9 research outputs found
Fabrication Method for Nanocluster Superatoms with High-Power Impulse Magnetron Sputtering
Correlated sputtering from a hydrogen-terminated Si surface by individual highly charged ion impacts
Dependence of Optical Emission Spectra on Argon Gas Pressure during Modulated Pulsed Power Magnetron Sputtering (MPPMS)
Modulated pulsed power magnetron sputtering (MPPMS) of titanium was investigated as a function of argon gas pressure using optical emission spectroscopy (OES). Delays in discharge and the formation of comb-like discharge current waveforms due to splitting and pulsing were observed with a decrease in pressure. This observation corresponds to the evolution from MPPMS condition to deep-oscillation-magnetron-sputtering (DOMS)-like condition by changing discharge gas pressure. The optical emission intensities of the ionic species (Ar+ and Ti+) increased as the comb-like current waveforms were formed with decreasing Ar pressure. This behavior showed a marked contrast to that of the neutral species (Ar and Ti). The Ar pressure dependence of OES was revealed to be due to the plasma build-up stage, which is the initial generation process of plasma discharge in pulsed dc magnetron sputtering, from the temporal profile for the atomic-line intensities of the optically emitting species in MPPMS and DOMS-like plasmas
Modification of HOPG Surface on Irradiation by Highly Charged Ar11+ and Xe26+ Ions Investigated by SEM, ESR, SQUID, and Raman Measurements
Delayed Discharge Bridging Two Sputtering Modes from Modulated Pulsed Power Magnetron Sputtering (MPPMS) to Deep Oscillation Magnetron Sputtering (DOMS)
Delayed discharges due to electrical breakdown are observed in modulated pulsed pow er magnetron sputtering (MPPMS) plasma of titanium. The delayed discharge, which is remarkable with decreasing argon gas pressure, transforms the discharge current waveform from a standard modulated pulsed discharge current waveform to a comb-like discharge current waveform consisting of several pulses with high power. In addition, the delay times, consisting of statistical times and formative times in the delayed MPPMS discharges, are experimentally measured with the help of Laue plot analysis. The pressure dependence of delay times observed indicates that the delayed discharge behavior matches the breakdown characteristics well. In the present study, the delayed discharge dynamics of the comb-like discharge current waveform, which can be the origin of deep oscillation magnetron sputtering, are investigated based on measurement of the delay times and the characteristics of discharge current waveforms
Correlation between Electronic Shell Structure and Inertness of Cu<sub><i>n</i></sub><sup>+</sup> toward O<sub>2</sub> Adsorption at <i>n</i> = 15, 21, 41, and 49
The
inertness of metal clusters in air is important for their application
to novel materials and catalysts. The adsorption reactivity of copper
clusters with O<sub>2</sub> has been discussed in connection with
the electronic structure of clusters because of its importance in
electron transfer from the cluster to O<sub>2</sub>. Mass spectrometry
was used to observe the reaction of Cu<sub><i>n</i></sub><sup>+</sup> + O<sub>2</sub> (<i>n</i> = 13–60)
in the gas phase. For O<sub>2</sub> adsorption on Cu<sub><i>n</i></sub><sup>+</sup>, the relative rate constants of the <i>n</i> = 15, 21, 41, and 49 clusters were clearly lower than those with
other <i>n</i>. Theoretical calculations indicated that
the inertness of Cu<sub>15</sub><sup>+</sup> with 14 valence electrons
was related to the large HOMO–LUMO gap predicted for the oblate
Cu<sub>15</sub><sup>+</sup> structure. The Clemenger–Nilsson
model was used to predict that the electronic subshell of oblate Cu<sub>49</sub><sup>+</sup> with 48 electrons was closed. This electronic
shell closing of Cu<sub>49</sub><sup>+</sup> corresponds to the inertness
for O<sub>2</sub> adsorption