Ternary Material System Research Articles

A 16.4% efficiency organic photovoltaic cell enabled using two donor polymers with their side-chains oriented differently by a ternary strategy

A ternary material system featuring two donor polymers with identical absorption spectra and differently-oriented side-chains was used in an organic photovoltaic (OPV) cell. It is the first ternary blended OPV cell with two donor polymers with >16% efficiency.

Development of Self-Healable Organic/Inorganic Hybrid Materials Containing a Biobased Copolymer via Diels-Alder Chemistry and Their Application in Electromagnetic Interference Shielding.

In this study, a novel biobased poly(ethylene brassylate)-poly(furfuryl glycidyl ether) copolymer (PEBF) copolymer was synthesized and applied as a structure-directing template to incorporate graphene and 1,1′-(methylenedi-4,1-phenylene)bismaleimide (BMI) to fabricate a series of self-healing organic/inorganic hybrid materials. This ternary material system provided different types of diene/dienophile pairs from the furan/maleimide, graphene/furan, and graphene/maleimide combinations to build a crosslinked network via multiple Diels–Alder (DA) reactions and synergistically co-assembled graphene sheets into the polymeric matrix with a uniform dispersibility. The PEBF/graphene/BMI hybrid system possessed an efficient self-repairability for healing structural defects and an electromagnetic interference shielding ability in the Ku-band frequency range. We believe that the development of the biobased self-healing hybrid system provides a promising direction for the creation of a new class of materials with the advantages of environmental friendliness as well as durability, and shows potential for use in advanced electromagnetic applications.

An ultrathin carbon layer activated CeO2 heterojunction nanorods for photocatalytic degradation of organic pollutants

Designing and constructing effective and stable photocatalysts is the major challenge in the development of photocatalysis. Herein, we demonstrate a conceptual strategy to effectively improve the charge separation in a ternary material system (CeO2/C/SnS2), by introducing ultrathin carbon layer between CeO2 nanorods and SnS2 particles as a conductive electron transport “highway”. Such ternary CeO2/C/SnS2 gives rise to a largely enhanced photocatalytic removal performance of phenol (100%, 60 min), comparing with CeO2/SnS2 (50%) and CeO2 (20%). Experimental results reveal that carbon layer acts as a high work function, superior electron mobility accepts and enables a fast transportation, accelerating the photocatalytic degradation performance of phenol. Our design introduces material components to provide a dedicated charge-transport pathway, conquering the materials’ intrinsic properties, providing a new perspective for water purity.

Evolution of the Length and Radius of Catalyst-Free III-V Nanowires Grown by Selective Area Epitaxy.

We present a new model for the length and radius evolution of catalyst-free III–V nanowires grown by selective area epitaxy. We consider simultaneous axial and radial growth of nanowires, which is more typical for this technique compared to the vapor−liquid−solid growth of nanowires. Analytic expressions for the time evolution of the nanowire length and radius are derived, showing the following properties. As long as the nanowire length is shorter than the collection length of group III atoms on the sidewalls, the length evolves superlinearly and the radius evolves linearly with time. For longer nanowires, both the length and radius increase sublinearly with time. The scaling growth laws are controlled by a single parameter that depends on group V flux. The model fits well the data on the selective area growth of InAs and GaAs nanowires by different techniques. Overall, these results can be used for controlling the catalyst-free growth of III–V nanowires and their morphology, including ternary III–V material systems.

Unique Energy Alignments of a Ternary Material System toward High-Performance Organic Photovoltaics.

Incorporating narrow-bandgap near-infrared absorbers as the third component in a donor/acceptor binary blend is a new strategy to improve the power conversion efficiency (PCE) of organic photovoltaics (OPV). However, there are two main restrictions: potential charge recombination in the narrow-gap material and miscompatibility between each component. The optimized design is to employ a third component (structurally similar to the donor or acceptor) with a lowest unoccupied molecular orbital (LUMO) energy level similar to the acceptor and a highest occupied molecular orbital (HOMO) energy level similar to the donor. In this design, enhanced absorption of the active layer and enhanced charge transfer can be realized without breaking the optimized morphology of the active layer. Herein, in order to realize this design, two new narrow-bandgap nonfullerene acceptors with suitable energy levels and chemical structures are designed, synthesized, and employed as the third component in the donor/acceptor binary blend, which boosts the PCE of OPV to 11.6%.

A low temperature co-fired ceramic power inductor manufactured using a glass-free ternary composite material system

A glass-free ternary composite material system (CMS) manufactured employing the low temperature (890 °C) co-fired ceramic (LTCC) technique is reported. This ternary CMS consists of silver, NiCuZn ferrite, and Zn2SiO4 ceramic. The reported device fabricated from this ternary CMS is a power inductor with a nominal inductance of 1.0 μH. Three major highlights were achieved from the device and the material study. First, unlike most other LTCC methods, no glass is required to be added in either of the dielectric materials in order to co-fire the NiCuZn ferrite, Zn2SiO4 ceramic, and silver. Second, a successfully co-fired silver, NiCuZn, and Zn2SiO4 device can be achieved by optimizing the thermal shrinkage properties of both NiCuZn and Zn2SiO4, so that they have a very similar temperature shrinkage profile. We have also found that strong non-magnetic elemental diffusion occurs during the densification process, which further enhances the success rate of manufacturing co-fired devices. Last but not least, elemental mapping suggests that strong magnetic elemental diffusion between NiCuZn and Zn2SiO4 has been suppressed during the co-firing process. The investigation of electrical performance illustrates that while the ordinary binary CMS based power inductor can deal with 400 mA DC, the ternary CMS based power inductor is able to handle higher DC currents, 700 mA and 620 mA DC, according to both simulation and experiment demonstrations, respectively.

Unique Energy Alignments of a Ternary Material System toward High-Performance Organic Photovoltaics

Unique Energy Alignments of a Ternary Material System toward High-Performance Organic Photovoltaics

High-Strength Nanocomposite Aerogels of Ternary Composition: Poly(vinyl alcohol), Clay, and Cellulose Nanofibrils.

Clay aerogels are foam-like materials with potential to combine high mechanical performance with fire retardancy. However, the compression strength of these aerogels is much lower than theoretically predicted values. High-strength aerogels with more than 95% porosity were prepared from a ternary material system based on poly(vinyl alcohol), montmorillonite clay platelets, and cellulose nanofibrils. A hydrocolloidal suspension of the three components was subjected to freeze-drying so that a low-density aerogel foam was formed. Cell structure was studied by field-emission scanning electron microscopy. Interactions at the molecular scale were observed by X-ray diffraction and Fourier transform infrared spectroscopy. Cross-linking was carried out using glutaraldehyde or borax, and moisture stability was investigated. These biobased ternary aerogels showed compression strength much better than that of previously studied materials and also showed strength higher than that of high-performance sandwich foam cores such as cross-linked polyvinyl chloride foams.

Electrodeposition of textured Bi27Sb28Te45 nanowires with enhanced electrical conductivity

This work presents the template based pulsed potential electrodeposition technique of highly textured single crystalline bismuth antimony telluride (Bi1-xSbx)2Te3 nanowires from a single aqueous electrolyte. Cyclic voltammetry was used as an electroanalytical tool to assess the effect of the precursor concentrations on the composition of the deposits and to determine the deposition potential for each element. Pulsed potential electrodeposition was then applied on a gold-coated anodised alumina template to examine the effect of the pulse parameters on the composition and texture of Bi27Sb28Te45 nanowires. The nanowires are cylindrical in shape formed during the deposition inside the porous template and highly textured as they are decorated with sparse distribution of small crystal domains. The electrical conductivity (24.1 × 104 S m−1) of a single nanowire was measured using a four-point probe technique implemented on a custom fabricated test chip. In this work, we demonstrated that crystal orientation with respect to the transport direction controlled by tuning the pulsed electrodeposition parameters. This allowed us to realise electrical conductivities ∼2.5 times larger than Sb doped bismuth-tellurium based ternary material systems and similar to what is typically seen in binary systems.

Influence of Droplet Size on the Growth of Self-Catalyzed Ternary GaAsP Nanowires.

The influences of droplet size on the growth of self-catalyzed ternary nanowires (NWs) were studied using GaAsP NWs. The size-induced Gibbs-Thomson (GT) effect makes the smaller catalytic droplets have lower effective supersaturations and hence slower nucleation rates than the larger ones. Large variation in droplet size thus led to the growth of NWs with low uniformity, while a good size uniformity of droplets resulted in the production of highly uniform NWs. Moreover, thinner NWs were observed to be richer in P, indicating that P is more resistant to the GT effect than As because of a higher chemical potential inside Ga droplets. These results provide useful information for understanding the mechanisms of self-catalyzed III-V NW nucleation and growth with the important ternary III-V material systems.

MOCVD grown HgCdTe barrier detectors for MWIR high-operating temperature operation

In the last decade, new architecture designs such as nBn devices or unipolar barrier photodiodes have been proposed to achieve high-operating temperature (HOT) detectors. This idea has been also implemented in HgCdTe ternary material systems. However, the implementation of this detector structure in an HgCdTe material system is not straightforward due to the existence of a valence band discontinuity (barrier) at the absorber-barrier interface. We report on midwavelength infrared HgCdTe barrier detectors with a zero valence band offset, grown by metal organic chemical vapor deposition on GaAs substrates. The experiments indicate the influence of the barrier on the electrical and optical performances of the p+BpnN+ device. The devices exhibit very low-dark current densities in the range of (2−3)×10−3 A/cm2 at 230 K and a high-current responsivity of about 2 A/W in the wide range of reverse bias voltage. The estimated thermal activation energy of about 0.33 eV is close to the full Hg0.64Cd0.36Te bandgap, which indicates diffusion limited dark currents.

Absorption properties of type-II InAs/InAsSb superlattices measured by spectroscopic ellipsometry

Strain-balanced InAs/InAsSb superlattices offer access to the mid- to long-wavelength infrared region with what is essentially a ternary material system at the GaSb lattice constant. The absorption coefficients of InAs/InAsSb superlattices grown by molecular beam epitaxy on (100)-oriented GaSb substrates are measured at room temperature over the 30 to 800 meV photon energy range using spectroscopic ellipsometry, and the miniband structure of each superlattice is calculated using a Kronig-Penney model. The InAs/InAsSb conduction band offset is used as a fitting parameter to align the calculated superlattice ground state transition energy to the measured absorption onset at room temperature and to the photoluminescence peak energy at low temperature. It is observed that the ground state absorption coefficient and transition strength are proportional to the square of the wavefunction overlap and the ground state absorption coefficient approaches a maximum value of around 5780 cm−1 as the wavefunction overlap approaches 100%. The absorption analysis of these samples indicates that the optical joint density of states is weakly dependent on the period thickness and Sb content of the superlattice, and that wavefunction overlap is the principal design parameter in terms of obtaining strong absorption in these structures.

Molecular beam epitaxy using bismuth as a constituent in InAs and a surfactant in InAs/InAsSb superlattices

Alloying bismuth with InAs provides a ternary material system near the 6.1 Å lattice constant, which covers the technologically important mid- and long-wavelength infrared region. One challenge for this material system is that it is not straightforward to incorporate bismuth into the bulk InAs lattice, since bismuth has a tendency to surface-segregate and form droplets during growth. In this work, the conditions for InAsBi growth using molecular beam epitaxy are explored. A growth window is identified (temperatures ⪞ 270 °C, V/III flux ratios 0.98 ⪝ As/In ⪝ 1.02, and Bi/In ≅ 0.065) for droplet-free, high-quality crystalline material, where InAsBi layers with compositions of up to 5.8% bismuth (nearly lattice-matched to GaSb) are attained. The structural quality of InAsBi bulk and quantum well samples is evaluated using x-ray diffraction and transmission electron microscopy. The optical quality is assessed using photoluminescence, which is observed from quantum well structures up to room temperature and from thick, low Bi-content bulk layers at low temperatures. Bismuth is also used as a surfactant during the growth of InAs/InAsSb superlattices at 430 °C where it is observed that a small bismuth flux changes the surface reconstruction of InAs from (2×1) to (1×3), reduces the sticking coefficient of antimony, results in a slight increase in photoluminescence intensity, does not significantly incorporate, and does not alter the surface morphology.

Interface Reactions and Synthetic Reaction of Composite Systems

Interface reactions in composite systems often determine their overall properties, since product phases usually formed at interfaces during composite fabrication processing make up a large portion of the composites. Since most composite materials represent a ternary or higher order materials system, many studies have focused on analyses of diffusion phenomena and kinetics in multicomponent systems. However, the understanding of the kinetic behavior increases the complexity, since the kinetics of each component during interdiffusion reactions need to be defined for interpreting composite behaviors. From this standpoint, it is important to clarify the interface reactions for producing compatible interfaces with desired product phases. A thermodynamic evaluation such as a chemical potential of involving components can provide an understanding of the diffusion reactions, which govern diffusion pathways and product phase formation. A strategic approach for designing compatible interfaces is discussed in terms of chemical potential diagrams and interface morphology, with some material examples.

Kinetic Analysis of InAsP by Metalorganic Vapor Phase Epitaxy Selective Area Growth Technique

The fundamental kinetics of metal organic vapor phase epitaxy (MOVPE) related ternary compound-InAsP has been systematically investigated by analyzing selective area growth. The overall surface reaction rate constant (ks-overal) of indium species in this material system is successfully obtained, it shows a composition dependence in which ks-overall increases with the amount of P in InAs1-xPx. On the basis of binary kinetics of InAs and InP, ks-overall can be estimated from the linear combination of the surface reaction rate constant (ks) in the As site and the ks in the P site. Result shows that the linear estimation of ks-overall is consistent with experimental data, which indicates that the incorporations of indium species in the P and As sites should be almost independent of each other. These results revealed that the real surface process of the ternary material system provides significant information and fundamental concepts for further modeling of more complicated quaternary compounds, such as InGaAsP.

Composition analysis of ternary semiconductors by combined application of conventional TEM and HRTEM

AbstractThe chemical composition of ternary material systems can be determined by a combined analysis of dark‐field imaging and quantitative high‐resolution transmission electron microscopy (qHRTEM). This method is restricted to material systems where on the one hand chemically sensitive reflections occur and on the other hand the material surrounding the nanostructure contains only those atomic species which are also present in the nanostructure. In the developed procedure the dark‐field image intensity is calculated as a function of chemical composition. Additionally, it is taken into consideration that the strained state of the system leads to a change of the symmetry. For analysing the chemically sensitive dark‐field images the composition must be normalized by a known concentration value. The method will be demonstrated for the following system: GaSbxAs1–x quantum dots (QDs) grown by metal‐organic chemical vapour phase deposition (MOCVD) on GaAs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Combinatorial Thin Film Synthesis of Cerium Doped Scintillation Materials in the Lutetium Oxide—Silicon Oxide System

The search for new scintillator crystals can be limited by the time consuming nature of the crystal growth process. In this paper, we demonstrate the use of a combinatorial thin film synthesis technique that is being used to explore new scintillator materials. The combinatorial synthesis process utilizes up to four individual R.F. magnetron sputtering sources which can be simultaneously powered to generate a wide composition space of binary, ternary, or quaternary material systems. In this work, we have investigated the lutetium oxide (Lu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> )-silicon oxide (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) material system doped with cerium. Lu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5-</sub> doped with cerium has been thoroughly characterized due to its use in PET imaging and provides a good benchmark for our proposed approach. Thin film, cerium doped lutetium oxide-silicon oxide gradients were synthesized to investigate the phases of the material system that exhibit scintillation properties and the results were compared to the results of bulk crystal samples. We have found that the emission spectra of the thin film materials have similar characteristics compared to the bulk crystals. Additionally, X-ray diffraction measurements have been correlated to the anticipated phases of the equilibrium phase diagram, and the intensity of the luminescence emission spectra have been correlated with the corresponding phases of the system.

MOVPE growth experiments of the novel (GaIn)(NP)/GaP material system

Highly compressively strained (GaIn)(NP) quantum wells have been grown on (1 0 0) GaP substrates by metal organic vapour-phase epitaxy (MOVPE). We achieve a high structural quality of the grown multiple quantum well structures for this novel, metastable material system. Competition between the group-V elements on the surface determines the N incorporation in Ga(NP) as well as (GaIn)(NP). For the ternary material system Ga(NP) the N content of the deposited layers does not depend on the growth rate in contrast to the quaternary system (GaIn)(NP), where the N incorporation is enhanced with increasing growth rate. This suggests a desorption controlled N incorporation process for the In-containing material. This is in accordance with the strong dependence of the N content in the material from the growth temperature and the In content. In addition — due to the metastability of the material systems under investigation — the maximal achievable N content in Ga(NP) and (GaIn)(NP) is limited when good crystal quality is to be retained.

A fabrication of coupling grating in the polymeric waveguide by using two-photon initiated photopolymerization

A ternary materials system, which comprises two-photon initiator, oligomer and poly(methyl methacrylate), was prepared. A polymeric waveguide film was manufactured by spinning the materials on ITO, and the two-photon initiated photopolymerization (TPIP) was carried out successfully in the waveguide film. Consequently, an approach using TPIP is demonstrated for fabrication of coupling grating in a thin polymeric film possessing waveguide properties. The results show that the incident laser can be coupled into the polymeric film by this coupling grating obtained from TPIP. The microstructure feature of coupling grating is illustrated, and waveguide mode and transmission loss of the polymeric film are investigated.

ITO-Schottky Photodiodes for High-Performance Detection in the UV–IR Spectrum

High-performance vertically illuminated Schottky photodiodes with indium-tin-oxide (ITO) Schottky layers were designed, fabricated, and tested. Ternary and quarternary III-V material systems (AlGaN-GaN, AlGaAs-GaAs, InAlGaAs-InP, and InGaAsP-InP) were utilized for detection in the ultraviolet (UV) (/spl lambda/<400 nm), near-IR (/spl lambda//spl sim/850 nm), and IR (/spl lambda//spl sim/1550 nm) spectrum. The material properties of thin ITO films were characterized. Using resonant-cavity-enhanced (RCE) detector structures, improved efficiency performance was achieved. Current-voltage, spectral responsivity, and high-speed measurements were carried out on the fabricated ITO-Schottky devices. The device performances obtained with different material systems are compared.