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In this study, we report the deposition of nanocrystalline carbon thin films by modified anodic jet carbon arc technique assisted with inert-helium and reactive-nitrogen gaseous environments. The modified anodic jet technique facilitates to generate a very high localized pressure near the arc spot for the growth of nanocrystallites of carbon at high arc temperature and high pressure. The deposited films were analyzed for the growth of nanocrystallites in amorphous carbon structure under high-resolution transmission electron microscopy (HRTEM). The HRTEM studies reveal the distribution of nanocrystallites in the amorphous carbon matrix. The temperature-dependent conduction behavior of the deposited films has also been analyzed under Mott’s variable range hopping conduction mechanism. Both sets of the film are found to follow three-dimensional variable range hopping conduction mechanisms for the transport of charge carriers. The deposited films are also analyzed for their applications to energy-saving light-dependent resistors under an illumination intensity of ~ 100 mW/cm2 of white light. The reasonably high value of detectivity values ~ 1.26 × 106 and 3.12 × 106 Jones and relatively lower values of trap depth 0.6826 and 0.6834 eV for the nanocrystalline films deposited in helium and nitrogen environments suggest trapped state-assisted significantly high power conversion efficiency. This supports the suitability of the deposited films for light-dependent resistor applications.

Wettability property of carbon nano-tubes (CNT)-graphene like films have been investigated. In this work, we have studied the wettability of CNT-graphene like film deposited on Ni substrate by Micr...

Theromochromism and electrochromic coatings have promising applications in smart windows, IR sensors, and bio-medical devices. In this paper, we report the growth of vanadium oxide films using cathodic vacuum arc method for thermochromic application. Successive annealing of the as grown film shows the formation of yellow color V2O5 films. The color of the as grown films suggest the growth of highly disordered black VxOy film which after annealing gets converted into yellow V2O5 as confirmed by the X-ray diffraction and Raman spectroscopy. The scanning electron microscopy equipped with energy dispersive X-ray analysis was used to investigate the morphology and chemical composition of V2O5 phase. Although, the films gets completely converted into the stable phase after annealing but heating cycling of temperature significantly changes the color of the films in a reversible manner that confirms the thermochromic behavior. We propose a breathing of oxygen (tailoring of Oxygen within the films) responsible for such reversible change in the color. These studies open new pathways for investigating these films to electrochromic properties by locally heating the materials through electric current (through Joule heating) and change the optical properties.

Amorphous carbon (a-C) films of varying thicknesses (0.5–18 nm) were deposited by the filtered cathodic vacuum arc technique on Ni/SiO 2 /Si substrate and then annealed in vacuum at 800 °C for 15 min and cooled down to room temperature to obtain graphene. The samples were characterized by Raman spectroscopy, transmittance, high resolution transmission electron microscope (HRTEM), optical microscopy and atomic force microscopy (AFM). Raman spectra showed that the values of I 2D /I G , I D /I G and full width at half maximum of D and 2D peaks were in the range 0.18–0.51, 0.82–1.02, 104-208.1 cm −1 and 101.2–128.0 cm −1 , respectively, for varying thicknesses of graphene. The transmittance decreases from 97 to 63.7% with the increase in thickness of prepared graphene film. The mobility of ∼725.4 cm 2 /V.s of field effect transistor using graphene synthesized from a-C film of 3 nm thickness has been obtained. HRTTEM and AFM image revealed monolayer graphene synthesized from a-C film of 1 nm thickness.

This paper reports the synthesis and properties of as grown and hydrogenated nanocrystalline silicon (nc-Si or nc-Si:H) thin films deposited by the filtered cathodic vacuum arc technique using boron doped solid silicon as a cathode. No hazardous gases like silane, diborane etc. (which are used in the conventional growth techniques) were used for the growth of nc-Si or nc-Si:H films in this process. These films have been characterized by X-ray diffraction (XRD), scanning electron microscopy, UV–visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and photo detection measurements. The XRD patterns show the amorphous and nanocrystalline coexisting nature of the films deposited under different deposition conditions. Raman spectra also reveal the amorphous nature of the film deposited at room temperature, whereas the films deposited at high temperature and under hydrogen environment silicon films showed the nanocrystalline nature. The evaluated values of dark conductivity (σD), activation energy (ΔE), optical band gap (Eg) vary from 3.6 × 10−5 to 7.2 × 10−3 ohm−1 cm−1, from 0.55 to 0.24 eV and from 1.24 to 2.12 eV, respectively, in nc-Si or nc-Si:H films. The fast response and recovery time as 4.92 and 4.06 s have been observed for the photo detectors developed from the nc-Si:H films deposited at room temperature.

We report the photoconduction behaviour of hybrid organic (polypyrrole) - inorganic (ZnO) nanostructures, synthesized by the surfactant mediated solution based chemical method at room temperature, for the energy saving light dependent resistor (LDR) applications. The formation of organic-inorganic hybrid nanostructures is confirmed by the combination of high resolution transmission electron microscopy and scanning electron microscopy, which revealed creation of cubical shaped wurtzite ZnO nanoparticles with different preferential orientations and transformation of clip-like nanofibres form of pure polypyrrole (PPy) into worm-like nanoribbons having embedded ZnO nanoparticles in it. Given p-type nature of PPy and n-type nature of ZnO, the embedment of ZnO nanoparticles in PPy is expected to create several localized discrete p-n junctions, which is why Raman spectroscopic results reveal the change in molecular structure of PPy due to its nanoscale interaction with ZnO. The photoresponse of PPy is found to continuously enhance from ∼4.5 to 10.7% with increase in ZnO concentration from 0 to 10% at the constant illumination intensity of 100 mW/cm2. The improved photoresponse can be attributed to the formation of localized p-n junctions (p-type PPy/n-type ZnO) in the structure. The photoresponse of PPy and its nanocomposites also increases with increase in illumination intensity from 30 to 100 mW/cm2, which is attributed to the increased number of photo-generated electron-hole pairs.

We present a new surface structure-dependent cold cathode material capable of sustaining high electron emission current suitable for next-generation low turn-on field-emission devices. The low turn-on electric field for electron emission in the cathode materials is critical, which facilitates the low-power room-temperature operation, a key factor required by the industrial sector. We demonstrate the facile synthesis of polypyrrole (PPy)/tin oxide (SnO2)-based core–shell hybrid cold cathode materials for large area applications. The technique used here is based on a simple and economical method of surfactant-mediated polymerization. The coupled investigation of X-ray diffraction along with electron microscopy reveals the formation of rutile phase SnO2 nanoparticles of size ∼15 nm. These SnO2 nanoparticles act as nucleation sites for the growth of PPy nanofibers, resulting in encapsulated SnO2 nanoparticles in the PPy amorphous matrix. The coupling of spherical-shaped core–shell structures of PPy/SnO2 resulted into the particle train-like nanostructured form of the hybrid material. These core–shell structures formed the local p–n junction between the n-type SnO2 (core) and p-type PPy (shell). The long chains of these p–n junctions in nanofibers result in the modification of the electronic band structure of PPy, leading to a reduction in the work function of the electrons. The significant surface structural modification in PPy/SnO2 causes a prominent reduction in the turn-on electric field for electron emission in PPy/SnO2 nanocomposite (∼1.5 V/μm) as compared to the pure PPy (∼3.3 V/μm) without significant loss in current density (∼1 mA/cm2). The mechanism of improved field-emission behavior and advantages of using such hybrid nanomaterials as compared to other composite nanomaterials have also been discussed in detail.

We have synthesized graphene film by the filtered cathodic vacuum arc (FCVA) technique and determined the number of layers in graphene films by various techniques. Amorphous carbon (a-C) films of different thicknesses (1, 2, 3, 6, 10 and 18 nm) were synthesized by the FCVA technique on Si/SiO2/Ni substrate and then annealed in vacuum at 800°C and cooled down to room temperature naturally to obtain graphene. Prepared graphene films were transferred on different substrates and characterized by the Raman spectroscopy, UV-VIS-NIR spectroscopy, high-resolution transmission electron microscopy (HRTEM), optical microscopy, atomic force microscopy (AFM) and sheet resistance to determine the number of layers present in the graphene films. Raman spectra of the prepared graphene films exhibit that there is red shift in the position of D, G and 2 D peak. The value of I2D/IG varied from 0.18 to 0.51, ID/IG varied from 0.82 to 1.02 and full width at half maximum of 2 D peak varied from 101.2 to 128.0 cm−1, for ...

This paper reports the effect of substrate bias on the multiwalled carbon nanotube (MWCNT) deposited on nickel foil by microwave plasma enhanced chemical vapor deposition technique. The MWCNTs have been characterized by the scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, field emission and current–voltage characteristic of the heterojunction diode. The SEM images exhibit unique hierarchical flowered-like bunched and conformally coated MWCNTs. Substrate bias induced ion bombardment helps in the enhancement of hydrocarbon dissociation and is responsible for flowered-like MWCNTs growth. The HRTEM micrographs show the base growth mechanism for MWCNTs. The value of turn on field for emission decreases from 5.5 to 1.9 V/μm and field enhancement factor increases from 927 to 4770, respectively, with the increase of substrate bias. The diode ideality factor of CNT/ n-Si heterojunction is evaluated as 2.4 and the on/off current ratio is found to be 7 at ±2 V, respectively.

A surfactant assisted chemical oxidation method has been employed for facial synthesis of polypyrrole/tin oxide (PPy/SnO2) hybrid nanoneedles. The charge transport properties of the prepared hybrid nanomaterials have been analyzed under different conduction mechanisms for their possible application for light dependent resistors (LDRs). The scanning electron microscopy studies revealed that the increased concentration of additive SnO2 quantum dots alters the surface morphology from nanowall-like to nanoneedle-like and the formation of PPy/SnO2 nanocomposites is confirmed X-ray diffraction studies. The strong coupling between the PPy and SnO2 results in the transformation of PPy from highly oxidized states to oxidized states and is confirmed through Raman analysis. The simple band conduction model and Kivelson's power law based conduction mechanism could not be applied to explain the conduction mechanism due to different reasons. The log σdc curves for all samples were well fitted for γ = 1/4, suggesting the applicability of Mott's three dimensional variable range hopping VRH model for charge transport. The room temperature dark conductivity of the samples was found to decrease with an increase in SnO2 concentration. The formation of p–n junctions between p-type PPy and n-type SnO2 changes the bandgap of PPy and the work function. This modifies the electronic structure of PPy which brings a synergistic effect in the photosensitivity of the PPy/SnO2 nanocomposites. The room temperature photoresponse of the PPy/SnO2 samples was found to increase from 2.85 to 6.25% at 100 mW cm−2 illumination intensity with an increase in the SnO2 doping concentration from 0 to 20%.

The identification of new materials capable of sustaining a high electron emission current is a key requirement in the development of the next generation of cold cathode devices and technology. Compatibility with large volume material production methods is a further important practical consideration with solution chemistry-based methods providing for routes to industrial scale-up. Here we demonstrate a new class of organic–inorganic hybrid material based on polypyrrole and zinc oxide (PPy/ZnO) nanofibers for use as a low-cost large-area cathode material. Solution chemistry based surfactant chemical oxidation polymerisation is used to synthesise the nanofibers and the macroscopic turn-on electric field for emission has been measured to be as low as 1.8 V μm−1, with an emission current density of 1 mA cm−2 possible for an applied electric field of less than 4 V μm−1. Specific surface area measurements reveal a linear increase in the nanofiber surface area with ZnO incorporation, which when coupled with electron microscopy and X-ray diffraction analysis reveals that the wurtzite ZnO nanoparticles (around 45 nm in size) act as nucleation sites for the growth of PPy nanofibers. Our study demonstrates for the first time how an inorganic nanocrystal acting as a nucleation site allows the tailored growth of the organic component without diminishing the overall electrical properties and opens the potential for a new type of organic–inorganic hybrid large-area cathode material. The broader impacts and advantages of using hybrid materials, when compared to other composite nanomaterial systems, as large area cathode materials are also discussed.

Vertically well aligned and highly dense ZnO nanowires (NWs) have been grown on biaxially textured Ni substrates by a simple thermal evaporation technique over a large area without using any catalyst. The grown ZnO NWs have crystallized in wurtzite hexagonal structure and have grown along [0001] direction. It is also observed that the degree of vertical alignment of NWs increases with increasing growth temperature. An intense photoluminescence peak at 383 nm with a negligible deep band emission revealed the good crystalline quality of ZnO NWs. Field emission properties of the grown NWs have been examined and a field enhancement factor of 1573 has been obtained, indicating the suitability of grown nanowires for field emission applications. Copyright © 2015 VBRI Press.

This paper reports the nanomechanical properties of as grown and hydrogenated tetrahedral amorphous carbon (ta-C, ta-C: H) films deposited by S-bend filtered cathodic vacuum arc technique measured with 1.4 mN load. It has been found that the hydrogenation of ta-C film improved the nanomechanical properties. Maximum hardness (H) of 38.15 GPa (with improvement of similar to 80%) has been obtained for ta-C: H film deposited at a hydrogen partial pressure of 1.4 x 10(-1) Pa and maximum elastic modulus (E) value of 410.1 GPa has been obtained when the hydrogen partial pressure reduced to 7.4 x 10(-3) Pa. The plastic index parameter (HIE) of ta-C: H film (0.11) is found to be superior to that of ta-C film (0.073), which is a measure of wear resistance for coating applications. The improved HIE of ta-C: H films may be due to the passivation of surface defects and favorable formation of sp(3) hybridized bonds.

This paper reports the direct deposition of multiwalled carbon nanotube (MWCNT)-graphene like hybrid films on nickel substrate using a 2.45 GHz microwave plasma enhanced chemical vapor deposition (MW PECVD) system in the temperature range of 500-700 degrees C at 20 Torr pressure. The films have been characterized by Raman spectra, high resolution transmission electron microscope (HRTEM), scanning electron microscope, high resolution X-ray diffraction and contact angle measurement. Raman spectroscopy and HRTEM reveal the formation of MWCNT and graphene like hybrid carbon sheet structures. The effect of processing temperature on the field emission properties of MWCNT-graphene like hybrid films has been investigated. Field emission measurement reveals that the turn-on field decrease and the emission current density increase with the increase of deposition temperature. The rambutan structure of MWCNT formed at 700 degrees C is responsible for the improvement in the field emission properties. The film deposited at 700 degrees C shows fast response and recovery time of 40 and 96 s, respectively, for ammonia gas sensing due to the high surface area of the film. It has also been found that the hydrophobic surface of the film helps to perform the gas sensing in the humid environment.

This paper reports the effect of helium partial pressures ∼1.2 × 10−5 (base pressure), 1.4 × 10−4, 8.6 × 10−3 and 0.1 mbar on the variable range hopping conduction in nanocrystalline carbon thin films deposited by filtered cathodic jet carbon arc technique. High resolution transmission electron microscopy studies suggest the random distribution of nanocrystallites (∼3–7 nm) in the amorphous matrix. The DC conduction behavior of the deposited nanocrystalline films has been studied in the light of Mott's variable range hopping (VRH) model and found to obey three dimensional VRH conduction. The randomly distributed nanocrystallites in amorphous matrix may lead to change in the distribution of density of states near Fermi level and hence, the conduction behavior. The enhanced electrical conductivity of the deposited films due to the helium environment makes them suitable for electromagnetic interference shielding applications. The sample deposited at a helium partial pressure of 0.1 mbar has a value of shielding effectiveness ∼7.84 dB at 18 GHz frequency.

Multiwall carbon nanotube (MWCNT)-graphene-like nanocarbon hybrid films were directly deposited on nickel substrate without any pre-treatment in a single-step by microwave plasma enhanced chemical vapor deposition (MW PECVD) technique at 600 °C. The effects of hydrogen partial pressure on the growth of MWCNT-graphene-like nanocarbon hybrid films and their structural, morphological and field emission properties were investigated. High resolution scanning electron microscope revealed MWCNT structure. High resolution transmission electron microscope images and Raman spectra revealed graphene-like nanocarbon film. Raman spectra showed 2D, G, D and D + G peaks at approximately 2690, 1590, 1350 and 2930 cm −1 , respectively. The minimum threshold field for electron emission was found to be 3.6 V/μm corresponding to 1 μA/cm 2 current density for the MWCNT-graphene-like nanocarbon hybrid film deposited at 20 Torr pressure whereas the maximum current density of 0.12 mA/cm 2 and field enhancement factor of ∼3356 was obtained for the sample deposited at 5 Torr pressure.

Phosphorus doped amorphous/nanocrystalline silicon (a-Si:H/nc-Si:H) thin films have been deposited by a filtered cathodic vacuum arc (FCVA) technique in the presence of hydrogen gas at different substrate temperatures (Ts) ranging from room temperature (RT) to 350 °C. The films have been characterized by using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, dark conductivity (σD), activation energy (ΔE), optical band gap (Eg) and secondary ion mass spectroscopy. The XRD patterns show that RT grown film is amorphous in nature but high temperature (225 and 350 °C) deposited films exhibit nanocrystalline structure with (111) and (220) crystal orientations. The crystallite size of higher temperature grown silicon film evaluated was between 13 and 25 nm. Raman spectra reveal the amorphous nature of the film deposited at RT, whereas higher temperature deposited films show crystalline nature. The crystalline volume fraction of the silicon film deposited at higher temperatures (225 and 350 °C) was estimated to be 58 and 72%. With the increase of Ts, the bonding configuration changes from mono-hydride to di-hydride as revealed by the FTIR spectra. The values of σD, ΔE and Eg of silicon films deposited at different Ts were found to be in the range of 5.37×10−4–1.04 Ω−1 cm−1, 0.05–0.45 eV and 1.42–1.83 eV, respectively. Photoconduction of 3.5% has also been observed in n-type nc-Si:H films with the response and recovery times of 9 and 12 s, respectively. A n-type nc-Si:H/p-type c-Si heterojunction diode was fabricated which showed the diode quality factor between 1.6 and 1.8.

Catalyst assisted carbon nanotubes (CNTs) were grown on multilayer graphene (MLG) on copper and silicon substrates by the microwave plasma enhanced chemical vapor deposition technique. The transmission of the MLG was found to vary between 82 to 91.8% with the increase of deposition time. Scanning electron microscopy depicted that the MLG film survived at the deposition condition of CNTs with the appearance of the damaged structure due to the plasma. Growth of CNTs was controlled by adjusting the flow rates of methane gas. The density of carbon nanotubes was observed to increase with a higher supply of methane gas. It was observed that the field emission properties were improved with the increased density of CNTs on MLG. The lowest turn-on field was found to be 1.6 V μm−1 accompanied with the highest current density of 2.8 mA cm−2 for the CNTs with the highest density. The findings suggested that the field emission properties can be tuned by changing the density of CNTs.

Polyurethane (PU) based composites were prepared by solvent casting techniques using different wt% (0–5 wt%) of reduced graphene oxide (RGO) as reinforcement. A nanoindentation study has been carried out on these composite sheets in order to investigate their nano-mechanical properties. Incorporation of different wt% RGO into the PU matrix led to a significant increase in the hardness and elastic modulus of the composites. The maximum nanoindentation hardness of 140 MPa for 5.0 wt% RGO loading was observed as compared to 58.5 MPa for pure PU (an overall improvement of 139%). The nanoindentation elastic modulus for the 5.0 wt% RGO loaded sample was 881.7 MPa as compared to 385.7 MPa for pure PU (an overall improvement of 129%). The enhancement in the nano-mechanical properties was correlated with spectroscopic and microscopic investigations using Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Due to their excellent nano-mechanical properties, these composites find usefulness in structural applications such as the automobile and wind mill blade industries. These composites can also be used in hard and scratch-less coatings on automotive vehicles. The experimental results were in good agreement with theoretical predictions.

Phosphorus doped micro/nano crystalline silicon thin films have been deposited by the filtered cathodic vacuum arc technique at different substrate temperatures (Ts) ranging from room temperature (RT) to 350 ∘C. The films have been characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, secondary ion mass spectroscopy, dark conductivity ( σ D), activation energy ( ΔE) and optical band gap (E g). The XRD patterns show that the RT grown film is amorphous in nature but high Ts (225 and 350 ∘C) deposited films have a crystalline structure with (111) and (220) crystal orientation. The crystallite size of the higher Ts grown silicon films evaluated was between 17 to 31 nm. Raman spectra reveal the amorphous nature of the film deposited at RT whereas higher Ts deposited films show a higher crystalline nature. The crystalline volume fraction of the silicon film deposited at higher Ts was estimated as 65.7 % and 74.4 %. The values of σ D, ΔE and E g of the silicon films deposited at different Ts were found to be in the range of 8.84 x 10 −4− 0.98 ohm −1 cm −1, 0.06 - 0.31 eV and 1.31-1.93 eV, respectively. A n-type nc-Si/p-type c-Si heterojunction diode was fabricated which showed the diode ideality factor between 1.1 to 1.5.

We present a low cost and scalable technique for the synthesis of graphene using solid carbon source. Filtered cathodic vacuum arc technique (FCVA) has been utilized to deposit amorphous carbon (a-C) films of thickness of 3 and 6 nm on nickel film grown on SiO2/Si substrate. Subsequently, a-C films were annealed at 750 and 800 degrees C in vacuum and cooled naturally to room temperature for transforming a-C films into graphene. These graphene films consist of regions of few layers. These films have been characterized using micro Raman spectroscopy, atomic force microscopy, optical microscopy, scanning electron microscopy, high resolution transmission electron microscopy, transmittance and sheet resistance. Field effect transistor (FET) has also been fabricated using graphene to calculate the mobility. Transmittance, sheet resistance and mobility of graphene films are in the range of 85.5-89.3%, 540-720 Omega/square and similar to 725 cm(2) V-1 s(-1), respectively. The graphene derived from a-C films of 3 nm thickness showed minimum sheet resistance, maximum transmittance accompanied with the high mobility of FET. This demonstrates that the FCVA technique has potential to grow better quality graphene.

This paper reports the synthesis of nanostructure carbon (ns-carbon) films deposited by microwave plasma-enhanced chemical vapor deposition (MW PECVD) technique at low pressure and room temperature. ns-carbon films have been characterized by scanning electron microscopy, electron dispersive x-ray spectroscopic analysis, atomic force microscopy, Raman spectroscopy, X-ray diffraction, UV-visible spectroscopy and high-resolution transmission electron microscopy. The shape of nanostructure is changing from granular to sheet-like structure when the pressure increased from 55 to 110 mTorr.

This paper reports the growth and properties of phosphorous doped hydrogenated amorphous silicon carbide (P doped a-SiC:H) thin films deposited at room temperature by a filtered cathodic vacuum arc (FCVA) technique using a phosphorous doped solid silicon target as a cathode in the presence of acetylene gas. These films have been characterized by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray analysis, dark conductivity, activation energy, optical band gap, secondary ion mass spectroscopy, Raman spectroscopy, current–voltage, capacitance–voltage and photoconductive measurements. XRD results exhibit predominantly an amorphous phase for the films. The effect of the arc current on the properties of P doped a-SiC:H films have been studied. A P doped a-SiC:H/c-Si heterojunction diode was fabricated which showed a diode ideality factor between 1.5 to 1.7 and the density of states were 9.6 × 1016 to 4.8 × 1017 cm−3 eV−1. The photo response behaviors of the P doped a-SiC:H films have been tested by measuring the change in the electrical resistance on light illumination with the fast response and recovery time as 7.8 to 9.5 and 6.2 to 12.8 s, respectively. The P doped a-SiC:H film deposited at a 30 A arc current has shown a photo response of ∼1.6% at an illumination intensity of ∼100 mW cm−2.

β-SiAlON ceramics have potential for biomedical implants but they suffer due to moderate hardness and high surface roughness. Attempts have been made to improve the hardness and surface properties by coating diamond-like carbon (DLC) on β-SiAlON ceramics using radio frequency-plasma-enhanced chemical vapor deposition. By optimizing the self-bias and bonding environment, we report the deposition of very hard (43.4 GPa) and ultra smooth (surface roughness 0.47 nm) DLC coating on β-SiAlON at a self-bias of − 140 V. Compared with uncoated β-SiAlON, DLC coated β-SiAlON show three times increment in hardness and ten times reduction in surface roughness. When the self-bias is changed, nano-mechanical properties of such DLC coated β-SiAlON ceramics, however, got modified, which correlated with the bias induced structural changes. When the indentation load is increased from 3 to 10 mN, hardness decreased significantly due to increase in substrate (or ceramic) effect. Owing to high hardness, high wear resistance and low surface roughness, DLC coated SiAlON structure can find wide biomedical applications such as prosthetic hip joint replacement.

The effect of self bias on structural and nano-mechanical properties of nanostructured diamond-like carbon (ns-DLC) thin films is explored. These films are grown at different negative self biases ranging from −100 V to −200 V using radio frequency (13.56 MHz) plasma enhanced chemical vapor deposition technique. The generation of nanostructured morphology at room temperature in these films is confirmed by scanning electron microscopy, whereas change in microstructure produced by varying the self biases is confirmed by Raman analysis. These ns-DLC films exhibit very high hardness, which varied from 16 GPa to 31 GPa. With the help of load versus displacement curves, various other important nano-mechanical parameters such as elastic modulus, elastic recovery etc are also estimated. The nano-mechanical properties are further correlated with the Raman and SEM analyses. Owing to their versatile nano-mechanical properties, these ns-DLC films may find application as hard and protective coatings.

Diamond like carbon (DLC) thin films with metallic interfacial layers of aluminum and nickel-chromium (Al and Ni-Cr) were grown using a low cost hybrid technique involving a resistive heating thermal evaporator and radio frequency plasma enhanced chemical vapor deposition techniques. Stress, hardness, elastic modulus, bonding, phase, and electrical conductivity of these films were investigated. Introduction of interfacial Al and Ni-Cr layers in DLC led to drastic improvement of its conductivity along with a significant reduction in residual stress but with some reduction of hardness and the elastic modulus. The structural and surface properties of thin films were studied using X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques.

Copper containing diamond like carbon (Cu-DLC) thin films were deposited on various substrates at a base pressure of 1×10 −3 Torr using a hybrid system involving DC-sputtering and radio frequency-plasma enhanced chemical vapor deposition (RF-PECVD) techniques. The compressive residual stresses of these films were found to be considerably lower, varying between 0.7 and 0.94 GPa and Cu incorporation in these films improve their conductivity significantly. Their structural properties were studied by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction techniques that clearly revealed the presence of Cu in the DLC structure. Raman analysis yields that Cu incorporation in DLC enhances the graphite-like sp 2 bonding. However, the sp 2 bonding was found to continuously reduce with the increasing C 2 H 2 gas pressure, this may be due to reduction of Cu nanocrystal at the higher pressure. FTIR results inferred various bonding states of carbon with carbon, hydrogen and oxygen. In addition, hydrogen content and sp 3 and sp 2 fractions in different Cu-DLC films were also estimated by FTIR spectra and were correlated with stress, electrical, optical and nano-mechanical properties of Cu-DLC films. The effect of indentation load (4–10 mN) on nano-mechanical properties of these films was also explored.

The properties of nitrogen incorporated amorphous carbon (a-C: N) films with embedded nanoparticles, deposited using a filtered cathodic jet carbon arc technique, are reported. X-ray diffraction, high resolution transmission electron microscope and Raman spectroscopy measurements reveal an amorphous structure, but on closer examination the presence of clusters of nanocarbon single crystals with d-spacing close to diamond cubic-phase have also been identified. The effect of substrate bias on the microstructure, conductivity, activation energy, optical band gap, optical constants, residual stress, hardness, elastic modulus, plastic index parameter, percentage elastic recovery and density of states of a-C: N films have been studied and the properties obtained are found to depend on the substrate bias.

High quality nitrogen incorporated hydrogenated amorphous carbon (a-C:N:H) thin films have been grown, using radio frequency-plasma enhanced chemical vapor deposition technique, under varied self biases from −25 to −400 V. Presence of nitrogen in carbon–nitrogen network and their bondings with carbon and hydrogen is confirmed by time of flight-secondary ion mass spectroscopy, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy measurements, respectively. By deconvoluting FTIR spectra, the various sp 3 CH n and sp 2 CH n bonding as well as % sp 3 and sp 2 fractions are estimated, which further correlated with nano-mechanical properties of a-C:N:H films. Observed maximum hardness and elastic modulus as 42 and 430 GPa, respectively in a-C:N:H film deposited at −100 V reveal superhard behaviour of coating. Residual stress in a-C:H:N films is found to be lower due to nitrogen incorporation that further decreases with increasing self bias. In addition, load versus displacement curves have also been employed to calculate various other nano-mechanical parameters, which further correlated with self bias as well as estimated % sp 3 and sp 2 fractions.

The effect of nitrogen incorporation and sandwich titanium and copper layers, on field emission, morphological and mechanical properties of diamond-like carbon (DLC) thin films is explored. The introduction of foreign element (N2) and sandwich Cu and Ti layers changed the amorphous morphology to nanostructured, reduced the stress, enhanced the hardness (except N2 incorporated DLC film) and improved the field emission (except Ti/DLC bilayer) of modified DLC films. The associated versatile electrical and mechanical properties of modified DLC film made it a material of great utility in the development of field emission display panels and also lead to its application as a hard and protective coating on cutting tools, automobile parts etc. It is important to mention that DLC-based electronic materials may replace currently used soft electronic materials (such as Si) due to their enhanced stability under high energy radiation.

In the present work the correlation of electrical, optical and nano-mechanical properties of argon-diluted diamond-like carbon (Ar-DLC) thin films with sp3 and sp2 fractions of carbon have been explored. These Ar-DLC thin films have been deposited, under varying C2H2 gas pressures from 25 to 75 mTorr, by radio frequency-plasma enhanced chemical vapor deposition technique. X-ray photoelectron spectroscopy studies are performed to estimate the sp3 and sp2 fractions of carbon by deconvoluting C 1s core level spectra. Various electrical, optical and nano-mechanical parameters such as conductivity, I–V characteristics, optical band gap, stress, hardness, elastic modulus, plastic resistance parameter, elastic recovery and plastic deformation energy have been estimated and then correlated with calculated sp3 and sp2 fractions of carbon and sp3/sp2 ratios. Observed tremendous electrical, optical and nano-mechanical properties in Ar-DLC films deposited under high base pressure conditions made it a cost effective material for not only hard and protective coating applications but also for electronic and optoelectronic applications.

Nanocluster carbon thin films (NC) were deposited at room temperature by cathodic arc process. These films were clustered, amorphous and disordered in nature which is verified using Raman spectroscopy. Density of defect states (DOS), which influences electronic and optical properties, were determined from the capacitance–voltage (C–V) characteristic of Al / NC / c - Si metal–insulator–semiconductor (MIS) structure near the Fermi level of undoped samples. Dielectric constant of the films was also estimated using the same technique. The DOS were found to be varying from 5.68 × 1016 to 4.9 × 1019 cm-3. The dielectric constant varied between 2.76 to 11.8.

Amorphous carbon films have been deposited by filtered cathodic jet carbon arc technique under different gaseous environments. Scanning electron microscope and atomic force microscope studies have been performed on the deposited films for the surface morphological studies. The morphology of the deposited film changes with the change in gas environment. X-ray photoelectron spectroscopic (XPS) and Raman studies have been carried out on the deposited samples for the evaluation of the chemical bonding of carbon atoms with the ambient gas atoms. The sp3 and sp2 contents have been evaluated from the XPS studies and found to be dependent on the gaseous environment. The film deposited under hydrogen environment has the highest value of the sp3 content (54.6 at.%) whereas the film deposited under helium environment has the lowest value of sp3 content (37 at.%). For the evaluation of the electrical and mechanical properties of the deposited films, the electrical conductivity and nanoindentation measurements have been performed on the deposited films. It has been observed that the film deposited under helium environment has the highest electrical conductivity and the lowest hardness (∼15 GPa) value whereas film deposited under hydrogen environment has the highest hardness (∼21 GPa) and the lowest conductivity.

The effect of thermally evaporated metallic Ni―Cr dots on the adhesion, electrical, optical and the mechanical properties of RF-PECVD grown diamond-like carbon (DLC) thin films was investigated. The DLC films deposited over Ni―Cr dots containing substrates exhibited a strong adhesion to the substrate. The observed drastic increase in magnitude of the current and the decrease of optical band gap due to presence of Ni―Cr dots revealed a considerable improvement in their electrical and optical properties, respectively. Further, load versus displacement curves were employed to estimate the hardness (H), elastic modulus (E), plastic resistance parameter (H/E) and elastic recovery (ER). The values of H and E in Ni―Cr dots containing DLC films were found to be comparatively less than that of DLC films. Overall, Ni―Cr metal dots improved adhesion, optical and electrical properties of DLC films with a little deterioration in their mechanical properties (e.g. H, E, ER and H/E).

Nanostructured copper/hydrogenated amorphous carbon (a-C:H) multilayer grown in a low base vacuum (1 × 10−3 Torr) system combining plasma-enhanced chemical vapor deposition and sputtering techniques. These nanostructured multilayer were found to exhibit improved electrical, optical, surface and structural properties, compared to that of monolayer a-C:H films. The residual stresses of such multilayer structure were found well below 1 GPa. Scanning electron microscopy and atomic force microscopy results revealed a nanostructured surface morphology and low surface roughnesses values. X-ray photoelectron spectroscopy, secondary ion mass spectroscopy and energy dispersive X-ray analysis confirmed a very small amount of copper in these films. These structures exhibited very high optical transparency in the near infrared region (∼90%) and the optical band gap varied from 1.35 to 1.7 eV. It was noticed that the temperature dependent conductivity improved due to the presence of both copper and the nano-structured morphology.

The influence of substrate bias and hydrogen/nitrogen incorporation on the optical properties [studied by spectroscopic ellipsometry (SE)] and surface morphology [studied by atomic force microscopy] of tetrahedral amorphous carbon (ta-C) films, deposited by S bend filtered cathodic vacuum arc (FCVA) process, is reported. SE spectra of the imaginary part of the dielectric constant are used to estimate carbon bonding ratios. In ta-C films, optical constants increase with substrate bias and hydrogen/nitrogen incorporation. The optical band gap (Eg) and sp3 content increase up to −200 V substrate bias and then decrease. Eg increases with hydrogen incorporation but is unchanged by nitrogen incorporation.

The effect of substrate bias on X-ray photoelectron spectroscopy (XPS) study of nitrogen incorporated amorphous carbon (a-C:N) films embedded with nanoparticles deposited by filtered cathodic jet carbon arc technique is discussed. High resolution transmission electron microscope exhibited initially the amorphous structure but on closer examination the film was constituted of amorphous phase with the nanoparticle embedded in the amorphous matrix. X-ray diffraction study reveals dominantly an amorphous nature of the film. A straight forward method of deconvolution of XPS spectra has been used to evaluate the sp3 and sp2 contents present in these a-C:N films. The carbon (C 1s) peaks have been deconvoluted into four different peaks and nitrogen (N 1s) peaks have been deconvoluted into three different peaks which attribute to different bonding state between C, N and O. The full width at half maxima (FWHM) of C 1s peak, sp3 content and sp3/sp2 ratio of a-C:N films increase up to −150 V substrate bias and beyond −150 V substrate bias these parameters are found to decrease. Thus, the parameters evaluated are found to be dependent on the substrate bias which peaks at −150 V substrate bias.

Nanoindentation testing was performed on nitrogen (N2) incorporated diamond-like carbon (N-DLC) films and deposited using radio-frequency plasma-enhanced chemical vapor deposition technique, with varied percentage of nitrogen partial pressures of 0, 44.4, 66.6, and 76.1%. The values of nanohardness (H) and elastic modulus (E) of these films were obtained from 38 to 22 GPa and 462 to 330 GPa, respectively, as the partial pressure of N2 increases from 0 to 76.1%. Further, these films were studied for % elastic recovery, ratio between residual displacement after load removal and displacement at maximum load (d res/d max ), plastic deformation energy and plasticity index parameter (H/E). Both hardness per unit stress and plasticity index per unit stress were found to be maximum at N2 partial pressure of 76.1%. X-ray photoelectron spectroscopy measurements confirmed the presence of N2 in these films.

This paper reports the electrical, mechanical, structural and field emission properties of as grown and also boron and phosphorous incorporated tetrahedral amorphous carbon (ta-C) films, deposited using a filtered cathodic vacuum arc process. The effect of varying boron and phosphorous content (up to 2.0 at.% in to ta-C) on the conductivity (σD), activation energy (ΔE1), hardness, microstructure, emission threshold (Eturn-ON) and emission current density (J) at 12.5 V/μm of ta-C: B and ta-C: P films deposited at a high negative substrate bias of −300 V are reported. It is observed that both boron and phosphorous incorporation leads to a nearly an order increase in σD and corresponding decrease in ΔE1 and a slight increase in hardness as compared to as grown ta-C films. In the case of field assisted electron emission, it is observed that Eturn-ON increases and J decreases. The changes are attributed to the changes in the sp3/sp2 ratio of the films due to boron and phosphorous incorporation. The effect of boron on ta-C is to give a p-type effect whereas the effect of phosphorous gives n-type doping effect.

Nitrogen incorporated hydrogenated amorphous carbon (a-C:N:H) films were grown in an asymmetric rf PECVD system using C2H2 and N2 gaseous mixture. Deposition rate, stress, hardness, optical bandgap, refractive index, and electrical characteristics have been studied as a function of self bias. Microstructures of these films were also studied using LASER Raman technique. Finally nitrogen diluted a-C:H films were realized as n-type semiconductor in n-type a-C:H/p-type crystalline silicon hetrojunction diodes. Current–voltage (I–V) and capacitance–voltage (C–V) characteristics have also been studied as a function of self bias on these heterojunction diodes.

This article reports the influence of substrate bias during growth and of hydrogen and nitrogen incorporation on density of states [N (EF)] and field-emission threshold (Eturn-on) in tetrahedral amorphous carbon (ta-C) films, deposited using an S-bend filtered cathodic vacuum arc process. The variation in negative substrate bias from −20 to −200 V was found to initially lead to a small decrease in N (EF) and Eturn-on, and a small increase in the emission current density (J) at 12.5 V/μm in the case of as-grown ta-C films; beyond −200 V substrate bias there is a reversal in the trend. The values of N (EF)=1.3×1017 cm−3 eV−1, Eturn-on=8.3 V/μm, and J=6.19 mA/cm2 were observed at −200 V substrate bias. However at −300 V the properties were not very different from those at −200 V substrate bias and so with a view to use the higher energy, hydrogen and nitrogen incorporation studies were carried out in this condition. It was observed that there was further enhancement in properties with hydrogen and nitrogen i...

Silicon thin films are deposited using plasma enhanced chemical vapor deposition (PECVD) of silane, argon, hydrogen mixture at various pressures in the range of 2–8 Torr. Raman scattering shows these to be amorphous in the pressure range 6–8 Torr, and nanocrystalline in the range 2–4 Torr. The volume fraction of nanocrystals is estimated by fitting the Raman data to three peaks and is found to be ∼75% for the films deposited at low pressure, density of states of these films was measured. It is observed that the electrical conduction in these films depends on the crystalline volume fraction (ρ), estimated from the laser Raman Spectroscopy. Temperature dependence electrical conductivity shows that at lower temperatures thermionic emission dominates for the films with lower ρ, whereas, hopping is the main conduction mechanism for the films having high ρ. The density of states is estimated from the space charge limited currents (SCLC) observed at high fields. Photoconductivity at room temperature is also measured. The amorphous films are found to be more photosensitive than the nanocrystalline one. In the context of these findings, changes in the properties of silicon from amorphous to nanocrystalline are described.

The application of a sufficiently high negative substrate bias, during the growth of tetrahedral amorphous carbon (ta-C), is usually associated with low sp3 bonding configuration and stressed films. However, in an effort to understand and utilize the higher pseudo thermo dynamical conditions during the film growth, at high negative substrate bias (− 300 V), reported here is a study on ta-C films grown under different hydrogen and nitrogen concentration. As grown ta-C films were studied under different negative substrate bias conditions. The variation of the sp3 content and sp3/sp2 ratio in the ta-C films exhibits a trend similar to those reported in literature, with a subtle variation in this report being the substrate bias voltage, which was observed to be around − 200 V, for obtaining the highest sp3 (80%) bonding and sp3/sp2 (3.95) ratio. The hydrogen and nitrogen incorporated ta-C films studied, at a bias of − 300 V, show an increase in sp3 (87–91%) bonding and sp3/sp2 (7–10) ratio in the range of studies reported. The inference is drawn on the basis of the set of data obtained from measurements carried out using X-ray photoelectron spectroscopy, X-ray induced Auger electron spectroscopy and Raman spectroscopy of as grown and hydrogen and nitrogen incorporated ta-C films deposited using an S bend filtered cathodic vacuum arc system. The study indicates the possibility of further tailoring ta-C film properties and also extending capabilities of the cathodic arc system for developing carbon based films for electronics and tribological applications.

The study of reflectance and photoluminescence (PL) spectra of as grown and also hydrogen and nitrogen incorporated tetrahedral amorphous carbon (ta-C) films, deposited using an S bend filtered cathodic vacuum arc process is reported here. First the effect of negative substrate bias on the properties of as grown ta-C films and next the effect of varying hydrogen and nitrogen partial pressure at a high substrate bias of − 300 V on the properties of hydrogen and nitrogen incorporated ta-C (ta-C:H and ta-C:N) films are reported for the first time. The values of the optical band gap ( E g ) evaluated using the reflectance spectra were found to decrease with the increase of the substrate bias in the as grown ta-C films. Hydrogen incorporation up to 1.9 × 10 − 2 Pa partial pressure in as grown ta-C films increased the values of E g and beyond which the values of E g decreased while the nitrogen incorporation up to 3.0 × 10 − 1 Pa partial pressure has no effect on the E g values. The PL spectra indicated a strong peak at ∼2.66 eV in as grown ta-C films deposited at − 20 V substrate bias. This main peak was found to shift to higher energy with the increase of the substrate bias up to − 200 V and thereafter the PL peak shifted towards the lower energy. Other peak at 3.135 eV starts appearing and this is found to start shifting to higher energy for films deposited at higher substrate bias. The intensity of the main PL peak was enhanced at low temperature and several other peaks started appearing in place of the broad peak at ∼3.16 eV. The peak width and area of both the main peak were found to decrease with the increase of substrate bias in as grown ta-C films and with the increase of the hydrogen and nitrogen partial pressure used in depositing ta-C:H and ta-C:N films. The current models on the source of luminescence in amorphous carbon have been discussed.

This paper reports the space charge limited conduction (SCLC) and electron paramagnetic resonance (EPR) studies of as grown and nitrogen incorporated tetrahedral amorphous carbon (ta-C) films deposited by pulsed unfiltered cathodic vacuum arc process. The effect of varying substrate bias and nitrogen content on the properties of as grown and nitrogen incorporated ta-C films have been studied. The values of density of states (N(EF)) evaluated from SCLC measurements and spin density (Ns) evaluated from EPR studies of as grown ta-C films deposited at 5 V substrate bias are found to be 1.6×1019 cm−3 eV−1 and 6.7×1019 cm−3, respectively, which decrease to 8.7×1018 cm−3 eV−1 and 4.6×1019 cm−3, respectively, with the increase of substrate bias up to 80 V and beyond 80 V substrate bias these values are found to increase. A small amount of nitrogen incorporation up to 3.6 at.% nitrogen content in nitrogen incorporated ta-C films reduces the values of N(EF) and Ns to 1.4×1019 cm−3 eV−1 and 4.3×1019 cm−3, respectively. Beyond 3.6 at.% nitrogen content, the values of N(EF) and Ns are found to increase monotonically to 2.6×1019 cm−3 eV−1 and 1.0×1020 cm−3, respectively, in nitrogen incorporated ta-C films with further increase of nitrogen content up to 15.6 at.%. The local minimum in the values of N(EF) and Ns in as grown ta-C films deposited at 80 V substrate bias arises due to the ability of sp2 sites to pair up. Nitrogen incorporation up to 3.6 at.% in nitrogen incorporated ta-C films seems to compensate the p-type nature and beyond 3.6 at.% nitrogen content the donor electron increases the values of N(EF) and Ns in the films.

This paper reports the X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy (XAES) studies of as grown and nitrogen incorporated tetrahedral amorphous carbon (ta-C) films deposited by pulsed unfiltered cathodic vacuum arc process. The effect of varying substrate bias and nitrogen content on the properties of the as grown and the nitrogen incorporated ta-C films has been studied. The XPS spectra indicate that in the as grown ta-C films the C 1s peak occurs at 285.15±0.08 eV and the binding energy (BE) marginally decreases with the increase of substrate bias. The nitrogen incorporated ta-C films show N 1s peak at 399.46±0.10 eV in addition to the C 1s peak. The peak position of C 1s remains unchanged with nitrogen incorporation, whereas the N 1s peak seems to marginally decrease in BE, with increasing nitrogen content. From the values of the parameter D, the energy width between the highest maximum and the lowest minimum value of the derivative of C (KLL) spectra, sp2, sp3 and sp3/sp2 ratio were evaluated. The values of D, sp2, sp3 and sp3/sp2 ratio for the as grown ta-C films are found to be 17.16 eV, 35.7%, 64.3% and 1.80, respectively. The values of D and sp2 fraction are found to decrease to 16.19 eV and 23.9% and those of sp3 and sp3/sp2 ratio are found to increase to 76.1% and 3.18 in the case of ta-C films deposited at an applied substrate bias of 40 V. In the case of applied substrate bias beyond 40 V, the values of these parameters show a reversal in the trend. The nitrogen incorporated ta-C films with 3.6 at.% nitrogen content do not show any change in the values of D, sp2, sp3 and sp3/sp2 ratio. With further increase in the nitrogen content up to 15.6 at.%, the values of D and sp2 fraction decrease continuously to 15.87 eV and 20.1% and the values of sp3 and sp3/sp2 ratio increase to 79.9% and 3.98, respectively. The study suggests that, at certain conditions of nitrogen incorporation in the case of ta-C films, there is an increase in sp3 fraction or the diamond like nature of the ta-C films.

This paper reports the effect of positive substrate bias ( V s ) varying from 0 to 180 V on the spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS) and X-ray Auger electron spectroscopy (XAES) studies of diamond-like carbon (DLC) films deposited using CH 4 gas as a feedstock into a saddle field fast atom beam (FAB) source. The values of optical constants like refractive index ( n ) and extinction coefficient ( k ) of the deposited DLC films were determined using a two phase model. The values of ‘ n ’ were found to fall in the range from 1.505 to 1.720 and ‘ k ’ from 0.03 to 0.125 by application of different values of V s . Value of these optical constants were found to decrease with the increase of substrate bias up to 90 V and then increase beyond this value. Position of C 1s peak evaluated from XPS data was found to occur at 286.09±0.18 eV in DLC films deposited by application of different values of V s . Observation of full width at half maximum (FWHM) ( τ ) value (1.928 eV at V s =0 V, 2.0 eV at V s =90 V and 1.89 eV at V s =180 V) clearly hinted the existence of a point of inflection in the properties of DLC films deposited using FAB source this way. A parameter ‘ D ’ defined as the distance between the maximum of positive going excursion and the minimum of negative going excursion was calculated in the derivative XAES spectra. The values of ‘ D ’ evaluated from XAES data for DLC films were found to be 14.8, 14.5 and 15.2 at V s =0, 90 and 180 V, respectively. The sp 2 percentage was calculated for samples deposited this way and was found to be low and lie approximately at 5.6, 2.8, 2.3, 5.7 and 11.5 for different values of V s =0, 50, 90, 150 and 180 V. The sp 3 content percentage and sp 3 /sp 2 ratio was found to be 94.4 and 16.7, 97.7 and 42.5 at V s =0 and 90 V, respectively. Beyond V s =90 V these values started decreasing. Mainly, a point of inflection in all the properties of DLC films studied over here at around 90 V of applied substrate bias has been observed, which has been explained on the basis of existing theories in the literature.

In this paper, we report field-emission measurements from ∼0.5-μm-thick hydrogenated amorphous carbon (diamond-like carbon (DLC)) films. These films were grown by a variety of easily implementable plasma-enhanced chemical vapor deposition (PECVD) based techniques and also by a method that uses a saddle-field fast atom beam source. Field-emission behavior in these materials has been discussed in light of residual stress, hardness, optical band gap, and characteristic energy of band tails (Urbach energy). Onset emission-fields as low as ∼6 V/μm, together with low residual stress of 0.25 GPa, hardness of 17.5 GPa, optical band gap of 1.5 eV, and Urbach energy of 165 meV, have been obtained in DLC films grown by pulsed-PECVD at 13.56 MHz. DLC films of comparable quality could also be grown using a saddle-field fast atom beam source, which operates on modest dc power supply and with no heated filaments or magnets.

A correlation has been observed between the residual stress and the optical absorption edge of diamond-like carbon films and on the basis of this correlation, an empirical relation has been established between the Urbach energy ( E 0 ) and the residual stress ( S ) in the films given by E 0 = E 00 + mS , where E 00 =140 meV and m =37 meV/GPa. The residual stress and the optical absorption edges of diamond-like carbon films, grown by different techniques, are then discussed in terms of amount of disorder in the network.