The roles of hydrogen in the diamond/amorphous carbon phase transitions of oxygen ion implanted ultrananocrystalline diamond films at different annealing temperatures

Abstract

We report that the diffusion and desorption of hydrogen (H) play a key role in the diamond/amorphous carbon phase transitions of O+-implanted UNCD films at different annealing temperatures (Ta) by using high resolution transmission electronic microscopy (HRTEM), vis-uv Raman, and Fourier transform infrared (FTIR) spectroscopy measurements. The results of HRTEM and uv Raman spectroscopy measurements show that with Ta increasing from 500 to 900 °C, the amorphous carbon in grain boundaries (GBs) transits to diamond phase. Visible Raman spectroscopy measurements show that the amount of H bonded to trans-polyacetylene (TPA) chains in GBs reduces with Ta increasing to 900 °C, while that of H terminating to the surfaces of diamond grains increases confirmed by FTIR measurements. It reveals that H diffuses from GBs to the surfaces of diamond grains. In this process, the active H extracts H which terminates the diamond surface, leaving a reactive surface site. This gives a chance for the neighbored amorphous carbon clusters to attach to the surface site, so that diamond grains become larger. After 1000 °C annealing, the amount of diamond phase dramatically decreases and diamond transits to amorphous carbon by HRTEM and uv Raman spectroscopy. It is observed that the amount of H bonded to TPA chains in GBs and that of H terminating to the surfaces of diamond grains dramatically decreases from visible Raman spectroscopy and FTIR measurements. It is revealed that H is desorbed from both surfaces of diamond grains and GBs, which forces diamond grains to collapse to amorphous carbon

High-Energy Excimer Annealing of Nanodiamond Layers

“…According to [ 45 ], diamond films prepared mainly by the CVD method consist of many small micro-/nano-crystalline diamonds surrounded by a graphitic or amorphous carbon phase mainly occurring at their grain boundaries. Due to the presence of these phases, C-H bonds and C-C and C=C transpolyacetal chains are bent/stretched, which causes the appearance of a Raman peak in the region of 1140 cm −1 [ 46 , 47 ] (see the NDs pattern in Figure 6 ). Additionally, the authors of [ 45 ] state that the graphitic (G) peak observed in NDs films prepared in this way was shifted from the graphitic peak of 1580 cm −1 downwards to a broad band in the region of 1500 to 1600 cm −1 .…”

Radiation-Induced Damage and Recovery of Ultra-Nanocrystalline Diamond: Toward Applications in Harsh Environments

“…Previous studies have revealed a temperature dependence of the preferred location of hydrogen within the structure of UNCD. 26 TPA chains are stable up to 1123 K, with temperatures greater than 1173 K resulting in the shortening of TPA chains and a subsequent decrease of the amount of hydrogen bonded to TPA chains in grain boundaries. During this transition, however, the amount of hydrogen bonded to the surface of diamond grains increases.…”

“…Raman spectra were analyzed by fitting a third-order background and five Gaussian peak shape functions to the collected spectra using a routine written in the software package Mathematica . Four of the peaks have previously been assigned to trans -polyactylene (TPA) at the grain boundary (ν 1 and ν 3 ) and carbon ( D and G ) components of the UNCD film. − ,− A fifth peak (ν 2 ) has previously been assigned to TPA (∼1210 cm –1 ) or vibrational density of states contributions from small diamond grains (∼1200 cm –1 ), and is only observed via fitting . The characteristic diamond Raman peak at 1332 cm –1 was not included in the analysis as its contribution is negligible in visible Raman analysis of films grown with minimal hydrogen in the plasma, and it was not discernible in any of the spectra.…”

“…The characteristic diamond Raman peak at 1332 cm –1 was not included in the analysis as its contribution is negligible in visible Raman analysis of films grown with minimal hydrogen in the plasma, and it was not discernible in any of the spectra. Constraints were applied to the peak fitting routine after an initial manual fit and based on previous studies , with the following tolerances: ν 1 , 1136–1140 cm –1 ; ν 2 , 1205–1210 cm –1 ; D , 1338–1342 cm –1 ; ν 3 , 1450–1455 cm –1 ; and G , 1545–1550 cm –1 . Visualization of the change in background photoluminescence (PL) signal with electron irradiation was realized by fitting a first-order gradient to the third-order fitting over the range 1050–1700 cm –1 .…”

“…25 The characteristic diamond Raman peak at 1332 cm −1 was not included in the analysis as its contribution is negligible in visible Raman analysis of films grown with minimal hydrogen in the plasma, 13 and it was not discernible in any of the spectra. Constraints were applied to the peak fitting routine after an initial manual fit and based on previous studies 25,26 with the following tolerances:…”