Effects of reactors on the deposition of DLC films using liquid electrochemical technique

摘要

Carbon films were deposited on silicon substrates by liquid electrochemical technique at low temperature (60 °C) in ambient atmosphere. Glass reactor, glass reactor with PTFE-coating inside, glass reactor with quartz-coating inside and quartz reactor were used with the same experimental setup to compare the effects of reactors on the deposition of carbon films. The applied potential, the distance between anode and substrate and the deposition time were fixed at 900 V (4.2 kHz, 50%), 6 mm and 5 h, respectively. The morphology and microstructure of the films were analyzed by scanning electron microscopy (SEM) and Raman spectroscopy. Energy Dispersive X-ray Spectrometry (EDX) was used to measure the composition of the films. The SEM observations showed that the films deposited using glass reactor were composed of crystals of several micrometers which contained nearly 10at.% of Ca. Raman spectroscopy analysis confirmed that DLC films have been deposited, but with an obvious sharp peak at 1085 cm~(-1) which is assigned to calcium carbonate (CaCO_3) crystals. The glass reactor is the possible source of Ca because the electrolyte was composed of analytically pure acetone and deionized water with the proportion of Ca below the determination of AAS (atomic absorption emission spectrophotometer AA-6200). Using glass reactor with PTFE-coating inside could successfully avoid the impurity of Ca from the glass reactor, but new non-metallic impurities coming from the PTFE-coating made the films rough. Continuous and smooth films were deposited by using a glass reactor with quartz-coating inside and quartz reactor, which could avoid both Ca (<1 at.%) and other impurities. Raman spectroscopy analysis confirmed typical DLC films without CaCO_3. It can be concluded that the materials of the reactors could play an important role not only in the composition, but also the morphology and microstructure of films deposited by liquid electrochemical technique.