Exemplary methods of forming a silicon-and-carbon-containing material may include flowing a silicon-oxygen-and-carbon-containing precursor into a processing region of a semiconductor processing chamber. A substrate may be housed within the processing region of the semiconductor processing chamber. The methods may include forming a plasma within the processing region of the silicon-and-carbon-containing precursor. The plasma may be formed at a frequency less than 15 MHz (e.g., 13.56 MHz). The methods may include depositing a silicon-and-carbon-containing material on the substrate. The silicon-and-carbon-containing material as-deposited may be characterized by a dielectric constant below or about 3.5 and a hardness greater than about 3 Gpa.