Experimental study of two-level system loss in surface acoustic wave resonators*

Progress in quantum acoustics suggests that truly powerful quantum technologies for computation and sensing may be within reach. However, fabricated devices are often limited by internal loss that can be modeled as a bath of two level systems (TLS) coupled to the resonator. Here I present a study of TLS sources in Lithium Niobate and Lithium Tantalate using 600-900 MHz surface acoustic wave resonators (SAW). TLS due to a variety of sources, including crystal defects and organics that lie on the substrate surface, make SAW resonators a good probe of these dissipation channels. SAW devices at these frequencies are made with a one mask photolithography process, meaning that fabrication is minimally destructive and easily iterated. TLS loss is characterized by studying changes in the internal quality factor and resonant frequency shifts as a function of resonator temperature. Several resonators with differing surface treatments of the piezoelectric substrate done prior to SAW deposition were measured and compared for TLS loss. Finally, I compare cryogenic measurement results with studies using X-ray photon spectroscopy on the same samples to better understand the effects of different chemical composition between the substrate surfaces.