Blazed gratings are periodic surface structures of great interest for applications such as friction control, light trapping, and spectrometry. While different laser processing methods have been explored to produce these elements, they have not yet surpassed conventional surface manufacturing techniques, often based on lithography processes or mechanical ruling. This work introduces a new approach based on the combination of ultrashort pulses and triangular beam shaping, which enables the generation of asymmetrical grooves in a single step. The main advantage of this strategy is that by simply changing the laser processing direction we can induce a significant modification in the ratio of asymmetry between the sidewall angles of the machined channels. The paper includes a comprehensive study, which has been supported by statistical tools, of the effect of this and other experimental parameters on the morphology of grooves machined on stainless steel. As a result, we achieved a wide range of geometries, with asymmetry ratios spanning from 1 to 5 and channel depths between 3 and 15 µm. Furthermore, we demonstrate the validity of the approach through the successful manufacture of blazed gratings of various slopes. The results reflect the versatility and cost-efficiency of the proposed fabrication strategy, and thus its potential to streamline the production of sawtooth gratings and other devices that are based on asymmetrical features.

Blistering of 11 nm and 45 nm-thick Al2O3 layers deposited by ALD on silicon substrates is studied in Al-Al2O3-Si structures fabricated using a field isolated process. Blisters are shown to be unevenly distributed and with different dimensions depending on the structure area. After chemical etching down to silicon, round voids are revealed underneath the blisters depending on the etchant used, indicating that some chemical reaction occurs at the Al2O3-Si interface at the blistered sites.

A quantized bands model capable to generate capacitance-voltage (C-V) curves of MOS capacitors was implemented and numerical details are discussed. This model is applied to the extraction of the dielectric constant of Al2O3 layers with known physical thicknesses by fitting experimental results. A comparison with a continuum band model is presented.

In this work, a systematic study of the electrical properties and the cycle-to-cycle variability in Ni/HfO2-based RRAM devices is presented. Besides the resistive switching behavior, attention is also given to the impact of temperature on device stability and variability.

Flexible gas sensing devices have been fabricated by directly integrating multilayer polymer-based platforms and highly crystalline tungsten oxide nanoneedles grown via aerosol-assisted chemical vapor deposition (AACVD). Thermal simulations and characterization of the heating element demonstrate these devices provide uniform temperature distribution at the sensing active area and gas sensing tests show repeatable and satisfactory responses towards hydrogen and ethanol. These devices go beyond traditional gas sensors, offering flexibility and functionality, with a fabrication method that provides great advantages for the integration of nanomaterials and flexible platforms and that can be used in a cost effective production for large-scale applications.

Flexible gas sensor devices comprised of heating and transducing elements are produced by directly integrating multilayer polymeric-based platforms and highly crystalline semiconducting metal oxide nanostructures grown via vapour-phase method, as main improvement over other methods for fabricating flexible gas sensors. Thermal simulations and characterizations of the heating element demonstrate these devices provide uniform temperature distribution at the sensing active area, and the electrical properties of the sensing film and electrodes indicate the networked-nanostructures are ohmically connected. Validation of the sensing device shows repeatable and satisfactory responses towards ethanol, demonstrating this fabrication method, with potential in a cost effective production for large-scale applications, is an attractive route for developing next generation of gas sensing devices provided of flexibility and functionality. (C) 2014 Elsevier B.V. All rights reserved.

In this letter, we focus on the cycle-to-cycle variability of the low resistive state in Ni/HfO2-based resistive switching structures. The results show that several discrete current levels can individually last hundreds of cycles. They are a result of the random nature of the reversible conductive path formation through percolation processes, which could be attributed to a different shape, size, or number of conductive filaments. After successive cycles, the same or new filaments will nucleate in the weaker zones of the dielectric. In addition, the switching voltages related to the creation and dissolution of localized conductive paths are found to be statistically associated.

In this work, a systematic study of the electrical characteristics of Al2O3 and HfO2 dielectrics based MOS capacitors is presented enabling the analysis of the impact of pre-existing electrically active defects, stress induced degradation and the dielectric breakdown phenomena on the leakage current behavior.

The electrical properties of HfO2-based metal–insulator–semiconductor capacitors have been systematically investigated by means of I–V and C–V characteristics, admittance spectroscopy, deep level transient spectroscopy, conductance transient, and flat band voltage transient techniques. Attention is also given to the study of the temperature dependence of the leakage current. HfO2 films were grown on p-type silicon substrates by atomic layer deposition using hafnium tetrakis(dimethylamide) as hafnium precursor, and ozone or water as oxygen precursors. The growth temperature ranged from 150 to 350 °C. Low growth temperatures prevent decomposition and high growth rate, as well as high contamination levels. As a result, the leakage current is lower for lower deposition temperatures. Some of the deposited samples were submitted to a postdeposition annealing at 650 °C in N2 atmosphere, showing a decrease in the leakage current and an increase in the equivalent oxide thickness (EOT), whereas interfacial state density increases and defect density inside the dielectric bulk decreases. Regarding dielectric reliability, in our experimental conditions, HfO2 layers grown at 150 °C exhibit the largest EOT and breakdown voltage. The electrical behaviour is clearly linked with structural properties, and especially with the formation of an interfacial layer between the HfO2 layer and the silicon substrate, as well as with the presence of several impurities.

2MeV electron irradiation effects on the electrical properties of Al2O3 and HfO2-based metal–insulator–semiconductor capacitors have been studied. High-k dielectrics were directly grown on silicon by atomic layer deposition. Capacitors were exposed to three different electron irradiation doses of 0.025, 0.25 and 2.5MGy. Capacitance–voltage, deep-level transient spectroscopy, conductance transients, flat-band voltage transients and current–voltage techniques were used to characterize the defects induced or activated by irradiation on the dielectric bulk and on the interface with silicon substrate. In all cases, positive charge is trapped in the dielectric bulk after irradiation indicating the existence of hole traps in the dielectric. When the samples are exposed to 2MeV electron beam (e-beam) irradiation, electron–hole pairs are created and holes are then captured by the hole traps. Insulator/semiconductor interface quality slightly improves for low irradiation doses, but it is degraded for high doses. Irradiation always degrades the dielectric layers in terms of gate leakage current: the trapped holes are mobile charge which can contribute to leakage current by hopping from trap to trap.

In this work, a study of the influence of the processing conditions on the blistering of Al2O3 layers grown by atomic layer deposition (ALD) on silicon substrates is presented. The phenomenon occurs when the as-deposited layers are annealed at high temperature in a N2 atmosphere. The characterization of the blistering in terms of density and dimensions indicates that the higher the annealing temperature the higher the density but also the smaller the blister diameter, while the thicker the oxide the larger the blisters. The processing of the blistered layers to obtain Al-Al2O3-Si structures enhances the blistering phenomenon and at the same time affects the silicon surface underneath the blister. This has been evidenced by chemical etching of the deposited layers that have revealed in circular silicon voids of the size of the blister. The influence of the oxygen precursor used in the ALD process has also been investigated, showing that the blister size is reduced when using O3 instead of H2O. Finally, the use of a thin thermally grown SiO2 layer is shown to avoid blistering of Al2O3 films.

Atomic layer deposition of high-k dielectrics is currently identified to be an enabling technology for a variety of applications. An overview of the characteristics of the technique is presented and its limiting factors and opportunities discussed. Particular attention is paid to Al2O3 and HfO2 films deposited on silicon in terms of material and electrical characteristics for their use in MEMS and radiation detectors technologies and the effects of post-deposition annealing processing are discussed.

In this work, the impact of electrical stress on the electrical characteristics of 2 MeV electron irradiated metal-oxide-silicon capacitors with atomic layer deposited (ALD) high permittivity (high-k) dielectric layers of Al2O3, HfO2 and a nanolaminate of them is evaluated. The aim is to investigate the susceptibility to electrical stress of the radiation effects created in irradiated MOS structures, paying especial attention to any possible interaction between the radiation-induced damage and the subsequent electrical stress degradation. For this study, MOS capacitors with a nominal dielectric physical thickness of 10 nm (equivalent oxide thickness (EOT) between 3 nm and 7 nm) on different p-type and n-type silicon substrates were investigated. An exponentially increasing stress current was forced to flow in accumulation through the different dielectric layers, registering the evolution of gate voltage versus stress time until dielectric breakdown occurred. Capacitance-voltage characteristics of the different irradiated and non-irradiated structures are analyzed as a function of electrical stress. Different charge trapping behaviors and significant polarity dependence in interface state generation are observed for the dielectric layers subjected to substrate and gate injections. No clear interaction between radiation and electrical stress damages is noticed under substrate injection (n-type samples). However, higher negative charge trapping near the metal/dielectric interface is registered for the irradiated Al2O3 and nanolaminate layers subjected to gate injection and, in the case of the most irradiated samples, the radiation-induced interface states damage is found to dominate against the damage generated in early stages of the electrical stress. (C) 2013 Elsevier Ltd. All rights reserved.

In this work, we focus on the effects of electrical stress on the charge trapping behavior and electrical degradation of Al2O3 layers deposited by ALD. For this purpose, current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Al/Al2O3/n(+)Si capacitors are analyzed before and after constant voltage stress (CVS). The results show that electron trapping and hard breakdown (HBD) phenomena are the main degradation mechanisms observed under positive bias stress (or substrate injection). While, the generation of positive charge and new defects as well as the occurrence of soft breakdown (SBD) and progressive breakdown (PBD) failure modes, are identified as the dominant contributions when a highly enough negative bias (or gate injection) stress is applied. (C) 2013 Elsevier B.V. All rights reserved.

In this work, the authors focus on the charge trapping behavior of Al2O3 layers deposited by atomic layer deposition. The goal is to give an insight into the effects of the oxidant source (H2O or O3) and the postdeposition anneal on the charging phenomena and the generation of new defects during electrical stress. For this purpose, current–voltage, capacitance–voltage, and conductance–voltage characteristics of Al/Al2O3/p-Si capacitors are analyzed before and after constant voltage stress and several phenomena such as the generation of neutral traps in the bulk dielectric, slow states, interface states, and charge trapping related degradation during the electrical stress are investigated. Finally, the impact of the oxidant source on the Al2O3 layer reliability is discussed.

The effects of 2 MeV electron irradiation on the electrical characteristics of atomic layer deposited layers of Al2O3 with different thickness are evaluated by using metal-oxide-semiconductor capacitors with a dielectric physical thickness ranging from 2.8 nm to 11.6 nm. The capacitance-voltage and current-voltage characteristics of the capacitors are analysed as a function of electron irradiation. A progressive radiation-induced positive charge trapping and increase of the leakage current with electron fluence is observed for the thickest layers subjected to electron irradiation. However, the effects are significantly lower or even negligible for the thinnest Al2O3 films. (C) 2013 Elsevier Ltd. All rights reserved.

Atomic layer deposition (ALD) of Al2O3 is of interest for a wide range of micro-nanoelectronic applications, where the electrical properties of the deposited layers can be strongly affected by deposition conditions and post-deposition treatments. In this work, a mercury-probe capacitance-voltage characterization is carried out on Al2O3 films deposited on silicon by ALD at different temperatures and subjected to various thermal treatments in N-2 ambient. Effective positive charges located at the semiconductor/dielectric interface are encountered for the films deposited at the lowest temperature (100 degrees C). Positive V-fb shifts are always registered after the different thermal annealing conditions studied; however, the impact of the thermal treatments is found to be different depending on the deposition temperature. A significant negative charges build-up is observed after a 30 min anneal at 450 degrees C, where improved surface passivation properties are achieved. Interestingly, the hysteresis, as well as the V-fb shifts, clearly diminish for higher deposition temperatures or after a thermal anneal. However, the highest temperature treatments (>= 800 degrees C) result in significant interface states generation. Finally, exploratory experiments about the stability of the Al2O3 layers under UV-light irradiation (in the 200-300 nm wavelengths range) show that this can be responsible for a significant degradation of their electrical characteristics. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3559458] All rights reserved.

In this work, the electrical characteristics of different atomic layer deposited high-permittivity dielectric films (Al2O3, HfO2, and a nanolaminate of them), with a physical thickness of about 10 nm, are evaluated. An extensive capacitance-voltage and current-voltage characterization at room temperature is carried out on metal-insulator-semiconductor structures fabricated on different p-type and n-type silicon substrates and with Al as metal gate. HfO2 layers are found to exhibit the higher dielectric constant, but they suffer from the largest hysteresis and leakage currents and the lowest breakdown voltages. The nanolaminate stacks, with an intermediate dielectric constant, are found to exhibit more similarities to the Al2O3 layers, withstanding the largest voltages of all the studied dielectric films. The electrical degradation of the layers is evaluated by means of consecutive current-voltage ramps and with constant voltage stress experiments. Results on n-type Si, with electron injection from the substrate, indicate a dominant negative charge trapping on all the studied layers, leading to a decrease in the leakage current levels. On the other hand, the results on p-type Si, with electron injection from the metal gate, suggest that not only charge trapping but also creation of new traps, particularly under the higher stress voltages, are responsible for the observed degradation. (c) 2011 American Vacuum Society. [DOI: 10.1116/1.3532544]

Alumina (Al2O3) thin films have been deposited on silicon substrates by atomic layer deposition at 200°C using TMA as Al precursor and H2O or O3 as oxygen precursor. The growth rate has been found to be lower for ozone-based processes as compared to H2O. The electrical characterization of the deposited layers has shown that when using O3 the films exhibit larger defect densities as compared to those grown using H2O, although these show larger trapping. A post deposition anneal process at 650°C has been shown to lower the defect densities, being this annealing more efficient for O3-grown layers. The effect of post-metallization annealing in forming gas is also investigated.