Inelastic Effects in Low-Energy Electron Reflectivity of Two-dimensional Materials

A simple method is proposed for inclusion of inelastic effects (electron absorption) in computations of low-energy electron reflectivity (LEER) spectra. The theoretical spectra are formulated by matching of electron wavefunctions obtained from first-principles computations in a repeated vacuum-slab-vacuum geometry. Inelastic effects are included by allowing these states to decay in time in accordance with an imaginary term in the potential of the slab, and by mixing of the slab states in accordance with the same type of distribution as occurs in a free-electron model. LEER spectra are computed for various two-dimensional materials, including free-standing multilayer graphene, graphene on copper substrates, and hexagonal boron nitride (h-BN) on cobalt substrates.Comment: 21 pages, 7 figure

Identifikasi Patahan Manado Dengan Menggunakan Metode Geolistrik Konfigurasi Wenner-Schlumberger Di Airmadidi Minahasa Utara

Telah dilakukan penelitian untuk mengidentifikasi dan memetakan Patahan Manado yang melintasi Kelurahan Rap-Rap Airmadidi Minahasa Utara. Penelitian dilakukan menggunakan alat geolistrik Multichannel and Multielectrode Resistivity MAE X612-EM. Pengambilan data dilakukan pada 3 lintasan pengukuran dengan panjang bentangan masing-masing 480 meter. Pengolahan data dilakukan dengan menggunakan perangkat lunak RES2DINV. Hasil pengolahan data tersebut memberikan gambaran penampang lintang 2 dimensi citra bawah permukaan pada ketiga lintasan. Berdasarkan hasil analisis, teridentifikasi rekahan pada jarak 30 meter dari jalur Patahan Manado, dengan kedalaman dari permukaan tanah 0-50 meter untuk lintasan 1, 0-25 meter untuk lintasan 2, 0-30 meter untuk lintasan 3, dengan harga resistivitas <70 Ωm.The research has been done to identify and to create a map of Manado Fault that passed through the Village of Rap-Rap, Airmadidi, North Minahasa. The research was carried out using a multichannel and multielectrode resistivity MAE X612-EM geoelectrical device.The data collection was carried out on 3 measurement lineswith a range of 480 meters each. The data processing was held using RES2DINV software. Its result gave an overview of the 2-dimensional transection of beneath-surface imaging on those 3 lines. According to the analysis outcome, the fracture is identified at 30 meters from the Manado fault, with a depth of 0-50 meters from the ground's surface (line 1), 0-25 meters (line 2), and 0-30 meters (line 3) with a resistivity value of <70 Ωm

Graphene formed on SiC under various environments: Comparison of Si-face and C-face

The morphology of graphene on SiC {0001} surfaces formed in various environments including ultra-high vacuum, 1 atm of argon, and 10^-6 to 10^-4 Torr of disilane is studied by atomic force microscopy, low-energy electron microscopy, and Raman spectroscopy. The graphene is formed by heating the surface to 1100 - 1600 C, which causes preferential sublimation of the Si atoms. The argon atmosphere or the background of disilane decreases the sublimation rate so that a higher graphitization temperature is required, thus improving the morphology of the films. For the (0001) surface, large areas of monolayer-thick graphene are formed in this way, with the size of these areas depending on the miscut of the sample. Results on the (000-1) surface are more complex. This surface graphitizes at a lower temperature than for the (0001) surface and consequently the growth is more three-dimensional. In an atmosphere of argon the morphology becomes even worse, with the surface displaying markedly inhomogeneous nucleation, an effect attributed to unintentional oxidation of the surface during graphitization. Use of a disilane environment for the (000-1) surface is found to produce improved morphology, with relatively large areas of monolayer-thick graphene.Comment: 22 pages, 11 figures, Proceedings of STEG-2 Conference; eliminated Figs. 4 and 7 from version 1, for brevity, and added Refs. 18, 29, 30, 31 together with associated discussio

Large Anomalous Hall and Nernst Effects in High Curie-Temperature Iron-Based Heusler Compounds

Abstract The interplay between topology and magnetism has recently sparked the frontier studies of magnetic topological materials that exhibit intriguing anomalous Hall and Nernst effects owning to the large intrinsic Berry curvature (BC). To better understand the anomalous quantum transport properties of these materials and their implications for future applications such as electronic and thermoelectric devices, it is crucial to discover more novel material platforms for performing anomalous transverse transport studies. Here, it is experimentally demonstrated that low-cost Fe-based Heusler compounds exhibit large anomalous Hall and Nernst effects. An anomalous Hall conductivity of 250?750 S cm?1 and Nernst thermopower of above 2 µV K?1 are observed near room temperature. The positive effect of anti-site disorder on the anomalous Hall transport is revealed. Considering the very high Curie temperature (nearly 1000 K), larger Nernst thermopowers at high temperatures are expected owing to the existing magnetic order and the intrinsic BC. This work provides a background for developing low-cost Fe-based Heusler compounds as a new material platform for anomalous transport studies and applications, in particular, near and above room temperature