[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.
Journal
Nanotechnology (Print); ISSN 0957-4484; 
; v. 20(4); [6 p.]
; v. 20(4); [6 p.]
[en] Chemically modified 5-nm detonation diamond nanoparticles (DNPs) are characterized by grazing angle reflectance (GAR) Fourier transform infrared spectroscopy (FTIR), Kelvin force microscopy (KFM), and X-ray photoelectron spectroscopy (XPS). Using GAR-FTIR we discuss the surface chemistry and stability of the as-received DNPs, and compare them with DNPs modified by annealing in air or by oxygen plasma treatment. Infrared spectra of the as-received DNPs are dominated by C–H bonds and carboxylic groups (COOH), probably related to the wet chemical treatment in acids. Annealing in air and oxygen plasma lead to a significant enhancement of C=O groups and vanishing C–H groups. After short-term (10 min) oxygen plasma treatment, infrared peaks change in intensity and position indicating a spontaneous reactivity of DNPs, probably due to the partial erosion of the graphitic shell. Prolonged oxygen plasma treatment (40 min) or annealing in air at 450 °C for 30 min provides a stable DNPs surface. Surface potentials of DNPs obtained by KFM are well correlated with the GAR-FTIR measurements. XPS characterization corroborates DNPs compositional changes after the modification procedures.
Journal
Journal of Nanoparticle Research; ISSN 1388-0764; ; v. 15(4); p. 1-9
; v. 15(4); p. 1-9
[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.
Journal
[en] Hybrid diamond-organic interfaces are considered attractive for diverse applications ranging from electronics and energy conversion to medicine. Here we use time-resolved and time-integrated photoluminescence spectroscopy in visible spectral range (380–700 nm) to study electronic processes in H-terminated nanocrystalline diamond films (NCD) with 150 nm thin, electrochemically deposited polypyrrole (PPy) layer. We observe changes in dynamics of NCD photoluminescence as well as in its time-integrated spectra after polymer deposition. The effect is reversible. We propose a model where the PPy layer on the NCD surface promotes spatial separation of photo-generated charge carriers both in non-diamond carbon phase and in bulk diamond. By comparing different NCD thicknesses we show that the effect goes as much as 200 nm deep inside the NCD film
Journal
[en] Two-dimensional photonic crystal can be exploited as the top part of a light source in order to increase its extraction efficiency. Here, we report on the room-temperature intrinsic photoluminescence (PL) behavior of a nanocrystalline diamond (NCD) layer with diamond columns prepared on the top and periodically ordered into the lattice with square symmetry. Angle-resolved far-field measurements in the Γ-X crystal direction of broadband visible PL revealed up to six-fold enhancement of extraction efficiency as compared to a smooth NCD layer. A photonic band diagram above the lightcone derived from these measurements is in agreement with the diagram obtained from transmission measurements and simulation, suggesting that the enhancement is primarily due to light's coupling to leaky modes.
Journal
New Journal of Physics; ISSN 1367-2630; ; v. 13(6); [13 p.]
; v. 13(6); [13 p.]
[en] Linear antenna microwave chemical vapor deposition process was used to homogeneously coat a 7 cm long silicon prism by 85 nm thin nanocrystalline diamond (NCD) layer. To show the advantages of the NCD-coated prism for attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) of nanoparticles, we apply diamond nanoparticles (DNPs) of 5 nm nominal size with various surface modifications by a drop-casting of their methanol dispersions. ATR-FTIR spectra of as-received, air-annealed, plasma-oxidized, and plasma-hydrogenated DNPs were measured in the 4000–1500 cm−1 spectral range. The spectra show high spectral resolution, high sensitivity to specific DNP surface moieties, and repeatability. The NCD coating provides mechanical protection against scratching and chemical stability of the surface. Moreover, unlike on bare Si surface, NCD hydrophilic properties enable optically homogeneous coverage by DNPs with some aggregation on submicron scale as evidenced by scanning electron microscopy and atomic force microscopy. Compared to transmission FTIR regime with KBr pellets, direct and uniform deposition of DNPs on NCD-ATR prism significantly simplifies and speeds up the analysis (from days to minutes). We discuss prospects for in situ monitoring of surface modifications and molecular grafting.
Journal
[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)
Journal
Canadian Journal of Physics; ISSN 0008-4204; ; v. 92(7-8); p. 819-821
; v. 92(7-8); p. 819-821
[en] Thin Si films prepared by plasma enhanced chemical vapor deposition at low temperature and containing microcrystalline grains in amorphous tissue were studied by two complementary microscopy techniques. The conductive atomic force microscopy was performed in standard ambient conditions, whereas the presence of the surface oxide was overcome by more sensitive (pA) current detection. The cross-sectional transmission electron microscopy images of the amorphous phase revealed the columnar structure, which was successfully correlated with the bumpy surface detected by the atomic force microscope
Journal
Journal of Physics. Conference Series (Online); ISSN 1742-6596; ; v. 61(1); p. 790-794
; v. 61(1); p. 790-794