  We describe a compact ultra-high vacuum (UHV) scanning tunneling microscope
(STM) system that does not need any external supply of cooling liquids. It
achieves temperatures down to 1.5 K and a z-noise down to 300 fmRMS for the
frequency range of 0.1 Hz - 5 kHz (feedback loop off). It employs a pulse tube
cryocooler (PTC) and a Joule-Thomson (JT) stage inducing only small temperature
oscillations at the STM with amplitude below 1 mK. The challenge to combine an
effective vibrational decoupling from the PTC with sufficient thermal
conduction is tackled by a multipartite approach. We realize a minimal
stiffness of the UHV bellows that connect the PTC and the STM chamber. Fine
Copper wires mechanically decouple the PTC stages from cooling plates that
carry the thermal shields, the JT stage and the STM. Soft springs decouple the
STM from the JT stage. Finally, the STM body has an optimized conical shape and
is made of the light and stiff material Shapal Hi MSoft such that a strong
reduction of low frequency vibrations results for the tunnel junction. The
voltage noise in the tunnel junction is 0.12 mV and an RF antenna close to the
tunnel junction provides radio frequency excitations up to 40 GHz with
amplitudes up to 10 mV.
