The microstructural and electrochemical properties of oxygen ion implanted nanocrystalline diamond films

Due to its smoothest surface, fewer defects, and better crystal quality, [100] textured diamond film is well suited for the application of optoelectronic and microelectronic devices. Carrier concentration and mobility are very important parameters of semiconductor materials. In order to further broadening the application of diamond films in optoelectronics and microelectronics, it is necessary to made a research on Hall effect characteristics of [100] textured and [111] textured films. In this paper, different textured polycrystalline diamond films are deposited on silicon substrates by hot filament chemical vapor deposition (HFCVD) method under different conditions. Microstructures of diamond films are characterized by X-ray diffraction (XRD). High quality [100] textured and [111] textured diamond films are obtained. Dark current-voltage (I-V) characteristics of different-oriented films after annealing are investigated at room temperature. The carrier concentration and mobility of diamond films are measured by Hall effect test system as the temperature changing from 100 to 500 K. Results indicate that the textures of diamond films affect the value of carrier mobility:carrier concentration increases and mobility decreases with the decrease of temperature; and the deposited films are of p-type materials. The carrier concentration and mobility of polycrystalline [100]-textured diamond films at room temperature are 4.3×104 cm-3 and 76.5 cm2/V·s, respectively.

Hall effect of different textured CVD diamond films

Qing-Feng¹,

Chang-Zhu²,

Wang³

et al. 2015

Microstructural and electrochemical properties of sulfur ion implanted nanocrystalline diamond films

Jiang¹,

Zhu²,

Chen³

et al. 2019

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/cm2, and the electrochemical reversibility is much better thanthose of samples annealed at 600 °C, 700 °C, and 800 °C, respectively.

Preparation and electrochemical properties of nano-diamond/vertical graphene composite three-dimensional electrodes

Jiang¹,

Wang²,

Chen³

et al. 2022

Diamond/graphene composite three-dimensional electrode has attracted extensive attention because of its low background current and wide potential window of diamond component, and its high electrochemical activity of graphite component. In this paper, by means of hot wire chemical vapor deposition method, nano diamond is embedded in the vertical graphene sheet on the surface of single particle layer of nano diamond by regulating the short-term growth time to form a composite three-dimensional electrode. The results show that the electrode exhibits a wide potential window (3.59 V) and a very low background current (1.27 mA/cm2) when nanocrystals grow on the top of the vertical graphene sheet. The composite structure of nanocrystals coated with graphite on the top of the graphene sheet is the key to broaden the potential window and reduce the background current. With the increase of growth time, the vertical lamellae grew and nano-diamond grains were embedded into the lamellae, and a novel nano-diamond/graphene composite vertical lamellae structure was constructed. The ordered graphite structure increases the electrochemical active area to 677.19 μC/cm2 and the specific capacitance to 627.34 μF/cm2. The increase of graphite components makes the potential window narrow, and the embedded nanodiamond effectively reduces the background current. This study provides a new method for preparing three-dimensional nanodiamond/graphene composite electrodes by hot wire chemical vapor deposition, and provides a new idea for fully exploiting the synergistic effect of diamond/graphene composite films.