de A Ariël Graaf

X-ray photoelectron spectroscopy reference data for identification of the C3N4 phase in carbon-nitrogen films

The β-C3N4 phase should have a tetrahedral (sp3-bonded) structure resulting in C1s and N1s XPS peaks with only one feature at a position defined by the electronegativity of four CN bonds. In this work we determined the binding energy of the C1s and N1s XPS peaks in melamine (C3N6H6). In this compound the carbon atoms have four bonds with nitrogen atoms (double and two single); the nitrogen atoms have two chemical states: CNC and CNH2. Since the total number of chemical bonds in this compound is the same as in the hypothetical β-C3N4 compound, this compound is more suitable as a C1s XPS reference for the β-C3N4 phase. The binding energy of the C1s and N1s XPS peaks in melamine was determined to be equal to 287.9 and 399.1 eV, respectively. The binding energies were determined relative to the C1s XPS peak for carbon contamination (adventitious carbon).

Argon ion-induced dissociation of acetylene in an expanding Ar/C2H2 plasma

Mass spectrometric and Langmuir probe measurements reveal that the plasma chemistry of an expanding Ar/C2H2 plasma which is used for deposition of hydrogenated amorphous carbon is dominated by argon ion-induced dissociation of the precursor gas. The ion-induced dissociation is very efficient leading to complete depletion under certain conditions. The ion fluence as determined from modeling the mass spectrometry results is in good agreement with Langmuir probe measurements suggesting a one-to-one relation between the argon ion and acetylene consumption. The good correlation found between the growth rate and the acetylene consumption rate expresses the efficient use of the dissociation products.

Characterization of carbon nitride thin films deposited by a combined RF and DC plasma beam

Abstract Thin carbon nitride films have been deposited on silicon(100) substrates downstream of a nitrogen plasma beam generated in a combined RF (13.56 MHz, 40–50 W) and DC (voltage ±200 V, power 1–10 W) discharge between a graphite electrode and a graphite nozzle. By combining the RF and DC sources the capability of RF field to create extended plasmas is used together with the enhanced sputtering and biasing effect of the DC source. The plasma characteristics (electron temperature, presence of molecular species) have been studied by optical emission spectroscopy. Deposition rates of 2.5–3 nm/s are obtained at the centre of the plasma beam and at a few centimetres distance from the nozzle. The films have been investigated by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, scanning and transmission electron microscopy, and microhardness measurements. The films have an overall N:C ratio of 0.28 but the distribution of different nitrogen bonds depends upon the DC bias conditions. In the spectral range 0.3–0.7 μm the refractive index increases slightly from 1.5 to 2.2. The films are amorphous, with morphology consisting of a columnar structure. The columns have a diameter of about 20 nm. A hardness of 24 GPa has been measured.

Plasma chemistry of an expanding Ar/C2H2 plasma used for fast deposition of a-C:H

Mass spectrometric measurements in combination with Langmuir probe measurements reveal that the plasma chemistry of an expanding Ar/C2H2 is dominated by argon-ion-induced dissociation of the precursor gas. Under high arc current conditions complete depletion of acetylene is observed, indicating an efficient consumption of the injected acetylene. A clear correlation between the ion fluence emanating from the arc determined from modeling the mass spectrometry results and Langmuir probe measurements is observed. First measurements by means of cavity ring down and optical emission spectroscopy of the products of the dissociation of acetylene indicate that the dominant dissociation channel is C2H and H.

Use of in situ FTIR spectroscopy and mass spectrometry in an expanding hydrocarbon plasma

In situ Fourier transform infrared (FTIR) spectroscopy and mass spectrometry have been used to investigate the gas phase of an expanding thermal argon plasma into which hydrocarbons are injected. With both techniques it is possible to determine the depletion of the precursor gas and the densities of new species formed in the plasma, each of the techniques with its own advantages and disadvantages. To determine absolute densities of different species in the plasma by means of mass spectrometry it is necessary to deconvolute the obtained mass spectra, whereas by means of FTIR spectroscopy different species are easily recognized by their infrared absorption at specific positions in the absorption spectrum. With mass spectrometry the gas composition is measured locally, i.e. close to the gas extraction point. On the other hand with FTIR spectroscopy all particles in the infrared beam are included in the measurement. When both techniques are combined most of the individual disadvantages cancel, leading to a very powerful plasma diagnostic tool. Aside from the power resulting from the combination of both techniques, FTIR spectroscopy data also contain information on the temperature of the stable species inside the plasma. A method to extract the rotational particle temperature (within 100 K) by means of infrared absorption spectra simulation is presented.

Investigation of processes in low-pressure expanding thermal plasmas used for carbon nitride deposition: I. Ar/N2/C2H2 plasma

The chemistry of argon, argon/nitrogen and argon/nitrogen/acetylene expanding thermal plasmas is investigated in order to unravel the role of plasma species in the fast deposition (up to 40 nm s-1) of hydrogenated amorphous carbon nitride (a-C:H:N) films. The precursor dissociation is determined and the emission from the different plasmas is compared in order to distinguish possible mechanisms for species production and excitation.

Investigation of processes in low-pressure expanding thermal plasmas used for carbon nitride deposition: II. Ar/N2 plasma with graphite nozzle

The chemistry of an argon/nitrogen thermal plasma expanding through a graphite nozzle is investigated in order to unravel the role of plasma species in the deposition (1-3 nm s-1 rate) of non-hydrogenated amorphous carbon nitride (a-C:N) films. The spectral emission of plasma species is studied and is used in combination with mass spectrometry and nozzle temperature measurements to distinguish possible mechanisms of species production and excitation.