Characterization of atomic oxygen from an ECR plasma source

Abstract

A low-power microwave-assisted electron cyclotron resonance (ECR) plasma system is shown to be a powerful and effective source of atomic oxygen (AO) useful in material processing. A 2.45 GHz microwave source with maximum power of 600 W was launched into the cavity to generate the ECR plasma. A catalytic nickel probe was used to determine the density of AO. The density of AO is studied as a function of pressure and axial position of the probe in the plasma chamber. It was found to vary from ∼1 × 10 20 to ∼10 × 10 20 atom m −3 as the plasma pressure was varied from 0.8 to 10 mTorr. The effect of AO in oxidation of silver is investigated by gravimetric analysis. The stoichiometric properties of the oxide are studied using the x-ray photoelectron spectroscopy as well as energy dispersive x-ray analysis. The degradation of the silver surface due to sputtering effect was viewed by scanning electron spectroscopy. The sputtering yield of oxygen ions in the plasma is calculated using the TRIM code. The effects of plasma pressure and the distance from the ECR zone on the AO density were also investigated. The density of AO measured by oxidation of silver is in good agreement with results obtained from the catalytic nickel probe.

Morphological Changes at a Silver Surface Resulting from Exposure to Hyperthermal Atomic Oxygen

“…Because high collision energies may facilitate large energy transfers and the crossing of high reaction barriers, these hyperthermal O-atom collisions are expected to proceed through mechanisms that are quite different from those involving molecular oxygen at thermal velocities. The desire to understand the unique chemistry of hyperthermal O-atom-surface reactions has motivated many studies which have employed various atomic-oxygen sources, including plasma ashers, high-temperature RF/DC discharges, laser breakdown, etc. − The hyperthermal source that generates neutral O atoms through breakdown of O 2 by a CO 2 laser is relatively well characterized and induces effects on materials that are similar to those observed in LEO exposures. , …”

“…The desire to understand the unique chemistry of hyperthermal O-atom-surface reactions has motivated many studies which have employed various atomic-oxygen sources, including plasma ashers, high-temperature RF/DC discharges, laser breakdown, etc. [4][5][6][7][8][9] The hyperthermal source that generates neutral O atoms through breakdown of O 2 by a CO 2 laser is relatively well characterized and induces effects on materials that are similar to those observed in LEO exposures. 9,10 Silver has a wide range of applications in LEO, such as an electron conductive material, 11 a reflective medium on a solar concentrator, 12,13 and a sensor material for calibrating atomicoxygen exposures.…”

Two-dimensional calculation of spatial distribution of neutral atoms for a planar inductively coupled oxygen discharge

“…The variation of the magnitude of the spatially averaged density of oxygen atoms with operating pressure was predicted by global modeling [15]. The oxygen atom density increases with pressure in the low-pressure range, and this was observed experimentally in an inductively coupled plasma [16] and a microwave discharge [3]. Fig.…”

“…Especially spatial distributions of density and flux of atomic oxygen are studied since atomic oxygen plays an important role in various plasma processes like surface modification of synthetics, surface cleaning, growth of silicon oxide films, and etching [1,3,4].…”

Review of radio frequency conditioning discharges with magnetic fields in superconducting fusion reactors

“…ECR plasmas are well known from industrial plasma processing [36][37][38][39][40]. However, important differences, such as the lower magnetic field or the different geometry, can lead to fundamental differences from ECC discharges as used in fusion devices.…”