Cadmium Sulfide (CdS) Thin Films with Improved Morphology for Humidity Sensing by Chemical Bath Deposition at Lower pH.

Cadmium sulfide (CdS), an II-VI group semiconductor material, is one of the most investigated semiconductors in thin film form. In this work, we synthesized CdS thin films with improved film morphology in the presence of ethylene diamine (EA) as the complexing agent by chemical bath deposition (CD) at lower pH. Detailed characterization reveals the presence of cubic phase CdS with a band gap of 2.39 eV with the resultant morphology significantly influenced by the composition of the growth solution. The resultant CdS films finds prospective application as a humidity sensor with a high sensor response of 2.61 corresponding to 80% relative humidity.

Field emission study of carbon nanotubes forest and array grown on Si using Fe as catalyst deposited by electro-chemical method.

Vertically aligned carbon nanotubes are synthesized by Low Pressure Chemical Vapor Deposition (LPCVD) on Si substrate coated with Fe as a catalyst at a pressure of 20 Torr and at a growth temperature of 600 degrees C. The catalyst film is prepared by electro-chemical method which is very unique and a low cost method. Three precursor gases Acetylene (C2H2), Ammonia (NH3) and Hydrogen (H2) at the flow rate of 20 sccm, 100 sccm and 100 sccm respectively are allowed to flow through the Low Pressure Chemical Vapor Deposition reactor for 10 minutes. Scanning Electron Microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. Raman analysis shows G-band at 1574 cm(-1) and D-band at 1370 cm(-1). The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission measurement reveals good field emission properties of as-grown vertically aligned carbon nanotubes with turn-on field of 1.91 V/microm at the current density 10 mA/cm2. The field enhancement factor is calculated to be 7.82 x 10(3) for as-grown carbon nanotubes.