A new approach to dry etching of GaAs, digital etching, has been demonstrated. In digital etching, the etchant and an energetic beam, which induces chemical sputtering at the surface, alternately impinge onto the surface. Electrons and Cl2 gas were used as the energetic beam and the etchant, respectively, in the present experiment. Etching rates of 1/3 monolayer/cycle, independent of Cl2 flux and electron current density, were obtained. The present results show that an inherent self-limiting mechanism is involved and that the etching process is limited by the adsorption of etchant. This digital etching technique is expected to be applied to the fabrication of well-defined quantum wire and quantum box structures.
Fundamental chemical reactions between an atmospheric nitrogen plasma jet and water or a water/ethanol solution have been investigated. When the nitrogen plasma jet was injected directly into pure water, active nitrogen species produced nitric acid and ammonia through fatal reactions with H 2 O. The interaction between nitrogen plasma and a liquid mixture of pure water and ethanol produced NH 4 + ions effectively. These experimental results clearly show that the active nitrogen species in the pulsed-discharge atmospheric plasma can interact strongly with materials in solution to extract oxygen or hydrogen from them and add atomic nitrogen to them.
Reactive gas plasma treatments of poly(ethylene terephthalate) (PET) and polyimide (Kapton) have been performed using an atmospheric plasmas jet source. Characteristics of surface modification have been examined by changing the distance between the plasma jet source and the treated sample, and by changing the working gas spaces. Simultaneously, each plasma jet source has been investigated by space-resolving spectroscopy in the UV/visible region. Polymer surfaces have been analyzed by X-ray photoelectron spectroscopy (XPS). A marked improvement in the hydrophilicity of the polymer surfaces has been made by using N 2 or O 2 plasma jet source with a very short exposure time of about 0.01 s, whereas the less improvement has been obtained using on air plasma jet source because of NO x compound production. Changes in the chemical states of C of the polymer surfaces have been observed in XPS spectra after N 2 plasma jet spraying.
Abstract— A 10‐in. flat‐panel display (FPD) with surface‐conduction electron‐emitter (SCE) cathodes can be fabricated through a printing process. Ultrafine particle films of the SCEs are deposited by using ink‐jet printing. A prototype achieves full‐color and full‐motion pictures comparable to CRTs. The feasibility of larger and low‐cost SCE displays has been confirmed.
The relations between motor unit global firing rates and established quantitative measures for processing the surface electromyogram (EMG) signals were explored using a simulation approach. Surface EMG signals were simulated using the reported properties of the first dorsal interosseous muscle in man, and the models were varied systematically, using several hypothetical relations between motor unit electrical and force output, and also using different motor unit firing rate strategies. The utility of using different EMG processing parameters to help estimate global motor unit firing rate was evaluated based on their relations to the number of motor unit action potentials (MUAPs) in the simulated surface EMG signals. Our results indicate that the relation between motor unit electrical and mechanical properties, and the motor unit firing rate scheme are all important factors determining the form of the relation between surface EMG amplitude and motor unit global firing rate. Conversely, these factors have less impact on the relations between turn or zero-crossing point counts and the number of MUAPs in surface EMG. We observed that the number of turn or zero-crossing points tends to saturate with the increase in the MUAP number in surface EMG, limiting the utility of these measures as estimates of MUAP number. The simulation results also indicate that the mean or median frequency of the surface EMG power spectrum is a poor indicator of the global motor unit firing rate.
A multiaperture ion source with adjustable optics to provide well-collimated, high-current-density, low-to mediumenergy ion beamsWe have developed a new type ofion source which is excited by a low energy and high current electron beam. The source has an extractable ion current density up to 0.62 A/cm 2 and a low acceleration voltage less than 60 V. This ion source will open a new way for low energy ion processing such as damageless ion etching, ion beam crystal growth, and deposition.
The nitriding of ferrous metals is primarily carried out to improve the surface hardness resulting from the formation of nitrogen compounds and diffused atomic nitrogen. In this study, we detail the achievements of the compound-layer-free nitriding of ferrous metallic surfaces using a low-power electron-beam-excited plasma in a nitrogen atmosphere. The X-ray diffraction and hardness results of our experiments indicate that the nitride layer consisting of CrN, Fe4N, and Fe3N compounds is drastically reduced when driving the system at 100 eV, while it maintains a hardness about 1.5 times that of the untreated surface. We have also confirmed that the present process can be applied to the nitriding of mechanical parts with narrow slit features.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.