National Institute Of Materials Physics - Romania

Atomic Structures and Defects in Advanced Materials Laboratory

Group of Nanomaterials and Nanostructures based on SiGeSn

Group Leader Dr. Ana-Maria Lepadatu


5 senior researchers (2 rank 1, 2 rank 2, 1 rank 3); 2 post-docs (1 junior researcher, 1 assistant researcher);
1 PhD student

Research Themes
  • frontier research in condensed matter physics at nanoscale and in science of advanced materials of #structures with nanocrystals (NCs) based on SiGeSn and #structures based on ferroelectric HfO2, all structures being deposited by magnetron sputtering and also of #materials and 2D heterojunctions based on transition metal dichalcogenides (2D-TMD):
    • study of optical, electrical, photoelectrical, ferroelectric and charge storage properties
    • strain and defects studies for improving the above mentioned properties
  • advanced materials for industry with global impact (fields of Eco-Nanotechnologies and Advanced Materials, Information and Communication Technology, Security, Energy, New and Emerging Technologies) for micro-, opto- and nanoelectronics applications and sensors for health, security and environment applications:
    • films and multilayered structures with NCs based on SiGeSn embedded in dielectric matrices (HfO2, ZrO2, SiO2, TiO2, Al2O3, Si3N4) photosensitive in SWIR, with ferroelectric and charge storage properties
    • HfO2, ZrO2 based structures with ferroelectric properties
    • 2D-TMD based materials and heterojunctions with electro-optic properties for health and environment applications
  • applied research and experimental development for environment, security, space, health and internet of thing applications using the above mentioned materials (fields of Eco-Nanotechnologies and Advanced Materials, Information and Communication Technology, Security, Energy, New and Emerging Technologies); fabrication of devices – demonstrators up to TRL 5: electronic and photoelectric nonvolatile memories, dosimeters, optical sensors for monitoring the slippery road conditions (wet and icy in respect to dry asphalt), SWIR photodetectors, sensors for food security
  • innovation and patents application activities
  • young people formation – doctoral, Master – in the hot topics of the group

Research Themes

SiGeSn Group research infrastructure consists mainly in: magnetron sputtering equipment (10-8 Torr high vacuum) for deposition of thin films and multilayer structures, equipped with in situ analysis techniques consisting of Auger electron surface spectroscopy – AES and low-energy electron diffraction – LEED, as well as real time in situ ellipsometric monitoring and profilometer for measuring thicknesses; rapid thermal processing (RTP) system for thermal annealing (RTA), oxidation (RTO) and nitration (RTN); three independent temperature zone horizontal split tube furnace for thermal annealing and physical vapor deposition (PVD); two set-ups for electrical (including ferroelectric and charge storage) and photoelectrical measurements; set-up for Hall effect and magnetoresistance measurements.

Magnetron sputtering equipment for deposition of thin films and multilayer structures, equipped with in situ analysis techniques consisting of Auger electron surface spectroscopy – AES and low-energy electron diffraction – LEED, as well as real time in situ ellipsometric monitoring

Rapid thermal processing – RTP system (left);
Three independent temperature zone horizontal split tube furnace (right).

Set-ups for electrical (including ferroelectric & charge storage) and photoelectrical measurements (left); Hall effect and magnetoresistance measurements (right).

Research Themes

1. Deposition of semiconductor thin films and multilayer structures by magnetron sputtering: dielectrics (SiO2, TiO2, ZrO2, HfO2, Al2O3, Si3N4) and semiconductors (Si, Ge, SiGe, SiGeSn) on heated substrates or on substrates mantained at room temperature

2. Rapid thermal annealing (RTA) and controlled oxidations (RTO) in the rapid thermal processing – RTP system (up to 3-inch silicon wafer) at 200 – 1250 oC with ramp rates up to 200 oC/s, in gas flow (N2, O2, Ar si H2) and thermal annealing in the three independent temperature zone horizontal split tube furnace at temperatures up to 1200 °C in vacuum or Ar, N2 flow

3. Electrical characterization in dark and under illumination and Hall investigations by measurements and modelling of experimental curves:

  • current-voltage (IV) at different temperatures T, in DC and AC regime
  • capacitance-voltage (C V), capacitance-frequency (C – f) and capacitance-time (C t)
  • polarization-voltage (P V)
  • IT and RT at different bias voltages
  • Photocurrent spectra (I– λ) under modulated and continuous light regime
  • Hall measurements: VI characteristics for different applied currents, magnetic fields and T

Achievements and Highlights

2020 Achievements of SiGeSn Group

I. GeSn-based structures by magnetron sputtering deposition for short-wave infrared photonics: In 2019, we have reported SWIR detection in optimized GeSn nanocrystals (NCs) embedded in SiO2 by MS deposition and rapid thermal annealing (RTA). SWIR detection was further improved (2020 papers) by two new MS methods of obtaining crystalline GeSn layers: i) GeSn NCs obtained by annealing of GeSn/SiO2 multilayer films; ii) GeSn obtained by sputtering epitaxy and its heterostructure with embedded GeSn NCs.

Publications:ACS Appl. Mater. Interfaces 12, 33879 (2020), ACS Appl. Mater. Interfaces 12, 56161 (2020)

Projects: M-Era.NET GESNAPHOTO/2016, PCE 122/2017, PD 39/2018

II. SiGe nanocrystals-based photosensors with high sensitivity from visible to short-wave infrared for detection of slippery road conditions: High photoresponsivities of 5.23 and 9.35 A/W at room temperature (RT) and 100 K, respectively were obtained, the wavelength cutoffs being extended in SWIR to ~1345 nm (RT) and ~1630 nm (100 K). Based on these findings we developed a sensor application for slippery road conditions, in the frame of M-Era.Net project PhotoNanoP that was awarded “Success Story”.

Publications:Sensors 20, 6395 (2020), Sci. Rep. 10, 3252 (2020)

Projects: TE 30/2018, M-Era.NET PhotoNanoP/2016, PCE 122/2017

III. SiGe-TiO2 films and multilayers based on SiGe nanocrystals in TiO2 with extended SWIR photosensitivity: SiGe NCs stabilization against fast Ge diffusion was achieved by the formation of SiO2 thinlayers with protective role against Ge diffusion through Si oxidation at the SiGe NCs surface in single films and at SiGe/TiO2 interface in multilayers. This enabled the obtaining of SWIR sensitivity up to 1.7 μm for films and 1.6 μm for multilayers in spectral photocurrent due to photocarrier generation in Ge-rich SiGe NCs.

Publications:J. Phys. Chem. C 124, 25043 (2020), Appl. Surf. Sci. 511, 145552 (2020)

Projects: PCE 122/2017, TE 30/2018, M-Era.NET PhotoNanoP/2016, PD 39/2018

Patent application: RO134049-A0 / Publ. Date 30 Apr 2020

New projects wined by competition: coordination of national projects Experimental-DemonstrationPED 280/2020 and PED 531/2020, Postdoctoral PD 11/2020

Young people formation: I. Dascalescu, PhD Thesis, defended 2020 (PhD adviser Dr. M.L. Ciurea)

2015-2019 Achievements of SiGeSn Group

The most important contributions of the SiGeSn group in the field are:

I. Trilayer structures based on SiGeSn NCs embedded in oxides (HfO2, SiO2, Al2O3) with high density of NCs, for nonvolatile memories with long retention times (10 years)

– long retention times in nonvolatile memory structures with floating gate formed of hexagonal Ge QDs with high density, that are positioned in a single layer and well separated by orthorombic/tetragonal HfO2 NCs

-nonvolatile memories with enhanced performance (6 V memory window) due to the cumulative contribution of Ge NPs charge storage centeres and ferroelectric HfO2 matrix

-dosimeter with high sensitivity (0.8 mV/Gy) to α particle irradiation at low doses (< 50 Gy), based on the mentioned nonvolatile memories

-photoelectric nonvolatile memories with photo-induced charging up to 1.6 electrons/NC and photosensitivity up to 110 mV/Mj

-determination of material parameters (dielectric constant and resistivity of each layer) in trilayer nonvolatile memory structure by simulation of the frequency dispersion of capacitance and resistance measured in accumulation regime

Publications: Nanotechnology 30, 445501 (2019), Appl. Surf. Sci. 428, 698 (2018), Appl. Phys. Lett. 113, 213106 (2018), Nanotechnology 28, 175707 (2017), P. Romanian Acad. A 17, 322 (2016), Phys. Status Solidi (a) 213, 255 (2016), Scripta Mater. 113, 135 (2016)

Projects: PCCF 7/2018, TE 19/2018, PED 203/2017, PED 42/2017, PED 89/2017, Parteneriate 9/2012

II. VIS-SWIR photosensitive films and multilayered structures with SiGeSn-based NCs embedded in dielectric matrices, deposited by magnetron sputtering

– photodetectors with Ge NCs in SiO2 with high responsivity (2.42 AW−1) and quantum efficiency, obtained by deposition on heated substrates (445%)

– Ge NCs in TiO2 / SiO2 / Si structures with exponentially increased photosensitivity by electrostatic doping

– determination of spectral optical constants (refractive index, extinction coefficient) of Ge NCs in TiO2 films by simulation of optical transmittance and reflectance spectra; evidencing the blue shift of the bandgap by selective nanocrystallization

– evidencing the dark conduction mechanism of Efros-Shklovskii Coulomb-gap variable range hopping in Ge NCs-TiO2 films

– increasing of photosensitivity of photodiodes based on SiO2/SiGe/SiO2/Si multilayers by hydrogen plasma annealing (in collaboration with Reykjavik University, School of Science and Engineering, Iceland in the frame of M-Era.NET PhotoNanoP project)

– elucidating the processes of GeSn NCs formation in SiO2 – modelling

– fabrication of photodiodes with GeSn NCs in SiO2 having spectral response in VIS-SWIR up to 2.5 μm

– high emission efficiency and detection in SWIR of LEDs with GeSn/SiGeSn multiple quantum wells (CVD depositions by partner Forschungszentrum Jülich, PGI-9, Germany in the frame of M-Era.NET GESNAPHOTO project)

Publications:Sci. Rep. 9, 10286 (2019), Nanotechnology 30, 365604 (2019), ACS Appl. Nano Mater. 2, 3626 (2019), Appl. Surf. Sci. 469, 870 (2019), Appl. Surf. Sci. 479, 403 (2019), Beilstein J. Nanotech. 10, 1873 (2019), Rom. Rep. Phys. 71, 504 (2019), Sci. Rep. 8, 4898 (2018), Optica 4, 185 (2017), Semicond Sci Technol 32, 105003 (2017), Optics Express 24, 1358 (2016), Beilstein J. Nanotech. 7, 1492 (2016), Dig. J. Nanomater. Bios. 10, 59 (2015)

Projects: PCE 122/2017, TE 30/2018, M-Era.NET PhotoNanoP/2016, M-Era.NET GESNAPHOTO/2016, PD 39/2018, Parteneriate 9/2012

Fabrication of demonstrators and services:

– optical sensors able to discriminate between different road slippery conditions (M-Era.NET PhotoNanoP) –TRL 5

– SWIR photodetectors (M-Era.NET GESNAPHOTO) –TRL 5

– electronic and photoelectric nonvolatile memories –TRL 3

– dosimeters – TRL3

– services: economic contract no. 1713/200/September 9, 2017 –XRD measurements on thin films for National Institute for Laser, Plasma & Radiation Physics (INFLPR)


– Coordination of national and international projects: PCE 122/2017, TE 30/2018, TE 19/2018, PD 39/2018, PED 203/2017, PED 42/2017, PED 89/2017, M-Era.NET PhotoNanoP/2016, M-Era.NET GESNAPHOTO/2016, Parteneriate 9/2012, NIMP group coordinator partner in PCCF 7/2018

– Participation in: PCCDI 47/2018, PCCDI 75/2018, EEA-RO-NO-2018-0438 /2018, PFE 12/2018, COST Action MP 1402/2014

National and international collaborations with:#National Institute for Research and Development in Microtechnologies – IMT Bucharest; #Transilvania University of Brasov; #National Institute for Laser, Plasma and Radiation Physics (INFLPR); #National Institute for Optoelectronics – INOE 2000; #Faculty of Physics, University of Bucharest; #Optoelectronica 2001 SA; #InterNET S.R.L.;#Reykjavik University, School of Science and Engineering, Iceland; #Pi Technology, Iceland; #Forschungszentrum Jülich, Peter Grünberg Institute (PGI-9), Germany; #nanoplus Nanosystems and Technologies GmbH, Germany; #Department of Physics and Astronomy, University of Catania, CNR-IMM, Catania, Italy; #Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Frascati, Frascati, Italy

Publications for 2015-2019:

– 37 Papers published in ISI quoted journals: Sci Rep. (2), Nanotechnology (3), ACS Appl. Nano. Mater. (1), ACS Photonics (1), ACS Appl. Mater & Interf. (1), Nano Res. (1), Chem. Mater. (1), Optics Express (1), Optica (1), Scripta Mater. (1), Appl. Phys. Lett. (1), Appl. Surf. Sci. (6), Beilstein J. Nanotech. (5), Semicond. Sci. Techn. (1), Phys. Status Sol. A (1), Rom. Rep. Phys. (3), Dig. J. Nanomater. Bios. (4), Astropart. Phys. (1), J. Appl. Polym. Sci. (1), J. Phys. Chem. Sol. (1)

– 1 invited book chapter “Electrical characterization techniques for porous silicon in Handbook of Porous Silicon, 2nd edition, Ed. L. Canham, Springer International Publishing AG, Cham (2018) – invited by Prof. L. Canham

– 6 papers in ISI-indexed IEEE proceedings

Communications to international conferences / colloquia / workshops / summer schools: ICASS 2019 Pisa, EuroNanoForum 2019 Bucharest, EMRS Spring 2019 Nice, EXMATEC 2018 Bucharest, ISTDM/ICSI 2018 Postdam, CAS 2018 Sinaia, ANNIC 2017 Rome, ROCAM 2017 Bucharest, E-MRS Spring 2016 Lille, ROCAM 2015 Bucharest etc.

– 10 invited lectures

– > 25 presentations (oral and poster): 22 communications by young people

Patents and patent applications:

– 2 OSIM patents: RO131968-B1 (BOPI Publ. date May 30, 2018), RO131074-B1 (Apr 27, 2018)

– 5 OSIM patent applications: RO133299-A0 (Apr 30, 2019), RO133300-A0 (Apr 30, 2019), RO133227-A0 (Mar 29, 2019), RO132946-A0 (Nov 29, 2018), RO132066-A0 (Jul 28, 2017)

Young people formation – doctoral activities:

– C. Palade, PhD Thesis, defended 2016 (PhD adviser Dr. M.L. Ciurea)

– I. Dascalescu, PhD Student since 2016 (PhD adviser Dr. M.L. Ciurea)

– O. Cojocaru, PhD Student since 2019 (PhD adviser Dr. M.L. Ciurea)

Achievements and Highlights


– “Success Story” distinction for M-Era.NET PhotoNanoP (

– 4 Best Paper Awards atIEEE International Semiconductor Conference CAS 2018, 2017 and 2016 editions

– Diploma of Excellence and Gold Medal – ProInvent 2017

– Diploma of Excellence – EuroInvent 2019

– Diploma of Excellence and ProInvent Medal – ProInvent 2019

– Diploma of Excellence and Silver Medal – ProInvent 2021

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