D. Tsamakis

Accurate measurements of the silicon intrinsic carrier density from 78 to 340 K

The intrinsic carrier density in silicon has been measured by a novel technique based on low‐frequency capacitancemeasurements of a p +‐i‐n + diode biased in high injection. The major advantage of the method is its insensitivity to uncertainties regarding the exact values of the carrier mobilities, the recombination parameters, and the doping density. The intrinsic carrier density was measured in the temperature range from 78 to 340 K. At 300 K the value of n i was found to be (9.7±0.1)×109 cm−3.

Simple method for the fabrication of a high dielectric constant metal-oxide-semiconductor capacitor embedded with Pt nanoparticles

We present a simple method for the fabrication of Pt nanoparticles embedded in a high-k dielectric. The nanoparticles are formed during the first deposition stages of a thin Pt layer on a 30A SiO2 tunneling layer, at room temperature, performed with electron-beam (e-beam) evaporation of metallic Pt. Then, the nanoparticles are covered, in situ, by a thicker HfO2 layer, which forms a control oxide. The fabricated nanoparticles have an average diameter of 4.9nm, sheet density of 3.2×1012cm−2 and they present high uniformity in their size. High-frequency capacitance-voltage (C-V) measurements demonstrate that this structure operates as a memory device.

An Experimentally Assisted Computational Analysis of Tin Oxide Deposition in a Cold-Wall APCVD Reactor

The design of a chemical vapor deposition (CVD) process in a complex reactor configuration was performed by combining computational fluid dynamics (CFD) simulations and experiments. This design methodology was implemented in a horizontal cold-wall reactor, where tin oxide deposition on silicon substrates at atmospheric pressure (APCVD) was experimentally investigated. A set of measured growth rates at different operating conditions was used to determine a Langmuir-Hinshelwood mechanism of the growth kinetics of tin oxide films by tin tetrachloride oxidation in a single-wafer reactor. The coupled kinetic/CFD model was then used to further analyze the influence of some key operating parameters on the process performance. Simulation results are suggestive of modifications in the operating parameters that could enhance the uniformity of the layer thickness. In particular, the uniformity of the layer thickness was investigated, with special attention paid to the origins of the axial and transverse heterogeneities on the wafer for each of the parameters examined, thus opening possible ways of process improvement.

Fabrication and characterization of a metal nanocrystal memory using molecular beam epitaxy

Recently, single and few electron devices have attracted a lot of attention due to their advantages when compared to the conventional DRAM or Flash memories. There is also a great effort to replace the silicon oxide (SiO2) with materials of high dielectric constant that could allow the further downscaling of MOSFET devices. In this work, initially we study the hafnium oxide (HfO2) deposition on thin SiO2. We fabricate a HfO2 layer, with good dielectric properties and with high dielectric constant. Then, we fabricate a novel MOS memory device with platinum (Pt) nanoparticles embedded in the HfO2/SiO2 interface.

Electron and hole mobilities in lightly doped silicon

The electron and hole mobilities were measured between 78 and 340 K. The method used is based on the frequency dependence of the conductance and the capacitance of a high resistivity diode biased in high injection. The method is insensitive to uncertainties regarding the ionized dopant densities. In the temperature range from 170 to 340 K the carrier mobilities vary as T−a, where a=2.34±0.08 for electrons while for holes a=2.85±0.05. At 77.8 K the hole mobility is 14000±400 cm2/V s while the electron mobility is 24000±800 cm2/V s.

Performance of a fractional dc electric motor equipped with plastic bonded Nd2Fe14B stator poles

Injection molding Nd2Fe14B plastic bonded magnetic material is pressed into the form of cylindrical ring segments in order to investigate its performance when used in the manufacturing of stator poles of fractional power dc motors. Measurements of speed and armature current versus different load torques were performed. The experimental results obtained for stator poles made by three plastic bonded Nd2Fe14B magnetic materials of different densities, are compared to those results obtained by using a pair of typical barium ferrite stator poles. The torque versus speed curves, the obtained mechanical power versus speed and the efficiency of the motor as a function of the speed are presented. The torque speed data in high speeds follow a linear law, as is expected by theory, while at low speeds, below a crossover point, a deviation from this linearity appears. This is attributed to temperature effects. In this work it is shown that in the region of light loads and high speeds, at a certain speed, the injection...

A modeling of the retention characteristics of non-volatile memories embedded with metallic nanoparticles

Despite the technological maturity of non-volatile memories (NVMs) embedded with metal or semiconductor nanoparticles (NPs) there is still considerable controversy over their discharging behaviour when the writing voltage is removed. Exponential [1,2] and logarithmic [3,4] discharge laws coexist in the literature.

Methane sensing properties of Cu x O thin films deposited by pulsed laser deposition

In the last years, semiconductor metal oxide films play an increasing role as sensing devices for various gases [1,2]. Copper oxides thin films (Cu2O and CuO) are p-type semiconductors that have attracted much interest due to their potential applications for solar cells and gas sensors [3,4]. Especially, the composites of copper oxides and n-type metal oxides such as ZnO/CuO and SnO2/CuO have been studied as gas sensors [5–7]. However, the research on copper oxide gas sensors is far from being satisfactory and only a few investigations have shown their gas-sensing properties to flammable gases such as CH4 [8].

Electrical characterization of Cr / p-ZnO Schottky contacts grown by pulsed laser deposition (PLD) on Si substrate

ZnO is an attractive wide band gap semiconductor and a promising material for transparent electronic applications such as short-wavelength LEDs [1,2], lasers [1] and UV detectors [3] because it can be obtained chemically stable and easily deposited on different semiconductor substrates (Si, InGaAs, GaAs) [4]. The use of ZnO in variety of applications is mainly due to its important properties of a direct band gap with an energy gap of 3.37 eV at RT and a large exciton binding energy of 60 meV.

Methane sensing properties of CuxO thin films deposited by pulsed laser deposition

In the last years, semiconductor metal oxide films play an increasing role as sensing devices for various gases [1,2]. Copper oxides thin films (Cu2O and CuO) are p-type semiconductors that have attracted much interest due to their potential applications for solar cells and gas sensors [3,4]. Especially, the composites of copper oxides and n-type metal oxides such as ZnO/CuO and SnO2/CuO have been studied as gas sensors [5–7]. However, the research on copper oxide gas sensors is far from being satisfactory and only a few investigations have shown their gas-sensing properties to flammable gases such as CH4 [8].