Recombination of atoms at surfaces. Part 6.—Recombination of oxygen atoms on silica from 20°C to 600°C

Abstract

The recombination coefficient y for oxygen. atoms on silica has been determined for the temperature range 20" to 600°C. The employment of Smith's method using two Wrede-Harteck gauges together with their associated Pirani gauges in a system in which there are temperature differences between the various parts is discussed and a satisfactory procedure devised. The activity of the surface increased from y = 1.6 x 10-4 at 20" to 1.4 x 10-2 at 600°C. The graph of log y against l/T was not a straight line showing that it is not possible to explain the change with temperature in terms of a single energy of activation. The significance of the present results in relation to the changes that are known from other data to occur in the surface of silica as the temperature is raised was discussed. It was concluded that the activity and its change with temperature could be accounted for by supposing that oxygen atoms from the gas phasecombined with loosely bound oxygen atoms in the surface, the defects then being replaced at once by other oxygen atoms. In these experiments oxygen atoms were produced by a micro-wave-maintained discharge. The apparatus for doing this is described. In an appendix details of some experiments that were carried out to study the usefulness of this method are given.

Enhanced Step Coverage of TiO2 Deposited on High Aspect Ratio Surfaces by Plasma-Enhanced Atomic Layer Deposition

“…24 Hence, the overall lower step coverage of TiO 2 grown at a higher temperature of 250°C can be explained by the fact that the recombination loss probability r for oxygen increases for increasing temperatures. 36 To get insight into the structure of the deposited films, TEM and grazing incidence X-ray diffraction (GIXRD) were employed as displayed in Figure 4. The high-resolution TEM (HRTEM) micrograph in cross-sectional view (taken at the top of the high AR trench substrate) in Figure 4a displays PEALD TiO 2 deposited at 250°C with a plasma exposure time of 60 s. The SiO 2 high AR substrate shows amorphous contrast whereas the deposited TiO 2 shows lattice fringes that are displayed in Figure 4b in an inverse (filtered) fast Fourier transformation (IFFT) image.…”

Conformality of Plasma-Assisted ALD: Physical Processes and Modeling

“…For instance, Greaves and Linnett reported an increase in the loss probability for oxygen on silica of 2 orders of magnitude from 1.6 ϫ 10 −4 to 1.4 ϫ 10 −2 for temperatures ranging from 20 to 600°C. 19 Wood and Wise reported that most metals have a fairly constant recombination probability for hydrogen radicals over a wide temperature range. 20 The surface conditions during ALD can differ from those in the reported studies, affecting the value of r.…”

Investigation of the radially resolved oxygen dissociation degree and local mean electron energy in oxygen plasmas in contact with different surface materials

“…Furthermore, the wafer material itself and the condition of the other wall materials in the reactor affect the absolute number densities of reactive species due to wall loss processes, the probability for which is dependent on many factors. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] This makes it particularly difficult to accurately control the densities of highly reactive species, such as atomic oxygen, in industrial processing applications. Previous investigations have sought insight into these processes by measuring the density of atomic oxygen and its surface recombination probability for various materials using twophoton absorption laser-induced fluorescence (TALIF), 12,[26][27][28][29][30] optical emission spectroscopy (OES), 21,22,[31][32][33][34] and VUV absorption spectroscopy.…”