Ge nanocrystals with highly uniform size distribution deposited on alumina at room temperature by pulsed laser deposition: structural, morphological, and charge trapping properties

In this work, we report on the synthesis of Ge nanocrystals (NCs) by pulsed laser deposition (PLD) at room temperature (RT) in an argon atmosphere without any further annealing process. Our results show that functional thin films of crystalline Ge nanoparticles with spherical shapes can be obtained by PLD directly on alumina layers deposited on n-doped Si (100) substrates. In addition, we also demonstrate that a uniform size distribution of NCs with an average diameter of about 3 nm and a density of 2.3x10^11 cm^-2 can be obtained by optimizing a shadow mask set-up, where a solid disk is introduced between the target and the substrate. Charge/discharge effects in Ge NCs deposited on a high-k amorphous alumina layer are also evidenced by conductive atomic force microscopy, which makes them suitable for memory applications.This work has been fully funded through the project PTDC/FIS/70194/2006 financed by the Portuguese Foundation for Science and Technology (FCT), European COST MP0901-NanoTP and COMPETE. SRCP, EMFV, and JMS are grateful for financial support through FCT grants SFRH/BD/29657/2006, SFRH/BD/45410/2008, and SFRH/BPD/64850/2009, respectively. We would like to thank David J. Barber, Augusto Lopes, Ana J. Martins, and Jose Santos for scientific discussion and technical support.European COST MP0901-NanoTPCOMPET