“…Several nanocrystalline materials reveal capacitance values owing to grain and GBs in the order of pF and nF, respectively [38]- [42]. UNCD films commonly exhibit grains with nanosize lies in the range of 5-10 nm, while their GBs width is 1-1.5 nm [43], [44]. Consequently, the capacitance associated with diamond grains in the UNCD/a-C:H film is anticipated to be approximately one order of magnitude lower than that produced by the GBs.…”
Nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous-carbon (UNCD/a-C:H) composite films, grown on Si substrates by the coaxial arc plasma gun, were investigated using temperature-dependent impedance spectroscopy. The measurements were carried out in frequency and temperature ranges of 100 Hz-2 MHz and 300-400 K, respectively. Structurally, the nitrogen incorporation into the deposited films as well as sp 2 /sp 3 ratio was studied by X-ray photoemission spectroscopy (XPS), measured with synchrotron radiation. The results of temperature-dependent electrical conductance characterization of the examined films revealed that the heterogeneous structure possesses a low-frequency conduction mechanism with an activation energy of 46 meV. This possibly originated from charge carriers hopping in the deposited composite. Furthermore, the results manifested a relaxation process, with an activation energy of 41 meV, originated from space charges in grain boundaries of the films. Cole-Cole plots of measured and fitted impedance spectra exhibited equivalent resistance due to grain boundaries that are much smaller than that related to UNCD grains. This is owing to the nitrogen incorporated in the composite film inside the grain boundaries instead of the grains. This increases the concentration of charge carriers within the grain boundaries and therefore enhances their conductivity. Moreover, the deduced capacitance corresponding to grain boundaries was larger than that originated from the UNCD grains. This is due to the difference between the grain-size and grain-boundary width of the UNCD/a-C:H composite.INDEX TERMS Nitrogen-doping; Coaxial arc plasma gun; Complex impedance spectroscopy, nanodiamond grains; grain boundaries.
“…Several nanocrystalline materials reveal capacitance values owing to grain and GBs in the order of pF and nF, respectively [38]- [42]. UNCD films commonly exhibit grains with nanosize lies in the range of 5-10 nm, while their GBs width is 1-1.5 nm [43], [44]. Consequently, the capacitance associated with diamond grains in the UNCD/a-C:H film is anticipated to be approximately one order of magnitude lower than that produced by the GBs.…”
Nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous-carbon (UNCD/a-C:H) composite films, grown on Si substrates by the coaxial arc plasma gun, were investigated using temperature-dependent impedance spectroscopy. The measurements were carried out in frequency and temperature ranges of 100 Hz-2 MHz and 300-400 K, respectively. Structurally, the nitrogen incorporation into the deposited films as well as sp 2 /sp 3 ratio was studied by X-ray photoemission spectroscopy (XPS), measured with synchrotron radiation. The results of temperature-dependent electrical conductance characterization of the examined films revealed that the heterogeneous structure possesses a low-frequency conduction mechanism with an activation energy of 46 meV. This possibly originated from charge carriers hopping in the deposited composite. Furthermore, the results manifested a relaxation process, with an activation energy of 41 meV, originated from space charges in grain boundaries of the films. Cole-Cole plots of measured and fitted impedance spectra exhibited equivalent resistance due to grain boundaries that are much smaller than that related to UNCD grains. This is owing to the nitrogen incorporated in the composite film inside the grain boundaries instead of the grains. This increases the concentration of charge carriers within the grain boundaries and therefore enhances their conductivity. Moreover, the deduced capacitance corresponding to grain boundaries was larger than that originated from the UNCD grains. This is due to the difference between the grain-size and grain-boundary width of the UNCD/a-C:H composite.INDEX TERMS Nitrogen-doping; Coaxial arc plasma gun; Complex impedance spectroscopy, nanodiamond grains; grain boundaries.
“…Another category of NCD is the ultra-nanocrystalline diamond (UNCD) [9] [10] [11]. To distinguish the difference between NCD and UNCD, UNCD is defined as diamond films with the grain size in the range of 2 to 10 nm and the film's boundary containing the sp 2 -C. The surface of UNCD is very smooth, moreover, the surface roughness do not increase with the thickness of the film…”
Section: Structural Characteristics Of Nanocrystalline Diamondmentioning
Due to its unique properties such as high hardness, light transmittance, thermal conductance, chemical stability and corrosion resistance, diamond has drawn tremendous attention in last two decades. These specific properties made diamond film a promising material for cutting tools, microwave windows, heat sinks for electronic devices and diamond electrodes. However, the diamond film with grain sizes at microscale usually exhibits high surface roughness and hinders its applications in the microelectro mechanical system (MEMS) and biological field because it is difficult to be polished by mechanical and chemical methods. With the development of the chemical vapor deposition, the nanocrystalline diamond (NCD) film has been fabricated and found new applications. The grain size of NCD film is in the range of 10 to 100 nm, which inherits the properties of the diamond and possesses the unique properties of the nanoscale materials, and the morphology of the NCD film is granular or needle-like structure. The microwave plasma chemical vapor deposition (MPCVD) has been regarded as the most promising method to deposit NCD film at low temperature. Compared to the hot filament CVD, MPCVD can grow high quality NCD film avoiding of the contamination from the filament materials. The MPCVD technique has high plasma density to activate carbonaceous compound and grow NCD film in high growth rate and low substrate temperature. The unique properties of NCD film, such as the superior electrical, mechanical and biological properties facilitate their application in various fields. The biological application, especially as a biocompatible coating, mainly includes the joint replacement implants and protective coatings and the ophthalmological prosthesis.
“…Further studies showed that neuronal growth on various diamond and DLC substrates can be manipulated by a combination of laminin coating and surface termination [ 125 – 127 ]. Similarly, neuroblastoma cells have also been preferentially grown on UNCD patterned with O, F or H terminations, and this may lead to new routes to studying neuronal cancer [ 128 ]. Figure 6.…”
Section: Diamond As a Substrate For Cell Culture And Biomedical Implamentioning
Progress made in the last two decades in chemical vapour deposition technology has enabled the production of inexpensive, high-quality coatings made from diamond to become a scientific and commercial reality. Two properties of diamond make it a highly desirable candidate material for biomedical applications: first, it is bioinert, meaning that there is minimal immune response when diamond is implanted into the body, and second, its electrical conductivity can be altered in a controlled manner, from insulating to near-metallic. In vitro, diamond can be used as a substrate upon which a range of biological cells can be cultured. In vivo, diamond thin films have been proposed as coatings for implants and prostheses. Here, we review a large body of data regarding the use of diamond substrates for in vitro cell culture. We also detail more recent work exploring diamond-coated implants with the main targets being bone and neural tissue. We conclude that diamond emerges as one of the major new biomaterials of the twenty-first century that could shape the way medical treatment will be performed, especially when invasive procedures are required.
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