Momentum-resolved direct and inverse photoemission spectra of the K͞Si͑111͒-͑ p 3 3 p 3 ͒R30 ±-B interface reveals the presence of strongly localized surface states. The K overlayer remains nonmetallic up to the saturation coverage. This system most likely presents the first experimental realization of a frustrated spin 1͞2 Heisenberg antiferromagnet on a two-dimensional triangular lattice. [S0031-9007(97)02423-X]
A saturation surface photovoltage is found to occur during ultraviolet photoemission at low temperatures ( r~ 20 K) on a variety of silicon (HI) surfaces. Below -50 K surface recombination becomes ineffective thereby allowing flat-band conditions to be achieved with mild uv irradiation. Temperature-dependent photoemission thereby provides a simple and direct method for determining band bending and barrier heights. Results for different silicon (111) surfaces and preparation conditions are discussed.
A series of monolithic poly[methyl
methacrylate-co-3-(trimethoxysilyl)propyl
methacrylate]−silica hybrid materials have been prepared via the sol−gel
reactions. The fracture
surfaces of the materials were systematically examined with atomic
force microscopy (AFM)
as a function of the silica content from ∼23 to 100 vol %. For
the transparent materials,
the AFM image of the sample at a low silica content of 23 vol % is
very smooth and essentially
featureless while those at higher silica contents show relatively
greater surface roughness
and development of domains of various shapes and sizes. In sharp
contrast, the optically
translucent and phase-separated samples exhibit significantly higher
surface roughness and
larger domain size than all the transparent hybrid materials,
suggesting that the transparent
materials might have little or no organic−inorganic phase
separation.
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