Spectroscopic ellipsometry on thin titanium oxide layers grown on titanium by plasma oxidation

Abstract : Electronic devices based on tunnel junctions require tools able to accurately control the thickness of thin metal and oxide layers on the order of the nanometer. This article shows that multisample ellipsometry is an accurate method to reach this goal on plain uniform layers, in particular for titanium. From these measurements, the authors carefully studied the oxidation rate of titanium thin films in an oxygen plasma. The authors found that the oxide thickness saturates at 5.4±0.4 nm5.4±0.4 nm after 10 min in the plasma with an ion acceleration power of 30 W. Increasing this power to 240 W increases the saturation value to 7.6±0.4 nm7.6±0.4 nm. An x-ray photoelectron spectroscopy study of the oxide has shown that the oxide created by O2O2 plasma is stoichiometric (TiO2)(TiO2). The developed model was also used to measure the thicknesses of titanium and titanium oxide layers that have been polished using a chemical mechanical planarization process and a material removal rate of 5.9 nm/min is found with our planarization parameters. I. INTRODUCTIO

On the resistivity at low temperatures in electron-doped cuprate superconductors

We measured the magnetoresistance as a function of temperature down to 20mK and magnetic field for a set of underdoped PrCeCuO (x=0.12) thin films with controlled oxygen content. This allows us to access the edge of the superconducting dome on the underdoped side. The sheet resistance increases with increasing oxygen content whereas the superconducting transition temperature is steadily decreasing down to zero. Upon applying various magnetic fields to suppress superconductivity we found that the sheet resistance increases when the temperature is lowered. It saturates at very low temperatures. These results, along with the magnetoresistance, cannot be described in the context of zero temperature two dimensional superconductor-to-insulator transition nor as a simple Kondo effect due to scattering off spins in the copper-oxide planes. We conjecture that due to the proximity to an antiferromagnetic phase magnetic droplets are induced. This results in negative magnetoresistance and in an upturn in the resistivity.Comment: Accepted in Phys. Rev.

Can dissuasive cigarettes influence young peoples’ perceptions of smoking?

Background In order to counter the attractiveness of cigarettes, Article 11 of the Framework Convention on Tobacco Control mentions the possibility of including a health warning on cigarettes. The objective of this study was toexplore perceptions of cigarettes designed to be dissuasive (either displaying a text health warning or pictogram, unattractively coloured, or a combination of these). Methods In-depth interviews were conducted with 31 people in France aged 15-25 years (11daily smokers, 10 occasional smokers, 10 non-smokers, 15 females, 16 males). Participants were shown the different dissuasive cigarettes (displaying the warning \u27Smoking kills\u27, a ‘skull and crossbones’ pictogram, unattractive shades of brown or green, or a combination of all three). Open-ended questions were asked about the attractiveness of the cigarettes, perception of risk, the image of the smoker, and influence on desire to quit or not to start. Discussions were audio-recorded and transcribed. Manual coding and « IRaMuTeQ » software was used to analyse the data. Results The different dissuasive elements used were found to increase negative health perceptions (e.g.  increase risk), reduce positive smoker image and the perceived pleasure of smoking (e.g. embarrassment of smoking in front of friends), decrease desire to start smoking and increase desire to quit. The most dissuasive cigarette was an unattractively coloured cigarette which displayed both the warning \u27smoking kills\u27 and \u27skull and bones\u27 pictogram. Conclusion This study highlights the importance of the appearance of the cigarette, and suggests that dissuasive cigarettes may be an innovative tobacco control measure for governments

Dissuasive cigarettes: which cues are the most effective at deterring young people from smoking?

Objectives In order to counter the attractiveness of cigarettes, Article 11 of the Framework Convention on Tobacco Control provides for the possibility of including warnings on cigarettes. The objective of our research was to explore perceptions of cigarettes designed to be dissuasive (either displaying the warning ‘Smoking kills’ in uppercase or lowercase, a ‘skull and crossbones’ pictogram, unattractive shades of brown or dark green, or a combination of all these negative cues). Study design In-depth interviews were conducted with 31 people in France aged 15-25 (10 daily smokers, 10 occasional smokers, 11 non-smokers; 15 females, 16 males). Methods Participants were shown different dissuasive cigarettes (displaying the warning ‘Smoking kills’, a ‘skull and crossbones’ pictogram, unattractive shades of brown or dark green, or a combination of all three), and current branded ones. Open-ended questions were asked about the attractiveness of the cigarettes, perception of risk, the image of the smoker, and influence on the desire to quit or not to start. Discussions were audio-recorded and transcribed. Results The different dissuasive cues were found to increase negative health perceptions (e.g., increase risk), reduce positive smoker image and the perceived pleasure of smoking (e.g., embarrassment of smoking in front of friends), decrease the desire to start smoking and increase the desire to quit. The most dissuasive cigarette was an unattractively dark-coloured cigarette which displayed both the warning ‘smoking kills’ and a ‘skull and crossbones’ pictogram. Conclusion This study highlights the importance of the appearance of cigarettes and suggests that dissuasive cigarettes may be an innovative tobacco control measure for governments

Peut-on influencer la représentation du tabagisme et l’envie de fumer chez les jeunes en modifiant le design des cigarettes

The objective of this research is to study the role of deterrent cigarettes (deterrence activated via colour, a warning label and a pictogram) on perceptions and smoking behaviour among youth people (15-25 years). The results show that different elements (green or brown colours, degree of covering, a warning, a « skull and cross bones » pictogram) impact the negative representations raised by the tobacco product (dangers), affect the image of smokers, reduce the pleasure to smoke and smoking behavioural intentions

Spin lifetime and charge noise in hot silicon quantum dot qubits

We investigate the magnetic field and temperature dependence of the single-electron spin lifetime in silicon quantum dots and find a lifetime of 2.8 ms at a temperature of 1.1 K. We develop a model based on spin-valley mixing and find that Johnson noise and two-phonon processes limit relaxation at low and high temperature respectively. We also investigate the effect of temperature on charge noise and find a linear dependence up to 4 K. These results contribute to the understanding of relaxation in silicon quantum dots and are promising for qubit operation at elevated temperatures.Comment: 8 pages, 6 figure

Qubits made by advanced semiconductor manufacturing

AbstractFull-scale quantum computers require the integration of millions of qubits, and the potential of using industrial semiconductor manufacturing to meet this need has driven the development of quantum computing in silicon quantum dots. However, fabrication has so far relied on electron-beam lithography and, with a few exceptions, conventional lift-off processes that suffer from low yield and poor uniformity. Here we report quantum dots that are hosted at a 28Si/28SiO2 interface and fabricated in a 300 mm semiconductor manufacturing facility using all-optical lithography and fully industrial processing. With this approach, we achieve nanoscale gate patterns with excellent yield. In the multi-electron regime, the quantum dots allow good tunnel barrier control—a crucial feature for fault-tolerant two-qubit gates. Single-spin qubit operation using magnetic resonance in the few-electron regime reveals relaxation times of over 1 s at 1 T and coherence times of over 3 ms.</jats:p

Poor prospects for avian biodiversity in amazonian oil palm

Expansion of oil palm plantations across the humid tropics has precipitated massive loss of tropical forest habitats and their associated speciose biotas. Oil palm plantation monocultures have been identified as an emerging threat to Amazonian biodiversity, but there are no quantitative studies exploring the impact of these plantations on the biome’s biota. Understanding these impacts is extremely important given the rapid projected expansion of oil palm cultivation in the basin. Here we investigate the biodiversity value of oil palm plantations in comparison with other dominant regional land-uses in Eastern Amazonia. We carried out bird surveys in oil palm plantations of varying ages, primary and secondary forests, and cattle pastures. We found that oil palm plantations retained impoverished avian communities with a similar species composition to pastures and agrarian land-uses and did not offer habitat for most forest-associated species, including restricted range species and species of conservation concern. On the other hand, the forests that the oil palm companies are legally obliged to protect hosted a relatively species-rich community including several globally-threatened bird species. We consider oil palm to be no less detrimental to regional biodiversity than other agricultural land-uses and that political pressure exerted by large landowners to allow oil palm to count as a substitute for native forest vegetation in private landholdings with forest restoration deficits would have dire consequences for regional biodiversity

A deep understanding of nanometer scale dielectric junctions for the fabrication of low power nanoelectronic devices

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