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Title: Deciphering Adsorption Structure on Insulators at the Atomic Scale

We applied Scanning Probe Microscopy and Density Functional Theory (DFT) to discover the basics of how adsorbates wet insulating substrates, addressing a key question in geochemistry. To allow experiments on insulating samples we added Atomic Force Microscopy (AFM) capability to our existing UHV Scanning Tunneling Microscope (STM). This was accomplished by integrating and debugging a commercial qPlus AFM upgrade. Examining up-to-40-nm-thick water films grown in vacuum we found that the exact nature of the growth spirals forming around dislocations determines what structure of ice, cubic or hexagonal, is formed at low temperature. DFT revealed that wetting of mica is controlled by how exactly a water layer wraps around (hydrates) the K+ ions that protrude from the mica surface. DFT also sheds light on the experimentally observed extreme sensitivity of the mica surface to preparation conditions: K atoms can easily be rinsed off by water flowing past the mica surface.
Authors:
 [1] ;  [2]
  1. Sandia National Lab. (SNL-CA), Livermore, CA (United States). Materials Physics
  2. Sandia National Lab. (SNL-CA), Livermore, CA (United States). Integrated Nanotechnologies
Publication Date:
OSTI Identifier:
1323606
Report Number(s):
SAND2014--17839
537609
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Research Org:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA). Lab. Directed Research and Development (LDRD)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 33 ADVANCED PROPULSION SYSTEMS