Instrument

Scanning Tunneling Microscopy (STM)

Quantum tunneling of electrons from tip to sample takes place in STM junction. We measure tunneling current at each position of surface while we scan our tip in x and y direction on surface. With some calculations, we are able to map out the atomic and electronic structures of the surface.

When the distance between the tip and sample is smaller than 0.5 nm, the quntum tunneling takes place. Such small gaps are obtained by careful approach mechanism of tip to sample. We utilizes Besoke beetle walker for the approach. Maintaining the small gap and good enough tip are another important tasks in STM, which can be achieved by using electronic feedback circuits and STM manipulation techniques, respectively.

Vacuum and low temperature are important conditions for STM, to maintain clean surface and to reduce thermal noises and drift. Our three STM systems are placed in the ultra high vacuum (UHV) chambers and based on cooling mechanisms either with continuous flow cryostat or vacuum-dewar cyostat. The STM heads are housed inside double radiation shields for thermal isolation from environment.