Electron Spin Resonance


     ESR continues to play an essential role in top scientific fields such as: the physical phenomena in nanometric particles; characterization of bulk and nanostructured semiconductor and dielectric materials with applications in nanoelectronics and nanophotonics, including quantum computing; characterization of materials for radiation detection and conversion; production of new catalysts; biomolecules and biomaterials investigation; creation of new medicines; understanding of living organisms functioning etc.


Investigation possibilities:


     Various multifrequency and multiresonance ESR experiments in the temperature range of 3.8 K < T < 500 K :


  • Continuous wave (cw) ESR experiments in the X (9 GHz) and Q (34 GHz) microwave frequency bands.
  • Fourier Transform and electron spin relaxation time measurements by Electron Spin Echo (ESE) and Free Induction Decay (FID) techniques.
  • ESEEM and 2D-HYSCORE measurements.
  • SECSY and EXSY measurements of the correlations and exchange rates.
  • Pulse ENDOR (Electron Nuclear DOuble Resonance) experiments to measure the hyperfine interaction between nuclear spins and paramagnetic electrons.
  • Pulse ELDOR (Electron Double Resonance) and DEER experiments to measure long range distances by electron-electron spin dipolar coupling.

     The ESR lab was upgraded recently with two new cw ESR spectrometers in the frame of the project PNII/65/CPI/2007: "Modernization and development of advanced ESR techniques in NIMP", Project Director: Dr. S. V. Nistor, and a FT-EPR spectrometer in the frame of the POS-CCE Project No. 141/2009: "Euro-Regional Centrum for Advanced Materials, Surfaces and Interfaces Studies". See more on CetRESav website.

ESR X Band Spectrometer

CW X-band ESR spectrometer model EMX-plus from Bruker
(upgraded Varian E12)

Operating parameters :


· Frequency range : 9.2 – 9.9 GHz;

· Temperature : 3.8 K < T < 500 K;

· Magnetic field : 0.03 T < B;

· Sensitivity : 2.5 x 109 spins/Gauss;

ESR Q band spectrometer

CW Q-band ESR spectrometer model ELEXSYS E500Q from Bruker with E560 ENDOR accessory

Operating parameters :


· Frequency : 34 GHz;

· Temperature : 3.8 K < T < 300 K;

· Magnetic field : 0.03 T < B < 1.8 T

· Sensitivity : 109 spins/Gauss;

· Effective RF range: 1- 250 MHz;


Available CW ESR experiments :


· Q-band ESR.

· Electron-Nuclear Double Resonance (ENDOR).

· ENDOR induced ESR (EIE).

· TRIPLE resonance.

ESR Pulse spectrometer

Pulse/CW X-band ESR spectrometer model ELEXSYS E580 from Bruker with E560 DICE II pulse ENDOR and E580-400 pulse ELDOR accessories

Operating parameters :


· Frequency range (cw): 9.2 – 9.9 GHz;

· Central frequency (pulse): 9.7 GHz;

· Temperature: 3.8 K < T < 300 K;

· Magnetic field: 0.03 T < B < 1.45 T;


CW ESR operation :


· Sensitivity : 1.2 x 109 spins/Gauss;

Pulse ESR operation :


· Pulse resolution 1 ns;

· Stripline Pulse Forming Unit with 4 high power pulse channels (+x, -x, +y, -y) with fixed phase;

· Microwave Pulse Former Unit with two additional microwave pulse channels with independent amplitude and phase adjustment;

· 1kW microwave power;


Pulse ESR techniques available :


· FT-ESR

· 2 and 3- pulse Electron Spin Echo Envelope Modulation (ESEEM)

· Hyperfine Sublevel Correlation (HYSCORE)

· Electron-Nuclear Double Resonance (ENDOR)

· Electron Double Resonance (ELDOR) (ELDOR detected NMR, DEER, Saturation Recovery ELDOR)

ESR compact spectrometer

Compact Microwave EPR Spectrometer CMS 8400

Operating parameters :


· Compact : Portable (56 kg), full computer control

· Sensitivity : Micromolar sensitivity

· Operating frequency : 9.1 – 9.6 GHz;

· Microwave cavity : Rectangular TE 102 with Q = 5.000

· Tuning : Automatic, and manual tuning possible

· Field range : 0.01 – 0.7 T

· Temperature range : 77 K and 85 – 473 K

· Samples : Aggregation from liquid to solid

· Accessories : Frequency counter, Temperature Controller, Flow through system, Flat cell, in-situ irrad.

ESR Pulse spectrometer

Jeol JES-ME-3X (X - and K - band)

Operating parameters :


· Frequency : 9.45 GHz and 24 GHz;

· Temperature : 77 K < T < 570 K;

· Magnetic field : 10 mT < B < 1.5 T;

· Sensitivity : 5 x 1011 spins/Gauss;

· In-situ UV irradiation at variable temperature;

· Bi-modal cavity - concentration measurements;

· Heat treatment in controlled atmosphere;


Specord 250 Plus

UV-VIS double beam spectrophotometer, model Specord 250 Plus, Analytik Jena

Technical details :


· Excitation sources: halogen and deuterium lamps;

· Double monochromator with imaging holographic grating for stray light reduction;

· Variable spectral bandwidths: 0.5 nm, 1 nm, 2 nm, 4 nm ;

· Detector: two photodiodes with Peltier cooling;

· Acquisition & control software: WinAspect;


Performances :


· Spectral range: 190-1100 nm;

· UV resolution (toluene-hexane): 2.3;

· Wavelength accuracy: ± 0.1 nm;

· Experiment types: absorbance (A), transmittance (%T), energy (E);


Automatic liquid He plant model Cryomech LHeP18

Automatic liquid He plant model Cryomech LHeP18

Operating parameters :


· Produces 18 l of liquid helium per 24 h;

· Operation without precooling with liquid nitrogen;

NISTOR Vasile Sergiu Senior Researcher I
Ph.D. Supervisor
Personal Page
STEFAN Mariana Senior Researcher II Personal Page
GHICA Daniela Researcher III Personal Page
VLAICU Ioana Dorina Researcher Personal Page
JOITA Alexandra Camelia Assistant Researcher Personal Page
BULAT Stefan Engineer -
ZERNESCU Dan Tehnician I -

Main scientific results (published and/or presented at scientific conferences):
 

  • Synthesis and characterization by structural, ESR and optical spectroscopy techniques of high quality small nanocrystals of pure and Mn2+ doped cubic ZnS with a tight size distribution self-assembled into a mesoporous structure.

  • Determination of accurate spin Hamiltonian parameters for the Mn2+ impurity ions localized at substitutional and surface sites of cubic ZnS quantum dots by multifrequency ESR investigations.

  • Preferential localization of the Mn2+ ions in the core of the cubic ZnS quantum dots at substitutional sites next to an extended planar lattice defect determined from correlated ESR and HRTEM investigations.

  • Observation and characterization by multifrequency ESR of new paramagnetic point defects in nominally pure and doped superhard cubic BN crystals.

 

Participation to international scientific actions

1. Laser treatment of plasma hydrogenated silicon wafers
C. Ghica, L. C. Nistor, M. Stefan, D. Ghica, B. Mironov, M. Dinescu, S. Vizireanu and G. Dinescu
E-MRS 2009 Spring Meeting, Symposium I: “Silicon and Germanium issues for future CMOS devices”, June 8 – 12, 2009, Strasbourg, France (poster)

2. EPR of transition ions in (nano)crystalline materials
S. V. Nistor
Joint IFIN-HH-ICTP-IAEA Workshop on “Trends in Nanoscience: theory, experiment, technology”, August 23-30, 2009, Sibiu, Romania (invited lecture)

3. Localization of Mn2+ impurity ions in cubic ZnS quantum dots
S. V. Nistor, M. Stefan, L. C. Nistor and C. D. Mateescu
Joint IFIN-HH-ICTP-IAEA Workshop on “Trends in Nanoscience: theory, experiment, technology”, August 23-30, 2009, Sibiu, Romania (oral)

4. Laser treatment of plasma hydrogenated silicon wafers
C. Ghica, L. C. Nistor, D. Ghica, M. Stefan, B. Mironov, M.Dinescu, S. Vizireanu and G. Dinescu
Joint IFIN- HH-ICTP-IAEA Workshop on “Trends in Nanoscience: theory, experiment, technology”, August 23-30, 2009, Sibiu, Romania (poster)

5. Study of the ground multiplet of Kramer’s rare earth ions in PbWO4 scintillator by multifrequency EPR spectroscopy
F. F. Popescu, V. Bercu, J. N. Barascu, M. Martinelli, C. A. Massa, L. A. Pardi, M. Stefan, S. V. Nistor, M. Nikl and P. Bohacek 5th International Symposium on Laser, Scintillator and Non Linear Optical Materials (ISLNOM-5), September 3 – 5, 2009, Pisa, Italy (poster)

6. Local structure at Mn2+ ions in small cubic ZnS nanocrystals self-assembled into a mesoporous structure.

S. V. Nistor, D. Ghica, L. C. Nistor, M. Stefan and C. D. Mateescu
3rd International Conference on nanostructures SELf-assembly, NanaoSEA 2010, 28 June - 2 July 2010, Cassis, France (oral)

7. Lattice defect assisted incorporation of Mn2+ ions in cubic II-VI semiconductor quantum dots.
S. V. Nistor, M. Stefan, L. C. Nistor, D. Ghica, C. D. Mateescu and J. N. Barascu
11th Europhysical Conference on defects in Insulating Materials, EURODIM 2010, 12-16 July 2010, Pecs, Hungary (oral)

Laboratory of Atomic Structures and Defects in Advanced Materials