Low microwave loss in deposited Si and Ge thin-film dielectrics at single-photon power and low temperatures

Abstract

Our study shows that deposited Ge and Si dielectric thin-films can exhibit low microwave losses at near single-photon powers and sub-Kelvin temperatures (≈40 mK). This low loss enables their use in a wide range of devices, including low-loss coplanar, microstrip, and stripline resonators, as well as layers for device isolation, inter-wiring dielectrics, and passivation in microwave and Josephson junction circuit fabrication. We use coplanar microwave resonator structures with narrow trace widths of 2-5 μm to maximize the sensitivity of loss tangent measurements to the interface and properties of the deposited dielectrics, rather than to optimize the quality factor. In this configuration, thermally-evaporated ≈1 μm thick amorphous germanium (a-Ge) films deposited on Si (100) have a single photon loss tangent of 1-2×10 -6 and, 9 μm-thick chemical vapor deposited (CVD) homoepitaxial Si has a single photon loss tangent of 0.6-2×10 -5 . Simulations indicate that interface losses are non-negligible.

Environmentally Sustainable and Multifunctional Chrome-like Coatings Having No Chromium Designed with Reinforcement Learning

“…Thus, they are seldom used in RF-based devices, e.g., automobile radars. Semiconductor materials such as Ge have much smaller losses in the RF regime, , so we designed S2, another chrome-mimicking stack that has high transmission in the RF regime simultaneously, as the structure involves thin layers of Ge and SiO 2 only. To demonstrate this, we experimentally measured the transmission and reflection of S2 in the range of 8–12 GHz as shown in Figure .…”