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Presents information on a study which characterized stain etched porous silicon layers using photoluminescence, electron paramagnetic resonance and infrared absorption spectroscopy. Methods; Results; Discussion.

Presents a study which measured room-temperature photoluminescence spectra using a two-band structure from porous silicon (PS) as a function of excitation wavelengths. Details of experimental techniques used; Assumption of the quantum confinement/luminescence centers model.

Study of electronic properties of graphene on an anisotropic crystal substrate including boron nitride (BN) has raised significant interest recently due to the application of graphene based vertical hetero-devices. We have performed scanning tunneling microscopy (STM) and scanning tunneling spectroscopy studies of single-layer graphene on hexagonal BN (h-BN) substrates with an applied perpendicular magnetic field at low temperature. Different periodic moiré superlattices can be resolved with STM, and their quantized Landau levels in high magnetic field are investigated. The renormalized Fermi velocities of massless Dirac fermions in graphene are revealed to show dependent on the moiré superlattice. Density functional theory calculation verifies that the interlayer interaction between graphene and h-BN is stronger with smaller twisting angle between lattices of graphene and h-BN, thus, leading to a reduction in the velocity of charge carriers. Our results should provide valuable insight of electronic properties and device performance of graphene on crystal substrates. [ABSTRACT FROM AUTHOR]

Lower hybrid wave (LHW)-plasma coupling experiments in HT-7 [J. K. Xie and HT-7 Group, Proceedings of the 16th International Conference on Fusion Energy, Montreal, 1996 (IAEA, Trieste, 1997), Vol. 1, p. 685] were carried out by means of puffing gas (CD4 and D2) just around the antenna. Both experiments show that wave-plasma coupling is improved by the gas puffing. The maximum distance between the plasma and the antenna is limited to about 8 cm due to the plasma disruption. The variation in the lined averaged density in the different channels gives a possible evidence of the mechanism of the ionization of neutral gas. The effect of the gas flow rate on the wave-plasma coupling shows that an optimized gas flow rate is necessary for good coupling, being consistent with simulation through Brambilla theory qualitatively. Experiments with puffing D2 show that the improved coupling results from the global density increase and the local gas puffing. Langmuir probe measurements indicate that the gas puffing effectively increases the density and decreases the temperature in scrape of layer. Studies show that the ionization of the puffed gas is affected by both LHW electric field and plasma temperature. Comparison of D2 and CD4 puffing shows that D2 improves coupling better with less effect on core density. [ABSTRACT FROM AUTHOR]

We report on the configurations and electronic properties of graphyne and graphdiyne nanoribbons with armchair and zigzag edges investigated with first principles calculations. Our results show that all the nanoribbons are semiconductors with suitable band gaps similar to silicon. And their band gaps decrease as widths of nanoribbons increase. We also find that the band gap is at the Γ point for all graphdiyne ribbons and it is at the X point for all graphyne ribbons. Of particular interest, the band gap of zigzag graphyne nanoribbons show a unique 'step effect' as the width increases. This property is good for tuning of the energy band gap, as in a certain range of the ribbon width, the energy gap remains constant and in reality the edge cannot be as neat as that in a theoretic model. [ABSTRACT FROM AUTHOR]

We report on epitaxial growth of graphene on Pt(111) surface. It was found out that the proportion of different rotational domains varies with growth temperature and the graphene quality can be improved by adjusting both the growth temperature and ethylene exposure. Rippled and unrippled domains of high quality graphene are observed. The adhesive energy and electronic structure of two models, representing rippled and unrippled graphene, are obtained with density functional theory calculation, which shows that the interaction between graphene and Pt(111) surface is very weak and the electronic structure is nearly the same as that of a free standing graphene. [ABSTRACT FROM AUTHOR]