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Spectroscopic ellipsometry and morphological characterizations of nanocrystalline Hg1-xMnxO oxide diluted magnetic semiconductor thin films
摘要： The structural, optical spectroscopic ellipsometry and morphological properties of nanocrystalline Hg1-xMnxO (0 ≤ x ≤ 0.2) oxide diluted magnetic semiconductor thin films synthesized by electron beam deposition technique have been investigated by means of X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and atomic force microscopy (AFM) techniques. All the deposited films crystallize in the form of a hexagonal crystal structure. The integration between X-ray and atomic force microscopy data shows a very good agreement for the nanosize nature of the deposited films. For the surface roughness, good matching between the results of SE and AFM measurements was observed. In the spectral range 200–1200 nm, the real part (ε1) and imaginary part (ε2) of the dielectric constant of nanocrystalline Hg1-xMnxO films have been extracted from SE measurements. At fixed energy value, the ε1, consequently the refractive index is found to decrease with increasing Mn2+ dopant. In contrary, the energy gap (Eg) of the deposited films determined from the ε2 is found to increase as the Mn2+ concentration increases. The variation of both the ε1 and Eg as a function of Mn2+ concentration is understood based on Lorentz-Lorenz relation and sp-d exchange interaction, respectively. The results reported here show that Mn-doped HgO nanocrystalline films could be employed in the fabrication of nanoscale optical and magneto-optical devices.
关键词： Atomic force microscope,Vapor deposition,Spectroscopic ellipsometry,Optical properties,Semiconductors,AFM,Optical materials,Nanostructured materials,Thin films,X-ray diffraction
更新于2025-09-19 17:15:36
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Many-body States Description of Single-molecule Electroluminescence Driven by Scanning Tunneling Microscope
摘要： Electron transport and optical properties of a single molecule in contact with conductive materials have attracted considerable attention owing to their scientific importance and potential applications. With recent progresses of experimental techniques, especially by the virtue of scanning tunneling microscope (STM)-induced light emission, where the tunneling current of the STM is used as an atomic-scale source for induction of light emission from a single molecule, it becomes possible to investigate single-molecule properties at sub-nanometer spacial resolution. Despite extensive experimental studies, the microscopic mechanism of electronic excitation of a single molecule in STM-induced light emission is yet to be clarified. Here we present a formulation of single-molecule electroluminescence driven by electron transfer between a molecule and metal electrodes based on a many-body state representation of the molecule. The effects of intra-molecular Coulomb interaction on conductance and luminescence spectra are investigated using the nonequilibrium Hubbard Green's function technique combined with first-principles calculations. We compare simulation results with experimental data and find that the intra-molecular Coulomb interaction is crucial for reproducing recent experiments for a single phthalocyanine molecule. The developed theory provides a unified description of both electron-transport and optical properties of a single molecule in contact with metal electrodes driven out of equilibrium, and thereby it contributes to a microscopic understanding of optoelectronic conversion in single molecules on solid surfaces and in nanometer-scale junctions.
关键词： Single molecule luminescence,exciton formation,nonequilibrium Hubbard Green's function technique,time-dependent density functional theory (TDDFT),scanning tunneling microscope-induced light emission,Vibronic interaction
更新于2025-09-19 17:15:36
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Active control of chiral optical near fields on a single metal nanorod
摘要： Chiral optical fields (typified by circularly polarized light) localized on the nanoscale enhance the chiral light-matter interaction, which may provide novel potential applications. This property enables the development of an ultrasensitive method for characterization of chiral molecules and nanoscale magnetic control realized by an all-optical method to interconnect spintronic nano-optical devices. A local chiral light source with switchable handedness or controllable chirality is indispensable for building such applications for practical use. In the current major method used for local chiral light generation, the handedness of the light is controlled by the handedness of the nanomaterial, which is not convenient when we need to change the handedness of the light. We experimentally achieve here generation and active control of a highly chiral local optical field by using a combination of an achiral gold nanorod and achiral linearly polarized optical field. By tilting the azimuth angle for the incident linear polarization relative to the axis of the nanorod, either left- or right-handed circularly polarized local optical fields can be generated. Our work may give us a chance to pioneer analytical applications of chiral optical fields and novel spintronic nano-optical devices.
关键词： near-field optics,chiral plasmonics,scanning near-field optical microscope,nanomaterial,polarimetry
更新于2025-09-19 17:15:36
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Anisotropic nanoscale and sub-nanoscale friction behaviors between phosphorene and silicon tip
摘要： Understanding the frictional properties of phosphorene is essential for reliable fabrication and sustainable operation of phosphorene-based nanotechnology devices. Although recent studies have revealed that phosphorene exhibits anisotropic frictional characteristics, the detailed mechanisms are not well analyzed, and the influence of some experimental parameters (e.g., spring stiffness, tip load force, and tip size), which are very sensitive to atomic frictional forces, were not considered. This study was carried out to address the above shortcomings. The anisotropic frictional behavior of phosphorene and its detailed mechanism were analyzed using potential energy profiles. Also, the effects of spring stiffness and tip load force on the stick-slip behaviors were investigated. Furthermore, we studied the sub-nanoscale stick-slip behavior during the nanoscale slip motion. The nanoscale and sub-nanoscale stick-slip phenomena were originated from the tip’s behavior of passing over the bond between the phosphorus atoms and over the puckered honeycomb structure along the zigzag and armchair directions. We utilized a simple one-dimensional model to explain the energy profiles. The influence of tip size on the stick-slip behavior was also examined and found related to the initial nanoscale slip velocity. As the tip diameter decreased, a high-frequency sub-nanoscale stick-slip phenomenon and shorter nanoscale slip duration were identified.
关键词： nano/sub-nanoscale friction,phosphorene,stick-slip,molecular dynamics,friction force microscope
更新于2025-09-19 17:15:36
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Imaging Carrier Inhomogeneities in Ambipolar Tellurene Field Effect Transistors
摘要： Developing van der Waals (vdW) homojunction devices requires materials with narrow bandgaps and simultaneously high hole and electron mobilities for bipolar transport, as well as methods to image and study spatial variations in carrier type and associated conductivity with nanometer spatial resolution. Here we demonstrate the general capability of near-field scanning microwave microscopy (SMM) to image and study the local carrier type and associated conductivity in operando by studying ambipolar field effect transistors (FETs) of the 1D vdW material tellurium in 2D form. To quantitatively understand electronic variations across the device, we produce nanometer resolved maps of the local carrier equivalence backgate voltage. We show that the global device conductivity minimum determined from transport measurements does not arise from uniform carrier neutrality, but rather from the continued coexistence of p-type regions at the device edge and n-type regions in the interior of our micron-scale devices. This work both underscores and addresses the need to image and understand spatial variations in the electronic properties of nanoscale devices.
关键词： 2D Materials,Field-Effect Transistor,Microwave,Near-Field Microscopy,Atomic Force Microscope
更新于2025-09-19 17:15:36
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Design of a laser-based autofocusing microscope for a sample with a transparent boundary layer
摘要： This study proposes a new type of autofocusing microscope. The microscope was combined with a polarized beam-splitting system and an image-processing program to overcome the complex signals generated when focusing on a transparent boundary layer. The polarized beam-splitting system divides a source laser beam into four parallel beams using a birefringent crystal. It also uses an axicon lens to focus individually on different positions of the sample surface when light is incident on the objective lens to observe multiple-spot defocusing information simultaneously. The transparent boundary layer exhibits intricate signals when a sensor detects laser spots. Therefore, an image-processing program is proposed to filter unnecessary signals for calculating the evaluation function and driving the motor, which enables a focused view of the test sample to be attained conveniently. To prove the feasibility of the proposed autofocusing microscope, a frame was developed using a simulation software for observing the initial characteristics of the microscope and for conducting a qualitative analysis. Moreover, the image-processing effect on the sample was tested to determine whether the aim of the study was achieved. The experimental results matched suitably with the simulation results, which indicates that the proposed autofocusing microscope can solve the problem caused by the transparent boundary layer and can achieve a high focusing accuracy within a short focusing time.
关键词： polarized beam-splitting system,birefringent crystal,autofocusing microscope,transparent boundary layer,image-processing program,axicon lens
更新于2025-09-19 17:13:59
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Imaging doubled shot noise in a Josephson scanning tunneling microscope
摘要： We have imaged the current noise with atomic resolution in a Josephson scanning tunneling microscope with a Pb-Pb junction. By measuring the current noise as a function of applied bias, we reveal the change from single-electron tunneling above the superconducting gap energy to double-electron charge transfer below the gap energy when Andreev processes become dominant. Our spatially resolved noise maps show that this doubling occurs homogeneously on the surface, and also on impurity locations, demonstrating that indeed the charge pairing is not influenced by disruptions in the superconductor smaller than the superconducting coherence length.
关键词： Josephson scanning tunneling microscope,Andreev reflections,current noise,atomic resolution,superconducting gap
更新于2025-09-19 17:13:59
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[IEEE 2019 International Conference on Optical MEMS and Nanophotonics (OMN) - Daejeon, Korea (South) (2019.7.28-2019.8.1)] 2019 International Conference on Optical MEMS and Nanophotonics (OMN) - An All-in-One FR4 Scanner Assembled with Optical Filters and a Photodetector for Very Low Cost Multiphoton Microscopes
摘要： In this article, authors present an all-in-one (AIO) scanner with 24 degrees of freedom and a photodetector as well as a photoelectric actuator for very low cost multiphoton microscopy (MPM). The main mirror, optical filters, the scan lens, the tube lens as well as the scanner in a conventional multiphoton microscope are replaced by a single AIO scanner. The AIO scanner plays a critical role on very low cost (VLC) multiphoton microscopy due to its compact size, less optical components and lower cost. The presented AIO scanner is instrumental for a very low cost multiphoton microscope (VLC-MPM) due to its compact size, less optical components and lower cost.
关键词： multiphoton microscope,dichroic mirror,silicon multiplier,optical filter,FR4 scanner
更新于2025-09-19 17:13:59
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A Simple Method to Test Microscope Objectives Using a Laser Pointer
摘要： The objective lens is regarded as the critical component for an optimal image in light microscopy. Not every damage to the lens surface may be easily visible during maintenance when the objective is removed and observed. The internal lens organization produces a magnified image of the outer lens surface. Shining the light of a laser pointer into the lens, and reproducing the image of the light exiting onto a flat surface, produces different images for intact and damaged objective lenses.
关键词： damaged lens,laser pointer,light microscope,maintenance,objective lens
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE Conference on Control Technology and Applications (CCTA) - Hong Kong, China (2019.8.19-2019.8.21)] 2019 IEEE Conference on Control Technology and Applications (CCTA) - Novel Micro Scanning with Integrated Atomic Force Microscope and Confocal Laser Scanning Microscope
摘要： Integrated atomic force microscope (AFM) and confocal laser scanning microscope (CLSM) can quickly obtain the three-dimensional (3-D) surface of the sample in large scanning range and recover the region of interesting (ROI) in nanoscale resolution. However, the traditional cooperative algorithm for integrated microscopes occupies too much scanning time. In this work, we develop a novel cooperative algorithm for the integrated microscopes to reduce scanning time of AFM and achieve higher scanning speed. First, the calibration of the microscopes will be implemented. Next, CLSM starts a large range scan first and then define the region of interesting (ROI) by edge detection. And then, the scan regions of the AFM are arranged based on the ROI and adaptive scanning region method is proposed to reduce the scanning time. Furthermore, variable speed scanning based on the height information obtained from CLSM image is applied to increase the AFM scanning speed. Finally, the scanning images obtained from AFM and CLSM are merged together. A series of experimental results show that proposed cooperative algorithm can save approximately 69.2% of scanning time compared with that obtained by traditional cooperative algorithm.
关键词： Atomic force microscope (AFM),adaptive scanning range,confocal laser scanning microscope (CLSM),regions of interest (ROI),variable speed scanning
更新于2025-09-16 10:30:52