Influence of Substrate Temperature and Film Thickness on Thermal, Electrical, and Structural Properties of HPPMS and DC Magnetron Sputtered Ge Thin Films

Ge was deposited as thickness gradient films at temperatures up to 800 degrees C by direct current (DC) and high power pulsed magnetron sputtering (HPPMS). Structural characterization shows increased crystallization with increasing substrate temperature and film thickness. Thermal conductivity was measured by a novel high-throughput time-domain thermo-reflectance method. Thermo-electrical properties correlate to the degree of crystallization. Conductivities increase with increasing substrate temperature up to 500 degrees C. For higher temperatures the trend reverses. A room temperature deposited/annealed film displays smaller crystallites (10 nm) and lower thermal conductivity (5 Wm(-1) K-1) compared to 25 Wm(-1) K-1 for hot DC deposition. Compared to DC, HPPMS films show higher thermal conductivities up to 45 Wm(-1) K-1.