AVS 56th International Symposium & Exhibition
    Nanometer-scale Science and Technology Tuesday Sessions
       Session NS-TuP

Paper NS-TuP15
STM Measurements at mK Temperatures for Higher Energy Resolution

Tuesday, November 10, 2009, 6:00 pm, Room Hall 3

Session: Nanometer-scale Science and Technology Poster Session
Presenter: Y. Kuk, NIST and Seoul National University, Korea
Authors: Y.J. Song, NIST and University of Maryland, College Park
A.F. Otte, NIST and University of Maryland, College Park
Y. Kuk, NIST and Seoul National University, Korea
J.A. Stroscio, National Institute of Standards and Technology
Correspondent: Click to Email
Since the invention of scanning tunneling microscopy (STM) in early 1980’s, STM and STM-based measurement techniques have been used in a variety of fields for their atomic resolution. With the advent of cryogenic microscopes operating around 4K, the high resolution spectroscopic capabilities of the STM have had significant impact. In this poster, we describe our efforts to make STM measurements at even lower temperatures approaching 10 mK to gain further energy resolution in spectroscopic measurements. To realize this enhanced energy resolution, we constructed an ultra high vacuum (UHV) Dilution Refrigerator (DR) based STM system. The DR was constructed very rigidly in order to have a high resonance frequency. Furthermore, it has two independent modes of He3-He4 mixture gas condensation: a traditional 1K pot condenser, and a Joule-Thomson condenser for possible lower noise operation. For STM measurements, we custom-designed and built an STM module suitable for operation at mK temperatures. The whole STM module can be transferred from the upper, room-temperature chamber where the sample and tip can be easily exchanged. The sample holder has five isolated electrical contacts which are also used for kinematic mounting of the sample. This allows four-probe electrical measurements to be performed simultaneously with STM measurements. A cryogenic current amplifier has been constructed and is mounted in the DR for low noise tunneling measurements. We describe the current progress and performance of this new system.