Search results for "Semiconductor"

Evaluation of the Spectroscopic Performance of 3D CZT Drift Strip Detectors

2021

CdTe/CZT is an attractive and consolidated material with which to realize detectors with good efficiency and energy resolution, operating at room temperature and suitable for a large variety of applications such as medical imaging, nuclear security, and astrophysics. Right in this last field several spectro-imagers based on these CdTe/CZT detectors were mounted onboard space missions such as INTEGRAL, Swift, and NuSTAR for hard X and gamma-ray astrophysics. Much effort has been expended in the development of CZT spectroscopic imagers for obtaining sub-millimeter spatial resolution in three dimensions (3D) and high energy resolution up to 1 MeV. The motivations are mainly related to the poss…

Exploiting the optical quadratic nonlinearity of zinc-blende semiconductors for guided-wave terahertz generation: A material comparison

2010

We present a detailed analysis and comparison of dielectric waveguides made of CdTe, GaP, GaAs and InP for modal phase matched optical difference frequency generation (DFG) in the terahertz domain. From the form of the DFG equations, we derived the definition of a very general figure of merit (FOM). In turn, this FOM enabled us to compare different configurations, by taking into account linear and nonlinear susceptibility dispersion, terahertz absorption, and a rigorous evaluation of the waveguide modes properties. The most efficient waveguides found with this procedure are predicted to approach the quantum efficiency limit with input optical power in the order of kWs.

Temperature and Isotopic Mass Dependence of the Direct Band Gap in Semiconductors: LCAO Calculations

2000

Characterization of single semiconductor nanowires by synchrotron radiation nanoprobe

2012

In this work, we report on the results of the characterization of single semiconductor nanowires by x-ray fluorescence nanoprobe. Wurtzite InGaN and Co-implanted ZnO single nanowires were studied. Ternary semiconductor nanowires show an axial inhomogeneous elemental distribution, with Ga accumulating at the bottom and In at the top of the wires. The ZnO NWs, on the other hand, show a homogeneous distribution of the Co implanted along the nanowires, without signatures of clustering or segregation effects induced by the implantation. No signatures of unintentional doping are observed neither in the InGaN nor the ZnO NWs. These overall results demonstrate the suitability of X-ray fluorescence …

Structure determination and homogeneous optical properties of CdS/HgS quantum dots

1997

The structural and optical properties of heterogeneous semiconductor nanoparticles consisting of CdS and HgS are investigated by High Resolution Electron Microscopy (HRTEM) and selective spectroscopy like Hole Burning (HB) and Fluorescence Line Narrowing (FLN). The HRTEM study shows that epitaxy is possible in nanocrystals, provided the crystallites have well defined faceted shapes to begin with. From the HB- and FLN experiments homogeneous absorption and fluorescence spectra are calculated. It could be shown that the absorption is coupled to HgS-like phonons (250 cm -1 ) whereas the emission frequency is closer to the LO phonon frequency of CdS.

Acid-Base Properties and their Influence on the Photoreactivity of Oxides

1988

It is described the existence on the surface of a solid of acidic and basic centres. The correlation with electron donor-acceptor properties is described. The influence of such centres in influencing the reactivity in a photocatalytic process is discussed. The case of ethanoic acid photodecarboxylation over a series of insulator and semiconductor oxides and their mixtures is briefly reported outlining how the acid-base properties affect the photoreactivity.

Intrinsic Organic Semiconductors as Hole Transport Layers in p–i–n Perovskite Solar Cells

2021

Thin polymeric and small-molecular-weight organic semiconductors are widely employed as hole transport layers (HTLs) in perovskite solar cells. To ensure ohmic contact with the electrodes, the use of doping or additional high work function (WF) interlayer is common. In some cases, however, intrinsic organic semiconductors can be used without any additive or buffer layers, although their thickness must be tuned to ensure selective and ohmic hole transport. Herein, the characteristics of thin HTLs in vacuum-deposited perovskite solar cells are studied, and it is found that only very thin (<5 nm) HTLs readily result inhigh-performing devices, as the HTL acts as a WF enhancer while still ens…

Polymer‐Based Composites for Engineering Organic Memristive Devices

2022

Memristive materials are related to neuromorphic applications as they can combine information processing with memory storage in a single computational element, just as biological neurons. Many of these bioinspired materials emulate the characteristics of memory and learning processes that happen in the brain. In this work, we report the memristive properties of a two-terminal (2-T) organic device based on ionic migration mediated by an ion-transport polymer. The material possesses unique memristive properties: it is reversibly switchable, shows tens of conductive states, presents Hebbian learning demonstrated by spiking time dependent plasticity (STDP), and behaves with both short- (STM) an…

Conductive polycaprolactone/gelatin/polyaniline nanofibres as functional scaffolds for cardiac tissue regeneration

2022

Abstract The endorsement of functional features such as biocompatibility, mechanical integrity, or electrical conductivity to tissue engineering (TE) scaffolds is essential to stimulate cell adhesion and proliferation. In this study, electrospun nanofibers based on polycaprolactone (PCL) and gelatin (Ge) (ratios 60/40, 50/50, and 40/60), and polyaniline (PAni) particles (0.25, 0.50, and 1.00%wt) were prepared. The time of dissolution in an acid solvent mixture before electrospinning allowed for obtaining nanofibers with controlled features. Changes in the molar mass (Mn from 90·103 to 15·103 g·mol−1), in the crystalline microstructure (Xc from 60 to 25%) and the surface morphology (diameter…

Density of states within the bandgap of perovskite thin films studied using the moving grating technique

2022

In this work, we further study the moving grating technique applied to halide perovskite thin-film materials. First, we show some problems that emerge when analyzing the experimental data with the classical formulation, which does not distinguish between free and trapped carriers and hence only gives average quantities for the transport parameters. We show that using a more general framework, taking into account the multiple trapping of carriers within a density of localized states, allows for an accurate description. Since it includes the density of states (DOS) of the material, it enables the possibility to test different DOS models proposed in the past for halide perovskite thin films. …