Structures of Yb nanoparticle thin films grown by deposition in He andN2 gas atmospheres: AFM and x-ray reflectivity studies

Abstract

Nanoparticles of lanthanide metals and their compounds are important from the viewpointof both basic research and application to many functional devices. In the present work, agas deposition technique was employed to prepare thin films composed of ytterbium(Z = 70) nanoparticles on a glass substrate. The influence of deposition conditionssuch as deposition temperature, time and gas pressure was studied indetail. In addition to an ordinary inert gas such as He, the possible use ofN2 was investigated. As a result of combined analysis using atomic force microscopy(AFM) and x-ray reflectivity, it was found that spherical nanoparticles ofaround 1–140 nm in diameter can be obtained upon deposition in both He andN2 atmospheres. The thin film is not amorphous but fcc crystals of metallicytterbium with a small amount of hcp phase are mainly formed. Whenexposed to air, the top surface is covered by an oxide layer due to naturaloxidation. The thickness and density were in the range of 5–30 nm and 4–9 g cm − 3, respectively, depending on the deposition conditions. As onlysmall amounts of nitrides were formed during deposition in anN2 atmosphere in many cases, it was concluded that the use ofN2 can be a feasible alternative to the ordinary gas deposition method with an inert gas. Finally, someself-organized hexagonally shaped structures, which are more frequently observed upon depositionin N2, are reported.