A compact electron cyclotron wave resonance (ECWR) source has been developed for the high rate deposition of hydrogenated tetrahedral amorphous carbon (ta-C:H). The ECWR provides growth rates of up to 900 A/mm and an independent control of the deposition rate and ion energy. The ta-C:H was deposited using acetylene as the source gas and was characterized in terms of its bonding, stress and friction coefficient. The results indicated that the ta-C:H produced using this source fulfills the necessary requirements for applications requiring enhanced tribological performance.

We report the design, manufacturing, and testing of a new cesium enhanced negative carbon ion source that can be useful to synthesize hard and/or electron emitting carbon nitride and diamond-like carbon (DLC) thin films. The design of the source includes a conventional magnetron-sputtering gun, low voltage ion extraction lenses, and a cesium oven to provide cesium vapor for formation of a fractional mono layer of Cs on the carbon target. Cs reduces the surface work function of the carbon target and enhances the emission of negative carbon ions. Argon and argon-nitrogen gas mixtures were used to ignite and sustain the plasma in the chamber. We compare the properties of carbon nitride and DLC films deposited with and without cesium. Nitrogen composition in the Ar-N2 gas mixture was observed to be an important process parameter affecting mechanical properties of the film. The effect of the Cs oven temperature on deposition rate and current absorbed at the substrate was also investigated for RF powers from 0 to 150 W.

We have deposited thin films of diamond-like-carbon by plasma enhanced chemical vapor deposition, and examined the electron emission characteristics of the optimized DLC-coated field emitters. The bonding spectra and microstractures are controlled by energetic ions depending on deposition parameters which affect the structural, optical, and electrical characteristics. Raman spectra and IR analysis identify that as-deposited DLC contains mixtures of sp2- and sp3-bonding with a wide range of hydrogen, but annealing causes its conversion to graphite structure due to a depletion of hydrogen. From the measurement of field emission characteristics, turn-on gate voltage is lowered to 50 V and anode current is increased for DLC-coated Si field emitter tip arrays.

Our preliminary results show that controllable doping of amorphous hydrogenated DLC films prepared by DC saddle-field glow-discharge technique is possible. We have found deposition conditions when the doping with boron is electrically effective.

Hydrogenated amorphous carbon (a-C:H) films were deposited on p-type Si(100) at room temperature by DC saddle-field plasma enhanced CVD using pure methane gas and diluted methane gas by inert gas. The effect of substrate bias (Vs) from 0 V to 400 V on deposition rate, hydrogen content, chemical bonding of the films have been investigated. FT-IR spectrum shows that a-C:H films consist of sp2 and sp3 bondings and the relative intensity ratio of sp2 and sp3,I(sp2)/I(sp3), decreases from 0.28 to 0.19 as the substrate bias changes from 0 V to 400 V. Deposition rates of the films rapidly decrease with increasing Vs up to 200 V, and then slightly decrease over Vs = 200 V. The hydrogen content of the films increase as Vs goes higher and the number of C-H bonds of a-C:H shows the same trend. Only in the range of Vs=0 V and Vs=100 V the Raman band of graphite and disorder is observed. The emission of white photoluminescence (PL) light from the films is observed with the naked eye even at room temperature. The intensity of PL has a maximum at Vs=200 V, then decreases as the Vs changes from 200 V to 400 V. The PL peak shifts to higher energy from 2.15 eV at 100V to 2.45 eV at Vs=400 V. The PL at Vs = 400 V was two times stronger without a peak shift by using an inert gas dilution into methane source compared with that of a film deposited using pure methane.

Tribochemical reactions between Si incorporated diamond-like carbon (Si–DLC) films and steel ball were investigated during initial stage of tribo-test. The films were deposited by r.f.–PACVD using mixtures of diluted silane (SiH4:H2=10:90) and benzene gases. Si concentration in the film was varied from 0 to 10 at.% by adjusting the diluted silane fraction in the reaction gases. A rotating type ball-on-disk wear rig was employed for the tribo-test in ambient atmosphere. When the Si concentration was less than 5 at.%, initial transient period of high friction coefficient was commonly observed. After the transient period, the friction coefficient becomes lower with increasing contact cycles. The initial transient period becomes shorter and the starting and maximum friction coefficients in transient period decreased with increasing Si concentration. Composition of the debris on the wear scar surface was analyzed by Auger spectroscopy at various stages in the initial transient period. We observed that when the friction coefficient increased in earlier stage of the transient period, iron and oxygen was observed in the debris. However, decrease in the friction coefficient in the later stage of the transient period was associated with the formation of silicon rich oxide debris. This result supports the friction mechanism of Si-DLC films that the formation of Si rich oxide debris results in low friction coefficient in ambient atmosphere.

The fabrication of an efficient cold cathode emitter from carbon is based on a combination of material properties, which must be carefully tailored during deposition. We present the electron emission characteristics of several carbon films deposited by cathodic arc evaporation, and their correlation with the chemical composition, microtexture and microstructure of the films. The emission threshold field voltage, emission site density, uniformity and stability of both tetrahedral amorphous carbon, nitrogen doped carbon and nanoclustered carbon films will be reviewed. We will also address issues related to the deposition method, such as substrate temperature, defect density and scalability, in connection with requirements for the fabrication of field emission displays.

It is shown that the facile electron field emission from diamond and diamond-like carbon occurs because surface groups such as C-H can produce large changes in electron affinity, so that electric fields from the anode can be focused towards unhydrogenated surface areas of high affinity, the fields ending on negative charges in an underlying depletion layer. The resulting downwards band bending creates very large fields which cause Fowler-Nordheim emission, while not exceeding the material's breakdown field, which is the highest for any solid.

In order to test whether field emission from tetrahedrally bonded amorphous (ta-C) is affected by the back contact material we have carried out a series of emission experiments on Filtered Cathodic Vacuum Arc (FCVA) produced ta-C films. The measurements were made on identical films of approximately 25 nm thickness which have been grown simultaneously on various substrates of different work function. For these experiments the substrates used were p-type c-Si, n-type c-Si, SnO2, tungsten, gold, lead, aluminium, molybdenum, chromium and titanium. Threshold fields for emission were generally in the range of 5–15 V/micron and showed no direct dependence on back contact material work function. Films grown on Ti and W however had much higher threshold fields in the range 30–35 V/micron and this is thought to be associated with the native oxide which was present between the back contact and the ta-C film. As grown ta-C is also known to have a 1–2 nm thick sp2 rich layer on its surface and this layer may also have some effect on field emission. The layer was etched in either an O2 or H2 plasma and both etched surfaces led to improved emission efficiency.

The electron emission switching property of the multilayer structures, which constitute of nitrogen doped tetrahedral amorphous carbon (n+-ta-C) film and intrinsic ta-C layer fabricated by the filtered cathodic vacuum arc (FCVA) technique has been investigated. Low voltage DC bias (9V) was applied between the top and bottom layers in conjunction with the conventional electric field applied between the cathode and anode. It has been demonstrated that by varying the low DC bias polarity, the on-set electric field for the electron emission can be varied by ∼ ±6 V/μm compared to the unbiased situation. A possible mechanism for the multilayer field emission and the switching property is proposed.

The field emission properties of a variety of nitrogen-containing hydrogenated amorphous carbon films have been characterised as a function of film thickness and substrate type. Identified trends have been discussed in terms of the optical band-gap and refractive index of the films, and the surface roughness of the substrates. In addition, carbon-based materials have been considered as inexpensive film-compatible substrates, and an in-situ oxygen plasma pre-treatment has been investigated as a means of changing the field enhancement factor of the system. We have achieved field emission with threshold voltages as low as 8 V μm−1, and we present data that supports the view that the electron emission from amorphous carbon is dependent on the nature of the back contact, and possibly the ease at which the film can be fully depleted, i.e. film thickness.

In this paper, we report on a substantial lowering of the threshold field for electron field emission from Si field emitter arrays (FEA), which have been coated with a thin layer of nanocrystalline diamond by microwave plasma-assisted chemical vapor deposition (MPCVD) from fullerene (C60) and methane (CH4) precursors. The field emission characteristics were investigated and the emission sites imaged using photoelectron emission microscopy (PEEM). Electron emission from these Si FEAs coated with nanocrystalline diamond was observed at threshold fields as low as 3 V/μm, with effective work functions as low as 0.59 eV.

The field emission properties of molybdenum and silicon emitter coated with tetrahedral amorphous carbon (or amorphous diamond) were studied. The tetrahedral amorphous carbon was deposited by laser ablation and showed a uniformly coated columnar structure over the entire emitter. In general, current conditioning improved stability and increased the current density. Coatings of ta-C on Mo emitters with and without nitrogen incorporated both yielded significantly higher emissivity than uncoated emitters. Nitrogen incorporation reduced the effective workfunction and the sp3/sp2 ratio. However similar depositions on Si emitters reduced the emissivity, and may be attributable to the residual oxide at the ta-C/Si interface. Annealing in a hydrogen atmosphere enhanced emissivity from both ta-C/Mo and ta-C/Si emitters. In general, thick coatings lowered the emissivity and the slope of the I-V curves. A temperature dependence of emission was observed only in the low field regions.

Nitrogen-doped diamond films were prepared for the first time using melamine (C3H6N6) as the nitrogen source. To explore the differences in the films produced with different precursors, nitrogen-doped films were also produced using pure nitrogen gas as the source. Since melamine has a ring structure with pre-existing C-N bonds, the incorporation of nitrogen on substitutional sites of diamond lattice are expected. Relatively large amounts of substitutional nitrogen were successfully doped into diamond without degrading its quality. However, when pure nitrogen gas was used as a doping source, the quality of the diamond was not as high as the sample doped with nitrogen by melamine. Raman spectroscopy, photoluminescence spectroscopy (PL), and field emission measurements were carried out to characterize the samples. Nitrogen-doped diamond samples did not exhibit any significant reduction in turn-on fields. It is suggested that nitrogen doping has only a minor effect on the field emission properties of the diamond films.

Boron nitride coatings and structures have demonstrated significant resistance to many corrosive environments. These coatings may have application in the protection of sensors needed for measuring a variety of properties such as temperature and chemistry. In addition, boron nitride materials may offer advantages as structural materials in high temperature materials processing. In this study, BN is assessed for use in aluminum smelting.

Amorphous carbon-nitrogen films, a-CNx, deposited by rf-magnetron sputtering in N2 atmosphere were annealed in vacuum at temperatures between 300 and 700 °C. The annealing time was 30 minutes. The modifications on the film microstructure were monitored by infrared spectroscopy (IR), while the composition and the atomic density were determined by Rutherford backscattering spectrometry (RBS), elastic recoil detection analysis (ERDA) and nuclear reaction analysis (NRA). The internal stress was determined by measuring the film-induced bending of the substrate and the hardness was measured by nanoindentation. Atomic force microscopy (AFM) provided the friction coefficient and the surface roughness. The ratio between nitrogen and carbon atomic concentration decreases for temperatures higher than 500 °C, whereas the film density increases with the annealing temperature: 40 % in the temperature range here studied. The behavior of the D and G Raman bands, IR active due to the nitrogen incorporation in the carbon network, suggests a progressive increase of the size of the graphite-like domains. The hardness of the as-deposited a-CNx film is around 2 GPa. However, both hardness and internal stress increase by a factor of three in samples annealed at 700 °C, while the surface roughness and the friction coefficient decrease by a factor of about two.

We have deposited carbon nitride (CNx) films by magnetron sputtering at varying nitrogen pressures and substrate temperatures. The films were deposited on silicon and quartz substrates simultaneously. The incoming ion energy was controlled by a radio frequency power supply. A magnet in front of the substrate holder was used to enhance the plasma density. The films deposited at room temperature (RT) were found to have nitrogen content of ≥ 40%. These films were semiconducting with an optical bandgap of greater than 2 eV and a RT resistivity of 1012 Ω-cm. Films deposited at low nitrogen pressure (< 7 mtorr), at RT and in the presence of a 15 mtesla magnetic field were found to be hard and also exhibited extremely high elastic recovery. The most interesting result we found was that the hard and elastic CN films were also semiconducting with an optical band gap of 1.7 eV, RT resistivity of 107 Ω-cm and an activation energy of 0.8 eV. In all cases the CN films were almost entirely sp2 bonded.

Carbon nitride films prepared by magnetic filtered plasma deposition were characterized using Fourier transform infrared (FTIR) absorption and X-ray photoelectron spectroscopy (XPS). Characteristic bands corresponding to C-N, C=N, C=N, and C=C bonds were observed in FTIR spectra. It was found that the XPS C 1s and N 1s signals could be deconvoluted into three and two gaussian peaks, respectively. A plausible suggestion on the assignments of the XPS peaks to C3N4, CNx and ta-C phases was discussed. The relative abundance of the various CN bonds, the relative abundance of the various bonding components from XPS results, and their dependence on the nitrogen partial pressure PN during deposition were analyzed. Assuming the assignments of the XPS peaks to the various phases, the XPS results suggested that there would be an optimal PN that would favor the growth of the C3N4 phase. The electrical conductivity, the optical band gap and the Vickers hardness of these films were measured and the effects of PN on these properties were studied.

Amorphous CNx films were obtained on monocrystalline silicon substrates by direct writing laser induced chemical vapor deposition from CCI4 and NH3 using CuBr vapor laser. The main process parameters (scanning speed, laser power, background temperature) were varied in wide ranges. The deposition rates in the laser spot were in the range of 1 – 10 μm/s. Scanning electron microscopy showed that the layers had rather rough surface. The deposited films were composed of carbon, nitrogen, silicon and oxygen, as detected by AES and EDX analyses. Chemical bonding structure was investigated by FTIR and showed absorption bands corresponding to different chemical groups - CH, CH2, CH3, C=C, C=N, C=O, Si-O, Si-C, Si-N and C-N. The electrical measurements of the deposited films showed that their resistivity varied from 0.15 to 1.40 MΩ.cm and it was very sensitive to the deposition conditions.

A systematic study of the growth and local atomic bonding (LAB) of a series of a-CxNyHz alloy films prepared via plasma enhanced chemical vapor deposition (PECVD) from mixtures of NH3/C2H2 and N2/C2H2 is presented. The effects of the reactants and their ratio on the film composition and bonding of hydrogen, the optical constants, and the optical energy gap have been determined. It is found that the presence of nitrogen and hydrogen in the plasma decreases the net film deposition rate due to enhanced etching and that incorporation of nitrogen into the film is limited to N/C ≈0.1. For the films deposited from N2/C2H2 as the concentration of N in the film increases, the concentration of C also increases while that of H decreases. No evidence for the type of bonding expected in the theoretically-predicted C3N4 compound has been found. It is observed that hydrogen is preferentially bonded to nitrogen and there is evidence for N-H…N hydrogen bonding in the films. The predictions of the free energy model (FEM) previously developed for the bonding in a-CxNyHz alloys are compared with these experimental results. The importance of entropy in determining the most stable state of these alloys is demonstrated. The FEM successfully predicts and explains some of the experimentally-observed properties of the alloys.