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PD 33 / 05 oct. 2011
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                         Ge NANOCRYSTALS EMBEDDED IN

AMORPHOUS MATRICES WITH PHOTOCONDUCTIVE  PROPERTIES

Project Coordinator: National Institute of Materials Physics

Project Manager: Dr. Ionel Stavarache

Results
Abstract Objective
Activities

Abstract

Few studies in the literature focused on the (photo)electrical properties of nanocrystalline germanium (nc-Ge) based materials, in contrast with the structural and optical ones. The aim is to prepare and to study nanostructured films consisting of nc-Ge immersed in amorphous matrix with good photoconductive properties. To achieve this goal we propose the following objectives: 1 Preparation of films with different concentrations of nc-Ge embedded in amorphous matrices; 2 Study of electrical properties in correlation with the morphology of layers. Experiment and modelling; 3 Study of photoconductive properties in correlation with morphology of layers. Experiment and modelling; 4 Dissemination of research results. The intended original results are: optimal preparation conditions will be determined to obtain films with improved photoconductive properties; dominant electrical transport mechanism will be proposed and percolation parameters will be calculated; transitions between energy levels evidenced in electrical and photransport phenomena will be identified and corresponding quantum confinement energy levels will be found; films with improved photoconductive properties will be obtained. The dissemination will be made by: 3 scientific reports; 5 articles published in ISI-quoted journals; 3 contributions to prestigious international conferences; project Web page. The aim and objectives frame themselves in the Human Resources programme, Postdoctoral research projects subprogram.




Objectives

Preparation of films with different concentrations of nc-Ge embedded in amorphous matrices;

Study of electrical properties in correlation with the morphology of layers. Experiment and modelling;

Study of photoconductive properties in correlation with morphology of layers. Experiment and modelling;

Dissemination of research results.

Activities


2011

 Deposition of amorphous layers by magnetron sputtering.
 Measurements for determining the composition (XRD, XPS, EDX, AES).
 Heat treatments in different atmospheric conditions in order to obtain nanocrystalline Ge in different  oxides matrix.
 Structural characterization (SEM, TEM, HRTEM, SAED)
 Setting-up the web page of the project.



2012

 Planar and sandwich contacts deposition.
 Experimental measurements of electrical transport phenomena (I-V, I-T, C-V characteristics).
 Finding of the dominant mechanisms from electrical measurements.
 Update of Web page.
 Publication of 2 papers in ISI journals and 1 contribution to prestigious international conferences.


2013

 Experimental investigations of phototransport phenomena (If-V, If-T, If-? and characteristics).
 Identification of optical transitions from the spectral dependence of the photocurrent.
 Update of Web page.
 Publication of 3 papers in ISI journals and 2 contributions to prestigious international conferences.
 Synthesis and comparative study of the results obtained from electrical and photoconductive  investigations, correlated with microstructure.

Results

 

ISI Papers

2012

1. „Dense Ge nanocrystal layers embedded in oxide obtained by controlling the diffusioncrystallization process”, A.M. Lepadatu, T. Stoica, I. Stavarache, V. S. Teodorescu, D. Buca, M. L. Ciurea, submitted to Journal of Nanoparticle Research (Manuscript Number: NANO-D-13-00485).

2. „Annealing temperature effect on structure and electrical properties of films formed of Ge nanoparticles in SiO2”, I. Stavarache, A.M. Lepadatu, T. Stoica, M. L. Ciurea, submitted to Applied Surface Science (Manuscript Number: APSUSC-D-13-02208).

 

Conferences

2012

1. „Electrical behaviour of ge nanoparticles network embedded in SiO2 matrix”, Ionel Stavarache, Ana-Maria Lepadatu, Adrian V. Maraloiu, Catalin Palade, Valentin S. Teodorescu, and Magdalena Lidia Ciurea, E-MRS 2012 Spring Meeting, May 14 - 18 , Strasbourg, France 2012.

2. „Electrical properties related to the structure of films with Ge nanoparticles embedded in SiO2 matrix”, Magdalena Lidia Ciurea, Ana-Maria Lepadatu, Ionel Stavarache, Catalin Palade, Valentin S. Teodorescu, (prezentata oral) EMRS 2012 Fall Meeting, 17 – 21 septembrie 2012, Varsovia, Polonia.

3.“Structure and electrical characterization of GeSi nanostructured films”, Ana-Maria Lepadatu, Ionel Stavarache, Adrian Valentin Maraloiu, Catalin Palade, Valentin Serban Teodorescu, Magdalena Lidia Ciurea, EMRS 2012 Fall Meeting, 17 – 21 septembrie 2012, Varsovia, Polonia.

4. “Electrical behaviour related to structure of nanostructured GeSi films annealed at 700 oC”, Ana-Maria Lepadatu, Stavarache Ionel, Adrian Maraloiu, Palade Catalin, Teodorescu Valentin Serban, Ciurea Lidia Magdalena, International Semiconductor Conference, publicata in Proceedings vol.1, p. 109-112, CAS 2012, 15 – 17 octombrie, Sinaia.

5. “Transport mechanisms in SiO2 films with embedded germanium nanoparticles”, Catalin Palade, Ana-Maria Lepadatu, Ionel Stavarache, Adrian V. Maraloiu, Valentin S. Teodorescu, Magdalena Lidia Ciurea, International Semiconductor Conference, publicata in Proceedings vol.1, p. 91-94, CAS 2012, 15 – 17 octombrie, Sinaia.

6. „Electrical and structural properties of nanostructured GeSi films”, A.-M. Lepadatu, I. Stavarache, A. Maraloiu, C. Palade, V. S. Teodorescu, L. M. Ciurea, 3rd International Colloquium “Physics of Materials” (PM–3), 15 – 16 noiembrie 2012, Bucuresti.

7. „Electrical behaviour related to the structure of SiO2 films with embedded Ge nanoparticles”, I. Stavarache, C. Palade, A. M. Lepadatu, A. V. Maraloiu, V. S. Teodorescu, M. L. Ciurea, 3rd International Colloquium “Physics of Materials” (PM–3), 15 – 16 noiembrie 2012, Bucuresti

2013

1. „Influence of annealing on Raman and electrical properties of Ge nanocrystals in amorphous SiO2”, I. Stavarache, A.M. Lepadatu, A. V. Maraloiu, C. Palade, V. S. Teodorescu, and M. L. Ciurea, E-MRS 2013 Spring Meeting, May 27 - 31, Strasbourg, France 2013.

2. „Study of Ge nanocrystals formation in Ge/SiO2 multilayer structures by TEM and Raman spectroscopy”, A.M. Lepadatu, I. Stavarache, V. S. Teodorescu, T. Stoica, M. L. Ciurea,EMRS 2013 Spring Meeting, 27 31, Stasbourg, France 2013.

3. „Raman and electrical properties of Ge-SiO2 films versus annealing temperature”, A.M. Lepadatu, I. Stavarache, T. Stoica and M. L. Ciurea,The 6-th Edition of the Conference on Amorphous and Nanostructured Chalcogenides (ANC-6), Brasov (Romania), June 24-28, 2013.

Updated: 31 ian 2012 - Ionel Stavarache: stavarache@infim.ro