Investigation on the morphology and optical properties of self-assembled Ag Nanostructures on [formula omitted]-plane GaN by the control of annealing temperature and duration

Abstract

In this paper, the systematic control of self-assembled Ag nanostructures (NSs) on c-plane GaN is demonstrated by the control of annealing temperature (AT) and annealing duration (AD) at diverse Ag film thicknesses based on the solid-state-dewetting. The Ag NSs evolve in four distinctive growth regimes in terms of size, density and configuration with the 10 nm initial film thickness such as (i) nano-voids and -mounds (ii) nanoclusters (iii) nanoparticles (NPs) and (iv) NPs with sublimation. However, only three growth regimes are observed with the 40 nm set with variant NSs morphology due to the suppression of dewetting and diffusion. Meanwhile, based on the AD control with 30 nm Ag film, the size of Ag NSs are exponentially decreased in terms of the RMS roughness (Rq) and surface area ratio (SAR) due to the extensive sublimation of Ag atoms. The formation of various Ag NSs is discussed based on the Volmer–Weber growth model under the influence of several diffusion condition and Ag sublimation. The optical properties of Ag NSs are studied by the reflectance, Raman and photoluminescence, and the spectral evolution including the peak intensity and shift are discussed in terms of the specific plasmon resonance absorption band and surface tensile strain in reference to the morphology evolution of Ag NSs. In specific, the dipolar resonance peak clearly demonstrates shifts depending on the evolution of Ag NSs.