SiGeSn nanocrystals with charge storage properties at nanoscale – SIGESNANOMEM

Project Director: Dr. Ana Maria Lepadatu

For project webpage in Romanian click here

Project ID: 19 from 1/05/2018 (PN-III-P1-1.1-TE-2016-2366)

Project Director: Dr. Ana-Maria Lepadatu

Project Type: National

Project Program: TE

Funded by: Romanian National Authority for Scientific Research, UEFISCDI

Contractor: National Institute of Materials Physics


Project Status: In progress

Start Date: Wednesday, May 1, 2019

End Date: Friday, April 30, 2021


SIGESNANOMEM Project Abstract: 

The project aims to obtain nanostructured materials based on SiGeSn nanocrystals (NCs) embedded in oxide matrix with charge storage properties for non-volatile memory applications. The material is completely new, beyond the state of the art as no reports on SiGeSn NCs in oxides are to be found in literature. The project goal will be achieved by 5 specific objectives: O1) obtaining trilayer capacitors with the floating gate of SiGeSn NCs embedded in oxide matrix (SiO2, HfO2) by magnetron sputtering deposition and nanostructuring by thermal annealing; O2) morphology and structure characterisation of NCs-based trilayers for optimizing technological parameters; O3) investigation of electrical and charge storage properties and their correlation with structure and morphology; O4) evaluation of memory parameters of SiGeSn NCs based capacitors in function of NCs morphology and composition; O5) dissemination of project results. For this, the trilayer approach will be used aiming to obtain memory capacitor-like structures with floating gate based on SiGeSn NCs playing the role of charge storage nodes, the NCs having optimal size and density, being properly positioned in respect to Si substrate at tunnelable distance as well as being well separated to each other. More than that, the SiGeSn NCs spatial distribution in the floating gate will be optimized for obtaining a 2D array. The memory properties (memory window and retention) will be controlled by varying the NCs composition and size, by obtaining tunnel oxide with high material quality and proper thickness. The good and complementary expertise of team members ensures the implantation of project in a thematic beyond the state of the art. The original scientific results will be published in 5 papers in high impact ISI-ranked journals and presented at prestigious international conferences.


Project Objectives: 

Obtaining nanostructured materials based on SiGeSn NCs with charge storage properties by convenient modification of the morphology of trilayer structures and NCs composition. The obtaining of a floating gate with SiGeSn NCs arranged in a 2D array is targeted.

Dr. A.M. Lepadatu - Project Director

Dr. I. Stavarache

Dr. V.A. Maraloiu

Dr. A. Slav

Dr. C. Palade

Stage I Results

In Stage I / 2019 we prepared trilayer memory capacitors of gate HfO2 / SiGeSn NCs - HfO2 floating gate / tunnel HfO2 / p-Si substrate in which the floating gate is formed of SiGeSn nanocrystals (NCs) acting as charge storage nodes, embedded in HfO2. The capacitors were prepared by magnetron sputtering and subsequently annealed by rapid thermal annealing for nanostructuring. Preliminary studies were carried out with the aim to optimize the technological conditions for obtaining structures with good memory properties.

Two types of structures were tested, i.e. M1 structures in which trilayers of gate HfO2 / SiGeSn / tunnel HfO2 were deposited on p-Si wafers and M2 structures with deposited trilayer configuration of gate HfO2 / SiGeSn-HfO2 / tunnel HfO2 on p-Si.

The formation of SiGeSn NCs in the floating gate was evidenced by X-ray diffraction (M1 structures). The capacitance-voltage characteristics measured on all structures (both M1 and M2 types) present counter-clockwise hysteresis loop with frequency-independent memory window demonstrating that the charge storage takes place only in SiGeSn NCs. The best memory characteristics were achieved on M2 structures, i.e. large memory window of 3.9 V.

In this stage, one article was published in Nanotechnology and 4 papers were presented at international conferences (ICASS – Italy, EMRS – France, IBWAP & EuroNanoForum – Romania). The project web page was created and updated.

ISI-quoted papers

  • C. Palade, A. Slav, A.M. Lepadatu, I. Stavarache, I. Dascalescu, V.A. Maraloiu, C.C. Negrila, C. Logofatu, T. Stoica, V. Teodorescu, M.L. Ciurea, S. Lazanu, “Orthorhombic HfO2 with embedded Ge nanoparticles in nonvolatile memories used for the detection of ionizing radiation”, Nanotechnology 30, 365604 (2019)

Papers at international conferences

  • „Advances in Ge nanocrystals-based structures for SWIR sensors and non-volatile memories”, C. Palade, A. Slav, A.M. Lepadatu, I. Stavarache, I. Dascalescu, O. Cojocaru, I. Lalau, S. Lazanu, C. Logofatu, T. Stoica, V.S. Teodorescu, M.L. Ciurea, IBWAP 2019, July 16-19, 2019, Constanta (invited presentation)
  • „Germanium nanocrystals in oxide matrix for non-volatile memories and ionizing irradiation sensors”, M.L. Ciurea, I. Stavarache, A. Slav, C. Palade, A.-M. Lepadatu, I. Dascalescu, I. Lalau, O. Cojocaru, V.S. Teodorescu, A.V. Maraloiu, S. Lazanu, T. Stoica, 3rd International Conference on Applied Surface Science (ICASS 2019), June 17-20, 2019, Pisa, Italy (poster)
  • „New advanced materials based on SiGeSn nanocrystals in oxides for SWIR phototodetectors and non-volatile memory devices”, C. Palade, I. Stavarache, A.M. Lepadatu, A. Slav, S. Lazanu, T. Stoica, V.S. Teodorescu, M.L. Ciurea, F. Comanescu, A. Dinescu, R. Muller, G. Stan, A. Enuica, M.T. Sultan, A. Manolescu, H.G. Svavarsson, EuroNanoForum 2019 (Nanotechnology and Advanced Materials Progress Under Horizon2020 and Beyond), June 12-14, 2019, Bucharest (poster)
  • „GeSnSiO2 layers with embedded GeSn nanocrystals for sensing in SWIR”, A. Slav, C. Palade, C. Logofatu, I. Dascalescu, A.M. Lepadatu, I. Stavarache, S. Iftimie, V. Braic, S. Antohe, S. Lazanu, V.S. Teodorescu, D. Buca, M.L. Ciurea, T. Stoica, M. Braic, EMRS 2019, May 27-31, 2019, Nice, France (oral presentation)


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