Influence of Co super 60 gamma irradiation on the surface and bulk recombination rates in silicon.
Cobalt 60 gamma irradiation effects on P doped p- and n-type Si surface and bulk recombination rates
Lade, R. W.↗
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The presence of deep levels in ion implanted junctions.
Deep trapping levels caused by ion implantation doping, discussing level effects on electrical characteristics of zinc implanted GaAs diodes
Hunsperger, R. G.↗
Electron-paramagnetic-resonance investigation of the dynamic Jahn-Teller effect in SrC12-La/2 plus/
Electron paramagnetic resonance spectral investigation of dynamic Jahn-Teller effect in La doped strontium chloride, discussing structural variations as function of temperature
Boatner, L. A.↗
Correlations and alloy properties - Growth, vacancies, surface segregation
The aspects of bonding interaction mechanisms which have an impact on the correlation state of alloy semiconductors are demonstrated. The effect of the correlation state on liquidus and solidus curves, on surface segregation, and on vacancy densities is deduced. Vacancy energies for several alloys are presented, and tentative conclusions are drawn about their effects on diffusion, doping, and ion beam processing. Features of the theory of surface segregation in semiconductor alloys are then presented.
Sher, A.↗
Oxygen Tracer Diffusion in LA(z-x) SR(X) CUO(4-y) Single Crystals
The tracer diffusion of O-18 in La(2-x)Sr(x)CuO(4-y) single crystals (x = 0 to 0.12) has been measured from 400 to 700 C in 1 atm of oxygen using SIMS analysis. Evidence for diffusion by a vacancy mechanism was found at low strontium contents. Oxygen diffusivities for x greater than or = 0.07 were depressed by several orders of magnitude below the diffusivity for undoped La2CuO(4+/-y). The observed effects of strontium doping on oxygen diffusivity are discussed in terms of defect chemical models. The decreasing oxygen diffusivity with increasing strontium was attributed to the ordering of oxygen vacancies at large defect concentrations. A diffusion anisotropy D(sub ab)/D(sub c) of nearly 600 was also found at 500 C.
OXYGEN DIFFUSIVITY↗
A Comprehensive Analysis of the Physical Properties of Advanced GaAs/AlGaAs Junctions
Extensive studies have been performed on MQW junctions and structures because of their potential applications as avalanche photodetectors in optical communications and imaging systems. The role of the avalanche photodiode is to provide for the conversion of an optical signal into charge. Knowledge of junction physics, and the various carrier generation/recombination mechanisms, is crucial for effectively optimizing the conversion process and increasing the structure's quantum efficiency. In addition, the recent interest in the use of APDs in imaging systems has necessitated the development of semiconductor junctions with low dark currents and high gains for low light applications. Because of the high frame rate and high pixel density requirements in new imaging applications, it is necessary to provide some front-end gain in the imager to allow operation under reasonable light conditions. Understanding the electron/hole impact ionization process, as well as diffusion and surface leakage effects, is needed to help maintain low dark currents and high gains for such applications. In addition, the APD must be capable of operating with low power, and low noise. Knowledge of the effects of various doping configurations and electric field profiles, as well as the excess noise resulting from the avalanche process, are needed to help maintain low operating bias and minimize the noise output.
Menkara, Hicham M.↗
Thermal emitter comprising near-zero permittivity materials
A novel thermal source comprising a semiconductor hyperbolic metamaterial provides control of the emission spectrum and the angular emission pattern. These properties arise because of epsilon-near-zero conditions in the semiconductor hyperbolic metamaterial. In particular, the thermal emission is dominated by the epsilon-near-zero effect in the doped quantum wells composing the semiconductor hyperbolic metamaterial. Furthermore, different properties are observed for s and p polarizations, following the characteristics of the strong anisotropy of hyperbolic metamaterials.
36 MATERIALS SCIENCE↗
Effect of MgO shell on electron transfer from Cu doped ZnInS quantum dots to FePt nanoparticles
Highlights: • MgO-coated FePt NPs were synthesized using 4 nm FePt cores as seeds for the growth of MgO shell. • Significant PL quenching took place in Cu doped ZnInS QD-FePt NP system owing to photoexcited electron transfer. • The formation of interfacial MgO barriers could efficiently restrain the electron transfer at QD-FePt interface. - Abstract: The effect of MgO shell on the electron transfer between luminescent Cu doped ZnInS quantum dots (QDs) and magnetic FePt/MgO core/shell nanoparticles (NPs) was studied by using steady-state and time-resolved photoluminescence (PL) spectroscopy. MgO-coated FePt NPs were synthesized using 4 nm FePt cores as seeds for the growth of MgO shell, having a reduced saturation magnetization Ms compared to the pure FePt NPs. It was found that the shortening in PL lifetime of Cu doped ZnInS QDs induced by FePt NPs demonstrated an electrons transfer process from excited QDs to the adjacent FePt NPs. When FePt NPs were coated with a MgO shell, the low work function of MgO shell resulted in a formation of higher interfacial barriers between Cu doped ZnInS QDs and FePt NPs, significantly suppressing the electron transfer at Cu doped ZnInS QD-FePt NP interface.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Dodecaborane‐Based Dopants Designed to Shield Anion Electrostatics Lead to Increased Carrier Mobility in a Doped Conjugated Polymer
Abstract One of the most effective ways to tune the electronic properties of conjugated polymers is to dope them with small‐molecule oxidizing agents, creating holes on the polymer and molecular anions. Undesirably, strong electrostatic attraction from the anions of most dopants localizes the holes created on the polymer, reducing their mobility. Here, a new strategy utilizing a substituted boron cluster as a molecular dopant for conjugated polymers is employed. By designing the cluster to have a high redox potential and steric protection of the core‐localized electron density, highly delocalized polarons with mobilities equivalent to films doped with no anions present are obtained. AC Hall effect measurements show that P3HT films doped with these boron clusters have conductivities and polaron mobilities roughly an order of magnitude higher than films doped with F 4 TCNQ, even though the boron‐cluster‐doped films have poor crystallinity. Moreover, the number of free carriers approximately matches the number of boron clusters, yielding a doping efficiency of ≈100%. These results suggest that shielding the polaron from the anion is a critically important aspect for producing high carrier mobility, and that the high polymer crystallinity required with dopants such as F 4 TCNQ is primarily to keep the counterions far from the polymer backbone.
Aubry, Taylor J.↗
Catalytic Ammonia Synthesis over Pure, Defective, and Metal-Doped Rutile TiO 2 : A Periodic DFT Study
In this work, we aim to describe the energetics associated with the formation of ammonia from N 2 interacting with doped hydroxylated rutile TiO 2 (110) surfaces with the vacant O 2c site, following the reaction N 2 + 3H 2 O → 2NH 3 + 3/2O 2 . The water molecules interact with the surface, creating exposed Ti−OH groups that can transfer hydrogen to the adsorbed N 2 molecule. Two metal dopants are evaluated: Mo and Ta. For both metals, calculations show a dramatic decrease in the energy of most intermediates during the entire mechanism, leading to more favorable reaction mechanisms. Nonetheless, it is worth noting that when the Ti 6c site of the vacant site is doped with either Mo or Ta, there is a stronger effect on the energetics than doping on the exposed Ti 5c sites. The effect of increasing the concentration of metal dopants on the vacant site was also investigated. In this case, calculations indicate that a higher percentage of the dopant on the surface results in a more substantial decrease in the energy of most intermediates, suggesting that increasing the dopant content could be beneficial for the catalytic process.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Structural and phonon anomalies in the superconducting Bi 2 Sr 2 CaCu 2 O 8+σ with varying doping level at high pressures
Here we examined the effect of the lattice compression on the crystal structure of the Bi 2 Sr 2 CaCu 2 O 8+σ superconductor with nearly optimally doped and overdoped composition using X-ray diffraction technique. Our studies show that at high pressures (up to 30 GPa ) the doping level does not affect the crystal structure of this superconductor. Along with this, structural anomalies in ratio appear at a pressure that corresponds to that at which T c begins to decrease. This fact indicates a close connection between the observed anomalies and superconductivity. We also studied the effect of doping and pressure on the T c (P) and on the Raman active lattice modes of the Bi 2 Sr 2 CaCu 2 O 8+σ superconductors. We find universal suppression of the T c by the pressure starting from the critical pressure P c in the range from 9 to 16 GPa, depending on the doping level of the Bi 2 Sr 2 CaCu 2 O 8+σ samples. Concomitantly, we observe phonon anomalies around 10 to 20 GPa, which indicate possible pressure-induced charge redistribution in BiO layers. These newly detected anomalies may be related to the changes in the electronic structure which compete with the superconductivity.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Effect of Reaction Parameters on Morphology and Photoluminescence of Intrinsic and Mn-doped ZnS Microspheres Synthesized by Hydrothermal Method
Intrinsic and Manganese (Mn)-doped ZnS microspheres have been synthesized by hydrothermal method. Thiourea and amino acid, and L-histidine have been used as sulfur source and capping agent, respectively. The synthesized materials have been characterized using x-ray diffraction, field emission scanning electron microscopy, photoluminescence (PL) and UV–Vis spectroscopy. The above-said characterizations conveyed the information regarding the crystallinity, existence of microspheres, size and optical properties of synthesized ZnS and Mn-doped ZnS samples. Formation of microspheres of intrinsic and Mn-doped ZnS has been observed when the reaction parameters are kept at 150 °C for 4 h, and similarly, the micropores have been noticed when reaction parameters are kept at 150 °C for 8 h. The PL of ZnS microspheres shows multiple defect emissions. The nature of PL for pure ZnS has been regulated based on reaction parameters. Doping of Mn in the ZnS enhances the PL emission. This study reveals the role of reaction parameters and effect of Mn doping on tuning the morphology and emission behavior of ZnS microspheres.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Revisiting the role of Zr doping in Ni-rich layered cathodes for lithium-ion batteries
We report the realization of high performance Ni-rich layered cathodes remains a challenge because of the multiple degradation factors that concurrently operate during battery cycling. In particular, depletion of oxygen charge and consequent lattice oxygen instability at deep charge state accelerate the subsequent chemomechanical degradation mechanisms. Among the proposed methodologies, doping has proven to be effective in enhancing the cathode cycle life by stabilizing the layered structure. Herein, we achieved the electrochemically stabilized Ni-rich LiNi 0.92 Co 0.04 Mn 0.04 O 2 through Zr doping, resulting in a 15% increase of the capacity retention after 100 cycles. In-depth investigations are conducted to unveil the effects of Zr doping on the layered cathode, and in particular, the critical role of Zr doping on the lattice oxygen stability is systematically studied. By combining state-of-the-art magnetometer characterization, X-ray analysis, and first-principles calculation, we reveal that Zr doping positively contributes the to lattice oxygen stability by alleviating the oxygen charge loss at deep charge, thereby improving the cathode electrochemical reversibility. Our findings provide an insight into the Zr doping mechanism and help to design the Ni-rich layered oxides for future applications.
25 ENERGY STORAGE↗
Influence of fluorine doped CdO thin films by an simplified spray pyrolysis technique using nebulizer
The Cadmium oxide (CdO) and Fluorine (F) doped CdO thin films were effectively synthesized on glass substrates for different F doping concentrations (2, 4, 6, 8 at.%) using nebulized spray pyrolysis technique. The XRD analysis showed that all the films were polycrystalline having cubic structure with (111) preferential orientation. It was seen from the SEM photographs that the doping causes remarkable changes in the surface morphology. EDAX analysis clearly confirmed that the presence of expected elements cadmium, oxygen and fluorine in the final product, in appropriate proportions. The electrical study showed that the minimum resistivity value of 1.9 × 10{sup −4} Ω cm with notable higher values of carrier concentration and mobility was achieved for 6 at.% of CdO:F film. Optical study exhibited that the band gap value of CdO film increases gradually with the increase in F-doping concentration, reaching maximum band gap value of 2.61 eV at 6 at.% and starts decreasing thereafter. Photoluminescence spectra depicted that the intensity of the emission peaks was significantly varied with doping concentrations. The high transparency, wide band gap energy, enhanced electrical properties and light sensitivity had been obtained infer that F-doped CdO thin films which find application in optoelectronic applications. Graphical abstract: .
36 MATERIALS SCIENCE↗
Spontaneous Hall effects in the electron system at the SmTiO 3 /EuTiO 3 interface
Magnetotransport and magnetism of epitaxial SmTiO 3 /EuTiO 3 heterostructures grown by molecular beam epitaxy are investigated. It is shown that the polar discontinuity at the interface introduces ~3.9 × 10 14 cm -2 carriers into the EuTiO 3 . The itinerant carriers exhibit two distinct contributions to the spontaneous Hall effect. The anomalous Hall effect appears despite a very small magnetization, indicating a non-collinear spin structure, and the second contribution resembles a topological Hall effect. Qualitative differences exist in the temperature dependence of both Hall effects when compared to uniformly doped EuTiO 3 . In particular, the topological Hall effect contribution appears at higher temperatures and the anomalous Hall effect shows a sign change with temperature. The results suggest that interfaces can be used to tune topological phenomena in itinerant magnetic systems.
36 MATERIALS SCIENCE↗
Diffusion length measurement using the scanning electron microscope
The present work describes a measuring technique employing the scanning electron microscope in which values of the true bulk diffusion length are obtained. It is shown that surface recombination effects can be eliminated through application of highly doped surface field layers. The effects of high injection level and low-high junction current generation are investigated. Results obtained with this technique are compared to those obtained by a penetrating radiation (X-ray) method, and a close agreement is found. The SEM technique is limited to cells that contain a back surface field layer.
Weizer, V. G.↗
Toward a systematic design theory for silicon solar cells using optimization techniques
This work is a first detailed attempt to systematize the design of silicon solar cells. Design principles follow from three theorems. Although the results hold only under low injection conditions in base and emitter regions, they hold for arbitrary doping profiles and include the effects of drift fields, high/low junctions and heavy doping concentrations of donor or acceptor atoms. Several optimal designs are derived from the theorems, one of which involves a three-dimensional morphology in the emitter region. The theorems are derived from a nonlinear differential equation of the Riccati form, the dependent variable of which is a normalized recombination particle current.
Misiakos, K.↗
Insights into Ti doping for stabilizing the Na 2/3 Fe 1/3 Mn 2/3 O 2 cathode in sodium ion battery
Iron- and manganese-based layered metal oxides, as cathodes for sodium ion batteries, have received widespread attention because of the low cost and high specific capacity. However, the Jahn-teller effect of Mn 3+ ions and the resulted unstable structure usually lead to continuously capacity decay. Herein, Titanium (Ti) has been successfully doped into Na 2/3 Fe 1/3 Mn 2/3 O 2 to suppress the Jahn-Teller distortion and improve both cycling and rate performance of sodium ion batteries. In situ high-energy synchrotron X-ray diffraction study shows that Ti-doped compound (Na 2/3 Fe 1/3 Mn 0.57 Ti 0.1 O 2 ) can maintain the single P2 phase without any phase transition during the whole charging/discharging process. Further, various electrochemical characterizations are also applied to explore the better kinetics of sodium ions transfer in the Na 2/3 Fe 1/3 Mn 0.57 Ti 0.1 O 2 . This work provides a comprehensive insight into the Ti-doping effects on the performance from both structural and electrokinetic perspectives.
25 ENERGY STORAGE↗