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41.
Determination of band offsets in a-Si:H/c-Si heterojunctions from capacitance-voltage measurements: Capabilities and limits 总被引:1,自引:0,他引:1
The capabilities and limitations of the well-known C-V technique for the determination of the conduction band offsets in (n)a-Si:H/(p)c-Si heterojunctions are presented. In particular, the effects due to the presence of an inversion layer in c-Si and a non-negligible defect density at the a-Si:H/c-Si interface on the reliability of the C-V intercept method are discussed. The influence of the Fermi level positions in (p)c-Si and (n)a-Si:H on the inversion layer formation and the influence of the interface defect density have been analysed using numerical simulations and experimental measurements. 相似文献
42.
Area selective epitaxy (ASE) of InP was performed by liquid phase epitaxy on Si (100) substrates without the use of buffer layers. At the start of epitaxy, the growth temperature was rapidly lowered to obtain high supersaturation. Epitaxial growth was then carried out at constant temperature. While small InP nuclei were observed in the broader open areas, ASE layers and layers showing slight epitaxial lateral overgrowth were formed in the narrow openings. Etch pit density of the InP ASE layers on Si is dependent on the length of open seed region and X-ray diffraction results indicate that the lattice strain in the InP nuclei on the Si substrate was fully relaxed. 相似文献
43.
KS Perez O Estevez A Mendez-Blas J Arriaga G Palestino ME Mora-Ramos 《Nanoscale research letters》2012,7(1):392
ABSTRACT: In this work, we report the experimental results and theoretical analysis of strong localization of resonance transmission modes generated by hybrid periodic/quasiperiodic heterostructures (HHs) based on Porous Silicon (PSi). The HHs are formed by stacking a quasiperiodic Fibonacci (FN) substructure between two Distributed Bragg Reflectors (DBRs). FN substructure defines the number of strong localized modes that can be tunable at any given wavelength and be unfolded when a partial periodicity condition is imposed. These structures show interesting properties for biomaterials research, biosensor applications and basic studies of adsorption of organic molecules. We also demonstrate the sensitivity of HHs to material infiltration. 相似文献
44.
45.
《International Journal of Hydrogen Energy》2020,45(15):8686-8694
An efficient synthesis method combining the advantages of defect and surface structure engineering is present to prepare oxygen electrode materials with a unique nanoarchitecture (namely, CoFe@NC heterostructures, for which lattice-dislocated CoFe alloy nanoparticles encapsulated in nitrogen-doped carbon layers). The CoFe@NC heterostructures provide an abundance active sites and are found to exhibit dramatically improved electrocatalytic activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). With the advantages of unique hierarchical nanostructure, the presence of crystal lattice dislocations of CoFe alloy and the synergistic effect between CoFe alloy and carbon layers, the CoFe@NC exhibits good performances for ORR and OER with the overpotential of 770 mV when used as bifunctional catalyst, much smaller than other reported electrocatalysts, suggesting the CoFe@NC is a promising candidate as an efficient bifunctional catalyst for fuel cells and metal-air batteries. 相似文献
46.
ABSTRACT: The effect of the dimensionality of metallic nanoparticle-and carbon nanotube-based fillers on the mechanical properties of an acrylonitrile butadiene styrene (ABS) polymer matrix was examined. ABS composite films, reinforced with low dimensional metallic nanoparticles (MNPs, 0-D) and carbon nanotubes (CNTs, 1-D) as nanofillers, were fabricated by a combination of wet phase inversion and hot pressing. The tensile strength and elongation of the ABS composite were increased by 39% and 6%, respectively, by adding a mixture of MNPs and CNTs with a total concentration of 2 wt%. However, the tensile strength and elongation of the ABS composite were found to be significantly increased by 62% and 55%, respectively, upon addition of 3-D heterostructures with a total concentration of 2 wt%. The 3-D heterostructures were composed of multiple CNTs grown radially on the surface of MNP cores, resembling a sea urchin. The mechanical properties of the ABS/3-D heterostructured nanofiller composite films were much improved compared to those of an ABS/mixture of 0-D and 1-D nanofillers composite films at various filler concentrations. This suggests that the 3-D heterostructure of the MNPs and CNTs plays a key role as a strong reinforcing agent in supporting the polymer matrix and simultaneously serves as a discrete force-transfer medium to transfer the loaded tension throughout the polymer matrix. 相似文献
47.
C. Voz I. Martin A. Orpella J. Puigdollers M. Vetter R. Alcubilla D. Soler M. Fonrodona J. Bertomeu J. Andreu 《Thin solid films》2003,430(1-2):270-273
In this work, we study the electronic surface passivation of crystalline silicon with intrinsic thin silicon films deposited by Catalytic CVD. The contactless method used to determine the effective surface recombination velocity was the quasi-steady-state photoconductance technique. Hydrogenated amorphous and nanocrystalline silicon films were evaluated as passivating layers on n- and p-type float zone silicon wafers. The best results were obtained with amorphous silicon films, which allowed effective surface recombination velocities as low as 60 and 130 cm s−1 on p- and n-type silicon, respectively. To our knowledge, these are the best results ever reported with intrinsic amorphous silicon films deposited by Catalytic CVD. The passivating properties of nanocrystalline silicon films strongly depended on the deposition conditions, especially on the filament temperature. Samples grown at lower filament temperatures (1600 °C) allowed effective surface recombination velocities of 450 and 600 cm s−1 on n- and p-type silicon. 相似文献
48.
49.
We present a semi-empirical sp3s? tight binding model to calculate the effects of alloy composition and strain on electronic band structure of Cd and Zn based group II-VI heterostructures for photovoltaic devices. The semi-empirical sp3s? TB model Hamiltonian includes second nearest neighbor interactions and spin-orbit splitting of p-states. Bond lengths and atomic energies of cation and anion forming ternary semiconductors are taken as nonlinear function of composition. The 2NN sp3s? tight binding model calculations are compared with those of the package program WIEN2k which uses the generalized gradient approximation (GGA) and local spin density approximation (LSDA) based scaling law for the scissor operator for the self energy corrections to the DFT energy band gaps of semiconductors. We found that both the GGA and LSDA corrected WIEN 2k simulations and 2NN sp3s? TB model accurately reproduces the band gaps and both the valence band and conduction band dispersion curves at Γ, X and L high symmetry points of Brillouin zone, also in good agreement with experiment. 相似文献
50.
K.R. Balasubramanian Feroz A. Mohammad Paul A. Salvador Jeffrey DiMaio 《Thin solid films》2006,515(4):1807-1813
Epitaxial hexagonal YMnO3 (h-YMnO3) films having sharp (00l) X-ray diffraction peaks were grown above 700 °C in 5 mTorr O2 via pulsed laser deposition both on as-received wurtzite GaN/AlN/6H-SiC(001) (w-GaN) substrates as well as on w-GaN surfaces that were etched in 50% HF solution. High-resolution transmission electron microscopy revealed an interfacial layer between film and the unetched substrate; this layer was absent in those samples wherein an etched substrate was used. However, the substrate treatment did not affect the epitaxial arrangement between the h-YMnO3 film and w-GaN substrate. The epitaxial relationships of the h-YMnO3 films with the w-GaN(001) substrate was determined via X-ray diffraction to be (001)YMnO3 ‖ (001)GaN : [11¯0]YMnO3 ‖ [110]GaN; in other words, the basal planes of the film and the substrate are aligned parallel to one another, as are the most densely packed directions in planes of the film and the substrate. Interestingly, this arrangement has a larger lattice mismatch than if the principal axes of the unit cells were aligned. 相似文献