An ultrasensitive radio-frequency single-electron transistor working up to 4.2 K

We present the measurement of a radio-frequency single-electron transistor that displays a very high charge sensitivity of 1.9 mu e/root Hz at 4.2 K. At 40 mK, the charge sensitivity is 0.9 and 1.0 mu e/root Hz in the superconducting and normal state, respectively. The sensitivity was measured as a function of radio frequency amplitude at three different temperatures; 40 mK, 1.8, and 4.2 K. (c) 2006 American Institute of Physics.