The multi-structure of oxidized-reduced tungsten carbide surface(s)

[cis‐(1,3‐Diene)2W(CO)2] Complexes as MOCVD Precursors for the Deposition of Thin Tungsten – Tungsten Carbide Films

“…For both samples, the spectra are now dominated by W 4f peaks, the binding energies of which are close to that typical for WC, however, due to the binding energies of metallic W ($31.1 and 33.3 eV for the W 4f 7/2 and 4f 5/2 levels, respectively) [39] being very close to that of WC, we cannot rule out that there is also a significant contribution of metallic tungsten in the near surface region. This could stem from selective sputtering, i.e., the effect that light atoms such as C and O are more effectively removed from a surface than the heavy tungsten atoms of WO 3 and WC, leaving behind a metallic species.…”

“…For the WC reference and for the MOCVD-grown film, the spectra before sputtering are dominated by a broad peak at $285 eV, which is assigned to elemental carbon in an amorphous phase and/or adsorbed hydrocarbons [39,43] and no signal from carbidic carbon, which would be expected to occur at a binding energy of 282.7 eV. [39,42] Only after sputtering is the carbidic form of carbon found. As expected, the unsputtered film surface contains considerable amounts of oxygen, which shows up in the oxygen 1s XP spectra, and which is strongly decreased after sputtering.…”

“…This could stem from selective sputtering, i.e., the effect that light atoms such as C and O are more effectively removed from a surface than the heavy tungsten atoms of WO 3 and WC, leaving behind a metallic species. [37][38][39] Additionally, possible influences of the high energy ions on the phase equilibrium of carbon, tungsten, and tungsten carbide cannot be ruled out.…”

“…In order to identify the phases, the observed binding energies are compared to spectra of a tungsten carbide (WC) reference sample, which were measured under identical conditions, and compared to earlier data. [39][40][41][42] Detailed XP spectra were taken in the W 4f, C 1s, and O 1s photoelectron regions; the W 4f and the C 1s spectra for the WC reference and for the MOCVD-grown films, before and after sputtering, are shown in Figures 9 and 10, respectively. The broken vertical lines in Figure 9 indicate the energetic position of the W 4f 7/2 states of WC (31.5 eV) [35,[39][40][41][42] , and WO 3 (35.6 eV), respectively.…”

Biomass Gas Cleanup Using a Therminator

“…The rates of CH 4 formation were also higher when all gases were present. The high activity in the presence of H 2 O and CO 2 could possibly be due to the introduction of O into the WC matrix resulting in the formation of WO x acid sites, which is a common phenomenon for WC [5,7,19]. This in situ formation of acid sites could be responsible for more cracking of toluene to benzene and CH 4 resulting in higher rates of reaction as observed in Figure 21 and Figure 22.…”