Design and assembly of a low temperature vacuum tunneling apparatus and preliminary measurements of the energy gap of an organic superconductor
A new approach to the design of a low temperature vacuum tunneling apparatus (VTA) is described along with pertinent construction details. Incorporated into the design is an automated tip positioning control combining a differential micrometer with piezoelectric transducers. Tests of apparatus performance included analysis of the noise spectrum of a tunnel junction, verification of the exponential dependence of current on distance, and determination of the energy gap for an ErRH/sub 4/B/sub 4/ single crystal. This apparatus is suitable for spectroscopic studies of metals, especially superconducting materials. Results include the first measurements on a single crystal of the newest ambient pressure organic superconductor ..beta..-(ET)/sub 2/AuI/sub 2/ i.e. ..beta..-(bis-ethylenedithiotetrathiafulvalene)/sub 2/AuI/sub 2/. Point-contact tunneling shows a surprisingly large energy gap ..delta..(0) in the electron excitation spectrum compared to T/sub c/ which is indicative of extremely strong electron-phonon coupling. Speculation that the origin of the large gap might be due to coupling to very low frequency modes is offered. Preliminary orientational measurements on a single crystal are suggestive of possible gap anisotropy. Noise measurements for vacuum tunneling between two Au electrodes shows the ubiquitous 1/f spectrum with a considerable temperature dependence. Evaluation of in situ cleaning of the sample surface by spark discharge is also included.
- Research Organization:
- Johns Hopkins Univ., Baltimore, MD (USA)
- OSTI ID:
- 7240747
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
42 ENGINEERING
ENERGY GAP
MEASURING METHODS
ORGANIC COMPOUNDS
SUPERCONDUCTORS
ANISOTROPY
ELECTRONIC EQUIPMENT
NOISE
TRANSITION TEMPERATURE
EQUIPMENT
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
360603* - Materials- Properties
420800 - Engineering- Electronic Circuits & Devices- (-1989)