Nanoscale morphology and optical property evolution of Pt nanostructures on GaN (0 0 0 1) by the systematic control of annealing temperature and duration with various Pt thickness

By the controlled fabrication of Pt nanostructures, various surface morphology dependent electronic, catalytic and optical properties can be exploited for a wide range of applications. In this paper, the evolution of Pt nanostructures on GaN (0 0 0 1) by the solid-state dewetting of Pt thin films is investigated. Controlling the annealing temperature, time and film thickness allows us to fabricate distinct size, density and configurations of Pt nanostructures. For 10 nm Pt thickness, tiny voids and Pt hillocks up to 550 °C, extensive void expansion and Pt nanostructure evolution between 600 °C-750 °C and finally Pt nanostructures assisted nanoholes penetration on GaN surface above 800 °C are demonstrated. Furthermore, comparatively elongated Pt nanostructures and NHs are resulted with 20 nm Pt thickness and voids growth and connected Pt nanostructure are formed by annealing duration control. The transformation of Pt films to nanostructures is governed by the surface diffusion, Rayleigh instability, Volmer-Weber growth and energy minimization mechanism whereas NHs penetration is commenced by the decomposition of GaN, Pt-Ga alloying and nitrogen desorption at high temperature. In addition, the optical characteristic of Pt nanostructures on GaN (0 0 0 1) by reflectance, photoluminescence (PL) and Raman spectroscopy demonstrate the surface morphology dependent spectral response.