The analysis of the current–voltage characteristics of the high barrier Au/Anthracene/n-Si MIS devices at low temperatures

The Au/Anthracene/n-Si/Al MIS device was fabricated on the basis of anthracene film covalently bonded to a Si substrate. The MIS device showed Schottky behavior with barrier heights of 0.85 eV and ideality factors of 1.88 at 300 K. The barrier height of the Au/n-Si has increased after deposition of the anthracene layer onto Si. Temperature dependent current–voltage (I–V) measurements were performed on the Au/Anthracene/n-Si/Al MIS diodes in the range 140–300 K. From the temperature dependence of forward bias I–V, the barrier height was observed to increase with temperature. However, the ideality factor decreased with increasing temperature. The values of activation energy (E_a) and Richardson constant (A*) were determined as 0.24 eV and 7.57 × 10⁻⁶ A cm⁻² K⁻² from the slope and the intercept at ordinate of the linear region of Richardson plot, respectively. The increase of the series resistance R_s with the fall of temperature was attributed to lack of free carrier concentration at low temperatures.     

Design and fabrication of linear pixel arrays for organic photovoltaic modules to achieve scalable power output

We describe a design and fabrication method to enable simpler manufacturing of more efficient organic solar cell modules using a modified flat panel deposition technique. Many mini-cell pixels are individually connected to each other in parallel forming a macro-scale solar cell array. The pixel size of each array is optimized through experimentation to maximize the efficiency of the whole array. We demonstrate that integrated organic solar cell modules with a scalable current output can be fabricated in this fashion and can also be connected in series to generate a scalable voltage output.     

Growth of Ge-Si nanowire heterostructures via chemical vapor deposition

The growth of Ge-Si and Ge-Si nanowire (NW) heterostructures was demonstrated via chemical vapor deposition. Due to the influence of interface energy, differing topographies of the heterostructures were observed. On initially grown Ge NWs, numerous Si NW branches were grown near the tip due to Au migration. However, on initially grown Si NWs, high-density Ge nanodots were observed.     

Characterization of surface roughness anisotropy on mismatched InAIAs/lnP heterostructures

We have studied surface roughness on mismatched In_0.65Al_0.35As epilayers of various thicknesses on (001) InP. The sample set spans the entire range from coherently strained to completely relaxed epilayers. As characterization tools, we have used atomic force microscopy (AFM), laser light scattering (LLS), and variable azimuthal angle ellipsometry (VAAE). AFM reveals that the surfaces are covered by densely packed ellipsoidal islands elongated along the [1-10] direction. The island size increases with layer thickness. Island anisotropy and the root mean square of the surface roughness increase with increasing thickness but decrease upon full lattice relaxation. LLS intensity displays a prominent azimuthal dependence that correlates well with the two-dimensional power spectrum of the surface topography, as predicted by theory. VAAE reveals a sinusoidal dependence of the ellipsometric parameter Δ on azimuthal angle. The amplitude of A correlates well with the short wavelength anisotropy of the surface power spectrum. Our work suggests that LLS and VAAE are fast, nondestructive, sensitive techniques for characterization of surface roughness in mismatched III-V heterostructures.     

Characteristics and uniformity of group V implanted and annealed HgCdTe heterostructure

This work presents characterization of implanted and annealed double layer planar heterostructure HgCdTe for p-on-n photovoltaic devices. Our observation is that compositional redistribution in the structure during implantation/ annealing process differs from that expected from classical composition gradient driven interdiffusion and impacts the placement of the electrical junction with respect to the metallurgical heterointerface, which in turn affects quantum efficiency and R_oA. The observed anomalous interdiffusion results in much wider cap layers with reduced composition difference between base and cap layer composition. The compositional redistribution can, however, be controlled by varying the material structure parameters and the implant/anneal conditions. Examples are presented for dose and implanted species variation. A model is proposed based on the fast diffusion in the irradiation induced damage region of the ion implantation. In addition, we demonstrate spatial uniformity obtained on molecular beam epitaxy (MBE) material of the compositional and implanted species profile. This reflects spatial uniformity of the ion implantation/annealing Processes and of the MBE material characteristics.     

Nonstoichiometry and solubility of impurity in In-doped PbTe films on Si substrates

The chemical quantitative composition, phase constitution, and crystal structure of doped with In lead telluride films on Si (1 0 0) or SiO₂/Si (1 0 0) substrates have been studied in this work. By EPMA and atomic absorption measurements, it has been found that the concentration of In atoms y_In varied from 0.0011 to 0.045 in these deposited Pb_1−yIn_yTe films. The results of EPMA, SEM, and X-ray diffraction (XRD) measurements show that formation of In solid solutions in lead telluride matrix revealed not only in PbTe–InTe cross-section, but in PbTe–In₂Te₃ pseudobinary system also. The results of XRD show that the lattice parameter a_PbTe of PbTeIn/Si and PbTeIn/SiO₂/Si heterostructures is described by nonmonotone function and does not obey the Vegard's law within concentration interval 0.0011y_In0.045.     

Syntheses,Properties, and Potential Applications of Multicomponent Magnetic Nanoparticles

Multicomponent hybrid nanostructures that contain two or more nanometer‐scale components have attracted much attention recently owing to the synergistic properties induced by interactions between these different nanometer‐scale objects. Herein, we give an overview of the efforts to synthesize multicomponent nanoparticles with at least one component being magnetic, and focus on our recent developments. The syntheses are based on heterogeneous nucleation and growth of a second and third component onto seed nanoparticles. These multicomponent nanoparticles show interesting magnetic, magneto‐optical, plasmonic, and semiconducting properties that can be modulated by interfacial interactions between different nanocomponents. This opens up a new avenue to advanced multifunctional nanomaterials for device concepts and applications.     

Promoted electrocatalytic hydrogen evolution performance by constructing Ni12P5–Ni2P heterointerfaces

Transition metal phosphides (TMPs) have been considered as cheap alternatives of precious metal platinum for electrochemical hydrogen evolution reaction (HER). In the past decades, many reports have indicated that the engineering of heterointerfaces between different components could efficiently enhance the activity of HER catalysts. Here, we report a facile method to construct Ni₁₂P₅–Ni₂P heterostructure by using a low temperature phosphorization strategy. The obtained Ni₁₂P₅–Ni₂P heterostructure shows high activity toward HER with an overpotential value of 166 mV at 10 mA cm^?2 and a Tafel slope of 60 mV dec^?1 in 0.5 M H₂SO₄. Compared with pure Ni₂P and Ni₁₂P₅, the Ni₁₂P₅–Ni₂P heterostructure has more active sites and faster HER kinetics due to the presence of the interfaces between Ni₁₂P₅ and Ni₂P. Furthermore, we used the obtained Ni₁₂P₅–Ni₂P as cathodic catalyst and IrO₂/Ti as anodic material to set up a proton exchange membrane (PEM) electrolyzer which shows good stability after 120 h continuous constant current electrolysis at 200 mA cm^?2. This work demonstrates the positive effect of heterostructure for HER catalysts and provides a feasible strategy for constructing earth-abundant electrocatalysts.     

Mixed-dimensional niobium disulfide-graphene foam heterostructures as an efficient catalyst for hydrogen production

Besides developing a large number of catalysts for hydrogen evolution reaction (HER) in alkaline electrolytes, its conversion efficiency remained low. Herein, we have developed mixed-dimensional heterostructures of niobium disulfide (NbS₂) with graphene foam grown on nickel foam (NbS₂-Gr-NF). The strong lateral fusion results in activating the catalytic sites of NbS₂, the three-dimensional substrate provides easy access of electrolyte to active sites and increased electrochemically active surface area, while enhanced conductivity provides faster transfer of electrons to and from active sites. Therefore, NbS₂-Gr-NF heterostructures resulted in an exceptionally high current density of 500 mA cm⁻² at a very low overpotential of 306 mV in 1 M KOH solution and even can achieve the current density values of 914 mAcm⁻² at 338 mV only at a slight increase in overpotential (32 mV). Moreover, a Tafel value of ~72 mV dec⁻¹ confirms that as-developed heterostructure provides fast reaction kinetics where the reaction is mainly controlled by the Volmer step. Achieving such high current density at a faster rate with high stability makes NbS₂-Gr-NF heterostructures a potential candidate for water-splitting, especially in alkaline electrolytes.     

Solution-processed,flexible and broadband photodetector based on CsPbBr_3/PbSe quantum dot heterostructures

Due to their promising applications in foldable displays,optical communication equipment and environmental monitoring systems,flexible and broadband optoelectronic devices have gained extensive attention in recent years.Here,a flexible and broadband photodetector based on CsPbBr₃/PbSe quantum dot(QD) heterostructures is firstly presented.The integrated QD heterostructures possess consecutive detection range from ultraviolet(UV) to long-wave length infrared(LW-IR) regions with efficient light absorption and chemical stability,in comparison with the pristine PbSe QDs.Systematic material characterizations reveal the improved exciton dissociation,carrier transport and carrier lifetime of the QD heterostructures.Flexible photodetector Ag/CsPbBr₃/PbSe/Ag demonstrate a high responsivity of 7.17 A/W with a specific detectivity of 8.97 × 10¹² Jones under 25 μW/cm² 365 nm illumination at 5 V.Furthermore,it could maintain 91.2 %(or 94.9 %) of its initial performance even after bending for thousands of times(or exposing in ambient air for 4 weeks).More importantly,its re s ponse time is shortened more than three orders of magnitude as that of pristine PbSe QDs-based photodetectors.Therefore,it provides a feasible and promising method for the next-generation high-performance broadband photodetectors via constructing heterostructures of various QDs.