019
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