title: Experimental and theoretical rationalization of the growth mechanism of silicon quantum dots in non-stoichiometric SiNx: role of chlorine in plasma enhanced chemical vapour deposition.
abstract: Silicon quantum dots (Si-QDs) embedded in an insulator matrix are important from a technological and application point of view. Thus, being able to synthesize them in situ during the matrix growth process is technologically advantageous. The use of SiH2Cl2as the silicon precursor in the plasma enhanced chemical vapour deposition (PECVD) process allows us to obtain Si-QDs without post-thermal annealing. Foremost in this work, is a theoretical rationalization of the mechanism responsible for Si-QD generation in a film including an analysis of the energy released by the extraction of HCl and the insertion of silylene species into the terminal surface bonds. From the results obtained using density functional theory (DFT), we propose an explanation of the mechanism responsible for the formation of Si-QDs in non-stoichiometric SiNxstarting from chlorinated precursors in a PECVD system. Micrograph images obtained through transmission electron microscopy confirmed the presence of Si-QDs, even in nitrogen-rich (N-rich) samples. The film stoichiometry was controlled by varying the growth parameters, in particular the NH3/SiH2Cl2ratio and hydrogen dilution. Experimental and theoretical results together show that using a PECVD system, along with chlorinated precursors it is possible to obtain Si-QDs at a low substrate temperature without annealing treatment. The optical property studies carried out in the present work highlight the prospects of these thin films for down shifting and as an antireflection coating in silicon solar cells.
authors.affiliation: Departamento de Materiales de Baja Dimensionalidad, Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n, C. U., A. P. 70-360, Coyoacán, C. P. 04510, México, D. F., Mexico.
authors.forename: E
authors.initials: E
authors.lastname: Mon-Pérez
authors.forename: J
authors.initials: J
authors.lastname: Salazar
authors.forename: E
authors.initials: E
authors.lastname: Ramos
authors.forename: J Santoyo
authors.initials: JS
authors.lastname: Salazar
authors.forename: A López
authors.initials: AL
authors.lastname: Suárez
authors.forename: A
authors.initials: A
authors.lastname: Dutt
authors.forename: G
authors.initials: G
authors.lastname: Santana
authors.forename: B Marel
authors.initials: BM
authors.lastname: Monroy