Zn nanodot patterning in borosilicate glasses by electron irradiation
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llic zinc nanoparticles are generated in two compositional ranges of borosilicate glasses upon 200 and 300 keV electron beam irradiation in a transmission electron microscope. Irradiation effects are studied either with a stationary electron beam as a time series or with spatially varying beams for line-scan patterning. The size of the zinc nanodots formed is inversely related to the distance from the center of the electron beam, and growth from 5 to 50 nm over time via ripening can be observed. Line-scan patterning via both thermal gun and field emission gun electron irradiation has been successfully achieved. Our findings also show the occurrence of selforganized particle ordering, such as formation of chains. Metal nanoparticles have a tendency to migrate toward the glass fragment center, unless high intensity radiation ablates the glass matrix, when Zn particles remain decorating the surface. High-resolution lattice imaging, scanning transmission electron microscopy, and electron energy loss spectroscopy are used to confirm particle identity.
I. INTRODUCTION
Contributing Editor: William J. Weber a) Address all correspondence to this author. e-mail: m.mohammed-sabri@sheffield.ac.uk DOI: 10.1557/jmr.2015.122
under high intensity electron irradiation. Formation of metallic zinc nanocrystals about 7–10 nm in size embedded in an amorphous silica layer by electron beam irradiation of a zinc oxide thin film on silicon substrate has been reported by Kim et al.12 Amorphous zinc nanoparticles were initially formed under thermal annealing followed by prolonged irradiation. Further irradiation resulted in phase transformation into crystalline zinc nanoparticles. These preliminary Zn particle formation studies used uniform irradiation without attempt at patterning. On the other hand, patterned particle formation in glasses is known, e.g., via ion implantation through nanoporous masks for cobalt implanted into amorphous silica13 and for zinc implanted into both crystalline CaF2 and amorphous silica.14 Against this background, “direct write” electron beam patterning of initially uniform glasses without a mask appears to be promising due to its greater flexibility and resolution. Outside the field of glasses, electron beam induced preparation of metal nanoparticles from their precursors has been demonstrated in a variety of materials.15–18 Our study on Zn nanocluster and nanocrystal formation derives its importance from the ability to generate nanoplasmonic surface-near arrays in a transparent matrix, e.g., for light-coupling applications (such as Ag in borosilicates19). After oxidation of the Zn nanocrystals to ZnO, these may find applications as UV-range semiconductor quantum dots, as previously attempted with ion implantation.14 We aim at advancing earlier studies in the directions of nanoscale pattern formation by TEM direct-write, assessing glass compositional influence and tracking particle formation in situ.
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Ó Materials Research Society 2015
Investigating oxide glasses under irradiation is a subject of great interest no
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