MEASUREMENT OF IN-PLANE THERMAL CONDUCTIVITY USING SUSPENDED SiNx ISLANDS

In order to measure in-plane thermal conductivity, electrical resistivity, and Seebeck Coefficient of Phononic Crystals (PnCs) a micro device is designed and fabricated to host different nano-scale samples. The device is comprised of two SiNx suspended membranes with patterned by Pt on top and covered by AIN. The Pt deposited on these two membranes or islands are dual-purpose temperature sensors and heaters. One side of a sample can be attached to each of the two islands. In this way 1-D heat flow can be established in the material to be tested. Covering the islands with AIN enhances the uniformity of temperature on each sensor. Moreover, AIN is an excellent electrical insulator, and it protects the platinum sensors from different sources of doping such as gallium ions used for patterning, depositing, mounting, or demounting different samples on the islands. This ensures the thermo-electric properties of the sensors on the platform do not change after each measurement. Using this design, it is demonstrated that one platform can be used for measurement of a silicon slab and then a separate measurement of a 1-D PnC fabricated from the same sample. The 1-D PnC had a Si-W structure that was fabricated using a Focused Ion Beam (FIB) and a Gas Injection System (GIS) capable of depositing W.