Low noise, low heat dissipation, high gain AC-DC front end amplification for scanning probe microscopy.
We report here on the design, construction and testing of a vacuum compatible AC-DC amplification system for low signal measurements with scanning probes. The most important feature of this new amplification system is incorporated within the head of a scanning tunneling microscope (STM). This is achieved with a very low thermal dissipation radio frequency amplifier at the STM head. The amplifier gain is higher than 40 dB and has a 50 dB maximum. Further, the AC noise figure is 0.7 dB between 100 and 1000 MHz. The noise induced in the DC amplifier is less than 2 pA RMS (root mean square), which enables the microscope to scan over soft insulating molecular layers. Thermal drift at the STM tip-sample interface is below 0.1 nm min(-1) both in air and in vacuum operation. Atomic resolution on highly oriented pyrolytic graphite surfaces is reliably achieved. Spin noise measurements are provided as an example of an application.
Messina
Paolo
P
Material Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
Fradin
F Y
FY
Pittana
Paolo
P
D000669:Amplifiers, Electronic; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008422:Materials Testing / Q000295:instrumentation*; D020527:Microscopy, Scanning Probe / Q000379:methods*; D036103:Nanotechnology / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity