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International audience; The development of simple and reproducible synthesis techniques for obtaining one-dimensional semiconducting nanostructures is essential for the advancement of gas sensor devices. We report a facile and versatile approach for the in-situ growth of vertically oriented hematite nanorods to be applied as a resistive ozone gas sensor. The α-Fe2O3 nanorods were grown via a hydrothermal treatment directly onto an Al2O3 substrate with interdigitated Pt electrodes, thus facilitating the integration of nanorods into the sensing platform. At 150 °C, the gas-sensing experiments revealed a good sensitivity of these nanorods to different ozone concentrations (10 to 570 ppb), besides a fast response time and repeatable response–recovery cycles. The present study offers a promising way for designing high-performance gas sensors based on hematite nanorods.

International audience; Chemiresistors are highly important for monitoring and detection of harmful gases produced from industrial processes and vehicle emissions. We report herein an experimental investigation of the gas-sensing properties of Zn0.95Co0.05O thin film deposited by spray pyrolysis technique. The X-ray photoelectron spectroscopy indicated the presence of Co2+ ions into de ZnO lattice. The gas-sensing measurements revealed the sensitivity of Zn0.95Co0.05O film towards ozone gas in a wide range of concentrations from 20 to 1040 ppb, exhibiting good repeatability and total reversibility after consecutive exposures. Selectivity towards ozone is observed in comparison to NO2, NH3, and CO gases even at low levels. This manuscript reports the effectiveness of spray-pyrolysis method for obtaining nanostructured Zn1-xCoxO thin films for practical applications as an ozone gas sensor.

International audience; In this work, the conductance behavior of tungsten trioxide based chemoresistive ozone sensors under ultra violet illumination was investigated. The tungsten trioxide sensitive layers were deposited on a SiO2/Si substrate by reactive radio frequency magnetron sputtering with several Argon / Oxygen ratios. The detection principle is based on a change in the conductance of the semiconductor oxides when ozone is present around the surface. We demonstrate the influence of Argon / Oxygen during the deposition of the sensitive layer, on ozone detection at 50°C under light illumination. The sensor shows good sensitivity to ozone, with a stable baseline, fast response and recovery time. These results are promising for the detection of ozone at low temperature.

A barium titanate thin film was deposited by drop coating for carbon dioxide detection. The measurements are based on a resistance change and provided a sensitive response to different CO2 concentrations under a humidity environment. The concentration measurement range was between 100 and 5000 ppm of CO2 in synthetic air, and likewise, the relative humidity was between 20 and 70%. The response and recovery times of the BaTiO3 based resistive sensors were determined to 2 min and 4 min, respectively, for 400 ppm of carbon dioxide and 50% relative humidity.

International audience; Over the past fifty years, gas sensors based on metal semiconducting oxides (MOXs) have drawn attention due to their performance in detecting various gases. Thus, we report herein on a BTEX gases sensor based on hematite (α-Fe2O3) microrhombuses synthesized via the hydrothermal method. X-ray diffraction and X-ray absorption spectroscopy analyses indicated the presence of a pristine hematite phase after hydrothermal treatment. Electron microscopy analyses revealed that the hematite sample consists of single-crystals with a rhombus-like shape and an average size of 140 nm. Electrical measurements pointed out that hematite microrhombuses were sensitive towards sub-ppm BTEX levels, in which the minimum detected level was 3 ppb and the long-term stability was 1 month. The results presented here demonstrate the potential of hematite microrhombuses as a sensing material to manufacture BTEX gas sensor devices.

The effects of white-light irradiation on similar to 15.nm diameter ZnO nanoparticles are investigated by means of electron paramagnetic resonance, near liquid-nitrogen and liquid-helium temperatures. Under dark conditions, usual core- and surface-defects are detected, respectively, at g = 1.960 and g = 2.003. Under white-light illumination, the core-defect signal intensity is strongly increased, which is to be correlated to the light-induced conductivitys augmentation. Beside, a four-lines structure appears, with the same gravity center as that of the surface defects. Simulations and intensity power-dependence measurements show that this four-line-structure is very likely to arise from a localized high spin S = 2, induced by light irradiation, and subjected to a weak axial anisotropy. At 85K, this high-spin state can last several hours after the light-irradiation removal, probably due to highly spin-forbidden recombination process. The possible excited resonant complexes at the origin of this signal are discussed. Other light-induced S = 1/2-like centers are detected as well, which depend on the nanoparticles growth conditions. Funding Agencies| [CNRS-FR3443]

The effects of white-light irradiation on ~ 20 nm diameter ZnO nanoparticles are investigated by means of electron paramagnetic resonance, near liquid-nitrogen and liquid-helium temperatures. Under dark conditions, usual core- and surface-defects are detected, respectively at g=1.960 and g = 2.003. Under white-light illumination, the core-defect signal intensity is strongly increased, which is to be correlated to the light-induced conductivity's augmentation. Beside, a four-lines structure appears, with the same gravity center as that of the surface defects. Simulations and intensity power-dependence measurements show that this four-line-structure is very likely to arise from a localized high spin S=2, induced by light irradiation, and subjected to a weak axial anisotropy. At 85 K, this high-spin state can last several hours after the light-irradiation removal, probably due to highly spin-forbidden recombination process. The possible excited resonant complexes at the origin of this signal are discussed. Other light-induced S=1/2-like centers are detected as well, which depends on the nanoparticles growth conditions.

Over the last decades, there has been considerable interest in the synthesis of one-dimensional (1D) metal oxide nanostructures that can be used in gas sensor devices. Heterostructures, obtained by a combination of different semiconductor nanomaterials with different band energies, have been extensively studied in order to enhance their gas-sensing performance. In this context, our present study focuses on the investigation of chemiresistive-sensing capabilities of a combination of TiO2 nanoparticles and V2O5 nanowires obtained via hydrothermal treatment of the peroxo-metal complex. The formation of V2O5/TiO2 heterostructures was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) measurements. This study also proposes an efficient approach to produce 1D V2O5/TiO2 heterostructures with a good range of detection (0.09–1.25 ppm) and remarkable ozone-sensing properties related to repeatability and selectivity., The authors gratefully acknowledge the financial support of the Brazilian research funding agencies FAPESP (under grant number FAPEP 2013/17639-4, 2013/07296-2, 17/18649-4, and 2017/12437-5), CNPq (311463/2017-7), and CAPES (Financial Code 001). Transmission electron microscopy (TEM-21464) and X-ray photoelectron spectroscopy (XPS20607 and XPS-21082) were performed at the LME/ LNNano/CNPEM. The electrodes used for the gas-sensing experiments were fabricated in the Laboratory of Microfabrication at the LNNano/CNPEM (Projects LMF-18580). The STEM-EELS and HRTEM measurements were performed in the Advanced Microscopy Laboratory (LMA) at the Institute of Nanoscience of Aragon (INA), University of Zaragoza (Spain). R.A. gratefully acknowledges the support from the Spanish Ministry of Economy and Competitiveness (MAT2016-79776-P) and the Government of Aragon through projct DGA E13_17R (FEDER, EU).

Introduction Environmental safety is attracting significant attention due to the increase of dust particles, and toxic gas species (e.g. CO, NOx, etc.) [1]. CO is identified as a major threat for human health. Since CO is a colorless, odorless, and tasteless gas, it can't be detected by human senses. Therefore, sensitive sensor operating in humid air is required for CO gas detection [2]. For metal oxide (MOX) gas sensors, the humidity interferes with the low-level detection of reducing and oxidizing gases. The performances of MOX gas sensors such as SnO2 or CuO can be enhanced, by metal doping, material functionalization or MOX composite [3]. In this work, a comparison between resistive sensors based on CuO and on BaTiO3-CuO bi-layer film will be presented. The sensor responses to three CO gas concentrations in dry air and in 50% of relative humidity (RH) will be discussed. Method BaTiO3 nanoparticles (NPs) (2 powder (0.2 g) was dissolved in acetic acid (5 ml), water (7 ml) and ethylene glycol (2ml). These two solutions were deposited by drop coating on a silicon oxide substrate provided with interdigitated platinum electrodes (figure 1). CuO films were prepared with one drop of Cu(OH)2 solution. BaTiO3-CuO films were fabricated with one drop of BaTiO3 NPs, an ambient drying for 5 minutes followed by one drop of Cu(OH)2 solution on the top of it. Then, the sensors were annealed at 500°C for 1 h. The sensing properties of these sensors were investigated by CO exposure. NI PXIe-4140 sourcemeter was used to measure the sensor resistance variations for an optimum operating temperature found at 280°C. Results and Conclusions Figure 2 shows the x-ray diffractograms of CuO and BaTiO3-CuO materials. The XRD patterns of CuO film indicate the existence of CuO nanoparticles in the monoclinic phase without CuO2 nanoparticles [4]. BaTiO3-CuO bilayer consists of a tetragonal phase of BaTiO3 in addition to monoclinic CuO [5]. Figure 3 presents the responses of CuO and BaTiO3-CuO to CO gas. In dry air, CuO gives a response equals to 1.22, while the response is more important for BaTiO3-CuO (1.41). In 50% RH, the sensor responses with CuO have almost disappeared while the sensors based on BaTiO3-CuO film gave a response equals to 1.32. Therefore, BaTiO3-CuO films have an enhanced response to CO in dry air as well as in the presence of 50% RH. The CO concentration effect on BaTiO3-CuO films was tested for 10, 50, and 100 ppm of CO in dry air and 50% RH (figure 4). Linear responses under CO in dry or wet air make BaTiO3-CuO bilayer films a potential candidate for the CO gas detection application. We have developed sensors based on BaTiO3-CuO composite for the CO gas detection under dry and wet air. The sensing properties are based on the resistance variation under CO gas. Our results show enhanced responses of BaTiO3-CuO concerning CuO in dry air and 50% RH. Future work will be focused on the proportion of BaTiO3 and CuO investigations to enhance the sensor response under CO. References [1] A. Kumar, A. Sanger, A. Kumar, et R. Chandra, « Highly sensitive and selective CO gas sensor based on a hydrophobic SnO2/CuO bilayer », RSC Adv., 6, 52, (2016), 47178–47184. doi: 10.1039/C6RA0653 [2] K. Sircar, J. Clower, M. Kyong Shin, C. Bailey, M. King, et F. Yip, « Carbon monoxide poisoning deaths in the United States, 1999 to 2012 », Am. J. Emerg. Med., 33, (2015), 1140–1145. doi: 10.1016/j.ajem.2015.05.002 [3] M. Hijazi, M. Rieu, V. Stambouli, G. Tournier, J.-P. Viricelle, et C. Pijolat, « Ambient temperature selective ammonia gas sensor based on SnO2 -APTES modifications », Sens. Actuators B Chem., 256, (2018), 440–447. doi: 10.1021/acsomega.9b02185 [4] K. Martin, G. McCarthy, North Dakota State Univ., Fargo, ND, USA., ICDD Grant-in-Aid, 1991. [5] S. B. Rudraswamy et N. Bhat, « Optimization of RF Sputtered Ag-Doped BaTiO3-CuO Mixed Oxide Thin Film as Carbon Dioxide Sensor for Environmental Pollution Monitoring Application », IEEE Sens. J., 16, (2016), 5145–5151. doi: 10.1109/Jsen.2016.2567220 Figure 1

International audience; In this work, we focus on ozone (O3) detection at room temperature in the main objective to be well suited for most of flexible substrates. Aluminum doped zinc oxide (AZO) nanoparticles were deposited in thin films to be used as ozone gas sensors. It was demonstrated that the nanoparticles had good sensitivity to O3 at low temperature ( 125°C) when the sensor was exposed to UV illumination. This study provides an easy and efficient way to obtain O3 gas sensors at temperature from 25°C up to 125°C by a simple and versatile solution-process. Electrical resistance measurements at 25°C under UV irradiation showed that AZO thin films were sensitive even at a low ozone concentration (35 ppb).

International audience; Ammonia detection at low temperatures below 150 °C is attractive to be well suited for flexible substrates in terms of thermal strain and to specific environment not allowing high temperature such as explosive one. In commercial gas sensors, tungsten trioxide is the mostly used semiconducting metal oxide after tin dioxide. We report herein the efficiency of tungsten trioxide nanowires deposited on rigid substrate by drop coating from colloidal solution. This study provides an interesting approach to fabricate ammonia sensors on conformable substrate with significant properties for applications in environmental monitoring devices.

The formation of voids on the surface of heavily implanted germanium has been known for more than 30 years. Recently there is a renewed interest in germanium due to its potential application in the complementary metal oxide semiconductor (CMOS) devices. Here we report the observation of germanium oxide microcrystals formed on the surface of tellurium implanted into a germanium substrate. The Ge target used was a (1 0 0) polished single crystalline germanium wafer and the implantation was carried out at room temperature with Te ions at 180 keV and a fluence of 3.6 × 1015 at/cm2. Under scanning electron microscope (SEM), the surface of the Ge substrate is evenly covered by microcrystals with a diameter about 1–2 μm and a coverage density of ∼107 particles/cm2. The initially smooth surface of the polished germanium substrate becomes very rough and mostly consists of voids with an average diameter of 40–60 nm, which is consistent with reports of heavily implanted germanium. The composition of the microcrystals was studied using energy dispersive X-ray analysis (EDX) and atom probe tomography (APT) and will be presented. Preliminary results indicate that tellurium is not detected in the microcrystals. The origin of the microcrystals will be discussed.

International audience; Specific filters can be used up-stream with metal oxide (MOX) gas sensors to trap ozone and allow the selective detection of NO2. These filtering media are based on nanoporous matrices doped with indigo-carmine that reacts selectively with O$_3$. The nanoporous materials, produced via the sol-gel process using functionalized silicon alkoxides as precursors, are tailored for the trapping of O$_3$. Depending on the nature of the filter, it is possible to entirely trap O$_3$ and allow NO$_2$ to partially pass over a certain range of concentration. For air depollution purpose, selected filters that efficiently trap both O$_3$ and NO$_2$ were exposed to harsh conditions under high concentrations of O$_3$ (350–475 ppb) and humidity (RH: 72%, T = 21 °C). Their trapping efficiency and lifetime are determined and compared with those of activated carbon.

International audience; Nitrogen dioxide (NO2) is a major component of the outdoor air pollution. Microsensors are interesting devices to check and to monitor this toxic oxidizing gas. Recent advances in flexible electronics, a complementary technology to the conventional rigid silicon technology, have motivated research efforts. Flexible substrates enable new applications such as wearable sensors, electronics on skin/organs as well as a possible reducing cost during the fabrication process. However, flexible substrates required low working temperature to avoid thermal degradation. This work aims to prove the possibility to use zinc oxide nanocrystals (ZnO NCs) post-annealed at low temperature as a sensitive material to detect NO 2 at low working temperature. Thus, our study has been performed on rigid substrates to check first the sensitive layer behaviour depending on the temperature. Then, to be able to reduce the working temperature, a continuous UltraViolet illumination has been used. We propose a NO 2 detection at room temperature by ZnO NCs deposited on rigid substrates by spin coating from colloidal solutions as sensitive layers for air quality monitoring.

In this work a novel process allowing for the production of nanoporous Ge thin films is presented. This process uses the combination of two techniques: Ge sputtering on SiO2 and dopant ion implantation. The process entails four successive steps: (i) Ge sputtering on SiO2, (ii) implantation preannealing, (iii) high-dose dopant implantation, and (iv) implantation postannealing. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the Ge film at different process steps under different postannealing conditions. For the same postannealing conditions, the Ge film topology was shown to be similar for different implantation doses and different dopants. However, the film topology can be controlled by adjusting the postannealing conditions.

International audience; We focus on ozone (O3) detection at ambient temperature by Zinc Oxide (ZnO) nanoparticles (NPs) deposited on Si/SiO2 by spin coating from colloidal solutions as sensitive layers for air quality monitoring. We establish that at room temperature using continuous Ultra-Violet (UV) light irradiation enhances the sensing responses. Three annealing temperatures of ZnO films were performed to compare the sensing properties. These sensors present repeatable responses towards O3 with fast responses for concentrations as low as 35 ppb with processes compatible with most of flexible substrates.

International audience; We report herein the efficiency of microwave-assisted synthesis for obtaining ZnO/SnO2 heterostructures for room-temperature gas-sensing applications. The sensing performances of the traditional oxide materials have been found for applications above 200 °C. However, these temperatures were here reduced to room temperature by considering sensing activity photoactivated by UV light, even for ppb ozone (O3) levels. The heterojunctions exhibited a fast response, total reversibility, and selectivity to oxidizing gases, especially O3 gas. This investigation provides an efficient way to obtain heterostructures exhibiting remarkable properties for practical applications as O3 gas sensor devices.

Text Presented at the Eurosensors 2017 Conference, Paris, France, 3–6 September 2017; International audience; The present study evaluates the ozone (O$_3$) and nitrogen dioxide (NO$_2$) removal performance of specific filters based on nanoporous materials. These materials, produced via the sol-gel process with functionalized silicon alkoxides as precursors, are tailored for O$_3$ trapping. The gas removal effectiveness of the filters was assessed through measurements of O$_3$ concentrations in the air upstream and downstream of the filters. Depending on the filter nature, O$_3$ can be totally trapped while NO$_2$ can pass over a specific concentration range.

Ozone gas sensors on flexible substrate with Ti/Pt interdigitated electrodes have been fabricated by standard photolithography and femtosecond laser ablation processes under the same conditions. ZnO nanoparticles deposited by drop coating method have been used as sensitive thin film material with 280 nm thickness due to their excellent characteristics on gas detection. The physical properties obtained by both processes have been studied and their critical effects on the gas sensitive response are discussed. It was found that although both samples present small dimensional variations, the samples fabricated by laser ablation shows a bigger sensitive response to ozone at 200 °C. However, both samples have been used as ozone gas sensor and present excellent sensing characteristics, giving good stability, fast response/recovery and excellent range of detection from 5 ppb to 300 ppb.

Our research work aims to develop a microfluidic system for gas analysis by using an original principle of integrated pumping. This microsystem can detect ammonia and the gas flow parameters inside the channel can be also controlled. The proposed microdevice consists in a microchannel including an integrated gas sensor with a heater. The trioxide tungsten (WO 3) is implemented as a sensitive layer. The integrated heater is used for two reasons: to optimize the sensor response and to induce the gas pumping inside the microchannel by thermal creep phenomenon, therefore, no external pumping system is required. The study of the pumping effect generation has been realized by thermal and microfluidic simulations. Thermal simulations have been performed to estimate the thermal gradient along the microchannel. In addition, the microfluidic modelling allows us to determine the mass flow rate for different thermal gradient profiles, obtained from the thermal simulations. Finally, a complete Pyrex microsystem has been realized to detect ammonia. The existence of the thermal pumping has been demonstrated experimentally.

International audience; The development of room-temperature gas sensors for nitrogen dioxide gases is of great importance for air quality monitoring due to unhealthy impact on human life and environment. In this work, we focus on Aluminum-doped Zinc Oxide sensing properties. We compare nitrogen dioxide detection at room temperature in dark and under ultraviolet or blue illuminations. Working temperature from 25°C up to 100°C have been also performed in dark and under UV and blue Light Emitted Diodes. Aluminum-doped Zinc Oxide nanoparticles have been deposited by drop coating from colloidal solution as sensitive layer for air quality monitoring on Si/SiO2 substrate. Herein, a brief description of the process steps will be provided. We demonstrate that UV light and temperature enhance gas-sensing properties with good reversibility and repeatability.

Made available in DSpace on 2018-11-26T17:55:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Brazilian Nanotechnology National Laboratory (LNNano), Microfabrication laboratory, Campinas, SP, Brazil The sensitivity of ZnO-SnO2 heterojunctions to ozone gas was investigated in this work, the two-phase materials of which were prepared via a hydrothermal route, resulting in nanocomposites in which the formation of heterojunctions was confirmed by microscopy analyses. While the sensing effectiveness of these materials is currently verified for application above 150 degrees C, these temperatures are here drastically reduced to room temperature by considering sensing activity under continuous UV irradiation, even for ozone concentrations as low as 20 ppb. This approach resulted in a fast sensing response, a short recovery time and a good selectivity compared to other gases, demonstrating a great potential of such heterojunctions for applications in environmental monitoring devices. (C) 2016 Elsevier B.V. All rights reserved. Sao Paulo State Univ, Inst Chem, LIEC, POB 355, BR-14800900 Araraquara, SP, Brazil Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil Aix Marseille Univ, CNRS, IM2NP 7334, F-13397 Marseille, France EMBRAPA Instrumentacao, Rua 15 Novembro 1452, BR-13560970 Sao Carlos, SP, Brazil Sao Paulo State Univ, Inst Chem, LIEC, POB 355, BR-14800900 Araraquara, SP, Brazil FAPESP: 2013/09573-3 FAPESP: 2013/07296-2 FAPESP: 2015/20124-1 FAPESP: 2012/15170-6 Brazilian Nanotechnology National Laboratory (LNNano), Microfabrication laboratory, Campinas, SP, Brazil: LMF-18580

A detailed study of the structural, surface, and gas-sensing properties of nanostructured Co

International audience; In this study a gas detection microfluidic system with a gas integrated pumping by thermal creep was realized. First, microfluidic and thermal simulations were done to determine the microsystem dimensions. Heat distribution in all microsystem was then simulated using Comsol Multiphysics software. These results allowed us the best material choices suited for our application. The microsystem includes an integrated gas sensor in a microchannel, with heater and trioxide tungsten (WO 3) sensitive layer. Conventional microelectronic methods have been used to achieve this microsystem. The thermal stability and the temperature gradient within the microsystem have been studied. Finally, the first microsystem tests under ammonia with concentrations between 10 and 100 ppm at 473 K have been made and give reproducible conductivity variations.

The aim of this study is to realize flexible photo- and gas sensors using low cost solution processing such as drop casting or ink jet printing. Two organic semiconductors, namely distyrylbithiophene (DS2T) and α,ω-hexyl-distyrylbithiophene (DH-DS2T), were used as active sensor materials. Both oligomers are p-type semiconductors with high mobility and good air stability. While DS2T has a poor solubility in common organic solvent and thus thin films could only processed by thermal evaporation, the highly soluble DH-DS2T allowed the fabrication of all solution processed photo- and gas sensors. The sensor responses were studied by measuring the current through the semiconductor organic film as a function of light intensity (from 2 mW/cm 2 to 100 mW/cm 2 ) and ammonia gas concentration (NH 3 : 25, 50, and 100 ppm) for light and gas sensors, respectively. We demonstrate here that both compounds have efficient sensor responses, Especially the use of DH-DS2T leads to an efficient fully solution processed multifunctional sensor on flexible substrate.

Extreme scaling in both silicon and alternative channel CMOS has highlighted the importance of localized characterization on the nanometer scale. We have used a conductive-contact atomic force microscopy (C-AFM) technique in ultra high vacuum (UHV) conditions to analyze and compare intrinsic stack degradation mechanisms leading to breakdown (BD) for ultrathin high-k dielectric films of (∼4 nm) HfxSiOy/SiO2 on Si and (∼2 nm) ZrO2/GeO2 on Ge. Simultaneous nanoscale current–voltage I–V characteristics, topography, tunneling current and relative tip–surface contact interactions as normal and lateral force maps revealed localized injected charge dependence on electrical stress. It is shown that the charge can propagate laterally. Successive voltage scanning is related to the overall post-BD conductivity for pre- to post-BD degradation propagation. In contrast with SiO2 interface, an increased GeO2 interlayer reactivity yielding more active interface defects is suggested.

E-MRS Spring Meeting 2015 Z entitled NanoMaterials and Processes for Advanced Semiconductor CMOS devices, Lille, FRANCE, MAY 11-14, 2015; International audience; 5 x 10(15) Te+ ions cm(-2) were implanted in an Ge(001) substrate using an industrial implanter with a Te+ beam energy of 180 key. In addition to usual implantation-mediated defects observed in Ge with usual dopants, Te implantations lead to the formation of amorphous surface GeO clusters exhibiting micrometer scale sizes, as well as deep extended defects. Implantation defects promote the formation of two distributions of dislocation loops and clusters located at two different depths in the Ge substrate during annealing. No interactions between Te atoms and dislocation loops were observed. However, the formation of non-equilibrium Te-Ge clusters, probably mediated by Ge self-interstitials, was found to prevent the Te solubility to exceed similar to 5 x 10(19) cm(-3) in Ge. The regular implantation method is shown to be ineffective for the production of high level n-type Ge doping using Te, due to the important Ge damage caused by Te implantation. (C) 2015 Elsevier Ltd. All rights reserved.

In this work, a conductive atomic force microscope (CAFM) has been used in order to detect and electrically characterize the evolution of dielectric degradation on thin (

This work concerns deeply bound charge centers in ultra thin high-k films. Non-contact Atomic Force Microscopy was used to simultaneously image topology and electric force data arising from unscreened fixed charges. These charges were produced using synchrotron radiation to pump Si L and K shell transitions. Defect charging then results from electron transfer between a defect state and a core hole state. We were able to demonstrate the local detection of x-ray absorption spectra using the probe tip. This enabled us to establish a possible link between film morphology, electronic defects and local stoichiometry in ultra thin high-k films on the nm scale.

We report extrinsic stacking fault generation at the Si surface of samples with HfAl"xO"y and HfO"2 high-k dielectrics grown by MOCVD at 500 and 350 ^oC respectively and discuss its origin. As opposed to a recent assertion [Kim and Yong, J. Appl. Phys. 100 (2006) 044106] ascribing the formation of dislocations in a HfSi"xO"y-Si system prepared by ALD at 300 ^oC to diffusion of Hf atoms during film growth into the Si substrate, we found no such evidence for samples whose Si substrate was ALD-covered with HfO"2 and HfSi"xO"y dielectrics at a comparable temperature to the above ALD and MOCVD cases.

Charges trapped within the gate dielectric layer, are known to result in substantial changes in electrical properties of Metal-Insulator-Semiconductor structures. In this paper, we present simulation results of tunnelling transparency for single insulator metal/SiO2/metal structures and double insulator silicon/SiO2/HfO2/metal structures using our own simulator. The simulations allow to predict the impact of fixed dielectric charges on tunnelling barrier shape and the modification of the Fowler-Nordheim injection parameters in MIM and MIS structures.

This paper summarizes various aspects of gate leakage on MOSFETs DC and AC characteristics. Based on measurements on test structures with various electrical silicon oxide thicknesses (from 21 to 13 A) and areas (from 27,000 to 2 μm 2 ), we show that gate current produces a channel surface potential debiasing that can strongly modify the I ( V ) and C ( V ) curves measured using conventional DC analyzer and LCR meters. In particular, we report unusual gate current density I G /( W × L ) area dependency and degraded C ( V ) curves at high gate leakage, that cannot be accounted for by compact models in series with parasitic gate resistances. We propose a segmented-MOS model, allowing discrete solution of the current continuity equation along the channel, which fits the measured C ( V ) and I ( V ) curves and provides a solution for first-order parameters extraction (such as oxide thickness or channel mobility).

In this manuscript, we report an investigation into the sensitivity of two oxidizing gases (ozone and nitrogen dioxide) for nanocrystalline SrTi 0.85 Fe 0.15 O 3 thin films deposited by the electron beam physical vapor deposition technique. Annealing treatment at 500 °C enhanced the crystallization and surface roughness of the thin film. Electrical measurements revealed that the thin film was sensitive to oxidizing gases, especially to low ozone gas levels, exhibiting a fast response time, a short recovery time as well as good reproducibility and reversibility. These findings demonstrate the great potential of the SrTi 0.85 Fe 0.15 O 3 compound to be applied as a selective ozone gas sensor.

International audience; One-dimensional (1D) ZnO nanorod-like structures were successfully grown via a hydrothermal method to be used as an ozone gas sensor. X-ray diffraction measurements (XRD) and field-emission scanning electron microscopy (FE-SEM) analysis revealed a preferential growth of the nanorod-like structures along the [002] direction. Electrical resistance measurements indicated a good sensitivity to different ozone concentrations (0.06–1.19 ppm) as well as long-term stability over a 6 month period at 250 °C. In addition, it was observed that the nanorods had a good sensitivity to ozone at room temperature when the sensor was exposed to UV illumination. This study provides an easy and efficient way to obtain 1-D ZnO nanorods exhibiting remarkable properties for applications as ozone gas sensing materials.

We report the ammonia gas sensing properties of ZnO nanoparticles on flexible substrates. The flexible platform contains Ti/Pt interdigitated electrodes for gas detection and a micro heater device. The Ti/Pt film has been deposited by Magnetron Sputtering with thickness of 5nm and 100 nm respectively. The circuit patterning has been fabricated by standard photolithography and femtosecond laser ablation processes. ZnO thin film has been deposited by drop coating process with a thickness of 275 nm and the gas sensing properties towards ammonia have been studied. The physical properties obtained by both processes have been observed and theirs effects on the gas sensitivity have been discussed. Despite there are small variations in the physical characteristics between the samples fabricated by different patterning processes, both devices present high sensitivity and reproducibility to different ammonia concentrations from 5 ppm to 100 ppm at 300 °C.

International audience; In this work the ozone detection in flexible substrate has been investigated. The flexible test platform with an integrated heater was designed and then characterized by thermal simulations using finite elements and its electrical properties have been studied. ZnO nanoparticles were deposited by drop coating process on the flexible substrate with platinum interdigited electrodes for gas detection. The gas sensing properties were determined by ozone exposure at different concentrations and temperatures. The gas sensing measurements present good response at different gas concentrations, good repeatability and fast recovery.

International audience; A method is proposed to determine the origin and the spatial oxide fixed charge repartition in memory tunnel oxide from Fowler–Nordheim current measurements after electrical stress. The Poisson equation resolution in the dielectric layer is required to account for the nonsymmetric tunneling barrier deformation, resulting from charges generated within the dielectric layer. From current–voltage characteristics measurements and simulations, we have determined the spatial distribution of the oxide fixed charges within the dielectric layer of metal/SiO2/metal structures. In addition, the kinetics of the oxide charge generation can be explained by a dispersive hydrogen transport model.