High-purity aluminum nitride (AIN) coatings were grown on sapphire wafers at thickness of 6 μm. This coating was measured with test spot of 20 μm and 40 μm, and values were within +/- 5% of each other. The measured AIN in-plane thermal conductivity was measured at average of 283.7 W/m·K across multiple sample locations. Thermal conductivity values were observed to vary widely (+/- 36.3 W/m·K) due to micro-structure, grain size and defect concentrations. Additional measurement of bulk thermal conductivity on coatings as thin as 1 μm are also possible with SSTR-F.