Microstructural and electrochemical properties of sulfur ion implanted nanocrystalline diamond films

Abstract

Nanocrystalline diamond (NCD) films have a composite structure composed of diamond grains and amorphous carbon grain boundaries. Compared with microcrystalline diamond (MCD) films, the NCD film grain boundaries are rich in a large number of π bonds, thus providing conductive channels. Its conductivity is 3−7 orders of magnitude higher than that of MCD, and the surface of NCD film is uniform and dense, and the roughness is lower, so the NCD film is a promising electrode material. In our previous study, microwave plasma chemical vapor deposition was successfully used to prepare n-type sulfur-doped diamond films with good electrical properties. However, the electrochemical properties of sulfur-doped nanocrystalline diamond films have not been studied till now. In the present work, the nanocrystalline diamond films are prepared by the hot-wire chemical vapor deposition. The films are subjected to ion implantation and vacuum annealing. The effects of annealing temperature on the microstructure and electrochemical properties of the films are investigated. The results show that the sulfur ion implantation is beneficial to the improvement of the electrochemical reversibility of the film. When annealed at 800 °C and below, the amorphous carbon phase at the grain boundary in the film gradually changes into the trans-acetylene phase, resulting in a gradual deterioration of electrochemical performance. When the annealing temperature rises to 900 °C, Raman spectrum and TEM results show that the film has more diamond phase content and better lattice quality, and the trans-polyacetylene in the grain boundary is cracked; XPS results indicate that the CO bond at this time, C=O bond, and π—π* content increase significantly; Hall test shows that the film mobility and carrier concentration are significantly higher than those of unannealed film. The redox peak in the electrolyte is highly symmetrical, the peak potential difference is reduced to 0.20 V, the electrochemical active area is increased to 0.64 mC/cm<sup>2</sup>, and the electrochemical reversibility is much better thanthose of samples annealed at 600 °C, 700 °C, and 800 °C, respectively.

Characterization, spectroscopic investigation of defects by positron annihilation, and possible application of synthesized PbO nanoparticles*

“…PbO is well known as a direct band semiconductor, [36] the optical band gap [37] for the synthesized samples are obtained by extrapolating the linear part of the (αhν) 2 against hν curve to zero on the y-axis. The band gap energies of the PbO nanocrystallites are in the range of 2.97-2.34 eV (Fig.…”

“…The wide bandgap semiconductor nanomaterials, especially sulfides and oxides [1] of alkaline earth and transition metal elements, have been broadly investigated in recent years due to their promising electrical, [2] electronic, [3] optical, [4][5][6] and unique chemical properties. [7][8][9][10] Generally, for oxide semiconductor nanoparticles, the UV-Vis absorbance peak is blue-shifted or, in other words, the band gap energy of the nanoparticles increases with decreasing nanocrystallite size, and the same happens in the case of the surface to volume ratio [11] as well.…”

Effects of Cu and Co additions on the crystallization and magnetic properties of FeNbB alloy

“…Transmission electron microscopy (TEM) is one of the most important testing methods for observing the microstructure of materials. [31,32] The grain size distributions are fitted by a log-normal function. [33] The mean grain sizes are shown in the upper right corner.…”

Surface structure modification of ReSe2 nanosheets via carbon ion irradiation

“…[12] In recent years, a large amount of work on ion beam modification of 2D or other film materials has been performed, showing an effective way to modify ReSe 2 . [17][18][19][20][21][22][23][24] In this work, the properties of multilayer ReSe 2 samples on Al 2 O 3 substrates are modified by ion irradiation technique. The irradiated C ions lose energy through two mechanisms: nuclear energy loss (originating from nucleus collision) and electronic energy loss ( arising from interaction between irradiated electron and lattice atoms).…”