Detected Electron Nuclear Double Resonance Research Articles

Electrically detected electron nuclear double resonance in amorphous hydrogenated boron thin films

We report on electrically detected electron nuclear double resonance (EDENDOR) observations via spin dependent trap assisted tunneling (SDTAT) in amorphous boron thin films at 250 K. We observe EDENDOR from both 10B and 11B nuclei, likely interacting with carbon impurities. In SDTAT, electron paramagnetic resonance (EPR) is detected through a change in the trap assisted tunneling current through the thin film. As in conventional electron nuclear double resonance (ENDOR) the ENDOR response is detected through a modest change in the EPR response. Since SDTAT detection sensitivity is about seven orders of magnitude greater than that of conventional EPR, it, in principle, can provide an enormous boost in ENDOR sensitivity. This enormous potential sensitivity improvement can be compromised by a coupling of the RF electromagnetic field driving the nuclear spin response and the electrical leads which are utilized to monitor the resonance induced changes in device current. We overcome this difficulty with the introduction of proportional-integral-derivative (PID) control of the RF circuitry which greatly suppresses fluctuations in the amplitude of the RF magnetic field at the thin film structure under investigation.

Observation of electrically detected electron nuclear double resonance in amorphous hydrogenated silicon films

We report on the electrical detection of electron nuclear double resonance (EDENDOR) through spin-dependent tunneling transport in an amorphous hydrogenated silicon thin film. EDENDOR offers a many orders of magnitude improvement over classical ENDOR and is exclusively sensitive to paramagnetic defects involved in electronic transport. We observe hyperfine interactions with 1H nuclei very close to silicon dangling bond defects. These observations substantially extend recent EDENDOR observations involving silicon vacancy defects and 14N hyperfine interactions with fairly distant nitrogen atoms in 4H-SiC bipolar junction transistors. We have improved the detection scheme utilized in the earlier study by combining magnetic field modulation with RF amplitude modulation; this combination significantly improves the operation of the automatic power leveling scheme and the overall sensitivity.

A New Technique for Analyzing Defects in Silicon Carbide Devices: Electrically Detected Electron Nuclear Double Resonance

We show that electrically detected electron nuclear double resonance (EDENDOR) can be detected with relatively high signal-to-noise ratios in fully processed 4H-SiC bipolar junction transistors (BJTs). We observe EDENDOR of nitrogen interacting with recombination center defects in the depletion region of forward-biased emitter-base junctions of these devices at room temperature. Our results indicate that EDENDOR has great potential in the investigation of SiC-based devices specifically, as well as in the investigation of solid-state devices based upon other material systems.

Apparatus for electrically detected electron nuclear double resonance in solid state electronic devices.

We have developed a sensitive electron nuclear double resonance spectrometer in which the detection takes place through electrically detected magnetic resonance. We demonstrate that the spectrometer can provide reasonably high signal to noise spectra of 14N interactions with deep level centers in a fully processed bipolar junction transistor at room temperature.

Electrically detected electron nuclear double resonance in 4H-SiC bipolar junction transistors

We demonstrate high signal-to-noise electrically detected electron-nuclear double resonance measurements on fully processed bipolar junction transistors at room temperature. This work indicates that the unparalleled analytical power of electron-nuclear double resonance in the identification of paramagnetic point defects can be exploited in the study of defects within fully functional solid-state electronic devices.

Quadrupolar effects on nuclear spins of neutral arsenic donors in silicon

We present electrically detected electron nuclear double resonance measurements of the nuclear spins of ionized and neutral arsenic donors in strained silicon. In addition to a reduction of the hyperfine coupling, we find significant quadrupole interactions of the nuclear spin of the neutral donors of the order of 10 kHz. By comparing these to the quadrupole shifts due to crystal fields measured for the ionized donors, we identify the effect of the additional electron on the electric field gradient at the nucleus. This extra component is expected to be caused by the coupling to electric field gradients created due to changes in the electron wavefunction under strain.

Nuclear Spins of Ionized Phosphorus Donors in Silicon

We demonstrate the coherent control and electrical readout of ionized phosphorus donor nuclear spins in (nat)Si. By combining time-programed optical excitation with coherent electron spin manipulation, we selectively ionize the donors depending on their nuclear spin state, exploiting a spin-dependent recombination process at the Si/SiO(2) interface, and find a nuclear spin coherence time of 18 ms for the ionized donors. The presented technique allows for spectroscopy of ionized-donor nuclear spins and enhances the sensitivity of electron nuclear double resonance to a level of 3000 nuclear spins.

Single defect centres in diamond: A review

AbstractThe nitrogen vacancy and some nickel related defects in diamond can be observed as single quantum systems in diamond by their fluorescence. The fabrication of single colour centres occurs via generation of vacancies or via controlled nitrogen implantation in the case of the nitrogen vacancy (NV) centre. The NV centre shows an electron paramagnetic ground and optically excited state. As a result electron and nuclear magnetic resonance can be carried out on single defects. Due to the localized nature of the electron spin wavefunction hyperfine coupling to nuclei more than one lattice constant away from the defect as dominated by dipolar interaction. As a consequence the coupling to close nuclei leads to a splitting in the spectrum which allows for optically detected electron nuclear double resonance. The contribution discusses the physics of the NV and other defect centre from the perspective of single defect centre spectroscopy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

On the problem of the EL2 structure in semi-insulating GaAs: high-frequency ODEPR/ODENDOR measurements in W-band

For almost two decades the structure model of the EL2 defect in semi-insulating (SI) GaAs has been controversially discussed. Neither the isolated As Ga with T d symmetry, nor the As Ga–As i pair model nor any other As Ga-related defect model could be unambiguously established. The reason was that the analysis of previous optically detected electron nuclear double resonance (ODENDOR) and optically detected electron paramagnetic resonance (ODEPR) spectra measured at 24 GHz was difficult and not unambiguous because of forbidden transitions, pseudo-dipolar couplings and higher order effects. However, the ODEPR spectra of the EL2 defect measured in W-band (93 GHz) can be fitted by first order perturbation calculation of the spin Hamiltonian thus allowing a much simpler analysis compared to X- or K-band. From ODEPR measurements in different SI GaAs samples both in K- and W-band we show that the ODEPR spectra of the EL2 defect together with the K-band ODENDOR data are not consistent with the As Ga–As i pair model, but the highly symmetric isolated As Ga model has to be excluded as well. First ODENDOR measurements in W-band are also reported.

Quantum computation using the 13C nuclear spins near the single NV defect center in diamond

We discuss the possibility of realizing quantum computation on the basis of a cluster of single interacting nuclear spins in solids. This idea seems to be feasible because of the combination of two techniques—Single Molecule Spectroscopy and Optically Detected Electron Nuclear Double Resonance. Compared to the well-known bulk Nuclear Magnetic Resonance (NMR), the proposed method of quantum computation has the advantage that quantum computation is performed with pure spin states and the quantum processor is more easily scalable. At the same time, the advantages of NMR quantum computation are kept: long coherence time and easy construction of quantum gates. As a specific system to implement the above idea, we discuss the 13C-nuclear spins in the nearest vicinity of a single nitrogen-vacancy (NV) defect center in diamond, which can be optically detected using the technique of scanning confocal microscopy. Owing to the hyperfine coupling of the ground state electron paramagnetic spin S=1 of the center to 13C nuclear spins in a diamond lattice, the states of nuclear spins in the vicinity of the defect-center can be addressed individually. Preliminary consideration shows that it should be possible to address up to 12 individual 13C nuclear spins. The dephasing time of the nuclear spin states at low temperatures allows realization up to 105 gates.

Magnetic resonance on single nuclei

The magnetic resonance signal of individual hydrogen nuclei has been detected. The experiments have been performed on a single pentacene molecule with the aid of optically detected electron nuclear double resonance. Two nuclear magnetic resonance lines of 30 kHz width have been observed as a 3% change in the fluorescence intensity of a single molecule. The results can be reproduced by a spin Hamilton operator describing the interaction of a single electron spin with two hydrogen nuclei.

Optically detected electron nuclear double resonance on the residual donor in GaN

Optically detected electron nuclear double resonance (ODENDOR) was measured in the 2.2 eV ‘yellow’ luminescence band associated with the residual donor in n-type undoped GaN. The ODENDOR lines are due to gallium and show a quadrupole splitting which can be described with an axial tensor. The quadrupole parameter was estimated to be q( 69Ga)/ h = 1/2 Q zz = 0.22 MHz. A hyperfine interaction for 69Ga of about 0.3 MHz for the isotropic and of about 0.15 MHz for the anisotropic part was estimated from the width of the ODENDOR lines. It is tentatively suggested that a Ga interstitial is the residual donor.

Optical detection of electron nuclear double resonance on a residual donor in wurtzite GaN.

Optically detected electron nuclear double resonance (ODENDOR) was measured in the 2.2-eV yellow luminescence band associated with a residual donor in $n$-type unintentionally doped GaN. The ODENDOR lines are due to gallium and show a quadrupole splitting that can be described with an axial tensor. The quadrupole parameter was estimated to be $\frac{q(^{69}\mathrm{Ga})}{h}=\frac{1}{2}{Q}_{\mathrm{zz}}=0.22$ MHz. A hyperfine interaction for $^{69}\mathrm{Ga}$ of approximately 0.3 MHz for the isotropic part and of approximately 0.15 MHz for the anisotropic part was estimated from the width of the ODENDOR lines. It is tentatively suggested that Ga interstitials are residual donors.

Optical Detection of Electron Nuclear Double Resonance on the Residual Donor in GaN

Optically detected electron nuclear double resonance (ODENDOR) was measured in the 2.2 eV ‘yellow’ luminescence band associated with the residual donor in n-type undoped GaN. The ODENDOR lines are due to gallium and show a quadrupole splitting which can be described with an axial tensor. The quadrupole parameter was estimated to be q(69Ga) = 1/2 Qzz = 0.22 MHz. A hyperfine interaction for 69Ga of about 0.3 MHz for the isotropic and of about 0.15 MHz for the anisotropic part was estimated from the width of the ODENDOR lines. It is tentatively suggested that a Ga interstitial is the residual donor.

Possibility of hydrogen migration in photoinduced defect creation process of a-Si:H

The possibility of hydrogen migration accompanying photoinduced defect creation has been proposed from optically detected electron nuclear double resonance (ODENDOR) measurements. The matrix-ODENDOR signal due to the dipole-dipole interaction between trapped holes and hydrogen nuclei changes its line shape upon light exposure. A similar effect is induced by the application of pressure. The change in the line shape is discussed, taking into account the hydrogen migration and other effects.

On the Microscopic Structures of Three Different Arsenic Antisite-Related Defects in Gallium Arsenide Studied by Optically Detected Electron Nuclear Double Resonance

On the Microscopic Structures of Three Different Arsenic Antisite-Related Defects in Gallium Arsenide Studied by Optically Detected Electron Nuclear Double Resonance

The role of hydrogen clusters in the Staebler-Wronski effect of amorphous silicon as elucidated by optically detected electron nuclear double resonance

Since the discovery of the Staebler-Wronski effect (SWE) the correlation with hydrogen has been pointed out by many workers. In this work, the optically detected electron nuclear double resonance (ODENDOR) experiment has been carried out for the purpose of elucidating microscopically the electron-hole recombination process and the role of hydrogen in the mechanism of the SWE. The SWE is suggested to correlate with the Si-H bond clusters.

Optically detected electron nuclear double resonance in a-Si:H

Optically detected electron nuclear double resonance (ODENDOR) experiments have been carried out to elucidate the microscopic structure of trapped hole centers ( A-centers) in a-Si:H. The matrix ODENDOR signal associated with the H 1 nuclei and the local ODENDOR signal associated with Si 29 nuclei have been observed for the first time. The average distance between the A-center and the H 1 nucleus is estimated at 5 ∼ 6 Å from the width of the former signal, while the extent of the wave function of the A-center is estimated at 5 ∼ 7 Å from the latter signal. Based on these results, it is suggested that the A-center is a self-trapped hole at a SiSi weak bond adjacent to a SiH bond.

Detection of hydrogen in nominally pure GaP:Zn by optically detected electron nuclear double resonance

Optically detected electron nuclear double resonance (ODENDOR) measurements of the triplet antisite center P Ga 3+ in GaP:Zn have revealed the presence of hydrogen atom impurities in a nominally pure sample. Strong ligand 31P signals have also been observed. Assuming a uniform distribution of hydrogen the intensity ratio of the 31P to 1H lines sets a rough lower limit of between 1–10 ppm on the hydrogen concentration. The possibility that the H 1 atoms form part of the antisite defects is also discussed.

Optically detected electron—nuclear double resonance and electron—nuclear—nuclear triple resonance study of 17O hyperfine coupling in the lowest nπ * triplet state of benzil

Optically detected ENDOR and electron—nuclear—nuclear triple resonance of 17O were measured via phosphorescence from 3(nπ *) benzil in benzophenone- d 10 crystals at high magnetic field. The n and π * spin densities on the oxygen atom are 0.201 and 0.092, respectively, the angle between the two CO bonds being 150°.