In this communication, we study the optical response of a semiconductor quantum dot (SQD) coupled with a metal nanoparticle (MNP). In particular, we explore the relationship between the size of the constituents and the response of the system. We identify, here, three distinct regimes of behavior in the strong field limit that each exhibit novel properties. In the first regime, we find that the energy absorption spectrum displays an asymmetrical Fano shape (as previously predicted). It occurs when there is interference between the applied field and the induced field produced by the SQD at the MNP. When the coupling is increased by increasing the size of the SQD, we find a double peaked Fano structure in the response. This second peak occurs when the induced field becomes stronger than the external field. As the coupling is further increased by increasing the sizes of both the SQD and the MNP, we find a regime of bistability. This originates when the self-interaction of the SQD becomes significant. We explo...

http://absimage.aps.org/image/MAR09/MWS_MAR09-2008-005780.pdf

Optical Response of Strongly Coupled Quantum Dot-Metal Nanoparticle Systems: Double Peaked Fano Structure and Bistability

InAs/(In,Ga)Sb type-II strained layer superlattices (T2SLs) have made significant progress since they were first proposed as an infrared (IR) sensing material more than three decades ago. Numerous theoretically predicted advantages that T2SL offers over present-day detection technologies, heterojunction engineering capabilities, and technological preferences make T2SL technology promising candidate for the realization of high performance IR imagers. Despite concentrated efforts of many research groups, the T2SLs have not revealed full potential yet. This paper attempts to provide a comprehensive review of the current status of T2SL detectors and discusses origins of T2SL device performance degradation, in particular, surface and bulk dark-current components. Various approaches of dark current reduction with their pros and cons are presented.

/pdf/inas-gasb-type-ii-superlattice-detectors-a5m5m0wdca.pdf

InAs/GaSb Type-II Superlattice Detectors

The performance of microwave devices mainly depends on the properties of materials used in the fabrication. Knowledge of material properties at microwave frequencies is a prerequisite to select suitable materials for various microwave applications and vice versa. In this review, seven categories of materials and their applications in a microwave regime are elaborately discussed. The categories include magnetic materials, carbon-based materials, flexible or stretchable materials, biomaterials, phantoms, tunable materials and metamaterials. A brief overview of other important microwave materials such as low-loss ceramic dielectric materials, low-loss polymer ceramic composites, glass ceramics and multilayer ceramics is also given. The objective of this review is to expose the world of materials for wide microwave applications and thereby properly assisting the material selection for specific applications. Moreover, this review has dual significance. It helps material scientists to develop new materials and modify the properties of the available materials with respect to the application requirements. It also assists microwave engineers to select and use appropriate materials for different microwave applications.

/pdf/applications-of-microwave-materials-a-review-4f9hm7lwau.pdf

Applications of Microwave Materials: A Review

The increasing demand for realizing ultra-fast, compact, and ultra-low power electronics/spintronics has propelled the creation of novel multiferroic heterostructures which enable voltage control of magnetism in an energy efficient way. In this progress report, we present an overview of recent advances and future prospects of the most attractive oxide multiferroic heterostructures, with an emphasis on the development of strong magnetoelectric coupling effects and their device applications. In particular, we review the recent progress in spinel/ferroelectric and garnet/ferroelectric multiferroic oxide heterostructures.

Recent advances in multiferroic oxide heterostructures and devices

A tunable active inductor is presented where the novel topology enables both the inductance and series resistance to be varied. With a discrete MMIC realization of this active inductor, Q-factors in excess of 15 000 have been measured over a wide range of inductance values. Applications for these active inductors include high-performance narrow-band filters, voltage controlled oscillators, and analog phase shifters. Analytical equations for the novel active inductor and a 3-resonator filter are given. The measured performance for a monolithic 2 GHz filter achieves a mean insertion loss of 0.9 dB, passband ripple of ±0.7 dB, with a 3 dB bandwidth of 70 MHz, and an excellent out-of-band rejection which exceeds 50 dB up to 18 GHz

Monolithic narrow-band filter using ultrahigh-Q tunable active inductors

We report new high quality factor (Q) integrated GHz magnetic inductors based on solenoid structures with FeGaB/Al2O3 multilayer films, which show significantly enhanced inductance and quality factor at GHz frequencies over their air core counterparts. These inductors show an excellent high-frequency performance with a wide operation frequency range 0.5-2.5 GHz, in which the inductance is flat and the peak quality factor can reach ~20. The inductance of the magnetic inductor shows >100% enhancement compared with that of the same size air core inductor. These novel GHz inductors with high inductance and Q enhancement show great promise for applications in radio frequency integrated circuits.

Significantly Enhanced Inductance and Quality Factor of GHz Integrated Magnetic Solenoid Inductors With FeGaB/ ${\rm Al}_{2}{\rm O}_{3}$ Multilayer Films

The effect of interface composition control on interfacial strain distribution in InAs/GaSb superlattices on (100)-GaSb substrates is investigated by atomic resolution scanning transmission electron microscopy. The interface composition was controlled by either depositing InSb at each interface or soaking the GaSb-on-InAs interface under Sb2 atmosphere. The strain profiles reveal a distinct difference in the extent to which the superlattice strain is balanced using the two methods. In particular, they indicate that the degree of strain balance achievable with soaking is inherently limited by the arsenic surface coverage during GaSb-on-InAs interface formation, emphasizing the influence of V/III flux ratio at this interface. The results also explain observed X-ray diffraction profiles.

Strain analysis of compositionally tailored interfaces in InAs/GaSb superlattices

Metal nanoparticles coupled to semiconductor quantum dots have been studied recently due to the enhancement in absorption, emission, and nonlinearities expected from these hybrid structures. These properties stem from the ability of the metal to focus light as well as shift the phase, which occurs at the metal–dielectric interface. To date, most quantum dots metal nanoparticle couples are formed by the attachment of a ligand to both particles. The extension of this idea to bulk semiconductor films is being attempted by the formation of a composite structure of ErAs, which forms semimetallic nanoparticles (SMNP) in GaAs, and InAs self-assembled quantum dots (SAQD). In this work, the authors analyze structures composed of periods of InAs SAQDs and ErAs SMNPs and analyze these with spectroscopic ellipsometry in the spectral region 0.7–4.0 eV with 0.02 eV steps. Initially, individual structures composed of InAs SAQD stacks or ErAs SMNP stacks, both capped with layers of GaAs, are analyzed. The authors have al...

Growth and spectroscopic ellipsometry evaluation of composite layers of ErAs and InAs nanoparticles

We develop a technique for accurately measuring thickness of planar InAs films grown on (001) GaAs by spectroscopic ellipsometry, using bulk optical constants. We observe that the critical point structure for the E1 and E1 + Δ1 transitions extracted from the measured dielectric properties varies with strain in the layer. Transmission electron microscopy confirms the extracted thickness and measures the residual strain based on the dislocation spacing in the film. At small thickness, the E1 critical point is seen to markedly deviate from the dependence predicted by deformation potential theory and appears to be consistent with additional quantum confinement effects.

Andrew Aronow

Papers

Significantly Enhanced Inductance and Quality Factor of GHz Integrated Magnetic Solenoid Inductors With FeGaB/ ${\rm Al}_{2}{\rm O}_{3}$ Multilayer Films

Strain analysis of compositionally tailored interfaces in InAs/GaSb superlattices

Growth and spectroscopic ellipsometry evaluation of composite layers of ErAs and InAs nanoparticles

Evaluation of thickness and strain of thin planar layers of InAs on GaAs(001) using spectroscopic ellipsometry