Autocompensated surface structure

Aqueous processing, precursors for ferroelectric thin films, 95-104 Autocompensated surface structure of GaN film on sapphire experimental description, 26-27 experimental procedure classical ion trajectory simulations, 28 GaN sample, 27 first-layer species... 

The autocompensation model states that the energetically most stable surfaces are those for which all the cation-derived dangling bonds are completely empty and all anion-derived dangling bonds are completely full. Thus, this model predicts which rearrangement of atoms and which surface terminations will be stable and exist.10 Surface autocompensation is a necessary but insufficient condition for a stable structure. This means that there may be several autocompensated surfaces that are stable but not observed, presumably because some other autocompensated surfaces are more stable energetically. However, the main drawback of this model is that it cannot predict interlayer... 

Once a particular surface structure has been determined to be stable (i.e., autocompensated), the primary factor determining the nature of the surface reconstruction is the energy that can be gained by rehybridizing the surface dangling bond charge density in response to the reduced coordination at the surface. As a consequence, a charge transfer between the atoms at the surface takes place and this results in the formation of new bonds between surface atoms adsorbed to the surface (also known as adatoms). The formation of new bonds on the surface leads to different chemical and physical properties at the surface.11... 

Hemai6(001) surface. By examination of the bulk structure, a low surface energy, non-polar bulk termination is found along (001) planes between the iron atoms in Fe-Fe bilayers (Fig. 42). The planar division creates two equivalent surfaces composed of a 1/3 monolayer of iron over a close-packed oxygen layer. Along a single [001] vector, the minimum repeat unit of 18 atomic planes (conventional cell) can be seen to have no net dipole moment and is thereby predicted to be stable from an electrostatic perspective. Similarly, using the covalent perspective, autocompensation predicts that this surface... 

Steps For the formation of steps on oxide surfaces and their stability, the same concepts, namely, charge neutrahty and autocompensation, as apphed for the stability of regular surfaces, may be apphed. Ions exposed at step sites have lower coordination than the respective terrace sites. The coordinative unsaturation leads also to slight structural relaxation at step sites. Experimentally, the step direction can be measured by quantitative J-V LEED, or may be inferred from microscopic data, where the principal crystal directions are directly seen. However, with the complexity of crystal structures that are possible for oxide surfaces, the determination of step structures is not straightforward. 

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