[en] A series of investigations were performed to study the influence of the substrate temperature on the structure and properties of silicon thin films. Substrate temperature was varied in the wide range of 35-200 deg. C. It has been shown that the films grown below 60 deg. C exhibit an unusual structural behavior. A sharp TO phonon peak at 520 cm^-1 was detected in Raman spectra, which is associated with the crystalline structure. In contrast to these results, the same samples do not show any crystallite-related peak by X-ray diffraction and their optoelectronic properties (dark conductivity, activation energy and subgap absorption spectra) show amorphous features. A similar discrepancy was observed for a hydrogen dilution ratio (r_H=([SiH₄]+[H₂])/[SiH₄]) series of samples deposited at 60 deg. C. Hydrogen dilution ratio was varied from 25 to 170. It seems that at low substrate temperature a parameter window exists where the silicon thin films can be grown with the properties combining both crystalline and amorphous behavior

[en] Field-enhanced metal-induced solid phase crystallization (FE-MISPC) of amorphous silicon is scaled down to nanoscale dimensions by using a sharp conductive tip in atomic force microscopy (AFM) as one of the electrodes. The room temperature process is driven by the electrical current of the order of 100 pA between the tip and the bottom nickel electrode. This results in energy transfer rates of 30-50 nJ s^-1. Amplitude of the current is limited by a MOSFET transistor to avoid electrical discharge from parasitic parallel capacitance. Limiting the current amplitude and control of the transferred energy (∼100 nJ) enables formation of silicon crystals with dimensions smaller than 100 nm in the amorphous film. Formation of the nanocrystals is localized by the AFM tip position. The presence of nanocrystals is detected by current-sensing AFM and independently corroborated by micro-Raman spectroscopy. The nanocrystal formation is discussed based on a model considering microscopic electrical contact, thermodynamics of crystallization and silicide formation.

[en] A way of influencing growth of silicon films by magnetic field is demonstrated. Permanent magnet(s) placed under the substrate influenced the discharge in a mixture of silane and hydrogen and led to formation of microcrystalline regions in otherwise amorphous film. The pattern of microcrystalline regions varied with the orientation of the magnetic field. Microscopic study by atomic force microscopy and by micro-Raman spectroscopy revealed that the microcrystalline regions resulted from a higher density of crystalline grain nuclei, increased at the locations where the magnetron effect could be expected. This phenomenon could be used to study the transition between amorphous and microcrystalline growth. Moreover, we suggest it as a kind of 'magnetic lithography' for the preparation of predefined microcrystalline patterns in otherwise amorphous silicon films

[en] Silicon nanowires and nanoneedles show promise for many device applications in nanoelectronics and nanophotonics, but the remaining challenge is to grow them at low temperatures on low-cost materials. Here we present plasma-enhanced chemical vapor deposition of crystalline/amorphous Si nanoneedles on glass at temperatures as low as 250 deg. C. High resolution electron microscopy and micro-Raman spectroscopy have been used to study the crystal structure and the growth mechanism of individual Si nanoneedles. The H₂ dilution of the SiH₄ plasma working gas has caused the formation of extremely sharp nanoneedle tips that in some cases do not contain a catalytic particle at the end.

[en] Dielectric properties of Eu_0.5Ba_0.5TiO₃ ceramics were investigated between 10 and 300 K in the frequency range of 1 MHz-100 THz. Permittivity exhibits a strong peak near the ferroelectric phase transition at 215 K. This is mainly due to softening of the lowest frequency polar phonon revealed in THz and infrared spectra. Dielectric relaxation was observed also below the ferroelectric soft mode frequency in the whole investigated temperature region, but it is probably caused by some defects such as Eu³⁺ cations or oxygen vacancies. This implies that the ferroelectric phase transition has predominantly a displacive character. Raman scattering spectra revealed a lowering of crystal symmetry in the ferroelectric phase and XRD analysis indicated orthorhombic A2mm symmetry below 215 K. The magnetic measurements performed at various frequencies in the field cooled and field heating regime after cooling in zero magnetic fields excluded spin glass behavior and proved an antiferromagnetic order below 1.9 K in Eu_0.5Ba_0.5TiO₃.

[en] Here we present two ways of preparing lateral (in plane) silicon nanowires with the help of gold nanoislands catalysed plasma enhanced chemical vapour deposition. The role of the applied potential and eventual consecutive hydrogen plasma treatment is tested together with the thickness of the thin Au layer used for self-organised preparation of Au nanoislands. (author)

[en] In this article, we investigate the nanocomposite material formation, particularly the deposition of nanocrystalline diamond and carbon nanowalls (CNWs) on single-wall carbon nanotubes buckypaper (BP). One part of the buckypaper substrate was nucleated by nanodiamond powder. The growth was carried out in a hot filament chemical vapor deposition (HFCVD) system. Contact angle measurements, scanning electron microscopy, and Raman spectroscopy were used for the surface morphology analysis and characterization of carbon phases. Due to a different surface pretreatment, different carbon nanostructures were formed: diamond film was grown on the nucleated BP area; non-treated area of the BP was covered with a dense field of CNWs. Covering a part of the BP surface prevented an access of the HF-plasma and so the growth of any carbon structures. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] Highlights: • Calcium carbonate partially decomposes during PLD deposition. • In-depth distributions of elements and resolved bonding states are inhomogeneous. • Surface of Ca-doped DLC layers is enriched by CaCO₃ and C sp^3. • Ca doping induces structural conversion from C sp³ to C sp² in a sub-surface region. In the present work we determined surface composition and chemical bonds at the top surface and in a shallow sub-surface region of the calcium-doped diamond-like carbon (DLC) layers using angular-resolved photoelectron spectroscopy (ARXPS) aided by the Maximum Entropy Method (MEM). The resulting non-destructive depth profiles showed that the composition and the chemical bonding vary significantly on the way from the top surface to the shallow sub-surface region. We demonstrate, for the first time, that Ca doping induced (i) the accumulation of the calcium carbonate, CaCO₃, at the surface, while the calcium oxide, CaO, is located in a deeper sub-surface region, (ii) structural conversion from the C sp²-rich top surface observed in the undoped DLC layer to the C sp³-rich top surface of the Ca-doped DLC samples, and (iii) conversion in the opposite direction which occurred in a sub-surface region. Our conclusions are consistent with Raman and Ion Surface Scattering spectra. Obtained results can be useful for deeper understanding the interaction between doped DLC layer surfaces with surroundings and particularly with living tissue.

[en] Polycrystalline silicon films for solar cells grown by atmospheric pressure chemical vapour deposition require hydrogenation to passivate defects at grain boundaries. Passivation by remote plasma hydrogenation of 12-μm-thick poly-Si films increased Hall effect carrier mobility from 3 to 20 cm²/Vs, photoluminescence intensity at 0.98 eV band more than 2 times and decreased contrast of local electronic conductivity between grains, observed by combined AFM. However, excessive hydrogenation led to surface damage and defect creation evidenced by widths of Raman LO-TO peak at 520 cm^-1 and X-ray rocking curve of (220) diffraction line. Depth profile by repeated etching of the surface and following the signature of Si-H₂ and H₂ bonding in Raman spectra showed that the damage extended up to 100 nm from the surface