Kinetic stabilization of Fe film on GaAs(100): An in situ x-ray reflectivity Study

TL;DR

This study investigates the low-temperature growth of Fe films on GaAs(100) using in situ x-ray reflectivity, revealing kinetic stabilization of the Fe film due to limited adatom diffusion and interface alloying upon annealing.

Contribution

It provides new insights into the growth mechanism and interface stability of Fe films on GaAs(100) at low temperatures using synchrotron x-ray reflectivity.

Findings

Fe film growth has a rough surface with a growth exponent of 0.51.

Negligible surface segregation and interface alloying at 140 K.

Ultrathin alloy formation occurs near the interface after annealing to 300 K.

Abstract

We study the growth of the Fe films on GaAs(100) at a low temperature, 140 K, by $in$-$situ$ UHV x-ray reflectivity using synchrotron radiation. We find rough surface with the growth exponent, $\beta_S$ = 0.51$\pm$0.04. This indicates that the growth of the Fe film proceeds via the restrictive relaxation due to insufficient thermal diffusion of the adatoms. The XRR curves are nicely fit by a model with a uniform Fe film, implying that the surface segregation and interface alloying of both Ga and As are negligible. When the Fe film is annealed to 300 K, however, the corresponding XRR can be fit only after including an additional layer of 9 A thickness between the Fe film and the substrate, indicating the formation of ultrathin alloy near the interface. The confinement of the alloy near the interface derives from the fact that the diffusion of Ga and As from the substrate should proceed via the inefficient bulk diffusion, and hence the overlying Fe film is kinetically stabilized.