Local Area Characterization of Evaporated TTF-TCNQ Complex Films with Scanning Tunneling Spectroscopy

Masakazu NAKAMURA  Masaaki IIZUKA  Kazuhiro KUDO  Kuniaki TANAKA  

IEICE TRANSACTIONS on Electronics   Vol.E85-C   No.6   pp.1323-1327
Publication Date: 2002/06/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Recent Progress in Organic Molecular Electronics)
Category: Fabrication and Characterization of Thin Films
STS,  electronic structure,  charge transfer complex,  TTF-TCNQ,  

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STM/STS measurements have been carried out for TTF-TCNQ complex films evaporated on hydrogen-terminated silicon substrates, and the variation of tunneling spectra has been investigated on morphologically different crystal grains. Very thin semiconductive adsorbed layers were found to cover the as-deposited film surfaces. By removing the adsorbed layers, the intrinsic electronic structures of two different phases were revealed. A 'needle phase' which appears at the early stage of film growth has a semiconductive character and a 'granular phase' which grows later has a metallic character similar to bulk crystals. The electronic structure of the needle phase is considered to be affected by the substrate although the crystallographic structure is similar to the bulk crystal of TTF-TCNQ.