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Investigation Group of the Microwave Interactions with the Condensed Matter

Current Research Focus
Group Staff
Recent Investigations
Retrospective Research Activities
Contact Information

The group's interests focus on understanding the physical processes of the interaction of the microwave with the insulators, semiconductors, semimetals and superconductors. Our goal is to obtain new regularities in these interactions and to explain them on the base of the physical theories. Other goal is to create new techniques for the investigation of the condensed matter with the use of the microwave influence on it.

• Electron Spin Resonance in the semiconductors in the insulator and metallic state:
  ESR spectra transformation in the vicinity of the insulator - metal phase transition of the semiconductors. Influence of the doping and technology on the ESR spectra of the carbon structures
• Non-resonance magnetosensitive microwave absorption in the semiconductors and superconductors
  Magnetoresistivity of the compensated semiconductor on microwave frequencies within the phase transition insulator - metal region and in the insulator state. Magnetic field dependent microwave absorption in the superconductors

1. Electron Spin Resonance in the semiconductors in the insulator and metallic state

   The peculiarities of the electron spin resonance were investigated in the n-Ge:As in the concentration range near the insulator - metal phase transition. It was shown that the new antiferromagnetic phase of the spin glass type was formed in this range. Early this phenomenon was investigated in the 4H-SiC:N. This effect in the both semiconductors resulted to the decrease of the paramagnetic phase and the resonance line of the shallow impurities decreases near the critical concentration. For n-Ge:As , it was found that the g-factor decrease took place in this concentration range with the dope level and the g-factor anisotropy appeared near the transition. Influence of the compensation and appeared antiferromagnetic ordering on the g-factor value was analyzed. It was found that the high temperature boundary of the ESR roughly grew near the transition point. [1 - 4].

   The influence of the spin interaction on the width and form of the ESR line was investigated in the compensated and noncompensated n-Ge:As. The resonance line width was decreased with the approach to the critical concentration for the phase transition from the insulator consistence to the metallic one. This was the result of the spin exchange interaction and the increase of the spin relaxation time. The narrowest line was observed along the [100] axes. The adding widening was appeared when the magnetic field was directed along the other axes. This widening was resulted of the inner electrostatic fields on g-factor through the stresses called by these fields. For the samples with the good conductivity what had the skin layer thinner then the sample thickness, the resonance line acquired the nonsymmetrical (Dyson) form. The characteristic for such form line wings ratio was determined by the ratio of the spin diffusion and spin relaxation velocities.[5]

   Electron spin resonance (ESR) was investigated on the phosphorus atoms in the alloys Si_1-xGe_x (0 < x < 0.057) under the temperatures 3 ÷ 30 K and the phosphorus concentrations 10¹⁵- 10¹⁶cm^-3. ESR spectra were considered with the same spectra in the pure Si:P. It was found that ESR spectra in the alloys contained two additional lines. We supposed that these lines were connected with the phosphorus impurities in the clusters with the increased Ge concentration. The cluster concentration was increased when Ge density was grown up to x = 0.024 but the Ge concentration inside the clusters remained the constant. Under the x > 0.024, this density was increased as inside as outside the clusters [6].

   The effect of an elastic spontaneous distortion of the crystal lattice of a doped semiconductor Ge:As was observed near the insulator-metal (IM) phase transition. This effect was explained on the base of the Peierls model as the result of the exchange interaction of spins in the singlet state, localized at As atoms [7, 8]. More deep investigation showed that only small part of this effect could be explain by this model. The main contribution in it was inserted by the glue what was used for the attachment the sample to the holder (unpublished).

   References

   1. A.I.Veinger, A.G.Zabrodskii, T.V.Tisnek, S.I.Goloshchapov. Electron Spin Resonance of Interacting Spins in n-Ge. 1. The Spectrum and g-Factor. Semicond. V.41, No.7, pp.790 - 798, (2007).
   2. A.I.Veinger, A.G.Zabrodskii, T.V.Tisnek, , S.I.Goloshchapov. Antiferromagnetic spin glass in doped Ge near insulator-metal transition. Appllied magnetic resonance. V.35, 3, pp 439 - 448, (2009).
   3. A.I.Veinger, A.G.Zabrodskii, T.V.Tisnek, S.I.Goloshchapov, E.N.Mokhov. Antiferromagnetic phase in doped semiconductors near the insulator-metal phase transition. Phys. Stat. Sol. V.3 (c), 2, pp 347 - 351 (2006).
   4. A.I.Veinger, A.G.Zabrodskii, T.V.Tisnek, S.I.Goloshchapov, E.N.Mokhov. Formation of an antiferromagnetic phase in highly doped 4H-SiC. Diamond and Related Materials. V.14, 3 - 7, pp 1131 - 1133 (2005).
   5. A.I.Veinger, A.G.Zabrodskii, T.V.Tisnek, S.I.Goloshchapov. Electron Spin Resonance of Interacting Spins in n-Ge:II. Change in the Width and Shape of Lines. Semicond. V.42, No.11, pp.1274 - 1281, (2008).
   6. A.I.Veinger, A.G.Zabrodskii, T.V.Tisnek, S.I.Goloshchapov and N.V. Abrosimov. Ge atoms clustering effect manifestation in the electron spin resonance of Si1-xGex alloys (0 < x < 0.057). Semicond. V.41, No.6, pp.662 - 672, (2007)
   7. A.I.Veinger, A.G.Zabrodskii, T.V.Tisnek, S.I.Goloshchapov. Spin Peierls transition in the random impurity sublattice of a semiconductor. Semicond. V.44, 6, pp705 - 711 (2010).
   8. A.I.Veinger, A.G.Zabrodskii, T.V.Tisnek, S.I.Goloshchapov. Lattica distortion (Peierls transition) caused by spin interaction in the chaotic impurity system of a semiconductor. Annalen der Physik, v.18, 12, pp 923 -927, (2009).

2. Non-resonance magnetosensitive microwave absorption in the lightly doped semiconductors

   The first observation of low-temperature magnetoresistance (MR) of interference nature in the case of a light doping is reported. The MR occurs in n- and p-type Ge samples at a frequency of 10 GHz at temperatures below 30 K in weak magnetic fields on the background of the classical MR effect associated with electrons in different valleys (n-Ge) and with heavy and light holes (p-Ge) [1].

   Magnetoresistivity (MR) of the lightly doped alloy p-Ge_1-xSi_x (x = 1-2 at. %) has been compared with the lightly doped p-Ge at the 10 GHz by the electron spin resonance technique use in the 10-120 K temperature range. It was established that the Si inhomogeneities (clusters) existence in the Ge lattice suppressed the interference part of the anomalous MR and went to the effect averaging from the light and heavy holes. This MR change evidences about the sharp decrease of the inelastic relaxation time under the transition from Ge to it solid solution.

   The microwave low temperature magnetoresistivity of the low doped (nondegenerated) p-Ge was investigated with the use of the electron spin resonance technique. This technique permits to detect the derivative of the microwave absorption with respect to magnetic field and its change with this field. In our case, this change is proportional to the magnetoconductivity of the sample under investigation. Because of the averaging time of the effective masses of the light and heavy holes is much more then microwave frequency (10 GHz), this method permits to investigate the reaction of the each kind of the holes on the magnetic field separately. It is show that the microwave magnetoconductivity connected with the light holes weakly depends from magnetic field direction angle with the crystal axes but the absorption connected with the heavy holes strongly depends from this angle. The experimental results are compared with the theory of the classical magnetoresistivity effect [3].

   References

   1. A.I.Veinger, A.G.Zabrodskii, T.V.Tisnek, S.I.Goloshchapov. Low-temperature magnetoresistance due to localization in lightly doped semiconductors. Solid St. Comm. V.133/7, pp.455-458, (2005) .
   2. A.I.Veinger, A.G.Zabrodskii, T.V.Tisnek. Low-temperature microwave magnetoresistance of lightly doped p-Ge and p-Ge_1-xSi_x. Semicond., v.39, 10, 1117 - 1121, (2005).
   3. A.I.Veinger, A.G.Zabrodskii, T.V.Tisnek, S.I.Goloshchapov. Peculiarities of the microwave low temperature magnetoresistivity of the low doped p-Ge due to light and heavy holes. Semicond. To be published

   Retrospective Research Activities

   
   

   Contact Information

   Tel.: +7 (812) 292 7152
   E-mail: anatoly.veinger@mail.ioffe.ru
   Contact person: Anatoly Veinger
   
   Investigation Group of the Microwave Interactions with the Condensed Matter
   Laboratory of Nonequilibrium Processes in Semiconductors
   Ioffe Physico-Technical Institute, Russian Academy of Sciences
   Politekhnicheskaya 26,
   St.Petersburg, 194021 Russia
   

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