Atomic-layer-deposited (ALD) aluminum oxide (Al2O3) has recently demonstrated an excellent surface passivation for both n-and p-type c-Si solar cells thanks to the presence of high negative fixed charges (Q f ∼ 10 12 −10 13 cm −2 ) in combination with a low density of interface states (Dit). This paper investigates the passivation quality of thin (15 nm) Al2O3 films deposited by two different techniques: plasmaenhanced atomic layer deposition (PE-ALD) and Thermal atomic layer deposition (T -ALD). Other dielectric materials taken into account for comparison include: thermally-grown silicon dioxide (SiO2) (20 nm), SiO2 (20 nm) deposited by plasma-enhanced chemical vapour deposition (PECVD) and hydrogenated amorphous silicon nitride (a-SiNx:H) (20 nm) also deposited by PECVD. With the above-mentioned dielectric layers, Metal Insulator Semiconductor (MIS) capacitors were fabricated for Q f and Dit extraction through Capacitance-Voltage-Conductance (C-V -G) measurements. In addition, lifetime measurements were carried out to evaluate the effective surface recombination velocity (SRV). The influence of extracted C-V -G parameters (Q f ,Dit) on the injection dependent lifetime measurements τ (Δn), and the dominant passivation mechanism involved have been discussed. Furthermore we have also studied the influence of the SiO2 interfacial layer thickness between the Al2O3 and silicon surface on the field-effect passivation mechanism. It is shown that the field effect passivation in accumulation mode is more predominant when compared to surface defect passivation.

No abstract

Enhanced upper critical field, critical current density, and thermal activation energy in new ytterbium doped CeFeAsO0.9F0.1 superconductor J. Appl. Phys. 113, 043924 (2013) Temperature-and field-dependent critical currents in [(Bi,Pb)2Sr2Ca2Cu3Ox]0.07(La0.7Sr0.3MnO3)0.03 thick films grown on LaAlO3 substrates J. Appl. Phys. 113, 043916 (2013) Transport critical current measurement apparatus using liquid nitrogen cooled high-Tc superconducting magnet with variable temperature insert Rev. Sci. Instrum. 84, 015113 (2013) Additional information on Appl. Phys. Lett.

A simple vapour deposition technique was used to prepare WO 3 one-dimensional nanostructures. WO 3 is sublimated at a relatively low temperature (550 1C) in air at atmospheric pressure. The sublimated species are condensed on mica substrate at 500 1C. Single crystalline nanorods are grown in epitaxy on the mica surface with a growth axis along [0 1 0] directions and (0 0 1) plane parallel to the substrate. A growth process is proposed in which the formation of a onedimensional tetragonal tungsten bronze as precursor is the determining factor. r

No abstract

The preparation and physical characterization of diverse porphyrin‐derived double‐walled carbon nanotubes (DWCNTs) conjugates are described. A porphyrin molecule is covalently linked and physically adsorbed to COOH‐derived DWCNTs. The photophysical properties of all porphyrin‐CNTs derivatives are studied in solution and in polymeric matrices. Definitive experimental evidence for photoinduced electron and/or energy transfer processes involving the porphyrin chromophores and the CNT wall is not obtained, but solid‐state UV‐vis absorption profiles display electronic transitions fingerprinting J‐ and H‐ type aggregates, where porphyrin molecules intermolecularly interact “head‐to‐tail” and “face‐to‐face”, respectively. In parallel, molecular modeling based on force‐field simulations is performed to understand the structure of the porphyrin‐CNTs interface and the nature of the interactions between the porphyrins and the DWCNTs. Finally, multilayered‐type devices are fabricated with the aim of investigating the interaction of the porphyrin‐derived DWCNTs with poly(3‐hexylthiophene)‐pyrene matrices containing small amounts of 1‐[3‐(methoxycarbonyl)propyl]‐1‐phenyl‐[6.6]C61.

No abstract

In this paper, we present two key process steps for potential applications in the fabrication of low-cost and high-efficiency ultrathin monocrystalline silicon (mono-Si) solar cells to effectively harvest solar energy. One is to grow an Al2O3 passivation layer on the rear side of an Si wafer by a successive atomic layer deposition (ALD) at room temperature (25 °C). The other is to produce a bio-inspired antireflection structure on the front side of the Si wafer by replicating butterfly wing patterns. The capacitance–voltage measurements reveal that the successive ALD procedure can yield a higher negative charge density at the Al2O3/Si interface relative to the conventional one. The measurement results of quasi-steady-state photoconductance indicate that after annealing, the 25 °C ALD Al2O3 layers reach a similar passivation level to the p-type Si wafers compared to that deposited at 250 °C. With the help of an ALD Al2O3 layer, butterfly wing patterns (Hypochrysops polycletus) are replicated on a PMMA layer which is on an SiO2/Si stack. This work demonstrates the ability for replicating the natural photonic features on Si wafers and other substrates by using nanoimprint.