- 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
-
[Texts and Readings in Physical Sciences] Open Quantum Systems Volume 20 (Dynamics of Nonclassical Evolution) || Quantum Tunneling
摘要： Tunneling is a bona?de quantum mechanical e?ect [175, 176]. Since it involves barrier penetration, it is also an inherently non-perturbative process. It serves a crucial role in the test of quantum coherence in macroscopic regimes, also known as Macroscopic Quantum Coherence (MQC) [68]. Development in technology has made the concept of tunneling crucial to the development of devices on the nanoscopic, nanometre 10?9m range, and mesoscopic, upto a few microns μm, scales. Further, tunneling has important rami?cations to almost all branches of physics, such as atomic, molecular, condensed matter physics as well as to quantum ?eld theory and cosmology. A very powerful technique for dealing with tunneling is the semiclassical approximation, which we detail below. Tunneling processes can be broadly classi?ed into two categories: coherent and incoherent tunneling. Coherent tunneling phenomena involve the coherent overlap of wavefunctions located in individual domains, such as, ground states of potential wells, and separated by energy barriers. Incoherent tunneling involves scattering between reservoirs or decay of metastable states into the continuum and hence no overlap of the wavefunction. Tunneling has two perspectives: time independent energy domain considerations and that invoking the time dependent dynamics.
关键词： Macroscopic Quantum Coherence,Semiclassical Approximation,Quantum Tunneling,Incoherent Tunneling,Coherent Tunneling
更新于2025-09-23 15:21:01
-
Substrate-Controlled Synthesis of 5-Armchair Graphene Nanoribbons
摘要： 5-Armchair graphene nanoribbons (5-AGNRs) have been successfully synthesized through on-surface reaction of 1, 4, 5, 8-tetrabromonaphthalene (TBN) on Ag(111) and characterized by scanning tunneling microscopy. Silver-naphthalene chains are observed as intermediate states toward the formation of 5-AGNRs. Similar reaction of TBN has been conducted on Cu(111), but no 5-AGNRs are obtained. Disordered amorphous products prevail on Cu(111) upon high temperature annealing (600 K), which is tentatively explained by the strong aryl-Cu bonds. Scanning tunneling spectroscopy measurements of 5-AGNRs on Ag(111) reveal three prominent peaks at bias voltages of -0.3, 1.0 and 1.5V, determining that the apparent band gap is 1.3 eV.
关键词： Ag(111),scanning tunneling microscopy,scanning tunneling spectroscopy,5-Armchair graphene nanoribbons,Cu(111),on-surface synthesis
更新于2025-09-23 15:21:01
-
Tailoring Bond Topologies in Open-Shell Graphene Nanostructures
摘要： Polycyclic aromatic hydrocarbons exhibit a rich spectrum of physico-chemical properties depending on the size, and more critically, on the edge and bond topologies. Among them, open-shell systems – molecules hosting unpaired electron densities – represent an important class of materials for organic electronic, spintronic and optoelectronic devices, but remain challenging to synthesize in solution. We report the on-surface synthesis and scanning tunneling microscopy- and spectroscopy-based study of two ultra-low-gap open-shell molecules, namely peri-tetracene, a benzenoid graphene fragment with zigzag edge topology, and dibenzo[a,m]dicyclohepta[bcde,nopq]rubicene, a non-benzenoid non-alternant structural isomer of peri-tetracene with two embedded azulene units. Our results provide an understanding of the ramifications of altered bond topologies at the single-molecule scale, with the prospect of designing functionalities in carbon-based nanostructures via engineering of bond topology.
关键词： open-shell polycyclic aromatic hydrocarbons,atom manipulation,non-alternant polycyclic aromatic hydrocarbons,scanning tunneling microscopy,density functional theory,scanning tunneling spectroscopy
更新于2025-09-23 15:21:01
-
Self-assembled indium nanostructures formation on InSe (0001) surface
摘要： The surfaces of 2D layered crystals are one among most perspective templates for self-assembling of metal nanostructures due to the dewetting. The initial InSe (0001) surface as topological template was characterized by means of scanning tunneling microscopy/spectroscopy (STM/STS) and low electron energy diffraction. InSe (0001) surface used in the process of formation of nanostructures found to be a template covered with array of triangular-shaped cites. The results of STM/STS studies on the formation of indium nanostructures on (0001) surface of InSe layered semiconductor crystal are presented. Indium was thermally deposited on structurally perfect InSe crystal cleavages obtained in situ. Geometrically heterogeneous (in height) initial (0001) InSe surface is used to activate the dewetting phenomenon in a manner that leads to the formation of 0D triangular-shaped nucleus of deposited indium nanostructures. STS acquired spatially averaged I–V curves changes their dependence from semiconductor one to almost metallic due to dewetting process. Moreover, the spatial arrangement of formed indium nanostructures is powered by hexagonal lattice symmetry of InSe surface on macroscale.
关键词： Hetero nanostructures,Nanostructures template-directed assembly,Layered crystals,Scanning tunneling microscopy/spectroscopy,Indium selenide,Low energy electron diffraction
更新于2025-09-23 15:21:01
-
Quantum Chip with the Optimized Tunnel Structure for Measuring a Charge Qubit Based on a Double Quantum Dot
摘要： A circuit of a measuring chip for determining an arbitrary pure state of a charge qubit is proposed. The strength of the current flowing through a single-electron transistor in the steady-state mode depends on the state of the qubit. To enhance the sensitivity of the transistor, its working part is built from three quantum dots (QDs) with the energy levels forming a symmetric configuration. The parameters of the system are calculated using a microscopic model of two-dimensional QDs. The time dependences of the population of the structure’s states are obtained and the current strength, sensitivity, and measuring contrast as functions of the geometric parameters of the system are determined. The effect of dissipative processes related to the acoustic phonons on the measurements is investigated and the rates of electron relaxation and dephasing in a two-level system are calculated.
关键词： quantum dot,charge qubit,acoustic phonons,single-electron transistor,quantum detector,electron tunneling
更新于2025-09-23 15:21:01
-
Development and Study of the pa??ia??n GaAs/AlGaAs Tunnel Diodes for Multijunction Converters of High-Power Laser Radiation
摘要： The creation of connecting tunnel diodes with a peak tunneling-current density higher than the density of the short-circuit current of photoactive p–n junctions is an important task in the development of multijunction photoconverters (III–V) of high-power optical radiation. Basing on numerical simulation of the J–U characteristics of tunnel diodes, a method is proposed for increasing the peak tunneling-current density by including a thin undoped i-type layer with a thickness of several nanometers between degenerate layers of the tunnel diode. The p–i–n-GaAs/Al0.2Ga0.8As structures of the connecting tunnel diodes with a peak tunneling-current density of up to 200 A/cm2 are grown by molecular-beam epitaxy.
关键词： quantum tunneling,molecular-beam epitaxy,tunnel diode,multijunction photoconverter,current–voltage characteristic
更新于2025-09-23 15:21:01
-
Imaging empty states on the Ge(100) surface at 12 K
摘要： Our understanding of bias-dependent scanning-tunneling-microscopy (STM) images is complicated not only by the multiplicity of the surface electronic structure, but also the manifold tunneling effects in probing semiconductor surfaces having directional dangling- and covalent-bond orbitals. Here we present a re?ned interpretation of empty-state STM images from the model semiconductor surface, Ge(100), on the basis of measurements at low temperature (12 K) combined with density-functional-theory calculations. In the lower-bias regime ((cid:2)1.6 V), the electron tunneling is found to occur predominantly in antibonding dangling-bond or/and dimer-bond states (π ? 2 , and σ ?) of Ge(100) at the surface-parallel wave vector k(cid:3) = 0, leading to the tunneling current maxima located directly on the dimer rows. At higher biases (e.g., at 2 V), the current maxima are shifted to the position in the troughs between the dimer rows, because the tunneling occurs ef?ciently in the π ? 2 states at k(cid:3) (cid:4)= 0 associated with the dimer-up atoms of two adjacent dimer rows, i.e., because of increased sideways tunneling. Thus, the empty-state STM images of Ge(100), albeit strongly bias-dependent, re?ect the dimer arrangement rather than the backbonds and surface resonances at all experimental conditions used. The results are also discussed in comparison with the counterpart system of Si(100).
关键词： STM,density-functional-theory,Ge(100),tunneling,semiconductor surfaces
更新于2025-09-23 15:21:01
-
Airline Head-Up Display Systems: Human Factors Considerations
摘要： As the key source of information for pilots, the human visual system has necessarily driven much of the evolution in cockpit technology. In contrast to the complicated, gauge-based systems of the past, the electronic flight displays of today’s modern airliners are testament to advances in human factors engineering. The next step in flight instrumentation, although already used for some 50 years in the military, is just beginning to emerge in civil transport aircraft. Head-up displays (HUDs) allow pilots to see key flight instrumentation while viewing the outside world. The need to look down at the flight instruments is removed by the HUD, resulting in increased situational awareness and greater precision in aircraft control. While the head-up display is a welcome development, as with many instances of human-technology interface, the benefits provided by HUDs are not without potential drawbacks. The present report provides a thorough grounding in key areas of importance to the development and operation of HUD systems, including the human visual system, the history and development of conventional cockpit instrumentation, and a summary of the technical aspects and human factors considerations relating to HUD systems. This basis is built upon with a more practical assessment of the HUD system used in a modern airliner, the Boeing 787.
关键词： aviation,Boeing 787,Attention capture,Head-up display,Airline,Visual attention,Human factors,Cognitive tunneling,HUD
更新于2025-09-23 15:21:01
-
The design and the performance of an ultrahigh vacuum 3He fridge-based scanning tunneling microscope with a double deck sample stage for in-situ tip treatment
摘要： Scanning tunneling microscope (STM) is a powerful tool for studying the structural and electronic properties of materials at the atomic scale. The combination of low temperature and high magnetic field for STM and related spectroscopy techniques allows us to investigate the novel physical properties of materials at these extreme conditions with high energy resolution. Here, we present the construction and the performance of an ultrahigh vacuum 3He fridge-based STM system with a 7 Tesla superconducting magnet. It features a double deck sample stage on the STM head so we can clean the tip by field emission or prepare a spin-polarized tip in situ without removing the sample from the STM. It is also capable of in situ sample and tip exchange and preparation. The energy resolution of scanning tunneling spectroscopy at T = 310 mK is determined to be 400 mK by measuring the superconducting gap with a niobium tip on a gold surface. We demonstrate the performance of this STM system by imaging the bicollinear magnetic order of Fe1+xTe at T = 5 K
关键词： Spin polarized scanning tunneling microscopy,Superconducting gap,Magnetic structure
更新于2025-09-23 15:21:01
-
Epitaxial Growth of Monolayer MoS <sub/>2</sub> on SrTiO <sub/>3</sub> Single Crystal Substrates for Applications in Nanoelectronics
摘要： Monolayer molybdenum disulfide (MoS2) crystals grown on amorphous substrates such as SiO2 are randomly oriented. However, when MoS2 is grown on crystalline substrates, the crystal shapes and orientations are also influenced by their epitaxial interaction with the substrate. In this paper we present the results from chemical vapor deposition growth of MoS2 on three different terminations of single crystal strontium titanate (SrTiO3) substrates. On SrTiO3(111) the monolayer MoS2 crystals form equilateral triangles with two main orientations, in which they align their <21?1?0>-type directions (i.e., the sulfur-terminated edge directions) with the <11?0>-type directions on SrTiO3. This arrangement allows near perfect coincidence epitaxy between seven MoS2 unit cells and four SrTiO3 unit cells. On SrTiO3(110) the MoS2 crystals tend to align their edges with both <11?0> and <11?2?> directions on SrTiO3 as these both provide favorable coincidence lattice registry. This distorts the crystal shapes and introduces an additional strain detectable by photoluminescence. When triangular MoS2 crystals are grown on SrTiO3(001), they again show a preference to align their edges with the <11?0> directions on SrTiO3. Our observations can be explained if the interfacial van der Waals (vdW) bonding between MoS2 monolayers and SrTiO3 is greatest when the maximum commensuration between the lattices is achieved. Therefore, a key finding of this paper is that the vdW interaction between MoS2 and SrTiO3 substrates determines the supported crystal shapes and orientations by the epitaxial relations. Controlled crystal orientations make the growth of large sheets of MoS2 possible when there are multiple nucleation sites. This minimizes the number of grain boundaries and optimizes electronic properties of the material, e.g., charge mobility, which is crucial for the application of monolayer MoS2 in next-generation nanoelectronic devices.
关键词： Raman spectroscopy,van der Waals epitaxy,scanning tunneling microscopy,SrTiO3,2D materials,chemical vapor deposition,MoS2,photoluminescence spectroscopy
更新于2025-09-23 15:21:01