Atomic-Scale Observation of Temperature and Pressure Driven Preroughening and Roughening

Abstract

Preroughening and roughening transitions are observed on the GaAs(001) surface using scanning tunneling microscopy. By tuning the substrate temperature or As4 pressure the surface morphology can be made free of islands, covered with one monolayer high islands or covered with islands on top of islands forming a wedding-cake-type structure. These three distinct surface morphologies are classified as ordered flat (OF), disordered flat (DOF), and rough within the restricted solid-on-solid model. Here, the DOF phase is macroscopically flat; however, an up-down-up-down step pattern persists across the entire surface. Using this model we have determined the next-nearest-neighbor interaction energy to be about 0.05 eV.

Predicting GaAs surface shapes during MBE regrowth on patterned substrates

“…The agreement with this simple KPZ continuum model suggests that the anomalous effects associated with the singular free energy of crystal facets are not important for the growth conditions in question [4]. This is likely a consequence of the fact that under our growth conditions the surface is above the roughening temperature [11].…”

Arsenic-rich GaAs(0 0 1) surface structure

“…Notice that this coverage varies from 80 to 40% as the substrate temperature is increased. Reprinted from [165], Copyright (2003) by the American Physical Society. been measured as a function of coverage and displayed a non-systematic variation between 2 and 3 [163].…”

“…In a series of similar but more extensive experiments, LaBella et al measured the surface morphology using in situ STM for GaAs(0 0 1) surfaces that were annealed using band edge temperature control and then quenched to room temperature [162,31,18,[163][164][165][166]. An exhaustive study of the accessible phase space was performed which included temperature ranges from 500 to 700 C, As 4 BEPs ranging from 0.01 to 10 mTorr and annealing times from 1 min to 33 h. These studies determined that the phase transitions and surface morphologies observed were consistent with the framework of the den Njis model.…”

“…The surface transformation that accompanies the change in RHEED patterns from the flat well-ordered (2 Â 4)-b-phase through the (2 Â 4)-a-phase to the (2 Â 1) phase is a roughening transition [162,31,18,[163][164][165][166]. However, this understanding has only come about very recently due in part to lack of accurate and reproducible temperature control and the driven searches to uncover the atomic structure of the various reconstructions that ignore larger nanoscale structures such as island formation that occur during roughening.…”

Graphene ripples as a realization of a two-dimensional Ising model: A scanning tunneling microscope study

“…Given the coupled two-state nature of graphene ripples and their potential for collective behavior, the celebrated and versatile Ising model might, in principle, be applicable. While Onsager's famous 2D solution was initially applied to the spontaneous magnetization of a 2D square lattice ferromagnet [11,12], through group renormalization [13] it has been established that a wide range of systems belong to the 2D spin-half Ising universality class [14][15][16][17][18][19][20][21]. Bonilla and Carpio treated graphene's individual carbon atoms with the 2D Ising model [22,23] and reproduced the existence of ripples [24,25].…”