Surface studies of carbon films from pyrolyzed photoresist (original) (raw)
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Synthesis and analysis of thin conducting pyrolytic carbon films
Carbon, 2012
We report on an adjustable process for chemical vapour deposition of thin films of pyrolytic carbon on inert substrates using an acetylene feedstock. Through modification of the reaction parameters control over film thickness and roughness is attained. These conducting films can be deposited in a conformal fashion, with thicknesses as low as 5 nm and a surface roughness of less than 1 nm. The highly reliable, cost effective and scalable synthesis may have a range of applications in information and communications technology and other areas. Raman and X-ray photoelectron spectroscopies, as well as high resolution transmission electron microscopy are used to investigate the composition and crystallinity of these films. The suitability of these films as electrodes in transparent conductors is assessed through a combination of absorbance and sheet resistance measurements. The films have a resistivity of ~ 2 × 10 -5 m but absorb strongly in the visible range. The electrochemical properties of the films are investigated and are seen to undergo a marked improvement following exposure to O 2 or N 2 plasmas, making them of interest as electrochemical electrodes.
Influence of oxygen on growth of carbon thin films
AIP Conference Proceedings, 2018
In this work we studied the influence of oxygen gas on growth of carbon thin films in a magnetron sputtering process. X-ray absorption spectroscopy (XAS), x-ray and neutron reflectivity techniques were used to probe carbon thin films deposited with and without oxygen at room temperature. XAS in particularly x-ray absorption near edge spectroscopy (XANES) is powerful technique to identify the nature of hybridization of carbon atoms with other elements. In a XANES pattern, presence of C=O and CO bonds is generally observed in spite of the fact that oxygen has not been deliberately included in the growth process. In order to confirm the presence of such features, we introduced a small amount of oxygen at 1% during the growth of carbon thin films. Though such additions do not affect the number density as observed by x-ray and neutron reflectivity, they severally affect the C K-edge spectra as evidenced by an enhancement in carbon-oxygen hybridization. Observed results are helpful in analyzing the C K-edge spectra more confidently.
Analytical characterization of thin carbon films
Analytical and bioanalytical chemistry, 2003
CH(x) films on silicon substrates deposited by a Mesh Hollow Cathode Process (MHC) were analyzed by various techniques. The films were produced with varying deposition times, resulting in thicknesses ranging from ~2-20 nm. X-Ray Reflectivity (XRR) was used to determine the film thicknesses and the deposition rate. A good correlation of measured XRR thicknesses with SIMS sputter depths down to the film-substrate transition was found. An AFM-based nanoscratching technique was applied to test the wear resistance of the thin overcoats. The MHC films reveal slightly decreasing scratch resistance for reduced film thicknesses, which can be explained by a higher fraction of soft interface zones for thinner films. This is in accordance with Raman spectroscopic measurements in the visible spectral range which were carried out to examine the carbon bonding properties. Combined analysis of G peak position and D/G peak intensity ratio indicates a more graphitic structure for film thicknesses les...
Ultrathin pyrolytic carbon films on a magnetic substrate
Materials Research Express, 2016
We report the growth of ultrathin pyrolytic carbon (PyC) films on nickel substrate by using chemical vapor deposition at 1000 °C under methane ambience. We find that the ultra-fast cooling is crucial for PyC film uniformity by controlling the segregation of carbon on nickel. We characterize the in-plane crystal size of PyC film by using Raman spectroscopy. The Raman peaks at ~1354 cm-1 and ~1584 cm-1 wavenumbers are used to extract the D and G bands. The corresponding peak intensities are then used in an excitation energy dependent equation to calculate the in-plane crystal size. Using Raman area mapping, the mean value of in-plane crystal size over an area of 100 μm × 100 μm is about 22.9 nm with a standard deviation of about 2.4 nm.
Photoresist-Derived Carbon for Microelectromechanical Systems and Electrochemical Applications
Journal of The Electrochemical Society, 2000
Conventionally, microelectromechanical systems (MEMS) have been based mostly on silicon. 1 In this paper, we describe work carried out to evaluate carbon films produced by the pyrolysis of photoresists for use in MEMS and as electrode materials. 2 These carbon electrodes have potential applications in batteries, electrochemical sensors, and capacitors and in electrochemically based MEMS devices. The advantage of using photoresists as the starting material is that the photoresists can be patterned by photolithography techniques, and hence complex-shaped electrodes can be produced. Photoresists are used extensively in the integrated circuits industry and are very reproducible in their behavior, and hence the carbon films produced by pyrolyzing these photoresists constitute a potentially reliable carbon source.
Journal of The Electrochemical Society, 2002
Carbon structures were fabricated by the pyrolysis of photopatterned negative photoresists ͑SU-8 and photosensitive polyimide͒ on silicon and fused silica wafers. Results here are compared with those of positive resists published earlier by this group. Negative resist films need exposure to ultraviolet light prior to pyrolysis to produce carbon films. The pyrolysis was carried out in a closed quartz tube furnace in a forming gas ͑95% N 2 , 5% H 2 ͒ atmosphere. The pyrolysis process was characterized using a combination of thermogravimetric analysis and differential thermal analysis. The pyrolysis of SU-8 involved gas evolution in a narower range of temperature than polyimide. The adhesion of the carbon film was found to depend on the resist, the substrate, and the heating cycle used. The carbon structures were characterized in terms of their shrinkage during the pyrolysis, the resistivity, the degree of crystallinity and the peak separation in cyclic voltammetry. Carbons derived from pyrolysis of negative resists showed higher resistivity, vertical shrinkage, and peak-to-peak separation voltage than positive resists. Transmission electron microscope results showed a distinct lack of crystallinity even after pyrolysis at 1100°C, unlike the positive resist derived carbon.
2011-Supported pyrolysis for lithographically defined 3D carbon microstructures.pdf
We present a facile and effective route for the fabrication of carbon microstructures by direct carbonization of polymeric photoresist patterns without distortion or collapse of the microstructure due to high-temperature pyrolysis. The 3D porous structure was a woodpile structure prepared by five-beam interference lithography. Pyrolysis of the SU-8 woodpile structure resulted in shrinkage of the structure into the film with loss of the pore structure. The silica shell support on this SU-8 microstructure provided effective mechanical support to resist pattern distortion or collapse by melting of the photoresist and subsequent large mass loss in the heat treatment. The shrinkages in lattice distance and layer-by-layer distance of the silica-coated SU-8 were measured to be 3% and 60%, respectively. The composition of pyrolyzed SU-8 photoresists was characterized by Raman spectroscopy. Current-sensing AFM was used to measure the local electrical conductivity of a 3D pyrolyzed carbon structure. Our pyrolyzed 3D carbon structures were composed of a glassy carbon and possessed the local conductivity of about 10 3 S m À1 . The fabrication of lithographically defined carbon structures with high fidelity will open new opportunities for carbon MEMS and various energy-related microdevices. ; Fax: +82 2 703 8971; Tel: +82 2 705 8921 † Electronic supplementary information (ESI) available: SEM images of the products of direct pyrolysis of SU-8 structures without silica coatings. TGA analysis of SU-8 films in an Ar atmosphere. See
On the Crystal Size Studies of Pyrolytic Carbon by Raman Spectroscopy
2013
We report the growth of ultrathin pyrolytic carbon (PyC) films on nickel substrate by using chemical vapor deposition at 1000 {\deg}C under methane ambience. We find that the ultra-fast cooling is crucial for PyC film uniformity by controlling the segregation of carbon on nickel. We characterize the in-plane crystal size of PyC film by using Raman spectroscopy. The Raman peaks at ~1354 cm-1 and ~1584 cm-1 wavenumbers are used to extract the D and G bands. The corresponding peak intensities are then used in an excitation energy dependent equation to calculate the in-plane crystal size. Using Raman area mapping, the mean value of in-plane crystal size over an area of 100 {\mu}m times{\times}times 100 {\mu}m is about 22.9 nm with a standard deviation of about 2.4 nm.
Substrate Impact on MR Characteristics of Carbon Nano Films Explored via AFM and Raman Analysis
Materials
Recent advances in the fabrication and classification of amorphous carbon (a-Carbon) thin films play an active part in the field of surface materials science. In this paper, a pulsed laser deposition (PLD) technique through controlling experimental parameters, including deposition time/temperature and laser energy/frequency, has been employed to examine the substrate effect of amorphous carbon thin film fabrication over SiO2 and glass substrates. In this paper, we have examined the structural and magnetoresistance (MR) properties of these thin films. The intensity ratio of the G-band and D-band (ID/IG) were 1.1 and 2.4, where the C(sp2) atomic ratio for the thin films samples that were prepared on glass and SiO2 substrates, were observed as 65% and 85%, respectively. The MR properties were examined under a magnetic field ranging from −9 T to 9 T within a 2-K to 40-K temperature range. A positive MR value of 15% was examined at a low temperature of 2 K for the thin films grown on SiO...