Micropatterned CdS thin films by selective solution deposition using microcontact printing techniques

The micropatterning of CdS thin-film on Si(100) substrate with a boundary resolution better than 100 nm was successfully obtained by a chemical bath deposition technique and microcontact printing (mu CP) method using octadecyltrichlorosilane (OTS) as the organic thin layer template. The selective deposition and lift-off condition of patterned CdS thin films could be controlled by the various parameters, e.g., solution concentration, pH, temperature, and sonicating time after the deposition. When the solution concentration is moderately high ([Cd] > 0.0025 M), depositions under conditions of pH 10.5-10.7, reaction temperature 60 degrees C, and Cd/thiourea/ethylenediamine ratio 1/1/3 produced CdS films all over the OTS and unmodified Si surfaces. The CdS on OTS layer could be lifted off by sonication in isopropyl alcohol to produce patterned CdS films. By using solutions with low concentration, deposition of the CdS thin films occurred selectively on the unmodified Si surface and patterning could be achieved even without the lift-off process.