Temperature-dependent change of the fractal dimension of Cu dendrites on Cu(111)

C Sprodowski,K Morgenstern

doi:10.1088/1367-2630/ab944b

Abstract

We investigate the shape of monatomic high Cu islands on a Cu(111) surface by variable-temperature scanning tunneling microscopy between 110 K and 240 K. Low temperature dendrites evolve towards more compact shapes at increasing temperature; finally reaching the equilibrium shape of a hexagon with rounded corners. Time-lapsed imaging at increasing temperature reveals the onset of shape change to be at ≈170 K, corresponding to the onset of edge and corner diffusion of atoms along the island’s borders. Despite a substantial variation for individual islands at each temperature, the mean fractal dimension increases monotonously between 170 K up to 240 K, from the smallest to the largest values feasible for islands grown on surfaces.

Highlights

General concepts based on a thorough atomistic-scale picture in model systems are important for designing growth routes for artificial material with custom-designed properties, e.g. nanoclusters or multilayers
We investigate the shape of monatomic high Cu islands on a Cu(111) surface by variable-temperature scanning tunneling microscopy between 110 K and 240 K
We followed the equilibration of dendritic Cu islands on Cu(111) in time-lapsed series from islands with a fractal dimension of 1.7 up to 2.0

Summary

Introduction

General concepts based on a thorough atomistic-scale picture in model systems are important for designing growth routes for artificial material with custom-designed properties, e.g. nanoclusters or multilayers. The ES barrier [10, 11] is an excess energy barrier that diffusing particles have to overcome, when diffusing over a step edge; reducing interlayer mass transport, if not surpassed in specific geometries [12, 13]. It causes the kinetically limited three-dimensional growth mode being predominate for Cu/Cu(111) between 115 K and 300 K as investigated by He scattering [14, 15] and by x-ray surface diffraction [9, 16]. The Cu/Cu(111) system served as a model system to manipulate growth, such that the kinetic limitations of the ES barrier can be overcome [6, 14]

Methods

Results

Conclusion