Kardar-Parisi-Zhang universality, anomalous scaling and crossover efects in the growth of CdTe thin films

• Ano de defesa: 2015
• Autor(a) principal: Almeida, Renan Augusto Lisbôa
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Telureto de cádmio; Filmes finos; Kardar-Parisi-Zhang, Equação de; Física da Matéria Condensada
• Link de acesso: http://www.locus.ufv.br/handle/123456789/6360

A relation between the mound evolution and large-wavelength fluctuations at CdTe surface has been established. One finds that short-length scales are dictated by an interplay between the effects of the for- mation of defects at colided boundaries of neighboring grains and a relaxation process which stems from the diffusion and deposition of particles (CdTe molecules) torward these regions. A Kinetic Monte Carlo model corroborates these reasonings. As T is increased, that competition gives rise to different scenarios in the roughening scaling such as: uncorrelated growth, a crossover from random to correlated growth and tran- sient anomalous scaling. In particular, for T = 250 ºC, one shows that fluctuations of CdTe surface are described by the celebrated Kardar-Parisi-Zhang (KPZ) equation, in the meantime that, the universality of height, local roughness and maximal height distributions for the KPZ class is, finally, experimentally demonstrated. The dynamic of fluctuations at the CdTe surface for other temperatures still is described by the KPZ equation, but with different values for the superficial tension (u) and excess of velocity (A). Namely, for T = 150 ºC one finds a Poissonian growth that indicates 1/ = A = O. For T : ZOOºC, however, a Random-to-KPZ crossover is found, vvith A > 0 in the second regime. The origin of the KPZ scaling for films grown at T 6 [200,250] ºC stems from a complex dynamic of grain packing during vvhich all available space at the neighborhood of grains are not filled. This aggregation mechanism has the same effect of the lateral aggregation of the balistic deposition model Which leads to an excess of velocity (A > O). Finally, for films grown at T = 300 ºC one demonstrates that a KPZ grovvth vvith A < 0 takes place. In particular, the KPZ mechanism at this T comes from the high refuse rate of the deposition of particles, Which depends on the local lepes. This phenomenon can be explained in terms of the sticking coeflicient Which is so smaller as more locally inclinated is the surface. Due to finite-time effects (temporal crossover and anomalous scaling) taking place in T = 200 ºC and T : SOOºC, scale exponents fail in reveal the Universality Class of the grovvth. Notvvhithstanding, a new scheme developed, vvhich advances over the simple comparison between exponents and their theoretically predicted values, allovv us, surely, to conclude that the growth of CdTe, in a Wide range of deposition temperature, belongs to the KPZ class.