Marcio Fontana

Electron-hole transport and photovoltaic effect in gated MoS2 Schottky junctions

Semiconducting molybdenum disulfphide has emerged as an attractive material for novel nanoscale optoelectronic devices due to its reduced dimensionality and large direct bandgap. Since optoelectronic devices require electron-hole generation/recombination, it is important to be able to fabricate ambipolar transistors to investigate charge transport both in the conduction band and in the valence band. Although n-type transistor operation for single-layer and few-layer MoS2 with gold source and drain contacts was recently demonstrated, transport in the valence band has been elusive for solid-state devices. Here we show that a multi-layer MoS2 channel can be hole-doped by palladium contacts, yielding MoS2 p-type transistors. When two different materials are used for the source and drain contacts, for example hole-doping Pd and electron-doping Au, the Schottky junctions formed at the MoS2 contacts produce a clear photovoltaic effect.

A New Approach for Condition Assessment of On-Load Tap-Changers using DiscreteWavelet Transform

On-load tap changers (OLTCs) are electromechanical devices used in the voltage regulation of the electrical networks. A non-invasive monitoring method was developed using discrete wavelet transform (DWT) for condition assessment of on-load tap-changers using vibration analysis signals. The transient vibration signals emitted during a tap change are recorded and processed using spectral analysis and standards recognition techniques. The monitoring systems which detect failure during the OLTC operation are quite complexes. In order to reduce this complexity, in this work we demonstrated a new approach based on DWT analysis. The proposed technique is presented and the experimental results as well as its simulation are discussed

A gain-scheduling PID-like controller for Peltier-based thermal hysteresis characterization platform

A linearized dynamic model for thermoelectric modules has been proposed and validated using experimental data. Employing this model, a digital temperature controller for sinusoidal thermal cycling of a vanadium-dioxide microbolometer has been designed. The controller permits the rate of change of temperature varying over a wide range with a tolerance of 0.01 /spl deg/C.

Corrigendum: Electron-hole transport and photovoltaic effect in gated MoS2 Schottky junctions.

Semiconducting molybdenum disulfphide has emerged as an attractive material for novel nanoscale optoelectronic devices due to its reduced dimensionality and large direct bandgap. Since optoelectronic devices require electron-hole generation/recombination, it is important to be able to fabricate ambipolar transistors to investigate charge transport both in the conduction band and in the valence band. Although n-type transistor operation for single-layer and few-layer MoS2 with gold source and drain contacts was recently demonstrated, transport in the valence band has been elusive for solid-state devices. Here we show that a multi-layer MoS2 channel can be hole-doped by palladium contacts, yielding MoS2 p-type transistors. When two different materials are used for the source and drain contacts, for example hole-doping Pd and electron-doping Au, the Schottky junctions formed at the MoS2 contacts produce a clear photovoltaic effect.

Condition Monitoring of Power Transformers Using Acoustic Signal Prony's Analysis

On-load tap changers (OLTCs) are electromechanical devices used for voltage regulation on electrical networks. A noninvasive monitoring technique was developed using Pronys method for condition assessment of on-load tap-changers using vibration analysis signals. The transient vibration signals emitted during a tap change are recorded and processed using Pronys spectral analysis and standard pre-processing techniques. Traditional condition monitoring techniques exhibit a certain degree of complexity, which may be a serious drawback when designing portable low-cost maintenance equipment. In order to reduce this complexity, we introduce a new index based on Pronys analysis. The proposed technique is presented and its diagnosis capabilities are evaluated using experimental results collected from field installed equipments during their maintenance inspection

Hysteresis modeling in ballistic carbon nanotube field-effect transistors.

Theoretical models are adapted to describe the hysteresis effects seen in the electrical characteristics of carbon nanotube field-effect transistors. The ballistic transport model describes the contributions of conduction energy sub-bands over carbon nanotube field-effect transistor drain current as a function of drain-source and gate-source voltages as well as other physical parameters of the device. The limiting-loop proximity model, originally developed to understand magnetic hysteresis, is also utilized in this work. The curves obtained from our developed model corroborate well with the experimentally derived hysteretic behavior of the transistors. Modeling the hysteresis behavior will enable designers to reliably use these effects in both analog and memory applications.

Influence of argon on field emission from CVD-grown in-plane single-walled carbon nanotube meshes

The influence of argon (Ar) on the growth of in-plane single-walled carbon nanotube (SWCNTs) meshes using chemical vapor deposition (CVD) was investigated in this study. The SWCNT samples were synthesized using a three-zone furnace (750°C-900°C-750°C) with a methane/hydrogen/argon mixture (total flow of 60 sccm). We verified that the use of argon influences the diameter distribution and the field emission properties of the resulting SWCNTs. The threshold voltage for electron emission was significantly decreased with higher argon concentration due to higher layer conductivity of the samples.