Figure 2: Quality factors of single-crystal diamond nanoresonators between 0.1 and 300 K.

(a) Two representative diamond devices (out of nine measured) are compared with refererence devices made from polycrystalline diamond and single-crystal silicon of similar thickness (100–300 nm). Q factors between 100,000–1,000,000 are observed for diamond devices at room temperature, roughly 10–100 × higher than the reference devices. Cooling to 3 K leads to an increase in Q for the electronic grade (low doping) as well as the two reference resonators that are dominated by surface friction (solid arrows). Conversely, a reduction is seen in Q for the optical-grade (high doping) diamond resonator that has a strong contribution of bulk friction (dashed arrow). Single-crystal diamond devices were made by ‘quartz sandwich’ method and all diamond cantilevers were oxygen terminated. Silicon cantilever was according to ref. 11. (b) Quality factor of a 660-nm-thick electronic-grade resonator in the millikelvin regime. Red dot data are obtained by sweeping refrigerator temperature, and red square data (with error bars) are obtained by varying the laser power incident at the resonator (see Methods). Solid black line is a power law fit with Q⁻¹∝T^1.6±0.2. Inset shows the 0.1–1 K data in a log-log plot against the standard tunneling model (solid line) and a model of thermally-activated two-level systems (TLS, dashed line). Additional parameters for all cantilevers can be found in Table 1.