Abstract
We report here on the design, construction and testing of a vacuum compatible AC–DCamplification system for low signal measurements with scanning probes. The mostimportant feature of this new amplification system is incorporated within the head of ascanning tunneling microscope (STM). This is achieved with a very low thermaldissipation radio frequency amplifier at the STM head. The amplifier gain ishigher than 40 dB and has a 50 dB maximum. Further, the AC noise figure is 0.7 dBbetween 100 and 1000 MHz. The noise induced in the DC amplifier is less than2 pA RMS (root mean square), which enables the microscope to scan over softinsulating molecular layers. Thermal drift at the STM tip–sample interface is below0.1 nm min−1 both in air and in vacuum operation. Atomic resolution on highly oriented pyrolyticgraphite surfaces is reliably achieved. Spin noise measurements are provided as an exampleof an application.
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