Bulk and surface thermal stability of ultra nanocrystalline diamond films with 10–30 nm grain size prepared by chemical vapor deposition

Abstract

The thermal stability of nanocrystalline diamond films with 10–30 nm grain size deposited by microwave enhanced chemical vapor deposition on silicon substrate was investigated as a function of annealing temperature up to 1200 °C. The thermal stability of the surface-upper atomic layers was studied with near edge x-ray absorption fine structure (NEXAFS) spectroscopy recorded in the partial electron yield mode. This technique indicated substantial thermally induced graphitization of the film within a close proximity to the surface. While in the bulk region of the film no graphitization was observed with either Raman spectroscopy or NEXAFS spectroscopy recorded in total electron yield mode, even after annealing to 1200 °C. Raman spectroscopy did detect the complete disappearance of transpolyacetylene (t-PA)-like ν1 and ν3 modes following annealing at 1000 °C. Secondary ion mass spectroscopy, applied to investigate this relative decrease in hydrogen atom concentration detected only a ∼30% decrease in the bulk content of hydrogen atoms. This enhanced stability of sp3 hybridized atoms within the bulk region with respect to graphitization is discussed in terms of carbon bond rearrangement due to the thermal decomposition of t-PA-like fragments.

An insight of p-type to n-type conductivity conversion in oxygen ion-implanted ultrananocrystalline diamond films by impedance spectroscopy

“…42 Hydrogen bonding to the diamond grain surface and GBs in nanodiamond films was stable up to elevated temperatures of ~800 o C and then decomposed at higher temperatures. 43 This is in consistent with IS result that H-terminated diamond surface changes to O-terminated in the T a range of 725-800 o C. The H-terminated diamond surface had localized surface states in the band gap which would comprise the electron conductivity in n-type doping as they were expected to act as electron traps. 44 The dramatically reduced value of the resistance of diamond grains in sample 900-A reveals the surface change of grains after 900 o C annealing.…”

Dissociative adsorption of molecular deuterium on polycrystalline diamond films activated by medium surface temperature

“…As shown in Fig. , C–D bonding is stable up to T A = 800 °C, which agrees well with previous studies of hydrogen thermal desorption from well‐defined diamond films . The small contribution at ∼85 meV (Fig.…”

Raman activity ofsp3carbon allotropes under pressure: A density functional theory study

“…These experimental peaks have been up to now interpreted as coming from the formation of "nanocrystalline" diamond. [49][50][51] In summary, in order to distinguish the several sp 3 structures by Raman experiments we propose the use of the following fingerprints: (i) For BcT carbon the most important mode is the B 1g mode at 1124 cm −1 , that should appear at above 18.0 GPa; (ii) M-carbon can be identified by the A g mode at 900 cm −1 at around 13.5 GPa; (iii) for W -carbon the A g mode is at 1300 cm −1 , i.e., below the diamond zone, at more than 12.3 GPa; and (iv) finally, the transition to Z-carbon at 10 GPa can be identified by the A g modes at around 1220 and 1090 cm −1 . We should emphasize that the calculated frequencies and transition pressures contain an error caused by the theoretical framework.…”