Search

Many applications require monitoring of increasingly high neutron flux levels. Pre‐neutron characterization is performed of a superconducting transition edge bolometric device, sensitive to neutrons by an enriched boron carbide (10B4C) layer. Heat from the absorption of neutrons is simulated using an attenuated laser, while the detector is cooled to the critical temperature, Tc. Frequency dependent (4–25 Hz) and constant input power measurements are performed on a 10B4C‐coated and a non‐coated pixel. Results are used to fit a two lumped element thermal model. The effective specific heat is highly dependent on the input pulse duration due to the interconnected stack structure. For modulated pulses, the active volume in the thermal circuit is the full depth of the substrate in the area under the pixel. For constant power input, a large portion of the substrate is heated and the interface conductivities to the cold finger are found to be important. The detectivity is D* = 3.5 × 108 cmHzW−1${{\rm cm}} \sqrt {{\rm Hz}}\,{{\rm W}^{-1}}$, and is only slightly lower than similar detectors. Understanding the dynamics of the detector better and using neutron excitation, it is expected that optimizations can lead to an equally good detector for cold to thermal neutrons at flux levels >106 n cm−2s−1. [ABSTRACT FROM AUTHOR]

Silicon radiation detectors, a special type of microelectronic sensor which plays a crucial role in many applications, are reviewed in this paper, focusing on fabrication aspects. After addressing the basic concepts and the main requirements, the evolution of detector technologies is discussed, which has been mainly driven by the ever-increasing demands for frontier scientific experiments. [ABSTRACT FROM AUTHOR]

After several decades of a dramatic development Penning-trap mass spectrometry now demonstrates unprecedented precision and sensitivity in measurements of the masses of a broad range of nuclides for various aspects of fundamental physics. This article reviews one facet of such mass measurements—a contribution of Penning-trap mass spectrometry to experiments on studies of neutrinos. These studies encompass the determination of the neutrino mass, the search for sterile and relic neutrinos and the search for neutrinoless double electron capture in order to determine the type of neutrinos as well as to check the conservation law of the total lepton number. [ABSTRACT FROM AUTHOR]

Nuclear β -decay provides a laboratory for investigating weak decays occurring inside the nuclear medium. This provides information on the resulting subtle nuclear and atomic effects, and on the underlying interaction and the properties of the particles that are involved, particularly of the neutrino. The Q value of the decay corresponds to the energy equivalent of the mass difference between parent and daughter atoms, and can be precisely and accurately measured using Penning trap mass spectrometry. In this paper we discuss Penning trap Q value measurements for forbidden β -decays of long-lived primordial nuclides, and for a subset of β -unstable nuclides that could potentially undergo a very low energy decay to an excited state in the daughter nucleus. We discuss applications of these measurements to tests of systematics in detectors that perform precise β -spectrum measurements, as inputs for theoretical shape factor, electron branching ratio and half-life calculations, and to identify nuclides that could serve as new candidates in direct neutrino mass determination experiments. [ABSTRACT FROM AUTHOR]

A photodetector with bias‐tuneable current is realized by adding a film of single‐walled carbon nanotubes (CNT), forming a CNT/Si3N4/Si capacitor, to a prefabricated Pt–Ti/Si3N4/Si metal–insulator–semiconductor (MIS) diode. Electrical characterization of the entire device is performed to extract the temperature‐dependent ideality factor and Schottky barrier height in the framework of the thermionic emission theory. The CNT/Si3N4/Si capacitor increases the reverse current of the parallel Pt–Ti/Si3N4/Si MIS diode by adding a Fowler–Nordheim tunneling current at high reverse voltage bias. This feature endows the photodetector with two different photocurrent levels, photoresponsivity up to 370 mA W−1 and external quantum efficiency up to 50% at 950 nm wavelength. The device also shows a different photoresponse when light is focused on the CNT/Si3N4/Si region or around the Pt–Ti/Si3N4/Si structure. The photodetector can also be used as an optoelectronic Boolean logic device, in which the applied voltage bias and the incident light are the two input signals, and the photocurrent is the output. Furthermore, light generates a photocurrent at zero voltage and a photovoltage at zero current, making the device a self‐powered photodetector. [ABSTRACT FROM AUTHOR]

Single-wall carbon nanotube (SWCNT)/n-type silicon (n-Si) heterojunctions with a high photoresponsivity are considered promising for use in photodetectors. However, the performance of large-area SWCNT film/n-Si heterojunction-based photodetectors has been much lower than that fabricated using isolated SWCNTs, where the efficient assembly of SWCNT networks with the desired structure is a key issue. In this study, we prepared a small-bundled SWCNT (SB-SWCNT) film with a carbon-welding structure at tube–tube junctions, which greatly decreased the contact resistance and improved the work function. The fabricated SB-SWCNT film/n-Si heterojunction-based photodetectors showed a very high detectability of 4.2 × 1013 Jones for an 890 nm laser with 0 bias, much higher than that of commercial photodetectors. The detectors also demonstrated good stability with a 97% R value retained after being exposed in air for 30 days, and a broad spectral response (540–1090 nm). [ABSTRACT FROM AUTHOR]

Over the last few years, metal halide perovskites have established themselves as important materials in the field of optoelectronics. After their first application in photovoltaics, they have been successfully used in other optoelectronic devices, especially photodetectors, owing to their unparalleled optical and electronic properties. Notably, because of their unique optical and electronic properties and small physical dimensions, various carbon nanomaterials have emerged as alternatives for next‐generation optoelectronic devices, and they have also been combined with other materials to realize optimal optoelectronic performance. Some implementations of hybrid photodetectors combining metal halide perovskites with carbon nanomaterials have been reported. Here, it is presented a comprehensive review of the recent advancements in the application of carbon nanomaterials in metal halide perovskite photodetectors, with particular focus on the possible working mechanisms behind the significant enhancement of their performance. First, a brief introduction to the fundamentals of photodetection devices is presented, followed by a short discussion of the intrinsic characteristics of metal halide perovskites and carbon nanomaterials. Detailed descriptions of the operation mechanisms, the evolution of different device structures, and their optoelectronic performance are then given. Finally, the potential challenges and future perspectives for the development of high‐performance stable photodetectors based on these materials are outlined. [ABSTRACT FROM AUTHOR]

A new method for analyzing the local reduced activation energy w (T) of the impurity conductivity is applied to Ga-doped p -Ge samples with a constant compensation ratio of K = 0. 3 reported by Zabrodskii and Andreev [Int. J. Mod. Phys. B8, 883 (1994)]. Here, the local reduced activation energy is defined as w (T) = d (ln σ) / d (ln T) , where σ and T denote conductivity and absolute temperature, respectively. The method enables us to deconvolute the w (T) curve into contributions from different conduction mechanisms such as free-hole conduction, nearest-neighbor hopping (NNH) conduction and variable-range hopping (VRH) conduction. As a result, it is shown that both the power exponents of the pre-exponential factors of NNH and VRH conductivity tend to decrease with increasing impurity concentration. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy (TEM) and ab initio calculations revealed that the Ni-Si reaction around 300 °C is significantly changed by adding Pt to Ni. TEM analysis clarified that NiSi2 was formed in a reaction between Ni thin film (∼1 nm) and Si substrate, while NiSi was formed when Pt was added to the Ni film. We also found that the Ni-adamantane structure, which acts as a precursor for NiSi2 formation around the reaction temperature, was formed in the former reaction but was significantly suppressed in the latter reaction. Theoretical calculations indicated that Pt addition increased stress at the Ni-adamantane structure/Si-substrate interface. The increase in interface stress caused by Pt addition should raise the interface energy to suppress the Ni-adamantane structure formation, leading to NiSi2 formation being suppressed. [ABSTRACT FROM AUTHOR]

Focuses on diffusion of platinum at low temperatures as a way to characterize vacancy profiles in silicon. Summary of experiments performed to find a standard procedure; Limitations of the method; Backside contamination with platinum after one-sided deposition; Drive-in diffusions; Depth profiles of substitutional platinum; FZ silicon; CZ silicon.

Provides information on a study which examined the solid state reaction between a nitrogen film and a silicon substrate by scanning electron microscopy, x-ray diffraction and Rutherford backscattering spectrometry. Methods; Results and discussion; Conclusion.

Discusses a study that induced silicide formation in platinum-silicon bilayers by rapid isothermal annealing using incoherent light from tungsten halogen lamps. Growth sequence of the Pt[sub2]Si and the platinum silicide (PtSi) phases; Identification of the phases; Determination of activation energies for the formation of the Pt[sub2]Si and the PtSi phase.

Presents a study which developed a simple method which uses numerical calculations to estimate diffusion fluxes into reactive interfaces during silicide formation processes. Computation of diffusion fluxes and release rates; Modified model for silicide formation; Analysis of data from other experiments; Conclusions.

Purpose: The aim of this paper is to assess the compliance with the characteristic of the relevance of disclosure in Management Reports, particularly dealing with Human Capital (HC) information. Design/methodology/approach: We codify all instances where narratives of IBEX-35 stock index companies over a five year period in Spain comply with the recommendations for a "high quality" Management Commentary (MC) in terms of the relevance characteristic of the information disclosed (IASB, 2005). Findings: The analysis results show that a greater quantity of information about HC in terms of the number of pages devoted is not always indicative of higher quality in terms of relevance if we look for the application of IASB recommendations. Research limitations/implications: Further research could assess compliance with other qualitative characteristics required by other standards or guidance that were internationally accepted. Practical implications: Among the areas that require improvement in HC disclosures we highlight forward-looking information. Social implications: We propose that an internationally accepted agreement must be struck to unite all the efforts that are being made to improve narrative information in the MC section, and specifically with reference to HC. Originality/value: This work compiles the HC disclosures identified as best practices that may serve as a reference to other companies. [ABSTRACT FROM AUTHOR]

The paper presents method for thermal generation reduction in low level light applications, especially where measured phenomena have random character. The algorithm was developed basing on cosmic ray measurements. The main parts of the system are: Silicon Photomultipliers (SiPM), front-end ASIC for amplifying and shaping signals. SiPM is a very sensitive device which can detect single photons. Comparing to a standard photomultiplier SiPM has a compact size, low operating voltage and it is immune to an electromagnetic field. Thermally generated signals are disadvantage of SiPM. This paper presents the measurement method to reduce influence of thermal generation. [ABSTRACT FROM AUTHOR]

We report a dose-dependent phase evolution in Mo/Si bilayer system upon Ar+ ion beam irradiation and subsequent flash annealing at 800 °C for 60 s. Micro-structural characterization with Grazing Incidence X-ray Diffraction and Raman scattering reveals a dose-dependent nucleation of polymorphic phases occurring at the amorphized interface region. The ion beam mixing process has been investigated by Secondary Ion Mass Spectrometry and Rutherford Backscattering Spectrometry. While low ion doses favour nucleation of only metastable MoSi2 phase, co-existence of polymorphic phases are observed at high ion doses. The persistence of such polymorphic phases even after a high-temperature anneal for high dose implanted specimen is indicative of phase retardation. The phase retardation of h-MoSi2 to t-MoSi2 is accounted in terms of nucleation and growth process. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]