- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2018
- computer statistical experiment
- statistical optimization
- resonant-tunneling diode
- negative voltage current differential resistance
- characteristics
- heterojunction
- quantum well
- resonant tunneling border
- Electronic Science and Technology
- Optoelectronic Information Science and Engineering
- Bauman Moscow State Technical University
- V.N. Karazin Kharkiv National University
-
Surface structures of tellurium on Si(111)–(7?×?7) studied by low-energy electron diffraction and scanning tunneling microscopy
摘要： The Te-covered Si(111) surface has received recent interest as a template for the epitaxy of van der Waals (vdW) materials, e.g. Bi2Te3. Here, we report the formation of a Te buffer layer on Si(111)–(7×7) by low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). While deposition of several monolayer (ML) of Te on the Si(111)–(7×7) surface at room temperature results in an amorphous Te layer, increasing the substrate temperature to 770 K results in a weak (7×7) electron diffraction pattern. Scanning tunneling microscopy of this surface shows remaining corner holes from the Si(111)–(7×7) surface reconstruction and clusters in the faulted and unfaulted halves of the (7×7) unit cells. Increasing the substrate temperature further to 920 K leads to a Te/Si(111)–(2√3×2√3)R30° surface reconstruction. We find that this surface configuration has an atomically flat structure with threefold symmetry.
关键词： scanning tunneling microscopy,surface reconstruction,Si(111),tellurium,low-energy electron diffraction
更新于2025-09-10 09:29:36
-
Operating regimes and contact resistance of side-bonded contacts to thin heavily doped semiconductor nanowires
摘要： In many nano-wire (NW) devices and during NW characterization, the contact is bonded on the surface or the side of the NW. The prior model of such side-bonded contacts assumes partial NW depletion and purely radial tunneling, both restricted to the contacted region. However, the real space-charge extends to the non-contacted NW, aided by the fringing field, and depletes the contacted NW fully for small NW radius, R. In addition, there are non-radial tunneling and generation-recombination near the contact edge. Supported by numerical calculations, the present work shows that when all the effects are included, different regimes of operation manifest in a side-bonded contact, and the space-charge and contact resistance can differ widely from prior predictions. Our calculations span contacts with barrier height, fb0 = 0.4–0.8 V on n-type silicon NWs of R = 7.5–20 nm and doping Nd = 1018–1020 cm?3 and include the effects of dielectric confinement, NW length, surface defects, image force barrier lowering, and heavy doping. We find that a side-bonded contact gets fully depleted at the contact edge for Nd (cid:1) αFD[4εsψ0=qR2], where ψ0 = contact potential and αFD = 0.73 (0.88) for air (SiO2) ambient. Furthermore, the behavior of a side-bonded contact approaches that of an end-bonded contact for Nd (cid:1) αEB[4εsψ0=qR2], where αEB = 0.16 (0.30), while surface space-charge widths in the two contacts match over a much wider Nd range for SiO2 ambient. We express the radial depletion width in the NW as an explicit function of the contact potential based on an available implicit relation.
关键词： side-bonded contact,contact resistance,tunneling,generation-recombination,space-charge,nano-wire
更新于2025-09-10 09:29:36
-
Orbital Control of Long Range Transport in Conjugated and Metal-Centered Molecular Electronic Junctions
摘要： Large area molecular junctions consisting of covalently bonded molecular layers between conducting carbon electrodes were compared for Co and Ru complexes as well as nitroazobenzene and anthraquinone, in order to investigate the effect of molecular structure and orbital energies on electronic behavior. A wide range of molecular layer thickness (d) from 1.5-28 nm was examined, and revealed three distinct transport regimes in attenuation plots of current density (J) vs thickness. For d < 5 nm, the four molecular structures had comparable current densities and thickness dependence despite significant differences in orbital energies, consistent with coherent tunneling and strong electronic coupling between the molecules and contacts. For d > 12 nm, transport depends on electric field rather than bias, with the slope of ln J vs d near zero when plotted at constant electric field. At low temperature (T < 150 K), transport is nearly activationless and likely occurs by sequential tunneling and/or field induced ionization. For d =5-10 nm, transport correlates with the energy gap between the highest occupied and lowest unoccupied molecular orbitals, and ln J is linear with the square root of the bias or electric field. Such linearity occurs for all three transport regimes, and is consistent with energy barrier lowering by the applied electric field. The results clearly indicate a strong dependence of charge transport on molecular orbital energies provided d> 5 nm, with a variation of seven orders of magnitude of J for different molecules and d=10 nm. The results provide insights into charge transport mechanisms as well as a basis for rational design of molecular electronic devices.
关键词： molecular electronics,molecular junction,charge transport,multistep tunneling
更新于2025-09-10 09:29:36
-
First Experimental Demonstration and Mechanism of Abnormal Palladium Diffusion Induced by Excess Interstitial Ge
摘要： This letter represents the ?rst direct experimental demonstrations and mechanism proposal regarding abnormal palladium diffusion into germanium (Ge). Our experiments indicated that excess Ge atoms among palladium germanide alloy formation indirectly induce the abnormal out-diffusion of mass palladium atoms into Ge. Consequently, palladium germanide alloy on both n-type and p-type Ge form ohmic-like Schottky junctions. To identify this phenomenon, ?rst-principle calculations and technology computer-aided design simulation were used to evaluate the electrical in?uence of palladium atoms in Ge. We discovered that the activated palladium atoms in Ge induce large midgap bulk-trap states, which contribute to a severe increment of trap-assisted tunneling current at the palladium germanide/Ge junction.
关键词： Schottky junction,First-principles calculations,palladium germanide,technology computer-aided design,germanium,trap-assisted tunneling,fermi-level pinning effect
更新于2025-09-10 09:29:36
-
High-Yield Formation of Graphdiyne Macrocycles Through On-Surface Assembling and Coupling Reaction
摘要： Rationally designed halogenated hydrocarbons are widely used building blocks to fabricate covalent-bonded carbon nanostructures on surface through a reaction pathway involving generation and dissociation of organometallic intermediates and irreversible covalent bond formation. Here we provide a comprehensive picture of the on-surface-assisted homocoupling reaction of 1,3-bis(2-bromoethynyl)benzene on Au(111), aiming for the synthesis of graphdiyne nanostructures. Submolecular resolution scanning tunneling microscopy and noncontact atomic force microscopy observations identify the organometallic intermediates and their self-assemblies formed in the dehalogenation process. The demetallization of the organometallic intermediates at elevated temperatures produces butadiyne moieties that spontaneously formed two different covalent structures, i.e. graphdiyne zigzag chains and macrocycles, whose ratio was found to depend on the initial coverage of organometallic intermediates. At the optimal condition, the stepwise demetallization and cyclization led to a high yield production of graphdiyne macrocycles up to 95 %. Statistical analysis and theoretical calculations suggested that the favored formation of macrocycles was resulted from the complex interplay between thermodynamic and kinetic processes involving the organometallic bonded intermediates and the covalently bonded butadiyne moieties.
关键词： on-surface reaction,graphdiyne macrocycle,organometallic intermediate,scanning tunneling microscopy,noncontact atomic force microscopy,thermodynamic and kinetic control
更新于2025-09-10 09:29:36
-
Large Errors from Assuming Equivalent DC and High-Frequency Electrical Characteristics in Metal–Multiple-Insulator–Metal Diodes
摘要： Metal-insulator-metal (MIM) tunnel diodes are essential for ultra-high speed rectification. We review an erroneous method for distributing DC voltage drops across multiple insulator layers that is used in all the published literature on these devices. It has resulted in large errors between designed and fabricated multi-insulator diodes. For multi-insulator MIM diodes, voltage division is dependent on both tunneling resistances and oxide capacitances. We demonstrate that correct voltage division at DC is determined by the rectification resistance, as opposed to the commonly used capacitive voltage division. We find that DC characteristics of multi-insulator diodes cannot be used to predict high frequency behavior.
关键词： solar energy,infrared,optical rectenna,Metal/insulator/metal (MIM) diode,tunneling diodes
更新于2025-09-10 09:29:36
-
Dislocations behavior in highly mismatched III-Sb growth and their impact on the fabrication of <i>top-down</i> n?+?InAs/p?+?GaSb nanowire tunneling devices
摘要： We study in this work the growth and fabrication of top-down highly doped n + InAs(Si)/p + GaSb(Si) Esaki tunneling diodes on (001) GaAs substrates. A careful investigation on the highly mismatched GaSb/GaAs growth is first conducted by means of Reflection High-Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM), and X-Ray Diffraction (XRD) analyses. These results are expected to pave the way to methods for III-Sb buffer layer’s integration with low threading dislocation (TD) densities. A comparison between AFM, XRD, defect revealing by chemical etching and transmission electron microscopy (TEM) is then presented to calculate the precise TD density and its influence on the device structure. In the last part, we report on first operating sub-30 nm III-V vertical NW tunneling devices on (001) commercial GaAs substrates.
关键词： III-Sb growth,AFM,dislocations,TEM,nanowire tunneling devices,XRD,RHEED,GaAs substrates
更新于2025-09-10 09:29:36
-
Competitive metal-coordination of hexaaminotriphenylene on Cu(111) by intrinsic copper versus extrinsic nickel adatoms
摘要： The interplay between self-assembly and surface chemistry of 2,3,6,7,10,11-hexaaminotriphenylene (HATP) on Cu(111) was complementarily studied by high-resolution Scanning-Tunneling-Microscopy (STM) and X-ray Photoelectron Spectroscopy (XPS) under ultra-high vacuum conditions. To shed light on competitive metal-coordination, comparative experiments were carried out on pristine and nickel-covered Cu(111). Directly after room temperature deposition of HATP onto pristine Cu(111) self-assembled aggregates were observed by STM, while XPS indicated non-deprotonated amino groups. Annealing up to 200 °C activated the progressive single deprotonation of all amino groups as indicated by chemical shifts of both N 1s and C 1s core levels in the XP spectra. This enabled the formation of topologically diverse π-d conjugated coordination networks with intrinsic copper adatoms. The basic motif of these networks was a metal-organic trimer, where three HATP molecules were coordinated by Cu3 clusters, as corroborated by accompanying Density Functional Theory (DFT) simulations. Additional deposition of more reactive nickel atoms resulted in both chemical and structural changes with deprotonation and formation of bis(diimino)-Ni bonded networks already at room temperature. Even though fused hexagonal metal-coordinated pores were observed, extended honeycomb networks remained elusive, as tentatively explained by a restricted reversibility of these metal-organic bonds.
关键词： Scanning Tunneling Microscopy,Cu(111),metal-coordination,hexaaminotriphenylene,X-ray Photoelectron Spectroscopy
更新于2025-09-10 09:29:36
-
Investigation of GaN-on-GaN vertical <i>p</i> - <i>n</i> diode with regrown <i>p</i> -GaN by metalorganic chemical vapor deposition
摘要： To mimic selective-area doping, p-GaN was regrown on an etched GaN surface on GaN substrates by metalorganic chemical vapor deposition. Vertical GaN-on-GaN p-n diodes were fabricated to investigate the effects of the etch-then-regrowth process on device performance. The crystal quality of the sample after each epitaxial step was characterized by X-ray diffraction, where the etch-then-regrowth process led to a very slight increase in edge dislocations. A regrowth interfacial layer was clearly shown by transmission electron microscopy. Strong electroluminescence was observed with three emission peaks at 2.2 eV, 2.8 eV, and 3.0 eV. The forward current density increased slightly with increasing temperature, while the reverse current density was almost temperature independent indicating tunneling as the reverse transport mechanism. This result is very similar to the reported Zener tunnel diode comprising a high doping pro?le at the junction interface. High levels of silicon and oxygen concentrations were observed at the regrowth interface with a distribution width of (cid:2)100 nm. This work provides valuable information on p-GaN regrowth and regrown GaN p-n diodes, which can serve as an important reference for developing selective doping for advanced GaN power electronics for high voltage and high power applications.
关键词： electroluminescence,tunneling,GaN,regrowth,p-n diode,metalorganic chemical vapor deposition
更新于2025-09-10 09:29:36
-
Research Advances in Quantum Dynamics || Dynamic Resonant Tunneling
摘要： The physics of dynamic resonant tunneling is investigated. First, the resonant tunneling effect through an opaque barrier via a delta-function well is illustrated. Then, it is shown that, even in the adiabatic regime, where the dynamics can be governed by an analytic solution, the particle can be activated to higher energies. If the well varies quickly enough that the particle cannot escape from the well during the energetic elevation, the activation can be enhanced, as was anticipated by Azbel. However, and this is the main result of this work, the quasi-bound state of the well can even “reduce” the activation. In fact, because the resonant energy of the well matches twice the incoming particle’s energy, and if the contribution to the wave function from both parts destructively interferes, then the particle cannot dwell in the well and activation is suppressed. This effect can be utilized in frequency-controlled transistors, and it is even speculated that it may explain the reason that humans can distinguish between tens of thousands of different odors with merely few hundreds of odor receptors. Lastly, the short time dynamics of a very fast perturbative well is also discussed.
关键词： Forbidden activation,Olfactory,Vibrational Tunneling,Dynamic Tunneling,Selected Activation,Resonant Tunneling,Odor detection
更新于2025-09-09 09:28:46