Identification of different concentrations of antibody by electrical property of DLC thin films

Abstract

Hydrophobic properties, electrical properties, ratio of diamond and graphite contents and X-ray diffraction pattern are characterized of diamond-like-carbon thin films which are grown on silicon substrate by RF-CVD. Seeding techniques are varied in this experiment. Silicon substrate is cleaned with three different solvents by ultrasonic cleaner i.e. acetone, methanol, and de-ionized water about 5 minutes in each solvent. The size of 4–5 nanometers diamond powder suspension in methanol of 0.0010g/50ml is used for electro-deposition technique. Voltage between electrodes is 30 V and seeding times is 25 minutes. These are seeding conditions. Normal seeding, normal seeding then cleaning by ultrasonic cleaner in methanol, and seeding and cleaning at the same time are three different seeding techniques. DLC thin films are grown by RF-CVD at power of 100 W, pressure of 8.5 mbar, growth time of 30 minutes and H2 and CH4 flow rate of 6.50 and 1.50 sccm respectively. It is found that the results of the three techniques of seeding are nearby, for example, they have a hydrophobic property and their XRD patterns are quite similar. IV-characteristic is measured by Van der Pauw 4 point probe technique. When pure water, and several concentrations of antibody are dropped on the films, their IV-curves can be distinguished.