Synthesis and characterization of diamond-like carbon thin films prepared by pulsed laser deposition method
Date
2009-05-27T10:25:50Z
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Abstract
arious diamond-like carbon (DLC) films were prepared using four different type synthesis setups. Optical microscopy data showed that the some film regions grown under excimer laser illumination were strongly interference colored and have very wide bandgap (ΔE > 3 eV) at certain energy densities of illumination. Raman scattering data indicated that the additional irradiation of the growing film between the ablation pulses is inevitable to create the individual diamond phase formation into DLC films. The existence of diamond clusters in these films was also confirmed using AFM method. The individual diamond phase forms only in a narrow window of irradiating laser beam energy density. At lower energy densities the irradiation promoted the growth of homogeneous DLC structures with high content of sp3 hybridized carbon. However, at higher laser irradiation intensities the DLC phase decomposition and graphitization takes place. Influence of H2O2 vapor on the film parameters can be described as increasing the number of ordered aromatic carbon rings with decreasing size of the aromatic clusters in DLC films. AFM measurements indicated that the DLC films grown under laser illumination conditions were smoother, and especially smooth surfaces were observed for the colored films (particles) deposited inside the laser beam irradiated surface regions. At lower deposition temperatures resulted in bigger grain size of the DLC film surface structures. A sudden drop in the root mean square roughness value has been observed in a relatively narrow range of temperature from 50 to 100ºC applied. The cyclic voltammetry and impedance data for the DLCE|xM NaF+H2O interface show that this system is nearly ideally polarizable in the potential region –0.4 < E < 1.1 V. The non-linear least squares fitting method of the experimental data shows that an excellent fit of the experimental impedance complex plane plots has been established using a circuit combining the total high frequency series resistance Rel of the electrode system, including the resistance of the bulk diamond film and bulk electrolyte solution, the capacitance C1 and the resistance R3 of the surface film, developed on the surface of the DLCE, the so-called interfacial (i.e. double layer) capacitance C2 (caused by the charging and discharging of the electrical double layer at the internal surface of DLCE), the partial or “true” faradaic reaction resistance of the film R2, the low frequency adsorption capacitance C3 and the Warburg-like diffusion impedance ZW. Käesolevas töös sünteesiti erinevaid süsiniku kilesid, kasutades selleks nelja erineva aparatuuri konfiguratsiooni. Teatud energiatihedusega eksimeerlaseri kiirguses sünteesitud süsiniku kiled on tugevalt interferents värvilised ja seega ka laia keelutsooni laiusega (ΔE > 3 eV). Raman spektroskoopia uuringu tulemused näitasid, et kasvatusaluse kiiritamine sadestustsüklite vahel täpselt kontrollitud energiatihedusega laseri kiirega võimaldab tekitada teemandi sarnases süsiniku struktuuris individuaalset teemandi faasi. Teemandi faasi tekkimine leiab aset kiiritava laseri kiire väga kitsas energiatiheduse vahemikus, mis samas on energeetiliselt väga lähedal süsiniku struktuuri grafitiseerimisele. Leiti, et kõrgematel energiatihedustel leiabki aset samaaegselt teemandi faasi tekkimisega ka olemasoleva teemandi sarnase süsiniku grafitiseerumine. Aatomjõu mikroskoopia mõõtmised näitavad, et madalama kasvatusaluse temperatuuri tulemuseks on suurema teralise pinna tekkimine. Suurimat ruutkeskmise pinnakareduse väärtuse muutust täheldati suhteliselt kitsas temperatuuride vahemikus sünteesitud kiledel. Tsüklilise voltamperomeetria ja elektrokeemilise impetantsi andmed näitasid, et DLCE|xM NaF+H2O süsteem on peaaegu ideaalselt polariseeritav potentsiaalide vahemikus –0.4 < E < 1.1 V. Eksperimendi andmete mittelineaarne vähimruutude lähendusmeetod näitab, et parim kokkulangevus on saavutatud eksperimentaalsete kompleksimpedantsi sõltuvuste modelleerimisel ekvivalent skeemiga, mis on kombineeritud elektroodi süsteemi kogutakistusest Rel, kile pindkihi mahtuvusest C1 ja pindkihi takistusest R3, kaksikkihi mahtuvusest C2, osalisest või ”tõelisest” faradi reaktsiooni iseloomustavast takistusest R2, adsorptsioonilisest mahtuvusest C3 ja Warburgi difusioonilisest impetantsist Zw.