Formation of alkanethiol monolayer on Ge(111)

S M Han; W R Ashurst; C Carraro; R Maboudian

doi:10.1021/ja993816c

Formation of alkanethiol monolayer on Ge(111)

J Am Chem Soc. 2001 Mar 14;123(10):2422-5. doi: 10.1021/ja993816c.

Authors

S M Han¹, W R Ashurst, C Carraro, R Maboudian

Affiliation

¹ Contribution from the Department of Chemical Engineering, University of California, Berkeley, California 94720, USA.

PMID: 11456892
DOI: 10.1021/ja993816c

Abstract

Alkanethiols, CH3(CH2)(n-1)SH, are shown to react readily with HF-treated Ge(111) surface at room temperature to form a high-quality monolayer. The resulting films are characterized by using contact angle analysis (CAA), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and high-resolution electron energy loss spectroscopy (HREELS). The octanethiol and octadecanethiol films on Ge(111) both exhibit 101 degrees and 40 degrees water and hexadecane contact angles, respectively. These values indicate that the thiol surface coverage is relatively high, and that the films possess a high degree of orientational ordering. The angle-resolved XPS analysis supports that thiols are bound to the Ge surface by Ge-S bonds at the monolayer/Ge interface. The film thickness values obtained by XPS and SE agree well with the earlier reported values on alkyl monolayers on Ge(111) prepared by Grignard reaction. On the basis of HREEL spectra taken after thermal annealing steps, the monolayers are found to be thermally stable up to 450 K. The thermal stability provides further evidence that thiols are covalently bonded to Ge(111).