Physical vapor deposition synthesis of amorphous silicate layers and nanostructures as cosmic dust analogs

¹ Department of Physic and AstronomyUniversity of Firenze, Largo Enrico Fermi 2, 50125 Firenze, Italy
e-mail: pace@arcetri.astro.it
² Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing, PR China
³ NSRL, University of Science and Technology of China, Hefei, 230029 Anhui, PR China
⁴ INFN, Laboratori Nazionali di Frascati, 00044 Frascati, Roma, Italy
e-mail: marcelli@lnf.infn.it
⁵ RICMASS, Rome International Center for Materials Science Superstripes, 00185 Rome, Italy
⁶ Dipartimento di Scienze, Università Roma Tre, Largo S. Leonardo Murialdo 1, 00146 Roma, Italy

Received: 20 August 2015
Accepted: 14 February 2016

Abstract

Cosmic dust grains (CD) are part of the evolution of stars and planetary systems and pervade the interstellar medium. Thus, their spectral signature may be used to deduce the physical features of the observed astronomical objects or to study many physical and chemical processes in the interstellar medium. However, CD samples are available only from sample-and-return space missions. Thus, they are rare and not sufficient to be used to perform laboratory experiments of astrophysical interest, such as to produce reference spectra. In this contribution, we describe a new physical vapor deposition (PVD) technique that allows the production of amorphous samples with controlled chemical and morphological characteristics. In particular, this technique was developed to grow uniform or microstructured layers of Mg-Fe amorphous silicates (olivine or pyroxene) that are materials of wide interest for laboratory experiments. We discuss the first results that were achieved by applying this new synthesis method. The layers were studied by combining infrared spectroscopy, scanning electron microscopy, and X-ray spectroscopy. The X-ray microscopy was used for the first time to characterize the internal structure of the grains in these synthetic samples. Finally, future improvements of the technique and foreseen applications are discussed.