Search

We developed a growth technique that improves the crystallinity and optical properties (photoluminescence intensity and lifetime) of Er-doped Gd2O3 (Er:Gd2O3) on a Si(111) substrate. Deposition of thin (7.5 Å thick) Gd metal on the SiOx-covered surface of the Si(111) substrate prior to the growth of Er:Gd2O3, and the successive, thermally-induced redox reaction gives rise to the solid-phase epitaxy of GdOx on Si, which protects Si from unintentional oxidation and fosters the epitaxial growth of Er:Gd2O3 on it; i.e., GdOx serves as a protection and seed (bifunctional) layer. This technique is promising for developing high-performance optical devices using high-quality rare-earth oxide films grown on Si substrates. [ABSTRACT FROM AUTHOR]

We recently introduced a novel model of step flow crystal growth – the so-called “C+–C-” model [B. Ranguelov et al., C.R. Acad. Bulgare Sci. 60, 389 (2007)]. In this paper we aim to develop a complete picture of the model’s behaviour in the framework of the notion of universality classes. The basic assumption of the model is that the reference (“equilibrium”) densities used to compute the supersaturation might be different on either side of a step, so CL/CR ≠ 1 (L/R stands for left/right in a step train descending from left to right), and that this will eventually cause destabilization of the regular step train. Linear stability analysis considering perturbation of the whole step train shows that the vicinal is always unstable when the condition CL /CR >1 is fulfilled. Numerical integration of the equations of step motion combined with an original monitoring scheme(s) results in obtaining the exact size- and time- scaling of the step bunches in the limit of long times (including the numerical prefactors). Over a broad range of parameters the surface morphology is characterized by the appearance of the minimal interstep distance at the beginning of the bunches (at the trailing edge of the bunch) and may be described by a single universality class, different from those already generated by continuum theories [A. Pimpinelli et al., Phys. Rev. Lett. 88, 206103 (2002), J. Krug et al., Phys. Rev. B 71, 045412 (2005)]. In particular, the scaling of the minimal interstep distance lmin in the new universality class is shown to be lmin = (Sn /N)1/(n+1), where N is the number of steps in the bunch, n is the exponent in the step-step repulsion law U ~ 1/d0 n for two steps placed a distance d0 apart and Sn is a combination of the model parameters. It is also shown that N scales with time with universal exponent 1/2 independent of n. For the regime of slow diffusion it is obtained for the first time that the time scaling depends only on the destabilization parameter CL/CR. The bunching outside the parameter region where the above scaling exists cannot be assigned to a specific universality class and thus should be considered non-universal. [ABSTRACT FROM AUTHOR]