The availability of easy and reproducible methods for formation of periodically nanostructured surfaces allows one to study the quasi-epitaxial growth of nanowires on such artificially modified ...substrates. Here, we demonstrate that crystalline nanofibers of
para
-hexaphenyl can grow on porous alumina templates with high pore regularity once the templates have been coated by a thin Au film. Nanofibers of that kind represent a model system for the general class of organic nanowires which have chemically changeable optoelectronic properties and hence are of interest for integration into future optoelectronic devices.
The photoluminescence (PL) at ∼2.2–2.3
eV from Ge-based nanocrystalline materials is described in the literature as nanocrystal size-independent. We have observed visible luminescence from two ...different types of stain-etched Ge samples, one prepared after Sendova-Vassileva et al. (Thin Solid Films 255 (1995) 282) in a solution of H
2O
2:HF at 50:1 volume ratio, and the other in a solution of HF:H
3PO
4:H
2O
2 at 34:17:1 volume ratio. Energy dispersive X-ray analysis (EDX), Raman and FTIR spectroscopy, and the near edge X-ray absorption structure (XANES), indicate that the chemically etched Ge layers of the former type of samples are composed of non-stoichometric Ge oxides, i.e. GeO
x
(0<
x<2), and free from any Ge nanoconstructions. It is also suggested from XANES that the latter type of chemically etched Ge samples comprise 8–9
nm nanocrystals of Ge, surface-covered with mainly oxygen. Photoluminescence occurred at ∼2.3
eV for all samples. The PL behavior of the latter type of chemically etched Ge on annealing in different chemical environments (air or H) allowed us to conclude that the PL from these materials, as well as that from those Ge-based nanocrystalline materials reported in the literature, is from GeO
x
s.
The structure of porous Si1–xGex films was characterized using Raman spectroscopy. As the film porosity increases the sizes of Si1–xGex nanocrystals decrease, and also the film composition slightly ...modifies in favor of Ge. The Si1–xGex nanocrystals were estimated to be 12.0 nm, 16.1 nm and 19.3 nm average diameter in three porous samples prepared from undoped Si0.87Ge0.13 films with 20 min, 10 min and 2 min etch times, respectively, at the same current density 22 mA cm–2. The final Ge fractions were determined for the samples as 17.4%, 14.5% and 13.0%, respectively. It is seen by this study that Raman spectroscopy is, as it has always been for bulk Si1–xGex alloys, a very useful technique for characterizing the structure of porous Si1–xGexfilms.
Thin film CdTe photovoltaic (PV) devices and reference layers obtained by the atmospheric pressure metalorganic vapour deposition (AP-MOCVD) method have been studied for their chemical structure ...using plasma profiling time-of-flight-mass spectroscopy (PP-TOFMS, also called glow discharge TOFMS). Different levels of arsenic (As) dopant in CdTe films were measured by PP-TOFMS and compared to results obtained from a more conventional depth profiling method (secondary ion mass spectrometry or SIMS). This comparison showed that PP-TOFMS has the sufficient sensitivity towards detection of the As dopant in CdTe and hence is suited as a rapid, low vacuum tool in controlling the large scale production of CdTe PV materials.
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