A HIGH-SPEED VARIABLE-TEMPERATURE ULTRAHIGH-VACUUM SCANNING TUNNELINGMICROSCOPE

An ultrahigh vacuum scanning tunneling microscopy (STM)system capable of collecting constant-current STM images at rates exceeding 1 image/s at temperatures up to 900 K was designed, built, and tested. The micr oscope uses an inchworm to push a scanner assembly through a quartz tu be towards the sample. When the scanner is within tunneling range of t he surface, the inchworm is decoupled from the scanner, resulting in a small, rigid mechanical loop with a high resonant frequency. The cyli ndrical symmetry and the use of low thermal expansion materials reduce s image distortion due to thermal drift. An analog proportional-integr al controller with tilt correction is used to maintain a constant tunn el current. A personal computer running Microsoft WINDOWS '95 is used to control all other instrument functions, as well as for data acquisi tion, manipulation, and storage. Problems associated with the non real time nature of the operating system were overcome by collecting the S TM images within a virtual device driver. By taking advantage of the W INDOWS '95 multimedia functions, the time required to display and save images was reduced below 5 ms using a standard personal computer with no special hardware other than data acquisition cards. Sample STM ima ges of Pd(111) and halogens adsorbed on Cu(100) are presented. (C) 199 8 American Institute of Physics. [S0034-6748(98)02209-6].