Kris's Research Notes

May 31, 2011

Substrate Growth without Extended Species

Filed under: GaAs Simulations — Kris Reyes @ 8:58 pm

This is a follow up of this post. In that post, we were able to grow droplets without using the notion of extended species. In this post, we examine substrate growth without extended species.



Droplets without Extended Species

Filed under: GaAs Simulations — Kris Reyes @ 2:53 pm

Recall we initially devised the notion of an atom’s extended species — that atom’s species along with nearest-neighbor information — in order to form Ga droplets. The idea was to encourage Ga(0) – Ga(0) bonds by making those bonds stronger than other Ga-Ga bonds. (Recall: Ga(0) means a Ga atom with no As neighbors. This led to droplet formation instead of wetting. In light of the recent problems with extended species to determine Ga-As bonds, we had considered possibly eliminating these different types of bonds in favor of just one type of Ga-As bond. Naturally, we may ask if extended species are even necessary for droplet formation. It turns out that they are not.


May 30, 2011

Basic Mixtures

Filed under: GaAs Simulations — Kris Reyes @ 3:09 pm

In this post, we consider a two species system where a droplet of species B sits on a substrate of species A. The atoms occupy positions on the same lattice as our GaAs system. Atoms move by hopping — exchanging with an adjacent vacuum position. There are no atom-atom exchanges. We have three types of bonds which occur in the system: \gamma_{AA}, \gamma_{BB}, \gamma_{AB}. These are bonds between two A atoms, two B atoms and an A and B atom, respectively.

May 19, 2011

More on the new energy barriers

Filed under: GaAs Simulations — Kris Reyes @ 6:51 am

In the previous post, we described how detailed balance can be violated for certain events. For such an event, we had assigned an incorrect energy barrier, and hence detailed balance was not satisfied. To address this, we now assign the correct energy barrier: E(X) - E(X\wedge Y), the energy difference between a state X and the resulting state when the diffusing atom is removed: X\wedge Y. In this note, we explore how this change affects certain events.