High Concentration Of Negative Ions Research Articles

One step reactive ion etching of black germanium conical nanostructures: Ultra-wide solar spectral absorption, finite element simulation, super hydrophilicity, photothermal conversion

We report a reactive ion etching process based on SF 6 –CHF 3 , which can prepare black germanium at low RF power and normal temperature. The absorption of black germanium in the spectral range of 300–1750 nm is greater than 99%. Spectral selectivity optimization allows nano tapered germanium to absorb nearly 98.1% of solar radiation. This nanostructure is uniform in a large area and also supports patterning design for the application in related fields such as photothermal imaging. Here, we discuss the effect of SF 6 and CHF 3 plasma concentrations on the progress of chemical reactions on the germanium surface and their essential role in forming tapered nanostructures. We observe its surface plasmon resonance by finite-difference time-domain way. Finally evaluate its feasibility in devices by photothermal conversion and water droplet evaporation experiments. The proposal of this work provides an available method for semiconductor micromachining, and also provides experimental and theoretical support for the efficient thermal utilization of solar energy. In conclusion, we analyzed the mechanism of one-step etching of highly absorbing tapered nanostructures by SF 6 –CHF 3 -based RIE process by SEM and XPS. The germanium surface tends to form particles at the initial stage of etching, and due to the very high concentration of negative ions in the SF 6 plasma, these particles gradually form GeS x clusters. The germanium fluoride is mainly present at the surface of the germanium sample, while the germanium sulfide extends to a greater depth, so these clusters are not effective in preventing etching. The CHF 3 plasma greatly reduces the negative ion concentration and reduces the tendency of particle formation in favor of smoother GeS x and C x H z F y layers, which are very favorable for the formation of nanostructures. Aggregation of the germanium sidewalls decreases with depth, so tapered nanostructures are gradually formed with etch time. In addition, over-etching leads to additional carbon deposition, which is mainly composed of fluorocarbon polymers (C x H y F z ) formed from the decomposition products of CHF 3 . The wide spatial distribution of the sizes of the tapered nanostructures makes the absorptivity of black germanium more than 99% in the 300–1750 nm spectral range. As an indirect bandgap semiconductor, the absorption of photons makes electrons excited from the valence band to the conduction band with a great probability of releasing energy to the lattice, converting it into phonons, and turning it into heat energy. The cone-shaped nanostructured germanium can be heated to 69.4 °C in 20 min, and the heating rate can reach 7.98 °C/min in 300 s. The conical nanostructure modification makes germanium exhibit superhydrophilicity, and the water droplets make wet contact with germanium and fill the grooves on the surface of the nanostructures, making it capable of completely evaporating 0.05 ml droplets within 101 s. It is very competitive in heating and evaporation of water droplets.a) Black germanium photos, and SEM images of nano cones; b) Comparison of absorptivity between black germanium and polished germanium; c) Infrared image of graphic germanium wafer; (the letter part is nano cone structure, and the rest is polished germanium) d) With the increase of etching time, the temperature change curve of the sample under simulated sunlight irradiation (1 solar intensity). • Disordered nanocrystalline germanium was prepared by metal induced one-step self masked RIE. • The absorbance in the 300-1750 nm regions was higher than 98%. • The structure has excellent optical properties due to light trapping effect and plasma resonance. • The excellent optical properties and super hydrophilic properties make the structure have excellent photothermal properties.

Joint radar/lidar observations of possible aerosol layers in the winter mesosphere

Narrow layers of enhanced radar echoes from the winter mesosphere have been observed by the ESRAD 52 MHz radar (68°N,21°E) during recent solar proton events. These layers have been named PMWE, Polar Mesosphere Winter Echoes. Comparison of the characteristics of the radar echoes to the expected characteristics of neutral turbulence in the winter mesosphere leads to the conclusion that PMWE are unlikely to be caused by neutral turbulence alone. Their strength, and their persistence in conditions when moderately high concentrations of negative ions can be expected, are however consistent with the expected influence of small charged aerosol particles on radar scatter. During a solar proton event in January 2002 measurements were made by both the ESRAD radar and a lidar situated at the same site. The lidar observed a region of enhanced backscatter in the same height interval as the radar observed PMWE. The lidar observations can be interpreted either as a sharp temperature minimum or as a layer of aerosol particles. The latter interpretation offers consistency with the radar observations.

The effect of high concentration of negative ions in the air on the chlorophyll content in plant leaves

This research was done on the effectof high concentration of negative ions in the air onchlorophyll contents and photosynthetic efficiency in leavesof Zea mays L. In vivo reflectance and chlorophyllfluorescence were measured in intact maize leaves before andafter exposing to the high concentration of negative ions inthe air. Reflectance, yield of chlorophyll fluorescence, redshift in chlorophyll fluorescence and blue shift inreflectance are observed in exposed species. These resultsindicate that high concentrations of negative ions inair cause significant change in: a) chlorophyll content andb) photosynthetic efficiency.

Modeling of a Pulsed-Power SF6 Plasma

Pulsing the input power has received much attention to eliminate anomalous side wall etching problems in high density discharges. A simple model consisting of mass conservation equations for ions, neutrals, and electrons and a power balance is used to analyze the characteristics of a pulsed-power SF6 plasma. The model shows an abundant production of negative ions in the after glow and a strong modulation of their density and production rate for a wide range of pulse periods and duty ratios. The results suggest that a pulse period of 100–250 µ s with a duty cycle 25–50% is sufficient to maintain low electron temperature and plasma potential and produce a high concentration of negative ions during the off-part of the cycle.

Modelling of radio frequency plasmas in tetrafluoromethane (CF4): the gas phase physics and the role of negative ion detachment

A fluid model is used to study a radio frequency (RF) CF4 discharge at various powers, pressures and electrode spacings and is found to compare successfully with experimental data. The discharge shows an electronegative behaviour with a high concentration of negative ions. The role of electron detaching radicals CFx is subsequently studied by varying their density. At high radical densities (1%), the discharge behaviour and operating point change drastically and attachment-induced ionization instabilities develop. The implications to plasma etching and experiments are discussed.

Effects of negative ions on interpersonal attraction: evidence for intensification.

In Study 1, female subjects received information suggesting either that a stranger (a female accomplice) shared their attitudes and evaluated them positively or that a stranger did not share their attitudes and evaluated them negatively. These procedures took place in the presence of a low (ambient) or high level of negative ions. On the basis of previous research, it was predicted that a high level of negative ions would intensify subjects' reactions to the stranger, thus enhancing their evaluations of her when she seemed to share their attitudes and to like them, but reducing these evaluations when she did not share their attitudes and disliked them. Results offered support for these predictions. In Study 2, female subjects performed two tasks (letter and digit copying) in the presence of a low or high concentration of negative ions. Their blood pressure and pulse were measured at several points during the experiment. Results indicated that on various trials both systolic and diastolic blood pressure were higher in the high-ions than in the low-ions condition. In addition, subjects reported higher levels of subjective arousal and made significantly more errors on the letter-copying task in the presence of a high concentration of negative ions. Together, the results of these studies were interpreted as offering support for the view that high concentrations of negative ions can increase both physiological and psychological (subjective) arousal.

Effects of negative ions on interpersonal attraction: Evidence for intensification.

In Study 1, female subjects received information suggesting either that a stranger (a female accomplice) shared their attitudes and evaluated them positively or that a stranger did not share their attitudes and evaluated them negatively. These procedures took place in the presence of a low (ambient) or high level of negative ions. On the basis of previous research, it was predicted that a high level of negative ions would intensify subjects' reactions to the stranger, thus enhancing their evaluations of her when she seemed to share their attitudes and to like them, but reducing these evaluations when she did not share their attitudes and disliked them. Results offered support for these predictions. In Study 2, female subjects performed two tasks (letter and digit copying) in the presence of a low or high concentration of negative ions. Their blood pressure and pulse were measured at several points during the experiment. Results indicated that on various trials both systolic and diastolic blood pressure were higher in the high-ions than in the low-ions condition. In addition, subjects reported higher levels of subjective arousal and made significantly more errors on the letter-copying task in the presence of a high concentration of negative ions. Together, the results of these studies were interpreted as offering support for the view that high concentrations of negative ions can increase both physiological and psychological (subjective) arousal.

Negative ions and behavior: impact on mood, memory, and aggression among type A and type B persons.

Individuals scoring high (Type As), intermediate, or low (Type Bs) on the Jenkins Activity Survey were given an opportunity to aggress against a stranger who, previously, had either provoked or not provoked them. The opportunity to aggress (as well as all other aspects of the study) took place in the presence of (a) a high concentration, (b) a moderate concentration, or (c) a low (ambient) concentration of negative air ions. Results indicated that exposure to moderate or high levels of negative ions significantly enhanced aggression by Type A subjects, but not by other participants. In addition, we found that negative ions produced positive shifts in subjects' reported moods in the absence of provocation, but negative shifts in moods in the presence of provocation. These findings suggest that moderate or high concentrations of negative ions serve as a source of heightened activation, thus enhancing individuals' dominant reactions or tendencies in a given situation.

Negative ions and behavior: Impact on mood, memory, and aggression among Type A and Type B persons.

Individuals scoring high (Type As), intermediate, or low (Type Bs) on the Jenkins Activity Survey were given an opportunity to aggress against a stranger who, previously, had either provoked or not provoked them. The opportunity to aggress (as well as all other aspects of the study) took place in the presence of (a) a high concentration, (b) a moderate concentration, or (c) a low (ambient) concentration of negative air ions. Results indicated that exposure to moderate or high levels of negative ions significantly enhanced aggression by Type A subjects, but not by other participants. In addition, we found that negative ions produced positive shifts in subjects' reported moods in the absence of provocation, but negative shifts in moods in the presence of provocation. These findings suggest that moderate or high concentrations of negative ions serve as a source of heightened activation, thus enhancing individuals' dominant reactions or tendencies in a given situation.

Effect of the air ion environment on influenza in the mouse.

The effects of small air ions were observed on the course of influenza in specific pathogen-free mice challenged by intranasal instillation of measured doses of influenza virus and maintained in a controlled micro-environment. Unipolar low densities of positive or negative ions increased the death rate, while mid-range densities of either charge were without effect. High concentrations of negative ions or low concentrations of mixed ions with negative ions predominating reduced the death rate. Ion depleted air, a common product of urban living conditions, significantly increased the mortality rate.

Production and Study of an Alkali Plasma with Negative Ions

The method of contact ionization is used to produce a three-component plasma (Cs+, Cl−, e−) in the Q-device BARBARA using a beam of Cesium chloride. The end-plate temperature controls the concentration of Cl−, which can be varied in a wide range. The density of negative ions is obtained from the difference between the positive ion density given by a Langmuir probe and the electron density given by a microwave resonator. A high concentration of negative ions is achieved.