22 research outputs found
Contact holes in vertical electrode structures analyzed by voltage contrast-SEM and conducting AFM
Soaring demands of multi-stacked memory devices request urgent development of
backside contact electrode technologies, such as high aspect ratio etching,
metallization, and inspection methods. Especially the complex metal contact
process should be monitored for each manufacturing step to filter the defective
samples and to maintain the high yield of production. Among the inspection
methods for detecting the electrical connections, there is voltage contrast
(VC)-SEM and conducting AFM (C-AFM). In this report, we investigated the two
inspection methods for testing designed samples with different contact hole
states. The VC-SEM data shows the contrast variation at the contact holes, from
which one may discern the contact status with an optimum voltage. The C-AFM
results clearly demonstrate a finite electrical current in the connected
contact, while a negligible current in the disconnected one. Finally, we
discuss insights of using the two methods for analyzing the contact hole
technologies with high aspect ratios.Comment: 17 pages, 4 figure
Electrical conductivity enhancement of epitaxially grown TiN thin films
Titanium nitride (TiN) presents superior electrical conductivity with
mechanical and chemical stability and compatibility with the semiconductor
fabrication process. Here, we fabricated epitaxial and polycrystalline TiN
(111) thin films on MgO (111), sapphire (001), and mica substrates at 640oC and
room temperature by using a DC sputtering, respectively. The epitaxial films
show less amount of surface oxidation than the polycrystalline ones grown at
room temperature. The epitaxial films show drastically reduced resistivity (~30
micro-ohm-cm), much smaller than the polycrystalline films.
Temperature-dependent resistivity measurements show a nearly monotonic
temperature slope down to low temperature. These results demonstrate that high
temperature growth of TiN thin films leads to significant enhancement of
electrical conductivity, promising for durable and scalable electrode
applications.Comment: 14 pages, 3 figure
Sign-tunable anomalous Hall effect induced by two-dimensional symmetry-protected nodal structures in ferromagnetic perovskite oxide thin films
Magnetism and spin-orbit coupling (SOC) are two quintessential ingredients
underlying novel topological transport phenomena in itinerant ferromagnets.
When spin-polarized bands support nodal points/lines with band degeneracy that
can be lifted by SOC, the nodal structures become a source of Berry curvature;
this leads to a large anomalous Hall effect (AHE). Contrary to
three-dimensional systems that naturally host nodal points/lines,
two-dimensional (2D) systems can possess stable nodal structures only when
proper crystalline symmetry exists. Here we show that 2D spin-polarized band
structures of perovskite oxides generally support symmetry-protected nodal
lines and points that govern both the sign and the magnitude of the AHE. To
demonstrate this, we performed angle-resolved photoemission studies of
ultrathin films of SrRuO, a representative metallic ferromagnet with SOC.
We show that the sign-changing AHE upon variation in the film thickness,
magnetization, and chemical potential can be well explained by theoretical
models. Our study is the first to directly characterize the topological band
structure of 2D spin-polarized bands and the corresponding AHE, which could
facilitate new switchable devices based on ferromagnetic ultrathin films
X-ray absorption spectroscopy study of diluted magnetic semiconductors: Zn1-xMxSe (M = Mn, Fe, Co) and Zn1-xMnxY (Y = Se, Te)
We have investigated 3d electronic states of doped transition metals in II-VI
diluted magnetic semiconductors, Zn1-xMxSe (M = Mn, Fe, Co) and Zn1-xMnxY (Y =
Se, Te), using the transition-metal L2,3-edge X-ray absorption spectroscopy
(XAS) measurements. In order to explain the XAS spectra, we employed a
tetragonal cluster model calculation, which includes not only the full ionic
multiplet structure but also configuration interaction (CI). The results show
that CI is essential to describe the experimental spectra adequately,
indicating the strong hybridization between the transition metal 3d and the
ligand p orbitals. In the study of Zn1-xMnxY (Y = Se, Te), we also found
considerable spectral change in the Mn L2,3-edge XAS spectra for different
ligands, confirming the importance of the hybridization effects in these
materials.Comment: This paper consists of 22 pages including 4 figures. This paper is
submitted to Physical Review
Advancement of a Pavement Management System (PMS) for the Efficient Management of National Highways in Korea
In order to maintain a suitable road pavement level with limited resources, a management system must be established. In order to achieve this goal, a program using AI (artificial intelligence) was developed to manage and evaluate a sizable volume of survey data. A national highway pavement data management system (PDMS) built on the WEB was also constructed. By connecting several artificial neural networks, the AI crack analysis algorithm was created and taught to automatically recognize cracks in road photos and calculate crack rates. In the PDMS, the current condition of a national highway can be shown on a map, and all the data are updated to allow for verification in increments of 100 m for each lane. The system was also improved to enable the collection of information on the detailed survey section’s pavement repair specifics according to survey year
Investigation on the Process of Eliminating Abnormal Objects from the Road for the Creation of an AI Program That Can Automatically Detect Potholes
For effective pothole control on national highways, autonomous pothole identification technology utilizing artificial intelligence was deployed in Korea. There are a number of different objects on the road’s surface that resemble potholes. The YOLOv7-E6E model was used to reduce noise, before classifying these objects and potholes. In the algorithm, aberrant objects other than potholes were classified using design and learning techniques. Manhole, automobile, lane-marking, garbage, and shadow elements that are similar to potholes were learned, in order to detect them. “Etc.” was used to summarize 15 characteristics, including a broken patch, spalling, crack, ramp, license plate, leaf, and pool. In light of this, learning was conducted using a total of seven classification criteria. The test dataset had a 91% accuracy rate
Electronic Structure of the Kitaev Material α-RuCl 3 Probed by Photoemission and Inverse Photoemission Spectroscopies
Recently, α-RuCl3 has attracted much attention as a possible material to realize the honeycomb
Kitaev model of a quantum-spin-liquid state. Although the magnetic properties of α-RuCl3 have been extensively studied, its electronic structure, which is strongly related to its Kitaev physics, is poorly understood. Here, the electronic structure of α-RuCl3 was investigated by photoemission (PE) and inverse-photoemission (IPE) spectroscopies. The band gap was directly measured from the PE and IPE spectra and was found to be 1.9 eV, much larger than previously estimated values. Local density approximation (LDA) calculations showed that the on-site Coulomb interaction U could open the band gap without spin-orbit coupling (SOC). However, the SOC should also be incorporated to reproduce the proper gap size, indicating that the interplay between U and SOC plays an essential role. Several features of the PE and IPE spectra could not be explained by the results of LDA calculations. To explain such discrepancies, we performed configuration-interaction calculations for a RuCl6 3− cluster. The experimental data and calculations demonstrated that the 4d compound α-RuCl3 is a Jeff = 1/2 Mott insulator rather than a quasimolecular-orbital insulator. Our study also provides important physical parameters required for verifying the proposed Kitaev physics in α-RuCl3. © The Author(s) 201619101sciescopu