On the synthesis of Zn/ZnO core–shell solid microspheres on quartz substrate by thermal evaporation technique

• Solid Zn/ZnO core–shell microspheres grown on quartz by thermal evaporation method.
• CeO2 layer changes quartz surface to hydrophobic enabling to form spherical shape.
• Elemental analyses reveal formation of Zn/ZnO core–shell.
• PL and Raman spectra shows high crystalline quality of the grown microspheres.

Well defined solid Zn/ZnO core–shell hetero-structures have been successfully synthesised on quartz substrate by thermal evaporation technique. By introducing a thin layer of CeO2 over quartz the ZnO micro-droplets have been converted into microspheres due to change of nature of quartz surface from hydrophilic to hydrophobic. The microspheres have wurtzite hexagonal structure and have an average size of about 40–60 μm. By using focussed ion beam etching and elemental analyses, the microspheres are found to have solid Zn core with a cover of ZnO on the surface confirming the formation of Zn/ZnO core–shell heterostructure. The photoluminescence spectrum exhibited an intense near band-edge emission peak at 377 nm along with a weak green band emission. The Raman spectrum of microspheres showed the characteristic wurtzite ZnO peak at 437 cm−1. A possible growth mechanism has been proposed for the growth of Zn/ZnO core–shell structures based on vapor–liquid–solid (VLS) process.