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In semiconductor device history, a trend is observed where narrowing and increasing the number of material layers improve device functionality, with diodes, transistors, thyristors, and superlattices following this trend. While superlattices promise unique functionality, they are not widely adopted due to a technology barrier, requiring advanced fabrication, such as molecular beam epitaxy and lattice-matched materials. Here, a method to design quantum devices using amorphous materials and physical vapor deposition is presented. It is shown that the multiplication gain M depends on the number of layers of the superlattice, N, as M = kN, with k as a factor indicating the efficiency of multiplication. This M is, however, a trade-off with transit time, which also depends on N. To demonstrate, photodetector devices are fabricated on Si, with the superlattice of Se and As2Se3, and characterized using current–voltage (I–V) and current–time (I–T) measurements. For superlattices with the total layer thicknesses of 200 nm and 2 μm, the results show that k200nm = 0.916 and k2μm = 0.384, respectively. The results confirm that the multiplication factor is related to the number of superlattice layers, showing the effectiveness of the design approach. [ABSTRACT FROM AUTHOR]

Many studies have shown that amorphous carbon films with reduced internal stress, improved adhesion strength, and diversified material properties are obtainable through doping process, but the presence of dopants was reported to promote surface evolution and alter the microstructures of carbon matrix. By combining analyses from experimental results and theoretical estimations, this work examines the mechanism behind the surface evolution and microstructural changes in laser fabricated nanostructured copper-carbon composite. We showed that the presence of metal ions during laser deposition increased the heat dissipation on carbon matrix, which enhanced the formation of nanoislands but graphitized the carbon matrix. In addition, theoretical estimations and XPS hinted that the presence of energetic species may force the carbon ions to react with the substrate interface and form silicon carbide bonds, which contributed to the improved adhesion strength observed in copper doped carbon films, along with a reduction in internal stress owing to the presence of nanoclusters. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) films doped with a small fraction of erbium (0.5–2.0 at. %, at 0.5 at. % interval) were prepared by using a 248 nm KrF pulsed laser deposition technique. The effects of erbium on the surface morphology, microstructure, chemical binding states, tribological property, and the adhesion strength of DLC films were investigated. Atomic force microscopy showed that the surface roughness of the films increased with the increasing of erbium fraction, but generally the nanocomposite films were smooth with rms below 1 nm. Raman analysis showed broad peaks centered at 1550 cm-1 on all the samples. The deconvoluted Raman spectra on DLC doped with different fractions of erbium showed that the ID/IG ratio increased with increasing erbium content, and the comparative percent of sp3 is between 50% and 58% for erbium fraction between 0.5 and 2.0 at. %. High resolution x-ray photoelectron spectroscopy confirmed that the C 1s peaks had slightly shifted away from 285.2 (diamond) to 284.5 eV (graphite). The deconvolution of the spectra further confirmed the influence of erbium to the sp3 contents and revealed the presence of SiC with the increasing of Er fraction. Microscratch tester results showed that the adhesion strength (critical load) of the films improved with the presence of SiC bonding at the interface. This hinted that the presence of the heavier erbium may force the impinging carbon ions to react more with the interface to form silicon carbide bonds, thus enhancing the adhesion strength. Although the presence of erbium increased the surface roughness of the films, the coefficients of friction of the erbium doped DLC films were still closely resembled to pure DLC, i.e., 0.11–0.12 compared to 0.10 for pure DLC. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon microspheres (NCSs) were fabricated via a simple, fast and energy-saving microwave-assisted method followed by thermal treatment under an ammonia atmosphere. NCSs thermally treated at different temperatures were investigated as anode materials for lithium ion batteries (LIBs). The results show that NCSs treated at 900 °C exhibit a maximum reversible capacity of 816 mA h g-1 at a current density of 50 mA g-1 and preserve a capacity of 660 mA h g-1 after 50 cycles, and even at a high current density of 1000 mA g-1, a capacity of 255 mA h g-1 is maintained. The excellent electrochemical performance of NCSs is due to their porous structure and nitrogen-doping. The present NCSs should be promising low-cost anode materials with a high capacity and good cycle stability for LIBs. [ABSTRACT FROM AUTHOR]

A recent study demonstrated that electron emission occurs from conduction bands of heavily nitrogen (N)-doped diamond, utilizing the benefit of negative electron affinity [H. Yamaguchi et al., Phys. Rev. B 80, 165321 (2009)]. In addition, doping N-doped diamond films with dimethylurea (DMU) allowed high reproducibility. In this article, field emission properties of N-doped diamond films were compared between samples doped with DMU and one doped with urea. Fowler-Nordheim analysis and voltage-distance plot analysis showed that the barrier height for the urea-doped film was smaller than for DMU-doped counterparts, while the barrier height showed only a slight decrease when the DMU concentration in the reactant solution was changed from 10 to 1000 ppm. Ultraviolet photoelectron spectroscopy indicated that this difference in barrier height did not originate from the electron affinity. Time of flight secondary ion mass spectroscopy (TOF SIMS) exhibited that the concentration of C-N bonds in the urea-doped sample was an order of magnitude higher than in the two DMU-doped samples. This result suggests that only nitrogen atoms incorporated as C-N enhance the field emission properties of N-doped diamond films. Further TOF SIMS analysis of N-doped diamonds with urea or DMU doping may clarify the C-N distribution in relation to the electron emission under low electric fields. [ABSTRACT FROM AUTHOR]

Microbial fuel cell (MFC) is an emerging and promising technology, particularly in the field of wastewater treatment. The MFC capability of achieving organic removal and generating in situ electricity could make it an attractive alternative wastewater treatment technology over conventional treatment technologies. However, MFC is still far from being economically viable, especially because of the cost of the platinum (Pt) catalyst that makes possible the reaction at the cathode. In this study, we tested alternative cathode catalysts, namely sputter-deposited Cobalt (Co) and denitrifying bacteria (biocathode). The performance of these innovative cathodes was compared with that of classic Pt-cathodes. Co competed well with Pt, but further research is still required for biocathodes. However, biocathodes MFC have showed promise. [ABSTRACT FROM AUTHOR]

The electronic properties of the junction formed between multinanolayer amorphous selenium and silicon are studied. The current- voltage (I-V) relationship of this type of junction was characterised and the result showed pn junction rectification. Capacitance-voltage (C-V) measurements were also used to obtain the value of the diffusion potential of the junction. From these data, the ideality factor and built-in potential were evaluated. The results show potential in the application of amorphous selenium and silicon as materials in tandem photovoltaic cells and in wide spectral range photodetectors. [ABSTRACT FROM AUTHOR]