Study of Shubnikov-de Haas oscillations and measurement of hole effective mass in compressively strained InXGa1−XSb quantum wells

In_XGa_1−XSb has the highest hole mobility amongst all III-V semiconductors which can be enhanced further with the use of strain. The use of confinement and strain in In_XGa_1−XSb quantum wells lifts the degeneracy between the light and heavy hole bands which leads to reduction in the hole effective mass in the lowest occupied band and an increase in the mobility. We present magnetotransport measurements on compressively strained In_XGa_1−XSb and GaSb quantum wells. Hall-bar and Van de Pauw structures were fabricated and Shubnikov-de Haas oscillations in the temperature range of T = 2-10 K for magnetic fields of B = 0-9 T were measured. The reduction of effective hole mass with strain was quantified. These results are in excellent agreement with modeling results from band structure calculations of the effective hole mass in the presence of strain and confinement.     

Data analytics in wireless systems and IoT issues and challenges

The emergence of data engineering along with the support of Online Social Networks is growing by millions every day due to the introduction of wireless systems and Internet of Things. The rapid growth of usage of smart devices helps to create new generation knowledge sharing platforms. Data Analytics has a major role to play in the growth and success of wireless and IoT applications. The growth of data has become exponential and is difficult to analyze. Many researchers depend on the data available on Wireless Systems and IoT for developing new generation services and applications. With the opportunity of information and communication technologies like heterogeneous networking, cloud computing, web services, crowd sensing and data mining, ubiquitous and asynchronous information sharing is feasible. But this also brings out a lot of provocations with respect to conflicting standards, data portability, data aggregation, data distribution, differential context and communication overhead. The smart information and communication technology has changed many features of human lifestyle: personal and work places.     

On reducing delay in mobile data collection based wireless sensor networks

In a wireless sensor network, battery power is a limited resource on the sensor nodes. Hence, the amount of power consumption by the nodes determines the node and network lifetime. This in turn has an impact on the connectivity and coverage of the network. One way to reduce power consumed is to use a special mobile data collector (MDC) for data gathering, instead of multi-hop data transmission to the sink. The MDC collects the data from the nodes and transfers it to the sink. Various kinds of MDC approaches have been explored for different assumptions and constraints. But in all the models proposed, the data latency is usually high, due to the slow speed of the mobile nodes. In this paper, we propose a new model of mobile data collection that reduces the data latency significantly. Using a combination of a new touring strategy based on clustering and a data collection mechanism based on wireless communication, we show that the delay can be reduced significantly without compromising on the advantages of MDC based approach. Using extensive simulation studies, we analyze the performance of the proposed approach and show that the packet delay reduces by more than half when compared to other existing approaches.     

Contact-Barrier Free,High Mobility,Dual-Gated Junctionless Transistor Using Tellurium Nanowire

The gate-all-around nanowire transistor, due to its extremely tight electrostatic control and vertical integration capability, is a highly promising candidate for sub-5 nm technology nodes. In particular, the junctionless nanowire transistors are highly scalable with reduced variability due to avoidance of steep source/drain junction formation by ion implantation. Here a dual-gated junctionless nanowire p-type field effect transistor is demonstrated using tellurium nanowire as the channel. The dangling-bond-free surface due to the unique helical crystal structure of the nanowire, coupled with an integration of dangling-bond-free, high quality hBN gate dielectric, allows for a phonon-limited field effect hole mobility of 570 cm² V⁻¹ s⁻¹ at 270 K, which is well above state-of-the-art strained Si hole mobility. By lowering the temperature, the mobility increases to 1390 cm² V⁻¹ s⁻¹ and becomes primarily limited by Coulomb scattering. The combination of an electron affinity of ≈ 4 eV and a small bandgap of tellurium provides zero Schottky barrier height for hole injection at the metal-contact interface, which is remarkable for reduction of contact resistance in a highly scaled transistor. Exploiting these properties, coupled with the dual-gated operation, we achieve a high drive current of 216 μA μm⁻¹ while maintaining an on-off ratio in excess of 2 × 10⁴. The findings have intriguing prospects for alternate channel material based next-generation electronics.     

Growth of Epitaxial (110) 0.7Pb(Mg<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3</Subscript>-0.3PbTiO<Subscript>3</Subscript> Thin Films on r-Plane Sapphire Substrates by RF Magnetron Sputtering

The role of substrate temperature and substrate surface geometry in determining the crystal structure and crystallinity of 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (PMN-PT) thin films grown on r-plane sapphire substrates is examined. A 30-nm-thick amorphous PMN-PT seed layer deposited at 250°C and subjected to rapid thermal annealing at 850°C results in the formation of an epitaxial (110) perovskite PMN-PT growth template that can be used for subsequent growth of single-crystal (110) perovskite PMN-PT films at elevated temperature. The data show that single-crystal perovskite is promoted when the films nucleate with the \( \langle \overline{1} 11 \rangle \) PMN-PT direction parallel to the \( \langle 0\bar{2}21 \rangle \) Al₂O₃ direction.     

Shot boundary detection in the presence of illumination and motion

Detection of gradual transition and the elimination of disturbances caused by illumination change or fast object and camera motion are the major challenges to the current shot boundary detection techniques. These disturbances are often mistaken as shot boundaries. Therefore, it is a challenging task to develop a method that is not only insensitive to various disturbances but also sensitive enough to capture a shot change. To address these challenges, we propose an algorithm for shot boundary detection in the presence of illumination change, fast object motion, and fast camera motion. This is important for accurate and robust detection of shot boundaries and in turn critical for high-level content-based analysis of video. First, the propose algorithm extracts structure features from each video frame by using dual-tree complex wavelet transform. Then, spatial domain structure similarity is computed between adjacent frames. The declaration of shot boundaries are decided based on carefully chosen thresholds. Experimental study is performed on a number of videos that include significant illumination change and fast motion of camera and objects. The performance comparison of the proposed algorithm with other existing techniques validates its effectiveness in terms of better Recall, Precision, and F1 score.     

Classification of sport videos using edge-based features and autoassociative neural network models

In this paper, we propose a method for classification of sport videos using edge-based features, namely edge direction histogram and edge intensity histogram. We demonstrate that these features provide discriminative information useful for classification of sport videos, by considering five sports categories, namely, cricket, football, tennis, basketball and volleyball. The ability of autoassociative neural network (AANN) models to capture the distribution of feature vectors is exploited, to develop class-specific models using edge-based features. We show that combining evidence from complementary edge features results in improved classification performance. Also, combination of evidence from different classifiers like AANN, hidden Markov model (HMM) and support vector machine (SVM) helps improve the classification performance. Finally, the performance of the classification system is examined for test videos which do not belong to any of the above five categories. A low rate of misclassification error for these test videos validates the effectiveness of edge-based features and AANN models for video classification.     

Simulation, modeling, and crystal growth of Cd0.9Zn0.1Te for nuclear spectrometers

High-quality, large (10 cm long and 2.5 cm diameter), nuclear spectrometer grade Cd_0.9Zn_0.1Te (CZT) single crystals have been grown by a controlled vertical Bridgman technique using in-house zone refined precursor materials (Cd, Zn, and Te). A state-of-the-art computer model, multizone adaptive scheme for transport and phase-change processes (MASTRAP), is used to model heat and mass transfer in the Bridgman growth system and to predict the stress distribution in the as-grown CZT crystal and optimize the thermal profile. The model accounts for heat transfer in the multiphase system, convection in the melt, and interface dynamics. The grown semi-insulating (SI) CZT crystals have demonstrated promising results for high-resolution room-temperature radiation detectors due to their high dark resistivity (ρ≈2.8 × 10¹¹ Θ cm), good charge-transport properties [electron and hole mobility-life-time product, μτ_e≈(2–5)×10⁻³ and μτ_h≈(3–5)×10⁻⁵ respectively, and low cost of production. Spectroscopic ellipsometry and optical transmission measurements were carried out on the grown CZT crystals using two-modulator generalized ellipsometry (2-MGE). The refractive index n and extinction coefficient k were determined by mathematically eliminating the ∼3-nm surface roughness layer. Nuclear detection measurements on the single-element CZT detectors with ²⁴¹Am and ¹³⁷Cs clearly detected 59.6 and 662 keV energies with energy resolution (FWHM) of 2.4 keV (4.0%) and 9.2 keV (1.4%), respectively.     

Dual‐Transmission‐Line Microstrip Equiripple Lowpass Filter with Sharp Roll‐Off

A novel application of a dual‐transmission line is proposed to design a lowpass filter (LPF). The proposed structure uses only transmission line elements to produce an equiripple LPF response with sharp roll‐off. Design equations are derived using a lossless transmission line model. Controlling the electrical lengths, three transmission‐zeros are realized in the stopband to obtain a sharp roll‐off rate and wide stopband bandwidth. A single unit microstrip LPF with a 3‐dB cut‐off frequency at 1.0 GHz having a roll‐off of 135 dB/GHz along with a stopband bandwidth of 69.5% is designed for validation.     

Design of compact two-port dual-band dual-polarized MIMO antenna for CBRS and WLAN sub-6-GHz applications

This communication presents a compact field de-correlation lines integrated dual band with dual-polarized (LP & CP) multiple-input multiple-output (MIMO) antenna for the fifth generation (5G) sub-6-GHz wireless communication systems. Dual working bandwidths, smaller interelement gaps, and superior isolation within the MIMO components are the distinguishing characteristics that give the proposed MIMO system an aspect of novelty. The modeled MIMO antenna has compact configurations of 20 × 21 × 0.8 mm³. The unit cell consists of a microstrip feed line with optimized rectangular slots branches etched from the radiated patch. The MIMO module is generated by the antiparallel replication of a single unit cell. To enhance the isolation, two rectangular slots are incorporated on the patch between the unit elements, which act as field de-correlation lines. The MIMO identity is supported by diversity performance calculations in terms of ECC, DG, and TARC. Simulated and measured counterparts are found in the agreement.