| The diamond film electrode exhibits lots of excellent properties, such as a wide electrochemical potential window, low and stable voltammetric and amperometric background current, long-term electrochemical stability and chemical inertness, weak adsorption of polar molecules and great fouling resistance. Therefore, diamond films have a great application prospect in electrochemistry. The π bonds in grain boundaries of nanocrystalline diamond (NCD) thin films can provide a conductive path to the films, so that the conductivity of NCD films is better than that of MCD films. From this point, NCD films are a kind of very promising electrode materials. The resistivity of NCD films is less than MCD films by3-6orders of magnitude, but its resistivity and migration rate still do not meet the requirements of electrode materials. Therefore, for realizing the application of NCD films in the field of electrochemistry, it is very important to add suitable impurities into the NCD films to improve its electrical performance. Our previous study indicates that the oxygen or phosphorus ion implanted and above800℃annealed samples exhibit good n-type conductivity, which is expected to become a good electrode material. However, there is not systematically research in this respect. Ion implantation has an important influence on the electrical properties and electrochemical performance of nanocrystalline diamond thin film surface. Immersion ion implantation is a new type of surface treatment and its effects on electrochemical properties of thin NCD films have not yet been studied. Based on these problems, we will systematically study the microstructure and electrochemical properties of ion implanted NCD films in this thesis.The nanocrystalline diamond (NCD) films were implanted by oxygen ion with the dose of1×1012cm-2and subsequently annealed at700,800,900and1000℃, respectively. The microstructure and electrochemical properties of these NCD films were investigated systematically and the results show that the potential window of the unannealed sample (0120) and1000℃annealed sample (0121000) is up to4.6V and3.61V, respectively. The mass transfer efficiency of the two samples is also better, indicating that oxygen ion implantation and1000℃annealing can improve the mass transfer efficiency of NCD films. The results of infrared spectroscopy measurements show that there are no hydrogen atoms are terminated to the surface of samples0120and 0121000, while hydrogen atoms terminate to the surface of the other samples. It is indicated that oxygen ion implantation and1000℃annealing have damaged hydrogen terminations in the surface, which improves the electrochemical performance of NCD films. Raman spectroscopy measurements suggest that high content of diamond phase, small internal stress and more disordered amorphous carbon prefer to improve the electrochemical properties of NCD films. When the amount or size of sp2carbon clusters in amorphous carbon grain boundaries decreases, the electrochemical properties of NCD films become better.Nanocrystalline diamond (NCD) films were implanted by phosphorus ion with the dose of1×1012cm-2and subsequently annealed at700,800,900and1000℃, respectively. The results showed that the potential window of P12700is larger and the catalytic oxidation of phenol performance of P12700is better. The amorphous carbon grain boundaries of sample P12900is more disordered and the amount or size of amorphous sp2C clusters of P12900is larger. It indicates that the ordered amorphous carbon grain boundaries and larger sp2C clusters are not favariate to improve the electrochemical properties of P+-implanted NCD films.Oxygen ions with low dose and high dose were implanted into NCD films by immersion ion implantation method, and the samples were annealed at900and1000℃in vacuum. The results show that in sulfuric acid solution the potential window of intrinsic F electrode is larger, while in KCl and KOH solution the potential window of sample O900high is larger. In three kinds of solution, the potential window of sample O1000low is smaller. The linear relationship of the peak current and square root of scan rate of NCD film electrode suggests that mass transfer efficiency of sample intrinsic F electrode is higher. Amorphous carbon of O1000low is more disordered, the potential window of O1000low is less and the performance of catalytic oxidation of phenol of O1000iowis poor. The number or size of amorphous sp2C clusters, which are in grain boundary of O900high, is less and the surface resistivity of O900high is smaller and its carrier concentration is larger, making the potential window of O900high larger and its catalytic oxidation performance higher. The catalytic oxidation current of phenol of O900low in neutral medium of KCl is also larger, suggesting that the n-type conductivity and higher carrier mobility can improve the catalytic oxidation performance of organic phenol of thin films. |
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