Influence of nitrogen incorporation on the electrical properties of MPCVD diamond films growth in CH4–CO2–N2 and CH4–H2–N2 gas mixtures (original) (raw)
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Surface and Coatings Technology, 2006
We present a study of the microstructural and electrical properties of nitrogen doped diamond (NDD) thin films deposited on Si(111) by microwave plasma enhanced chemical vapor deposition (MWCVD). The conductivity of NDD thin film increases with increasing bias. In contrast, we also found the conductivity decreased with the increasing growth temperature and the increasing thickness of the diamond film after longer deposition. According to the microstructural analysis of NDD thin films by means of SEM, we found that the thicker the diamond thin film is, the bigger the grain size of the diamond grows, and the fewer interfaces the grain boundary of the NDD has, yield to a larger resistance. We propose that the nitrogen in the NDD was not doped into diamond crystallines but was located in the interlayer of the grain boundaries of the NDD. D
The effect of nitrogen on the growth, morphology, and crystalline quality of MPACVD diamond films
Diamond and Related Materials, 1999
The influence of varying nitrogen concentrations (5-1000 ppm) on the conventional CH 4 /H 2 diamond film deposition process using a microwave plasma disk reactor is investigated. This reactor has important differences, such as reactor volume, power density, gas flow, from the common tubular microwave reactors. The experimental behavior indicates, that similar to the tubular reactors, the addition of small amounts of a nitrogen stabilizes the growth of high quality, {100} faceted films. However, the actual threshold nitrogen concentrations and the variation of these threshold concentrations versus other independent experimental variables differs considerably from tubular reactor performance. This suggests that reactor design has an important influence on the deposition process in the presence of impurities.
Nitrogen Doping Effects on Electrical Properties of Diamond Films
Japanese Journal of Applied Physics, 1998
Chemical-vapor-deposited (CVD) diamond films with intentional nitrogen doping have been characterized by various standard techniques. Electrical resistance measurements demonstrate that the nitrogen doping significantly varies the surface conductivity of as-grown diamond films; the surface resistance of N-doped diamond films can reach as high as 1011 Ω, which is about six orders of magnitude higher than that of an undoped one. Such high surface resistance remains stable even after 8 hours of exposure to hydrogen plasma. It is also found that the photoemission threshold energy of N-doped diamond films is about 0.55 eV less than the diamond band-gap energy, which implies the existence of compensated surface gap states and possibly, negative electron affinity in the as-grown N-doped diamond films. The particular properties observed in the N-doped diamond films are discussed in relation to the fabrication of diode-type diamond electron emitters.
Journal of Applied Physics, 2000
The presence and concentration of nitrogen and hydrogen impurities in thick diamond films grown by microwave plasma chemical vapor deposition at various H 2 gas flow rates, keeping a constant ͓CH 4 ͔:͓H 2 ͔ϭ2.5% concentration ratio, have been determined by electron spin resonance and optical absorption spectroscopy. The relative concentration of both impurities, present as paramagnetic atomic species with different relaxation properties, has been found by ESR measurements to decrease exponentially with the increase in the H 2 gas flow rate. Moreover, the resulting values were proportional to the content of substitutional nitrogen and CH x groups obtained from infrared and ultraviolet-visible optical absorption measurements, respectively. The decrease in the concentration of both impurities with an increase in the quality of the studied diamond films, early observed from high resolution electron microscopy studies on the same samples, strongly suggests that the incorporation of both impurities, as paramagnetic atomic species, is directly related to the concentration of the extended lattice defects.
Structural and electrical properties of nanocrystalline diamond (NCD) heavily doped by nitrogen
Diamond and Related Materials, 2005
Gas mixtures containing up to 40% nitrogen by volume and 1% CH 4 with the balance being argon have been used for the deposition of nitrogen doped nanocrystalline diamond (NCD) films by means of microwave plasma enhanced chemical vapour deposition (MPECVD). The CVD plasma was monitored by optical emission spectroscopy to reveal the plasma species, e.g., CN molecules, as a function of the nitrogen additive. Structural properties of the deposited NCD films were studied by FESEM and Raman spectroscopy. Effects of nitrogen doping on the electrical resistivity and electron field emission characteristics of the NCD films were measured. In this work, correlation between the structural and electrical properties of NCD films and the nitrogen additive to the CVD plasma will be presented and discussed.
Applied Physics Letters, 2016
The influence of N 2 concentration (1%-8%) in CH 4 /H 2 /N 2 plasma on structure and optical properties of nitrogen doped diamond (NDD) films was investigated. Thickness, roughness, and optical properties of the NDD films in the VIS-NIR range were investigated on the silicon substrates using spectroscopic ellipsometry. The samples exhibited relatively high refractive index (2.6 6 0.25 at 550 nm) and extinction coefficient (0.05 6 0.02 at 550 nm) with a transmittance of 60%. The optical investigation was supported by the molecular and atomic data delivered by Raman studies, bright field transmission electron microscopy imaging, and X-ray photoelectron spectroscopy diagnostics. Those results revealed that while the films grown in CH 4 /H 2 plasma contained micron-sized diamond grains, the films grown using CH 4 /H 2 /(4%)N 2 plasma exhibited ultranano-sized diamond grains along with n-diamond and i-carbon clusters, which were surrounded by amorphous carbon grain boundaries.
Diamond and Related Materials, 1994
Diamond films with different surface morphologies were produced by the electron cyclotron resonance microwave-plasma-assisted CVD method from gas mixtures containing CO-Hz-O 2 at a relatively low pressure. The electrical conductivity of the samples along the growth direction was measured in the temperature range from 200 to 800 °C. The films with (111) morphologies have conductivity activation energies of between 0.3 and 0.4 eV consistent with boron incorporation in such films. On the contrary, films with (100) morphologies have a conductivity activation energy of 1.5 eV consistent with nitrogen incorporation in such films. Electron spin resonance and cathodoluminescence measurements show the simultaneous existence of boron and nitrogen impurities. Owing to their high solubility, boron and nitrogen are the most common impurities in natural and synthetic diamonds. The results suggest that electrically active boron and nitrogen incorporation takes place more etficiently when growth proceeds along the (111) and (100) directions respectively.
Surface & Coatings Technology, 2000
Ž. Dielectric properties of diamond films grown by microwave plasma enhanced chemical vapor deposition MPECVD on Ž. tungsten carbide WC substrates from Ar᎐H ᎐CH gas mixture were studied using an impedance analyzer. The dielectric 2 4 dispersion is observed in the frequency range from 100 Hz to 15 MHz. The real and imaginary parts of impedance of diamond films deposited at the different Ar ratios of the reactive gases consist of a semicircle in the complex plane and can be fitted to the theoretical circuit model. The frequency dependence of the imaginary part of the impedance implies different time constants , which are closely related to the diamond film's AC resistivity and dielectric constant. The values of the resistivity of diamond films increase with increasing Ar gas ratio, which is an indication of lower graphite content of the samples with higher Ar gas ratio. Raman spectroscopy also confirmed the results. It is found that Ar ions in a microwave plasma possess the ability to remove the unexpected non-diamond phases and improve the diamond quality.
Diamond and Related Materials, 2006
Nitrogen doped diamond-like carbon (DLC:N) thin films were deposited on p-type silicon (p-Si) and quartz substrates by microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD) at low temperature (b100°C). For films deposition, argon (Ar: 200 sccm), acetylene (C 2 H 2 :10 sccm) and nitrogen (N: 5 sccm) were used as carrier, source and doping gases respectively. DLC:N thin films were deposited at 1000 W microwave power where as gas composition pressures were ranged from 110 Pa to 50 Pa. Analytical methods such as X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy, FTIR and Raman spectroscopy were employed to investigate the chemical, optical and structural properties of the DLC:N films respectively. The lowest optical gap of the film was found to be 1.6 eV at 50 Pa gas composition pressure.