Carbon nitride (CNx) thin films were deposited using radio frequency plasma enhanced chemical vapor deposition (rf PECVD) from a mixture of ethane (C2H6), nitrogen (N-2) and hydrogen (H-2) gases. The C2H6 and N-2 flow rates were kept constant, while the H-2 flow rate was varied. The effects of hydrogen dilution on the growth rate and structural properties of the films were studied. It was found that a significant increase in the films growth rate was observed with the introduction of H-2 at as low as 25 standard cubic centimeters per minute (sccm). A set of CNx films deposited from C2H6:N-2 mixture without any inclusions of H-2 were also presented in this work as a reference to compare the differences between those two sets and to understand the roles of H-2 to the films properties. At highest H-2 flow rate, the structure of the films changed from polymeric to graphitic and the quenching of PL was observed. Furthermore, higher N incorporation with lower E-g was obtained for these films compared to those of C2H6:N-2 films. The change in the structure of the films corresponds to changes in their chemical bonding. As N incorporation increased, the porosity of the films increases and thus affects the disorder in the film structures. (C) 2014 Elsevier B.V. All rights reserved.