Variable Temperature STM
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The UHV chamber sits on the frame supported by four airlegs for vibration isolation from the building. Main UHV tools are present: Auger, LEED, mass spectrometer for sample characterization, sputter gun for sample cleaning and preparation. Vacuum is created by a series of a roughing and two turbopumps, ion pump, titanium sublimation pump and heteropump. Cooling is achieved by delivering liquid helium from dewar to the end of cryostat coupled to the sample stage allowing us to go down to 35K. The sample stage is vibrationally isolated from the cryostat and the whole chamber reducing vibrational noise drastically. A number of modifications were made since first construction of the system: "beetle" type of STM head [1] was replaced with "stick-slip" type which allows to cool down the STM tip as well, reducing thermal noise. Sample holder and stage design was modified to maintain 3-point contacts along all the way from the tip to the sample reducing mechanical impact greatly. Current noise level allows to resolve features as low as 2pm high. More detailed information of our STM design you may find in the paper "Scanning tunneling microscope with continuous flow cryostat sample cooling" [1] Rev. Sci. Instr. 68 (1997) 2479 |
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