The DAMA/LIBRA apparatus

The $\simeq$ 250 kg highly radiopure NaI(Tl) DAMA/LIBRA apparatus, running at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N., is described.Comment: 37 pages, 27 figure

Unveiling surface dynamics: in situ oxidation of defective WS 2 †

Applications of transition-metal dichalcogenides (TMDs) are affected by defects and oxidation in air. In this work, we clarify the relationship between oxidation dynamics and O2 availability for highly defective (and therefore reactive) surfaces of WS2 crystals. Grazing incidence Ar+ sputtering was used to induce a significant concentration of S vacancies in the sample, rendering it highly susceptible to oxidative degradation. In this paper we observe that oxidation occurs slowly under low O2 pressures (<10−4 mbar) due to reduced O2-vacancy interactions. At higher O2 pressures, the reaction progresses rapidly, as tracked by changes in the oxidation state of W using XPS. The density functional theory calculations support the experimentally observed changes in the oxidation state of W after sputtering and oxidation. They provide the mechanisms of O2 dissociation on S vacancy clusters, demonstrating that the reaction barrier depends on the coordination of surface W atoms. These results can be useful for protecting samples from degradation in device applications

Towards edge engineering of two-dimensional layered transition-metal dichalcogenides by chemical vapor deposition

The manipulation of edge configurations and structures in atomically thin transition metal dichalcogenides (TMDs) for versatile functionalization has attracted intensive interest in recent years. The chemical vapor deposition (CVD) approach has shown promise for TMD edge engineering of atomic edge configurations (1H, 1T or 1T'-zigzag or armchair edges), as well as diverse edge morphologies (1D nanoribbons, 2D dendrites, 3D spirals, etc). These rich-edge TMD layers offer versatile candidates for probing the physical and chemical properties, and exploring new applications in electronics, optoelectronics, catalysis, sensing and quantum field. In this review, we present an overview of the current state-of-the-art in the manipulation of TMD atomic edges and edge-rich structures using CVD. We highlight the vast range of unique properties associated with these edge configurations and structures and provide insights into the opportunities afforded by such edge-functionalized crystals. The objective of this review is to motivate further research and development efforts in using CVD as a scalable approach to harness the benefits of such crystal-edge engineering

Further results from DAMA/LIBRA-phase2 and perspectives

The data collected by the DAMA/LIBRA-phase2 set-up during two additional annual cycles have been analyzed, further investigating the long-standing model-independent annual modulation effect pointed out by DAMA deep underground at the Gran Sasso National Laboratory of the I.N.F.N. by using various different experimental configurations. Including the new results, the total exposure of DAMA/LIBRA-phase2 over 8 annual cycles is 1.53 t·yr and the evidence for a signal that meets all the requirements of the model-independent Dark Matter annual modulation signature is 11.8 σ C.L. in the energy region (1 - 6) keV. In the (2 - 6) keV energy interval, where data are also available from DAMA/NaI and DAMA/LIBRA-phase1, the achieved C.L. for the full exposure of 2.86 t·yr is 13.7 σ. No systematics or side reaction able to mimic this signature (i.e., to account for the whole measured modulation amplitude and to simultaneously satisfy all the requirements of the signature) has been found or suggested by anyone throughout some decades thus far. A preliminary result on the further lowering of the software energy threshold and perspectives are also mentioned

Modalità di relazione oggettuale e connotazione dei vissuti vissuti religiosi nella depressione.

vengono riportati i dati emersi in una ricerca su un campione di religiose che presentavano sintomi depressivi

Band structure and spin texture of 2D materials for valleytronics: insights from spin and angle-resolved photoemission spectroscopy

In this review, we present a perspective on the use of angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES (SARPES) for the study of the electronic properties of semiconducting transition metal dichalcogenides (TMDCs), a prime example of two-dimensional (2D) materials for valleytronics applications. In the introductory part, we briefly describe the structural and electronic properties of semiconducting TMDCs and the main valleytronics related physical effects. After a short presentation of theoretical methods utilized in the band structure and spin texture calculation of semiconducting TMDCs, we illustrate the basic principles and methodology of photoemission techniques and then provide a detailed survey on the electronic band structure studies of these materials. In particular, by selecting and comparing seminal results in the field, we highlight the critical role played by the sample preparation strategy on the amount and quality of information that can be extracted in the ARPES investigations of TMDCs. This is followed by a detailed discussion on the impact of interface potential landscape and doping on their electronic properties, considering the importance of their contact with metal electrode and/or dielectric substrate in determining the electrical transport in real devices’ architecture. Finally, we summarize key SARPES findings on the spin texture of TMDCs and conclude by pointing out current open issues and potential directions for future photoemission-based studies on these 2D systems

Mechanism of the Fermi level pinning at organic donor-acceptor heterojunction interfaces

10.1016/j.orgel.2011.01.003Organic Electronics: physics, materials, applications123534-54

First model independent results from DAMA/LIBRA-phase2

The first model independent results obtained by the DAMA/LIBRA-phase2 experiment are presented. The data have been collected over 6 annual cycles corresponding to a total exposure of 1.13 t x yr, deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. The DAMA/LIBRA-phase2 apparatus, ≃ 250 kg highly radio-pure NaI(Tl), profits from a second generation high quantum efficiency photomultipliers and of new electronics with respect to DAMA/LIBRA-phase1. The improved experimental configuration has also allowed to lower the software energy threshold. New data analysis strategies are presented. The DAMA/LIBRA-phase2 data confirm the evidence of a signal that meets all the requirements of the model independent Dark Matter (DM) annual modulation signature, at 9.5 sigma C.L. in the energy region (1 - 6) keV. In the energy region between 2 and 6 keV, where data are also available from DAMA/NaI and DAMA/LIBRA-phase1 (exposure 1.33 t x yr, collected over 14 annual cycles), the achieved C.L. for the full exposure (2.46 t xyr) is 12.9 sigma; the modulation amplitude of the single-hit scintillation events is: (0.0103 ± ± 0.0008) cpd/kg/keV, the measured phase is (145 ± 5) d and the measured period is (0.999 ± 0.001) yr, all these values are well in agreement with those expected for DM particles. No systematics or side reaction able to mimic the exploited DM signature (i.e. to account for the whole measured modulation amplitude and to simultaneously satisfy all the requirements of the signature), has been found or suggested by anyone throughout some decades thus far

Physical Strategies for Geometric Control of Transition Metal Dichalcogenide Atomic Layers by Chemical Vapor Deposition

Abstract The diverse morphologies of 2D transition metal dichalcogenides (2D TMDs) motivate their broad potential applications in the next generation of electronic, optical, and catalytic technologies. It is advantageous to develop controllable growth techniques that afford versatility through direct manipulation of the growth parameters. A fundamental understanding of the physical mechanisms driving various growth modes is crucial for achieving the process precision necessary for obtaining reproducible morphologies in 2D TMDs. Thermodynamic and kinetic considerations are two key physical strategies. Thermodynamic strategies mainly involve the manipulation of parameters like temperature and the chemical potential of precursors to ensure the thermostability of various morphologies. Conversely, kinetic strategies, focusing on the factors, like precursor diffusion, adsorption, and desorption during the growth, also enable atomic‐level kinetics control of the resulting morphologies. Often, an interplay of both mechanisms drives the growth of a particular morphology. This review aims to provide an updated guidance for exploiting these physical strategies in the versatile technique of chemical vapor deposition. The opportunities for further exploring the control of these physical mechanisms are discussed through recent examples with an eye on unlocking the untapped potential of 2D TMDs in areas such as phase engineering and shape control for advanced applications