Characterisation of sol-gel PZT films on Pt-coated substrates

A conventional sol-gel process was used to spin-cast PZT films on oxidized Si wafers coated with sputtered Pt layers. After annealing at 550 degrees C-800 degrees C, the resulting perovskite-type PZT films showed different textures and surface morphologies, depending on whether or not a Ti adhesion layer was used. If a Ti layer was present, Ti diffusion into and through the Pt film leads to a compound Pt3Ti, which facilitates crystallization of the perovskite PZT phase; without Ti, crystallization is more difficult and occurs via the growth of dendritic crystallites. Several optical and electrical properties of the PZT films have been measured; the first results indicate high dielectric constants ( epsilon approximately=480) and acceptable ferroelectric behaviour

Tin dioxide sol-gel derived thin films deposited on porous silicon

Undoped and Sb-doped SnO2 sol¿gel derived thin films have been prepared for the first time from tin (IV) ethoxide precursor and SbCl3 in order to be utilised for gas sensing applications where porous silicon is used as a substrate. Transparent, crack-free and adherent layers were obtained on different types of substrates (Si, SiO2/Si). The evolution of the Sn¿O chemical bonds in the SnO2 during film consolidation treatments was monitored by infrared spectroscopy. By energy dispersive X-ray spectroscopy performed on the cross section of the porosified silicon coupled with transmission electron microscopy, the penetration of the SnO2 sol¿gel derived films in the nanometric pores of the porous silicon has been experimentally proved

Identification of temperature profile and heat transfer on a dielectric membrane for gas sensors by `COSMOS' program simulation

The application of commercial 3-D software `COSMOS' for the design and thermal analysis of the low power consumption test structures with dielectric membrane for gas microsensors is presented. Within this work, the simulation provides the estimation of the temperature profile on the active area and the whole membrane including the four bridges and the heating efficiency in the temperature range 20-500 °C. Unravelling of the heat loss mechanisms in terms of radiation, convection, conduction by air and solid materials during heat transfer on the dielectric membrane is reported for the first time as a mean to evaluate by 3-D simulation the contribution of technological processes and lay-out design to the total heat losses

Electrical characterisation of gate dielectrics deposited with multipolar electron cyclotron resonance plasma source

Silicon oxide films have been deposited by plasma-enhanced chemical vapour deposition, at glass compatible temperatures. A multipolar electron cyclotron resonance plasma (ECR) source with SiH4/He and N2O was used. The electrical properties of the films were determined by means of C-V and I-V measurements. The dependencies of the electrical properties on gas-flow ratio and pressure were investigated. Critical electric fields as high as 6 MV/cm and net oxide charge densities as low as 1×1011 ions/cm2 have been obtained for the optimal deposition conditions. The oxide integrity versus CVD conditions was investigated by charge to breakdown measurements. MOSFETs have been fabricated in order to test the dielectric quality

Thermal modelling of a porous silicon-based pellistor-type catalytic flammable gas sensor with two supporting beams

A three-dimensional transient thermal mathematical model of a porous silicon based pellistor with two supporting beams was developed. The model was numerically solved using the implicit alternating-direction finite difference method. A computer program written in ANSI C and run on a VAX/VMS computer was utilized to study the influence of the power consumption and the main geometrical dimensions (membrane, beam and heater size) of the pellistor mentioned above on its transient and steady-state thermal behaviour. It was found that considerable improvement in the thermal behaviour of the pellistor could be achieved by reducing the membrane size (length and width). The optimal beam length was determined as 100 μm. By comparing the main sources of energy dissipation it was found that energy was lost predominantly through the heat conduction into the supporting beams

An intensive study of LPCVD silicon morphology and texture for non volatile memory

Results of an intensive study by means of XRD, SEM, AFM and TEM of the microstructure (i.e. the texture and morphology) of LPCVD silicon layers as a function of different process parameters are described. The influence of different deposition parameters, like partial and total pressure, doping, deposition and anneal temperature is shown. In particular the roughness of the silicon surface is investigated. The relation of surface roughness to the electrical properties of dielectrics, grown on these silicon layers, is briefly discussed

Plasmonic hot-electron reconfigurable photodetector based on phase-change material Sb2S3

Hot-carrier based photodetectors and enhanced by surface plasmons (SPs) hot-electron injection into semiconductors, are drawing significant attention. This photodetecting strategy yields to narrowband photoresponse while enabling photodetection at sub-bandgap energies of the semiconductor materials. In this work, we analyze the design of a reconfigurable photodetector based on a metal-semiconductor (MS) configuration with interdigitated dual-comb Au electrodes deposited on the semiconducting Sb2S3 phase-change material. The reconfigurability of the device relies on the changes of refractive index between the amorphous and crystalline phases of Sb2S3 that entail a modulation of the properties of the SPs generated at the dual-comb Au electrodes. An exhaustive numerical study has been realized on the Au grating parameters formed by the dual-comb electrodes, and on the SP order with the purpose of optimizing the absorption of the device, and thus, the responsivity of the photodetector. The optimized photodetector layout proposed here enables tunable narrowband photodetection from the O telecom band (λ = 1310 nm) to the C telecom band (λ = 1550 nm).Horizon 2020 Framework Programme (No 899598 – PHEMTRONICS

Dispersion force for materials relevant for micro and nanodevices fabrication

The dispersion (van der Waals and Casimir) force between two semi-spaces are calculated using the Lifshitz theory for different materials relevant for micro and nanodevices fabrication, namely, gold, silicon, gallium arsenide, diamond and two types of diamond-like carbon (DLC), silicon carbide, silicon nitride and silicon dioxide. The calculations were performed using recent experimental optical data available in the literature, usually ranging from the far infrared up to the extreme ultraviolet bands of the electromagnetic spectrum. The results are presented in the form of a correction factor to the Casimir force predicted between perfect conductors, for the separation between the semi-spaces varying from 1 nanometre up to 1 micrometre. The relative importance of the contributions to the dispersion force of the optical properties in different spectral ranges is analyzed. The role of the temperature for semiconductors and insulators is also addressed. The results are meant to be useful for the estimation of the impact of the Casimir and van der Waals forces on the operational parameters of micro and nanodevices

Polarimetry analysis and optical contrast of Sb₂S₃ phase change material

Phase-change materials (PCMs) are the cornerstone for the development of reconfigurable and programmable photonic devices. Sb2S3 has been recently proposed as an interesting PCM due to its low-losses in the visible and near-IR. Here, we report the use of imaging polarimetry and spectroscopic ellipsometry to reveal and directly measure the optical properties of Sb2S3 both in crystalline and amorphous states obtained upon crystallization by annealing in air of chemical bath deposited amorphous Sb2S3. The Mueller Matrix polarimetric analysis reveals the strong anisotropy of the Sb2S3 crystallites which crystallize in radial spherulitic domains in contrast to the optical isotropy of the amorphous films. A refractive index contrast of Δn = 0.5 is demonstrated while maintaining low-losses at telecommunications C-band, i.e., λ = 1550 nm

CMOS-compatible SOI micro-hotplate-based oxygen sensor

© 2016 IEEE. The paper reports upon the design and characterization of a resistive O2 sensor, which is fully CMOS-compatible and is based on an ultra-low-power Silicon on Insulator (SOI) micro-hotplate membrane. The microsensor employs SrTi0.4Fe0.6O2.8 (STFO60) as sensing layer. Thermo-Gravimetric Analysis (TGA) Energy-Dispersive X-ray Spectroscopy (EDX), X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) techniques have been used to assess the quality of both the sensing layer and STFO-SOI interface. At room temperature, the SOI sensor shows good sensitivity and fast response time (≤ 6 seconds) to O2 concentration ranging from 0% to 20% in a nitrogen atmosphere. This is the first experimental result showing the potential of this structure as O2 sensor