Materials and Microsystem Center

Trento, Italy

Materials and Microsystem Center

Trento, Italy
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Skarlatos D.,University of Patras | Bersani M.,Materials and Microsystem Center | Barozzi M.,Materials and Microsystem Center | Giubertoni D.,Materials and Microsystem Center | And 2 more authors.
ECS Journal of Solid State Science and Technology | Year: 2012

In the present work nitrogen (N2+) has been implanted in crystalline germanium at a constant dose and its diffusion has been studied as a function of implantation energy, annealing temperature and various capping layers deposited on substrate surface. Nitrogen diffusion in germanium appears to be, as in the case of silicon, anomalous toward the capping layer/germanium interface not obeying the second Fick's law. In addition, it appears independent on the capping layer composition. As the implantation energy increases, characteristic nitrogen pileups appear in the region beyond the former amorphous/crystalline interface, attributed to the formation of nitrogen-Ge point defects (in particular interstitials) clusters. There is an evidence that N diffusion in Ge is related to the presence of Ge interstitials gradients maintained during post-implantation annealing between the capping layer/Ge interface and the region beyond the former amorphous/crystalline interface of the substrate. This unique diffusion behavior of N could find applications in Ge based MOS (Metal-Oxide-Semiconductor) technology as proposed in the body of the present article. © 2012 The Electrochemical Society.


Skarlatos D.,University of Patras | Barozzi M.,Materials and Microsystem Center | Bersani M.,Materials and Microsystem Center | Vouroutzis N.Z.,Aristotle University of Thessaloniki | Ioannou-Sougleridis V.,Institute of Microelectronics, Greece
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2013

In the present work diffusion of implanted nitrogen in germanium is studied as a function of implantation energy and post-implantation annealing temperature. Implantations have been performed at a constant dose and energies leading to the amorphization of the substrate. Nitrogen diffusion in Ge is anomalous (not obeying the 2nd Fick's law) towards the substrate surface on which an Al2O3 layer has been deposited before annealing for protection. There is evidence that N diffusion in Ge is interstitial-assisted and takes place in the presence of Ge interstitials gradients between the Al2O3/Ge and the former amorphous/crystalline (a/c) interface of the substrate during annealing. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Vanzetti L.,Materials and Microsystem Center | Pucker G.,Materials and Microsystem Center | Milita S.,CNR Institute for Microelectronics and Microsystems | Barozzi M.,Materials and Microsystem Center | And 2 more authors.
Surface and Interface Analysis | Year: 2010

Nanocrystalline silicon embedded in dielectric matrices is currently studied for Si-photonics, memory devices and solar cells. A common method for the preparation of silicon nanocrystals embedded in oxides is the phase separation of silicon rich oxide (SRO) in SiO2 and Si via thermal annealing. Phase separation, nucleation and crystallization of SRO are known to depend on the thickness of the SRO layer. Here we investigate the structural changes in a sample consisting of alternated nanometer-thick SRO and SiO 2 layers - a so-called superlattice (SL) - during thermal annealing. Under a thermal treatment the material undergoes a series of modifications due to sintering, phase separation, crystallization and layer mixing. In this work we investigate these transformations in an SL grown by plasma enhanced chemical vapor deposition (PECVD) with several analytical techniques: XPS, variable angle ellipsometric spectroscopy (VASE), SIMS, and X-ray reflectivity (XRR). Both SIMS and XRR measurements clearly reveal the periodicity of the samples. XPS analysis reveals that phase separation of SRO in silicon and SiO2 occurs in the annealing temperature range 600-925°C.The process is accompanied by reduction in overall thickness of the samples (ongoing also at higher temperatures) as evidenced from the ellipsometric spectra. A maximum form birefringence is achieved at 925°C and stays nearly constant until 1100°C. Eventually, the form birefringence decreases at the highest annealing temperature of 1150°C, which according to SIMS measurements is caused by a partial oxidation of silicon in the outermost SRO layer. Copyright © 2010 John Wiley & Sons, Ltd.


Barozzi M.,Materials and Microsystem Center | Gennaro S.,Materials and Microsystem Center | Bersani M.,Materials and Microsystem Center | Vanzetti L.,Materials and Microsystem Center | And 4 more authors.
Surface and Interface Analysis | Year: 2013

Multilayers (MLs) consisting of alternating nanometer-thick silicon-rich oxide (SRO) and SiO2 layers are attractive structures to produce Si nanocrystals embedded in SiO2 matrix, with controlled size and distribution. The resulting materials are of great interest for applications in silicon light emitting diodes, memory devices and solar cells. The electro-optical properties depend strongly on the phase separation process and crystallization of the silicon nanocrystals. In addition to furnace annealing (FA), rapid thermal annealing (RTA) can be used to induce the phase separation process. RTA reduces the thermal budget considerably with respect to FA. Here, we present a study on SiO2/SRO MLs annealed either with RTA or FA. Dynamic SIMS depth profiles were acquired to analyze how the excess silicon distribution is influenced by the annealing and to confirm that the ML structure is maintained during the annealing process. In addition, we used photoelectron spectroscopy (XPS) to analyze the composition of the films and to monitor the phase separation process. The SIMS profiles indicate that the layered structure is stable at all temperatures for both FA and RTA annealing. During annealing the concentration of excess Si increases at the centre of the SRO-rich layer due to formation of Si-rich dots. Also, the XPS measurements indicate that 10 s of annealing at 1000 or 1100 °C induces substantial phase separation. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.

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