A new design of the vibrating reed apparatus for studying the high-resonant overtones of very small samples is described. Using the high Q (∼10 3) helical rf resonator as a capacitive transducer, great sensitivity has been obtained. The theoretical sensitivity of the detector is investigated with transmission-line theory, and the result shows that the Johnson-noise-limited sensitivity is proportional to the Q of the resonator instead of Q1/2, as is the case of lumped LC-tuned circuit analyses. For a nonsuperconducting resonator, the Johnson-noise-limited minimum detectable displacement (Δdmin) at room temperature, with bandwidth B, is about 10-7 Å √B/Hz, if the rf electrical field level is only limited by vacuum breakdown. An application of the apparatus in studying the temperature-dependent changes in the Young's modulus of single crystals of TaS3 is shown.
|Number of pages
|Review of Scientific Instruments
|Published - 1989
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