Effect of Sb incorporation on the electronic structure of InAs quantum dots

On the basis of optical characterization experiments and an eight band kp model, we have studied the effect of Sb incorporation on the electronic structure of InAs quantum dots (QDs). We have found that Sb incorporation in InAs QDs shifts the hole wave function to the center of the QD from the edges of the QD where it is otherwise pinned down by the effects of shear stress. The observed changes in the ground-state energy cannot merely be explained by a composition change upon Sb exposure but can be accounted for when the change in lateral size is taken into consideration. The Sb distribution inside the QDs produces distinctive changes in the density of states, particularly, in the separation between excitation shells. We find a 50% increase in the thermal escape activation energy compared with reference InAs quantum dots as well as an increment of the fundamental transition decay time with Sb incorporation. Furthermore, we find that Sb incorporation into quantum dots is strongly nonlinear with coverage, saturating at low doses. This suggests the existence of a solubility limit of the Sb incorporation into the quantum dots during growth.

Electronic, structural, and optical properties of the host and Cr-doped cadmium thioindate

The cadmium thioindate spinel CdIn2S4 semiconductor has potential applications for optoelectronic devices. We present a theoretical study of the structural and optoelectronic properties of the host and of the Cr-doped ternary spinel. For the host spinel, we analyze the direct or indirect character of the energy bandgap, the change of the energy bandgap with the anion displacement parameter and with the site cation distribution, and the optical properties. The main effect of the Cr doping is the creation of an intermediate band within the energy bandgap. The character and the occupation of this band are analyzed for two substitutions: Cr by In and Cr by Cd. This band permits more channels for the photon absorption. The optical properties are obtained and analyzed. The absorption coefficients are decomposed into contributions from the different absorption channels and from the inter-and intra-atomic components.

Reducing the dimensionality effect in importance sampling simulations

The dimensionality effect is avoided by the use of sufficient statistics in event probability estimators realised by importance sampling. If the system function is not a sufficient statistic, an approach is proposed to reduce the dimensionality effect in the estimators. Simulation results of false-alarm probability estimations, applied to radar detection, confirm a clear concordance with the theoretical results

The counteractive effect of the sensor housing on the unit sensitivity across a series of dynamic temperature profiles.

The advantages of wireless sensing implemented on the cold chain of fresh products are well known. These sensor systems consist of a combination of delicate internal electronic circuitry enclosed in a special housing unit. Manufacturers however are presented with the challenge that the housing required to withstand the harsh environment in which the sensors are being used all too often take from the functionality of the sensor. Therefore the target of this study is to determine the dynamic behavior and the counteractive effects of the sensor housing on temperature recording accuracy in the wireless nodes of Wireless Sensor Network (WSN) and Radio Frequency Identification (RFID) semi-passive tags. Two kind of semi-passive Turbo Tags were used (T700 and T702-B), which consisted of sensors with and without a cover, and two kind of WSN nodes, IRIS (sensors Intersema and Sensirion soldered in the motherboard) and NLAZA (Sensirion in a cable and soldered to the motherboard). To recreate the temperature profiles the devices were rotated between a cold room(5 ºC) through a ambient room(23 ºC) to a heated environment (35ºC) and vice versa. Analysis revealed the differences between housing and no housing are 308.22s to 21.99s respectively in the step from 5 to 35 ºC. As is demonstrated in these experiments the influence of the housing significantly hinders sensor accuracy.

Effect of van der Waals interaction on the properties of SnS2 layered semiconductor

Nowadays, dispersion correction applied on layered semiconductors is a topic of interest. Among the known layered semiconductors, SnS2 polytypes are wide gap semiconductors with a van der Waals interaction between their layers, which could form good materials to be used in photovoltaic applications. The present work gives an approach to the SnS2 geometrical and electronic characterization using an empirical dispersion correction added to the Perdew–Burke–Ernzerhof functional and subsequent actualization of the electronic charge density using the screened hybrid Heyd–Scuseria–Ernzerhof functional using a density functional code. The obtained interlayer distance and band-gap are in good agreement with experimental values when van der Waals dispersion forces are included.