Synthesis and characterization of fluorene-type and hydrogenated amorphous carbon thin films in RF and DC glow discharges

Mansuroğlu, Doğan
Fluorene (C13H10)-type and hydrogenated amorphous carbon (a-C:H) thin films were synthesized under a capacitively coupled single radio frequency (RF) and a direct current (DC) plasma systems. In the first system, the RF plasma reactor, circular parallel plate electrodes were used; the upper electrode was connected to 13.56 MHz RF power while the lower electrode was grounded. To control the positive ion bombardment, a negative bias voltage was applied between the holder of the substrate and the wall of the chamber. For the second system, the DC plasma reactor, consisted of three cylindrical electrodes and two quartz tubes. In both systems, the thin films were deposited on glass discs and silicon wafers. The fluorene-type thin films were produced in the RF plasma reactor under the biphenyl (C12H10)/methane (CH4) and biphenyl/ethylene (C2H4) mixtures, and the methane plasma was used to produce the a-C:H films. In the DC plasma reactor, the vaporization of the powder monomer (fluorene) was used. To improve the electrical and optical properties of the thin films, the generated films were doped by Iodine (I2) and annealed under variable temperatures. The thin films were applied to a crystalline silicon (c-Si) solar cell and an increase around 5 % was observed in the efficiency of the solar cell. The chemical structures and physical properties of the thin films were examined under such plasma parameters as the plasma power, gas flow rate, negative bias voltage, deposition time, and plasma pressure. Diagnostics of the system was done using a double Langmuir probe. To characterize the chemical structural properties of thin films Fourier Transform Infrared (FTIR) and X-ray Photoelectron (XPS) Spectroscopy were used, and the changes in the plasma chemistry during the deposition were measured by Residual Gas Analysis (RGA) Mass Spectrometer and Optical Emission Spectroscopy (OES). According to results, applying negative bias voltage could be considered an effective way in controlling the reactions in plasma depositions, and an increase in the quality of generated films when the plasma power and gas flow rate increased as well as the deposition time was generally observed. Moreover, the morphology of the films was analyzed by X-ray diffraction (XRD) and the nanotopographic properties of the surfaces were examined using an Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM). The surfaces of fluorene-type thin films had remarkable nanostructured characteristics generated by various negative bias voltages, and the rough surfaces made them useful for photovoltaic applications. Furthermore, the optical properties of the films were examined with UV-visible Spectroscopy and the thickness was measured with an ellipsometer and Dektak Profilometer. From the results, it could be suggested that the structures of thin films produced by plasma polymerization technique were different than the ones produced by the conventional techniques. Additionally, the different chains order were observed in the film structure with respect to independent plasma parameters and the conductivity of the films was improved by controlling of the plasma parameters and iodine doping. Finally, for the determination of hydrophobic behavior of the thin films, the contact angle measurement method was used.


Synthesis of acrylic based high internal phase emulsion polymers and their application in chromatography
Tunç, Yeliz; Hasırcı, Nesrin; Department of Polymer Science and Technology (2009)
High internal phase emulsion polymers (PolyHIPEs) are new generation materials with their high porosity and interconnected open-cell structures and finds applications in areas such as supports for catalytic systems, separation media and tissue engineering scaffolds. Styrene based PolyHIPEs are currently the most popular choice, but solvent compatibility and poor mechanical properties of these materials prevent their applications. Therefore development of new polyHIPEs with desired mechanical and cellular pr...
Synthesis and characterization of boron carbide films by plasma-enhanced chemical vapor deposition
Eroglu, OD; Sezgi, Naime Aslı; Ozbelge, HO; Durmazucar, HH (2003-03-01)
The plasma-enhanced chemical vapor deposition of boron carbide was investigated on quartz glass and alumina substrates from a gas mixture of BCl3, H-2, and CH4 in an inductively coupled plasma (ICP) medium produced by a radio frequency (RF) discharged onto the gases passing through a tubular reactor under atmospheric pressure. A thin solid boron carbide coating with a gray color was deposited on both substrates. The results of XRD revealed that the major solid phase formed in the coating material was beta-r...
Optical Characterization of Amorphous Hydrogenated Carbon (a-C:H) Thin Films Prepared by Single RF Plasma Method
Mansuroğlu, Doğan; GÖKŞEN, KADİR; Bilikmen, Sinan (IOP Publishing, 2015-06-01)
Methane (CH4) plasma was used to produce amorphous hydrogenated carbon (a-C:H) films by a single capacitively coupled radio frequency (RF) powered plasma system. The system consists of two parallel electrodes: the upper electrode is connected to 13.56 MHz RF power and the lower one is connected to the ground. Thin films were deposited on glass slides with different sizes and on silicon wafers. The influence of the plasma species on film characteristics was studied by changing the plasma parameters. The chan...
Fabrication of CdSexTe1-x thin films by sequential growth using double sources
Demir, Medine; Terlemezoglu, M.; Parlak, Mehmet (2021-10-15)
CdSexTe(1-x) (CST) ternary thin films were fabricated by stacking thermally evaporated CdSe and electron beam evaporated CdTe layers. The final structure was achieved in a stoichiometric form of approximately Cd:Se:Te = 50:25:25. The post-annealing processes at 300, 400, and 450 °C were applied to trigger the compound formation of CST thin films. The X-ray diffraction (XRD) profiles revealed that CdTe and CdSe have major peaks at 23.9° and 25.5° corresponds to (111) direction in cubic zinc-blend structure. ...
Synthesis of carbon nanotubes by a plasma based pulsed electron beam generator
Goktas, H.; Ayhan, U. B.; Gündüz, Güngör; Disbudak, H.; Eryilmaz, E.; Oke, G.; Cicek, B.; Somer, M. (IOP Publishing, 2006-01-01)
Carbon nanotubes (CNTs) were synthesized by using a plasma based electron beam generator, which has a fast filamentary discharge formed from the superposition of an ordinary low-pressure dc glow and a high-current pulsed discharge. To our knowledge, CNTs are synthesized for the first time by this method. Acetylene was used as the carbon source and the iron catalyst coated silica substrates were prepared by the sol-gel technique. The silica plates were first coated with an appropriate iron (III) nitrate solu...
Citation Formats
D. Mansuroğlu, “Synthesis and characterization of fluorene-type and hydrogenated amorphous carbon thin films in RF and DC glow discharges,” Ph.D. - Doctoral Program, Middle East Technical University, 2015.