Search results for "SILICON"
showing 10 items of 1391 documents
Ab initio studies on the lattice thermal conductivity of silicon clathrate frameworks II and VIII
2016
The lattice thermal conductivities of silicon clathrate frameworks II and VIII are investigated by using ab initio lattice dynamics and iterative solution of the linearized Boltzmann transport equation(BTE) for phonons. Within the temperature range 100-350 K, the clathrate structures II and VIII were found to have lower lattice thermal conductivity values than silicon diamond structure (d-Si) by factors of 1/2 and 1/5, respectively. The main reason for the lower lattice thermal conductivity of the clathrate structure II in comparison to d-Si was found to be the harmonic phonon spectra, while in the case of the clathrate structure VIII, the difference is mainly due to the harmonic phonon spe…
Phonon-plasmon coupling in Si doped GaN nanowires
2016
Abstract The vibrational properties of silicon doped GaN nanowires with diameters comprised between 40 and 100 nm are studied by Raman spectroscopy through excitation with two different wavelengths: 532 and 405 nm. Excitation at 532 nm does not allow the observation of the coupled phonon–plasmon upper mode for the intentionally doped samples. Yet, excitation at 405 nm results in the appearance of a narrow peak at frequencies close to that of the uncoupled A 1 (LO) mode for all samples. This behavior points to phonon–plasmon scattering mediated by large phonon wave-vector in these thin and highly doped nanowires.
Electron-phonon heat transport and electronic thermal conductivity in heavily doped silicon-on-insulator film
2003
Electron–phonon interaction and electronic thermal conductivity have been investigated in heavily doped silicon at subKelvin temperatures. The heat flow between electron and phonon systems is found to be proportional to T6. Utilization of a superconductor–semiconductor–superconductor thermometer enables a precise measurement of electron and substrate temperatures. The electronic thermal conductivity is consistent with the Wiedemann–Franz law. Peer reviewed
Stabilisation of tetragonal zirconia in oxidised ZrSiN nanocomposite coatings
2004
Abstract ZrSiN coatings were deposited on steel and silicon substrates by reactive sputtering of a composite ZrSi target. The coatings were oxidised in air in the 600–750 °C temperature range. As-deposited and oxidised films were characterised by X-ray diffraction, micro-Raman spectroscopy, X-ray photoemission spectroscopy and glow discharge optical emission spectroscopy. The oxidation behaviour of ZrSiN coatings was compared to that of ZrN ones. It was demonstrated that addition of silicon in the 3–5 at.% range into ZrN-based coatings promotes the onset of oxidation by nearly 100 °C. The structure of the oxide layer was strongly dependent on the film’s silicon content: monoclinic zirc…
Nanocrystal metal-oxide-semiconductor memories obtained by chemical vapor deposition of Si nanocrystals
2002
We have realized nanocrystal memories by using silicon quantum dots embedded in silicon dioxide. The Si dots with the size of few nanometers have been obtained by chemical vapor deposition on very thin tunnel oxides and subsequently coated with a deposited SiO2 control dielectric. A range of temperatures in which we can adequately control a nucleation process, that gives rise to nanocrystal densities of ∼3×1011 cm−2 with good uniformity on the wafer, has been defined. The memory effects are observed in metal-oxide-semiconductor capacitors or field effect transistors by significant and reversible flat band or threshold voltage shifts between written and erased states that can be achieved by …
Characterization of SiPM properties at liquid nitrogen temperature
2016
SiPM operation at cryogenic temperatures fails for many common devices. A particular type with deep channels in the silicon substrate instead of quenching resistors was thoroughly characterized from room temperature down to liquid nitrogen temperature by illuminating it with low light levels. The devices were mounted in vacuum with the temperature stabilized to allow long-term operation. SiPM signals from a LED pulser were acquired with single-pixel resolution. Generalized fits to the charge collection spectra were used to extract properties like single-pixel gain, inter-pixel variation, breakdown voltage, and photon detection efficiency. With these measurements a deeper investigation of th…
Peculiar aspects of nanocrystal memory cells: Data and extrapolations
2003
Nanocrystal memory cell are a promising candidate for the scaling of nonvolatile memories in which the conventional floating gate is replaced by an array of nanocrystals. The aim of this paper is to present the results of a thorough investigation of the possibilities and the limitations of such new memory cell. In particular, we focus on devices characterized by a very thin tunnel oxide layer and by silicon nanocrystals formed by chemical vapor deposition. The direct tunneling of the electrons through the tunnel oxide, their storage into the silicon nanocrystals, and furthermore, retention, endurance, and drain turn-on effects, well-known issues for nonvolatile memories, are all investigate…
Effects of partial self-ordering of Si dots formed by chemical vapor deposition on the threshold voltage window distribution of Si nanocrystal memori…
2006
We study the role that the denuded zone around Si nanocrystals obtained by chemical vapor deposition plays on the fluctuations of the dot surface coverage. In fact, the capture mechanism of the silicon adatoms in the proximity of existing dots restricts the number of possible nucleation sites, the final dot size, and the dot position, thus driving the process toward partial self-order. We numerically evaluate the relative dispersion of surface coverage for several gate areas and compare the results to the fully random case. The coverage dispersion is related to the fluctuations from bit to bit of the threshold voltage window (Δ Vth) distribution of nanocrystal memories. The evaluations, com…
Development of dark Ti(C,O,N) coatings prepared by reactive sputtering
2008
Accepted manuscript
Effect of germanium addition on the properties of reactively sputtered ZrN films
2005
For the first time, Zr-Ge-N films were deposited on silicon and steel substrates by sputtering a Zr-Ge composite target in reactive Ar-N2 mixture. The films were characterised by electron probe microanalysis, X-ray diffraction, micro-Raman spectroscopy and depth-sensing indentation. The effects of the Ge content and substrate bias voltage on the films' structure, internal stress, hardness and oxidation resistance were investigated. Substrate bias strongly influenced the chemical composition of the films being observed by means of a steep decrease in the Ge content for negative bias voltages higher than -80 V. In these cases, a significant hardness improvement was registered. For -100 V bias…