Scanning tunnelling microscopy in extreme fields: very low temperature, high magnetic field, and extreme high vacuum

We present the performance of our newly developed very-low-temperature scanning tunnelling microscope (VLT-STM). This system can operate with high spatial and energy resolution at temperatures down to 350 mK, and in a magnetic field up to I I T. The uniqueness of our VLT-STM is that the system possesses extreme-high-vacuum chambers (XHV) (similar to10(-10) Pa). System operation ranges from sample preparation, such as cleaning and deposition, to observations in an extremely clean environment. XHV will have a significant impact within material sciences, particularly when treating a semiconductor surface. Test results have revealed STM images obtained below I K and with atomic resolution of highly oriented pyrolytic graphite (HOPG), Si(100) dimers, and Au(111) surfaces. Our Si(l 00) experiments are the first atomically-resolved STM images of the semiconductor surface obtained below I K. The results of those tests have conclusively determined its true ground state structure-a subject under debate for many years. Some of the STM images acquired in a high magnetic field are included in this paper. The XHV-VLT-STM system is state-of-the-art and a very powerful instrument for exploration of the nano-sciences.