Laser-assisted CVD Fabrication and Characterization of Carbon and Tungsten Microhelices for Microthrusters

Abstract: Laser-induced chemical vapor deposition (LCVD) is a process enabling the deposition of solid material from a gas phase in the form of free-standing microstructures with high aspect ratios. The deposition rate, wire diameter, and material properties are sensitive to changes in temperature and gas pressure. Through experimentation these dependencies are clarified for carbon and tungsten-coated carbon microhelices to be used as heating elements in cold gas microthrusters for space applications. The integration of heaters into the thruster will raise the temperature of the gas; thus, improving the efficiency of the thruster based on specific impulse.Deposition rate is measured during the fabrication process, and the geometrical dimensions of the spring are determined through microscopy analysis. By experimentally measuring the spring rate, material properties such as shear modulus and modulus of elasticity for LCVD-deposited carbon can be determined as a function of process parameters. Electrothermal characterization of carbon and tungsten-coated microcoils is performed by resistively heating the coils and measuring their surface temperature and resistance in atmospheres relevant to their operating environments. Through high-resolution microscopy analysis, sources having detrimental effects on the coils are detected and minimized. The results gained from these experiments are important for efforts in improving the performance of cold gas microthrusters.