Effects of high energy Au-ion irradiation on the microstructure of diamond films

Abstract

The effects of 2.245 GeV Au-ion irradiation and subsequent annealing processes on the evolution of microstructure of diamond films with microcrystalline (MCD) or ultra-nanocrystalline (UNCD) granular structure were investigated, using near edge x-ray absorption fine structure and electron energy loss spectroscopy in transmission electron microscopy. For MCD films, the Au-ion irradiation disintegrated some of the diamond grains, resulting in the formation of nano-sized carbon clusters embedded in a matrix of amorphous carbon (a-C). The annealing process recrystallized the diamond grains and converted the a-C into nano-sized graphite particulates and, at the same time, induced the formation of nano-sized i-carbon clusters, the bcc structured carbon with a0 = 0.432 nm. In contrast, for UNCD films, the Au-ion irradiation transformed the grain boundary phase into nano-sized graphite, but insignificantly altered the crystallinity of the grains of the UNCD films. The annealing process recrystallized the materials. In some of the regions, the residual a-C phases were transformed into nano-sized graphites, whereas in other regions i-carbon nanoclusters were formed. The difference in irradiation-induced microstructural transformation behavior between the MCD and the UNCD films is ascribed to the different granular structures of the two types of films.

Structural properties of highly conductive ultra-nanocrystalline diamond films grown by hot-filament CVD

“…[19][20][21][22] In contrast, the diamond phase exhibits a peak at 33 eV (ω d2 -band) corresponding to bulk plasmon with a shoulder at 23 eV (ω d1 -band) corresponding to surface plasmon and the ω d1 /ω d2 peak ratio is ∼1/ √ 2. [19][20][21][22] The core-loss EELS spectrum of highly conducting nanocrystalline diamond films ( figure 6(a)) exhibits an abrupt rise near ∼289.5 eV (σ * -band) and a deep valley near 302 eV with a smaller peak near ∼284.5 eV (π * -band). These bands indicate the presence of predominantly sp 3 -bonded carbon, the diamond, along with some proportion of sp 2 -bonded carbon.…”

“…Notably, while the core-loss EELS spectrum shows different feature for diamond (σ * -band near 289.5 eV) and the sp 2 -bonded carbon (π * -band near 284.5 eV), it is the plasmon-loss EELS spectrum, which can unambiguously differentiate the a-C (the noncrystalline sp 2 -bonded carbon) and the graphite phases (the crystalline sp 2 -bonded carbon) in sp 2 -bonded carbon. [19][20][21][22] In plasmon-loss EELS spectrum, a-C phase exhibits a peak near 22 eV (ω a -band), whereas the graphite phase shows a peak near 27 eV (ω g -band). [19][20][21][22] In contrast, the diamond phase exhibits a peak at 33 eV (ω d2 -band) corresponding to bulk plasmon with a shoulder at 23 eV (ω d1 -band) corresponding to surface plasmon and the ω d1 /ω d2 peak ratio is ∼1/ √ 2.…”

“…[19][20][21][22] In plasmon-loss EELS spectrum, a-C phase exhibits a peak near 22 eV (ω a -band), whereas the graphite phase shows a peak near 27 eV (ω g -band). [19][20][21][22] In contrast, the diamond phase exhibits a peak at 33 eV (ω d2 -band) corresponding to bulk plasmon with a shoulder at 23 eV (ω d1 -band) corresponding to surface plasmon and the ω d1 /ω d2 peak ratio is ∼1/ √ 2. [19][20][21][22] The core-loss EELS spectrum of highly conducting nanocrystalline diamond films ( figure 6(a)) exhibits an abrupt rise near ∼289.5 eV (σ * -band) and a deep valley near 302 eV with a smaller peak near ∼284.5 eV (π * -band).…”

The potential application of ultra-nanocrystalline diamond films for heavy ion irradiation detection

“…The change in electrical properties of MCD films due to heavy ion irradiation will be affected by the hydrogen content in the diamond that results in some ambiguity in radiation detection, as the control of hydrogen content in the diamond films is difficult. Moreover, the MCD films are susceptible to the induction of structural defects due to heavy ion irradiation 10 that is detrimental to the application of these materials as a radiation detector. Such a phenomenon is due to the fact that the principle of radiation detection in diamond relies on the measurement of electron-hole pairs created within the diamond during the interaction of the incident particles or photons to be detected.…”

The microstructural evolution of ultrananocrystalline diamond films due to P ion implantation and annealing process-dosage effect

“…2(b) shows that the pristine UNCD films cause an abrupt rise at around 289.5 eV (the σ*-band) and a deep valley at about 302 eV, the secondary absorption band. These characteristics indicate clearly that these films are diamond in nature [22][23][24]. The P-ion implantation with a dosage less than 1 × 10 14 ions/cm 2 insignificantly influences the NEXAFS spectra (curves I to III, Fig.…”