Electric Dipole Spin Resonance Research Articles

Electronic states associated with dislocations in p-type silicon studied by means of electric-dipole spin resonance and deep-level transient spectroscopy.

Dislocation loops consisting of long and straight segments of 60\ifmmode^\circ\else\textdegree\fi{} and screw parts were introduced in p-type Si by deformation under a high stress at a relatively low temperature. Electronic states associated with such dislocations were investigated by means of electric-dipole spin resonance, with and without photoexcitation, and deep-level transient spectroscopy. The effect of relaxation in the shape of dislocations due to annealing was also investigated. All of the experimental results were interpreted consistently with the model that the straight part of the dislocation accompanies rather shallow one-dimensional energy bands which were split off from the valence and conduction bands of the Si matrix crystal and that point defects having rather deep electronic levels were located discretely along dislocations.

Electric dipole spin resonance of grain boundaries in multicrystalline silicon

An electrically induced electron paramagnetic resonance signal is reported, which is observed at grain boundaries of multicrystalline solar silicon. The characteristic properties are a phase shift of 180° relative to the P° signal and a superlinear increase of the intensity with microwave power. These properties can be qualitatively explained by a model of Koshelev et al., which was developed for conducting dislocations. This signal is considered to be the evidence for electrical conductivity of grain boundaries at low temperatures (20 K). Es wird uber ein elektrisch induziertes Elektronenspinresonanz-Signal berichtet, das an Korngrenzen in multikristallinem Solarsilizium beobachtet wird und sich durch eine Phasenlage von 180° relativ zum P°-Signal sowie durch eine uberproportional mit der Leistung wachsende Amplitude auszeichnet. Diese Eigenschaften konnen von einem von Koshelev et al. fur leitfahige Versetzungen entwickelten Modell qualitativ erklart werden. Danach wird dieses Signal als Nachweis einer Tieftemperaturleit-fahigkeit (20 K) von Korngrenzen gedeutet.

Electric-dipole spin-resonance study on extended defects in Czochralski-grown silicon developed by thermal treatment.

A series of electric-dipole spin-resonance (EDSR) lines, termed Si-SC1 lines, are found to develop in Czochralski-grown Si crystals due to annealing at 650 \ifmmode^\circ\else\textdegree\fi{}C. Some of these lines are very close to Si-2K and Si-3K reported in a previous work. The experimental data are self-consistently explained by use of a model that shows that the EDSR signals are caused by additional electrons trapped by long quasi-one-dimensional defects lying along the 〈110〉 directions. The localization length of the trapped electrons is determined to be of the order of 100 nm and their mobility to be rather high along the defects, suggesting that a quasi-one-dimensional energy band is associated with the straight part of the defect. Si-SC1 centers are attributed to the so-called rodlike defects that are developed in the Czochralski-grown Si crystals due to the above heat treatment.

Effect of spin injection on the conduction-electron spin resonance at a ferromagnet-semiconductor contact

A theory of the electric dipole spin-resonance (EDSR) absorption for conduction electrons at a ferromagnet-semiconductor interface is given on the basis of quasiclassical transport equations for moments of the spin density matrix. It is supposed that a uniform DC magnetic field is applied perpendicular to the interfacial contact plane. An electric current passing through the interface is attended by a spin density flow which causes polarization of conduction electrons in a semiconductor. It is shown that spin injection leads to a considerable increase (exceeding one order of magnitude) of the EDSR signal intensity in semiconductors having the zinc blende or the wurtzite structure.

Electric-Dipole Spin Resonance on Extended Defects in Silicon

Electric-Dipole Spin Resonance on Extended Defects in Silicon

Hole bound states in the deformation field of screw dislocations in cubic semiconductors.

For the spherically averaged Hamiltonian approximation an accurate nonvariational calculation is reported of the energies of the one-dimensional bands split off from the edge of the valence band by the shear strain fields of screw dislocations in various cubic semiconductors. The calculation gives significantly greater binding energies for holes than previous variational calculations and also a different order of the first two levels when the ratio of light- and heavy-hole masses is less than 0.19. The calculation was performed on the basis of the effective-mass and deformation-potential approximations. This approach is justified because the resulting binding energies are much smaller than the energy gaps. The results may be used for the interpretation of various dislocation-related phenomena such as luminescence, absorption, microwave conductivity, and combined resonance (a kind of electric-dipole spin resonance).

Electric-Dipole Spin Resonance of Electrons on 60°-Dislocations in Plastically Deformed nGe and nSi

A theory is suggested to explain the symmetries and values of g-tensors observed in 60°-dislocation-related electric-dipole spin resonance (EDSR) in nGe and nSi. The theory assumes that EDSR spectra originate from electrons bound in one-dimensional dislocation bands split off from the conduction band by the strain field of 60°-dislocations.

Exchange-induced optical spin transitions in semimagnetic semiconductors.

Electron-spin flip by electric dipole light absorption in semimagnetic semiconductors (SMSC) is allowed not only by the generally invoked spin-orbit coupling but also due to a possibility of exchange scattering of an electron by a magnetic impurity. The theory of such exchange-induced electric dipole spin resonance (EDSR) in Mn- and Fe-based SMSC is presented. Since exchange scattering changes the electron spin, as well as the impurity state, the bound-electron absorption occurs at the photon energy \ensuremath{\Elzxh}\ensuremath{\omega}=\ensuremath{\Elzxh}${\mathrm{\ensuremath{\omega}}}_{\mathit{s}}$+${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{M}}$, where \ensuremath{\Elzxh}${\mathrm{\ensuremath{\omega}}}_{\mathit{s}}$ is the electron giant spin splitting and ${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{M}}$ is an excitation energy of the magnetic impurity. In the case of Mn-based SMSC, ${\mathrm{\ensuremath{\varepsilon}}}_{\mathit{M}}$ is simply the Zeeman energy of a Mn ion, while, since an Fe ion may be excited to a set of states, several absorption lines exist in Fe-based SMSC. Exchange-induced EDSR differs from the conventional spin-orbit EDSR in the polarization and magnetic-field dependences of absorption. For free carriers exchange-induced spin-flip absorption has nonresonant character and leads to a rather broad absorption band.

Electric‐Dipole Spin Resonance of Dislocations in Plastically Deformed p‐Type Silicon

On attribue la conductivite, suivant les dislocations, aux bandes du potentiel de deformations peu profondes. Ainsi l'interaction spin-orbite semble etre assez elevee pour compenser la localisation plus faible des fonctions d'onde dans de telles bandes superficielles

Effect of uniaxial stress on the electron spin resonance in zinc-blende semiconductors.

We present a study of the effect of uniaxial stress on the electric-dipole spin resonance absorption in zinc-blende semiconductors. We show that previous work in this field omits an important contribution to the transition amplitude, leading to an underestimate of the strength ${C}_{2}$ of the stress-induced spin-orbit coupling in InSb. The necessary correction factor is between 3 and 4. We suggest experimental configurations that would permit an accurate measurement of this and other related material parameters. One of these exploits the possibility of an interference between stress-induced and stress-free spin-flip transition amplitudes. In this way, not only the magnitude of ${C}_{2}$, but also its sign, could be determined.

Electron spin resonance in Zinc-blende semiconductors under uniaxial stress

We present a study of the effect of uniaxial stress on the electric-dipole spin resonance in zinc-blende semiconductors. The stress-induced spin-orbit coupling of the conduction electrons gives rise to a large enhancement of the spin resonance intensity. Previous workers have used this effect to measure the strength, C 2, of the coupling. Omission of a significant term in the electron-photon coupling has led to underestimates of C 2 by factors ranging from 3 to 4. We discuss the origin of this discrepancy and the possibility of a determination of C 2 by taking advantage of an interference between stress-induced and stress-free transition amplitudes.

Parity violation and electron-spin resonance of donors in semiconductors

This paper presents a theory of the g-factors and the intensities of the electric dipole spin-resonance absorption for conduction electrons and electrons bound to donors in zinc blende and wurtzite semiconductors. The results of the theory are compared with relevant data on InSb and Cd 1− x Mn x Se. The best fits of the theory to the experimental results yield values for the strength of the spin-orbit coupling in the conduction band of these materials as well as parameters describing the anisotropic Zeeman splitting of the electron energy levels.

Inversion asymmetry and magneto-optical selection rules in n-type zinc-blende semiconductors.

Far-infrared studies of magnetotransmission in n-type InSb, carried out in the parallel Voigt configuration, reveal an unusual dependence of the spin-resonance absorption on the orientation of the applied field B${\ensuremath{\rightarrow}}_{0}$ and on the direction of propagation q\ensuremath{\rightarrow} of the incident radiation with respect to the crystallographic axes. It was found that reversal of B${\ensuremath{\rightarrow}}_{0}$ leaving q\ensuremath{\rightarrow} fixed altered the intensity of the electric-dipole spin resonance. This result can be understood as an interference between electric-dipole and magnetic-dipole interactions when the former become allowed by virtue of mixing of Landau and Zeeman levels by a spin-orbit interaction lacking inversion symmetry. A theoretical study of this phenomenon is presented together with selection rules for magnetoabsorption in the parallel and perpendicular Voigt configurations as well as in the Faraday geometry. The results can be used to determine the inversion asymmetry parameter characterizing the spin-orbit interaction in connection with far-infrared experimental data.

Far-infrared observation of the electric-dipole spin resonance of donor electrons inCd1−xMnxSe

Far-infrared (FIR) measurements of electric-dipole spin resonance (EDSR) of donor-bound electrons in ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Se}$ ($x=0.10 \mathrm{and} 0.20$ are reported. The EDSR transition is allowed in ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Se}$ by the combined effects of spin-orbit interaction and the acentric uniaxial symmetry of this wurtzite system. The far-infrared EDSR is observed at magnetic fields of the order of 1 T, indicating extremely large effective $g$ factors (in excess of 100) due to contributions from the exchange interaction between the band electrons and the localized magnetic moments. Measurements as a function of temperature and frequency reveal a strong temperature dependence of the $g$-factors, and a dramatic increase in the strength of EDSR with frequency. Studies with linear and circular polarization were used to determine the selection rules governing EDSR, as well as the sign of the exchange integral for the conduction band of ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Se}$. EDSR is observed only in samples characterized by low resistivities (\ensuremath{\sim}1 \ensuremath{\Omega} cm at 77 K), with donor concentrations in the range of ${10}^{16}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. In addition to EDSR, the FIR magnetotransmission spectra show several other interesting features, which are interpreted in terms of conduction-electron cyclotron resonance and magnetic field dependence in the $1s\ensuremath{\rightarrow}2p$ transitions of the donor levels.

Optical properties of donor electrons in semimagnetic semiconductors

The cross section of the spin-flip Raman scattering and the absorption coefficient of the electric-dipole spin-resonance of donor electrons in Cd 1− x Mn x Se are calculated. The exchange induced spin-splitting of a donor level is described taking into account three sources of a local magnetization: external magnetic field, thermodynamical fluctuations of magnetization and molecular field of the donor electron (bound magnetic polaron). The theory takes into account the selection rules appropriate for the hexagonal CdMnSe. The role played by fluctuations of composition is considered. It is suggested that a spin-flip line is inhomogeneously broadened by thermodynamical fluctuations of magnetization and additionally, in high fields, by fluctuations of the composition.