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[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] Various types of conductive tips in atomic force microscope (AFM) are used to localize field-enhanced metal-induced solid phase crystallization (FE-MISPC) of amorphous silicon at room temperature down to nanoscale dimensions. The process is driven by electrical currents ranging from 0.1 nA to 3 nA between the tip and the bottom nickel electrode. The amplitude of the current is controlled by a metal-oxide-semiconductor field-effect transistor-based regulation circuit using proportional and derivative feedback loops. We analyze the results of the FE-MISPC process as a function of exposition current profiles, topographic changes, local conductivity changes (using current-sensing AFM) and regulation parameters. We found out that the FE-MISPC crystallization requires fluctuations of the exposition current rather than its stability. This is independent of the actual current set-point level. We also show the influence of the process on the AFM probes employed and vice versa. Bulk diamond probes exhibit superior endurance compared to bare or coated silicon probes, nevertheless all tips produce similar FE-MISPC results.

[en] Four pairs of p#En Dash#i#En Dash#n structures based on polymorphous Si:H (pm-Si:H) are fabricated by the method of plasma-enhanced chemical vapor deposition. The structures in each pair are grown on the same substrate so that one of them does not contain Ge in the i-type layer while the other structure contains Ge deposited by molecular-beam epitaxy as a layer with a thickness of 10 nm. The pair differ from one another in terms of the substrate temperature during Ge deposition; these temperatures are 300, 350, 400, and 450°C. The data of electron microscopy show that the structures formed at 300°C contain Ge nanocrystals (nc-Ge) nucleated at nanocrystalline inclusions at the pm-Si:H surface. The nc-Ge concentration increases as the temperature is raised. The study of the current–voltage characteristics show that the presence of Ge in the i-type layer decreases the density of the short-circuit current in p#En Dash#i#En Dash#n structures when they are used as solar cells, whereas these layers give rise to an increase in current at a reverse bias under illumination. The obtained results are consistent with known data for structures with Ge clusters in Si; according to these data, Ge clusters increase the coefficient of light absorption but they also increase the rate of charge-carrier recombination.

[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] Silicon nanocrystals are formed in the i layers of p–i–n structures based on a-Si:H using pulsed laser annealing. An excimer XeCl laser with a wavelength of 308 nm and a pulse duration of 15 ns is used. The laser fluence is varied from 100 (below the melting threshold) to 250 mJ/cm"2 (above the threshold). The nanocrystal sizes are estimated by analyzing Raman spectra using the phonon confinement model. The average is from 2.5 to 3.5 nm, depending on the laser-annealing parameters. Current–voltage measurements show that the fabricated p–i–n structures possess diode characteristics. An electroluminescence signal in the infrared (IR) range is detected for the p–i–n structures with Si nanocrystals; the peak position (0.9–1 eV) varies with the laser-annealing parameters. Radiative transitions are presumably related to the nanocrystal–amorphous-matrix interface states. The proposed approach can be used to produce light-emitting diodes on non-refractory substrates.

[en] A boundary between amorphous and microcrystalline growth of silicon thin films was explored for the study of grain growth by changing parameters of plasma enhanced deposition (substrate temperature, silane dilution or deposition duration and thus the film thickness). Resulting series of a-Si:H/μc-Si:H samples were characterized by values of dark conductivity and corresponding activation energy and prefactor, diffusion length, hydrogen content and morphology. The abrupt change of conductivity at the boundary is accompanied by a peak in surface roughness and diffusion length, which were connected to the formation of a percolating network of microcrystalline large grains. Results are discussed using the idea of barriers for electronic transport forming at the large grain boundaries. Comparison of transport properties with the hydrogen content pointed out the fundamental role of hydrogen present at the grain boundaries

[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 paper we focus on silicon nanowires (Si-NWs) which were fabricated on transparent conductive substrates by plasma-enhanced chemical vapor deposition (PECVD) method using Sn as stimulated catalyst metal. Transparent conductive substrates which we used are ZnO fabricated by direct current (dc) sputtering. Property of ZnO thin film was investigated by x-ray diffraction (XRD), volt-ohm-miliampere (VOM) meter, and Stylus method. In order to grow Si-NWs using PECVD we need to use metal as catalyst. We used Sn as catalyst to synthesize Si-NWs. Sn catalyst nanoparticles were fabricated by high vacuum evaporation system (SenVact). Size and density of Sn catalyst nanoparticles were investigated by scanning electron microscope (SEM). The influence of the thickness of metal layers on forming Sn catalyst nanoparticles was studied. In particular, the factors affecting the formation of Si-NWs such as temperature and rate of gas were examined. Si-NWs’ properties were investigated by SEM, Raman spectroscopy and energy dispersive x-ray (EDX) spectrocopy. (paper)