Arsenic Donor Research Articles

Ramsey Fringes in Germanium Doped with Arsenic Donors

Ramsey Fringes in Germanium Doped with Arsenic Donors

AsCCAs]-Coordinated Rhenium Hydrides and Their Reactivities Toward Unsaturated Hydrocarbons, Heterocumulenes, and CO2.

An [AsCCAs] ligand featuring a central alkyne and two flanking arsenic donors was employed for the synthesis of a trihydrido rhenium complex, while the corresponding phosphorus ligand was shown to be less suited. The reactivity of the former trihydride [AsCCAs]ReH3 (3) was examined in detail, which revealed that two alternative reaction channels may be entered in dependence of the substrate. Upon reaction of 3 with PhC≡CPh, ethylene, and CS2, monohydrides of the general formula [AsCCAs]Re(L)H with L = η2-PhC≡CPh (4), η2-H2C═CH2 (5), and η2-CS2 (6) were formed along with H2. In contrast, insertion products of the type [AsCCAs]Re(X)H2 (7-9) were obtained upon treatment of 3 with CyN═C═NCy, PhN═C═O, and Ph2C═C═O, while CO2 failed to react with 3 under identical reaction conditions. Given that several productive reactions between CO2 and hydrido rhenium carbonyls have been reported in the literature, 3 was further derivatized by introducing CO and tBuNC coligands, respectively. This led to the isolation of trans-[AsCCAs]ReH(CO)2 (trans-10) and trans-[AsCCAs]ReH(CNtBu)2 (trans-11), which were shown to thermally isomerize to the corresponding cis-configured products, cis-10 and cis-11. Interestingly, only the cis-complexes were found to react with CO2, which was rationalized by evaluating the relative nucleophilicities of the hydrides in cis-10, trans-10, cis-11, and trans-11 via Fukui analysis. The formates cis-[AsCCAs]Re(OCHO)(CO)2 (12) and cis-[AsCCAs]Re(OCHO)(CNtBu)2 (13) were isolated and shown to contain κ1-O-coordinated formate moieties. Treatment of 12 with [LutH]Cl/B(C6F5)3 (or with Ph3SiCl) led to the liberation of [LutH][OCHO···B(C6F5)3] (or triphenylsilyl formate) with concomitant formation of the expected chloro complex cis-[AsCCAs]ReCl(CO)2 (14). In a closed synthetic cycle, hydride 12 was regenerated from the latter chloride using NaBEt3H as a hydride source.

Detection of arsenic donor electrons using gate-pulse-induced spin-dependent recombination in silicon transistors

The detection of donor electrons is important for Si-based spintronics and quantum computers, as well as complementary metal–oxide–semiconductor (MOS) circuits. One of the detection schemes is based on the spin-dependent recombination, for which photoexcitation has, so far, been used to generate electrons and holes. In this study, we rather induce the recombination electrically by a gate pulse in Si MOS transistors. Under the spin resonance conditions, we detect signals from arsenic (As) donors, located in the channel edge regions close to the As-implanted source/drain. The analysis suggests that the detection is owing to the spin pairs formed by an As donor electron spin and an electron spin of a defect center at the MOS SiO2/Si interface and to their spin-dependent process during the recombination.

Междолинные процессы релаксации состояний мелких доноров в германии

The role of the intervalley processes of electron-phonon interaction in the relaxation of excited shallow arsenic donors in germanium is analyzed. The rates of intracenter inter-valley transitions with emission of TA phonons in ger-manium are calculated in dependence on the uniaxial compression stress along {111} crystallographic direction. It is shown that inter-valley transitions to the ground state of the donor with emission of phonons can play a significant role in the relaxation of excited impurities only upon uniaxial stress of the crystal, since at zero stress, there are no exact resonances between impurity transitions and intervalley phonons. There are also transitions from highly excited states lying in a narrow band of energies (~ 0.5 meV) under very bottom of the conduction band to the first excited state 1s(3)(Г5) (in stressed germanium crystal to 1s(3)(Г3) state). The average rate of these transitions is estimated at 0.3×109 s-1.

Терагерцовое стимулированное излучение при оптическом резонансном возбуждении германия, легированного мелкими донорами

The mechanisms responsible for terahertz stimulated radiation under resonant intracenter excitation of shallow donors in bulk germanium are considered to be the inversion laser mechanism (ILM) and electron stimulated Raman scattering (e-SRS). The e-SRS cross-section was estimated in the case of resonant excitation of odd levels of a shallow arsenic donor in germanium. The output intensity under resonant excitation of germanium doped with arsenic is calculated. It is shown that at an intensity exceeding the threshold for e-SRS, there should be a competition of mechanisms leading to a decrease in the intensity of ILM, which can be detected by the dependence of the output intensity on time.

Relaxation of the Excited States of Arsenic in Strained Germanium

The relaxation times of the lower p states of the arsenic donor in a germanium crystal strained along the [111] crystallographic direction are studied. Measurements are performed by the pump–probe method, using free-electron laser radiation. The states are excited from the 1s (Γ1) ground state. The experimentally measured decay times of the 2p0, 3p0, and 2p± states are 1.3, no more than 0.2, and 0.4 ns, respectively. It is shown that the relatively high relaxation rate of the 2p± state is defined by the interaction with intravalley TA photons.

Influence of Uniaxial Deformation along the [110] Direction on the Relaxation of Arsenic Shallow Donor States in Germanium

The relaxation rates of arsenic donor states in germanium upon interaction with acoustic phonons are analyzed depending on uniaxial crystal compression deformation along [110] direction at low temperatures (<10 K). It is shown that the formation of the inverse population of donor levels, which depends on the crystal-deformation magnitude, occurs under optical excitation, which gives us grounds to assume the possibility of the effect of stimulated radiation in the THz frequency range at intracenter transitions of shallow arsenic donors under their optical excitation. It is shown that uniaxial deformation can lead to switching of the laser transition and, consequently, to a variation in the stimulated-radiation frequency.

Влияние одноосной деформации в направлении [110] на релаксацию состояний мелких доноров мышьяка в германии

Analysis of acoustical phonon assisted relaxation rates of arsenic donor states has been carried out in depends on uniaxial compressive stress of crystal along [110] direction under low temperature (&lt; 10 K). As shown, under optical excitation the inversion population of donor energy levels is formed that depends on deformation of crystal. This give grounds to suppose that stimulated emission on arsenic shallow donor intracenter transitions in THz range is possible under optical excitation. As shown, uniaxial stress along [110] direction can result to switch laser transition and stimulated emission frequency

Relaxation Times and Population Inversion of Excited States of Arsenic Donors in Germanium

The relaxation times of excited states of arsenic dopant in germanium at cryogenic temperatures T < 15 K have been experimentally studied by the optical pump-probe method using radiation of a free-electron laser. Two variants of the excitation of impurity centers have been used in the experiment: (i) from the 1s(A1) ground state of the dopant and (ii) from the 1s(T2) first excited state having a finite thermal population. In the former variant, it has been shown that the decay times of the 2p0 and 3p± states are about 0.8 and 0.6 ns, respectively. In the latter variant, a single measurement can simultaneously provide the relaxation times of two 2p± and 1s(T2) states about 0.6 and no more than 0.16 ns, respectively. The data obtained have indicated the possibility of forming population inversion and the gain of terahertz radiation at the 2p± → 1s(T2) and 2p0 → 1s(T2) transitions at the optical excitation of the mentioned impurity centers.

On the Intracenter Relaxation of Shallow Arsenic Donors in Stressed Germanium. Population Inversion under Optical Excitation

The relaxation rates of lower excited states 1s(T), 2p0, 2s, 3p0, and 2p± of arsenic donors in a germanium crystal are calculated upon the interaction with long-wavelength acoustic phonons depending on the uniaxial stress in the crystallographic direction [111]. The populations of states under optical excitation are estimated for calculated times. It is shown theoretically that optical excitation of the medium forms an inverse population of arsenic donor levels and leads to the possibility of the implementation of a four-level laser scheme with the radiative transition between 2p states and the 1s triplet state at zero strain. The estimated value of the expected gain in the medium under optical excitation conditions by CO2 laser radiation in the medium at a donor concentration of 2 × 1015 cm–3 is ~0.35 cm–1 at a frequency of 1.98 THz if the laser transition is 2p± → 1s(T) and 1.25 THz if the laser transition is 2p0 → 1s(T).

Внутрицентровая релаксация мелких доноров мышьяка в деформированном германии. Инверсия населенностей при оптическом возбуждении

AbstractThe relaxation rates of lower excited states 1 s ( T ), 2 p _0, 2 s , 3 p _0, and 2 p _± of arsenic donors in a germanium crystal are calculated upon the interaction with long-wavelength acoustic phonons depending on the uniaxial stress in the crystallographic direction [111]. The populations of states under optical excitation are estimated for calculated times. It is shown theoretically that optical excitation of the medium forms an inverse population of arsenic donor levels and leads to the possibility of the implementation of a four-level laser scheme with the radiative transition between 2 p states and the 1 s triplet state at zero strain. The estimated value of the expected gain in the medium under optical excitation conditions by CO_2 laser radiation in the medium at a donor concentration of 2 × 10^15 cm^–3 is ~0.35 cm^–1 at a frequency of 1.98 THz if the laser transition is 2 p _± → 1 s ( T ) and 1.25 THz if the laser transition is 2 p _0 → 1 s ( T ).

Systematics of boron halide complexes with dichalcogenoether ligands – Synthesis, structures and reaction chemistry

The complexes [BX3(μ-L−L)BX3] (X = Cl, Br, I; L−L = EtS(CH2)2SEt, MeSe(CH2)2SeMe), [BX′3{o-C6H4(SMe)2}] (X’ = Cl, I), [(BBr3)2{o-C6H4(SMe)2}], [(BBr3)2{o-C6H4(SeMe)2}] and [BI3{o-C6H4(SeMe)2}] have been prepared as moisture-sensitive pale solids by reaction of the appropriate BX3 with the dichalcogenoether in anhydrous n-hexane solution, and characterised by microanalysis, IR and multinuclear (1H, 11B, 77Se{1H}) NMR spectroscopy. In contrast, the [BF3(μ-L−L)BF3], [(BF3)2{o-C6H4(SMe)2}] and [(BF3)2{o-C6H4(SeMe)2}], made from BF3 and the neat ligands, are viscous oils which have a significant vapour pressure of BF3 at ambient temperatures. X-ray crystal structures are reported for [BX3{μ-EtS(CH2)2SEt}BX3] (X = Cl, Br, I), [BBr3{μ-MeSe(CH2)2SeMe}BBr3], [BCl3{o-C6H4(SMe)2}] and [(BBr3)2{μ-o-C6H4(SeMe)2}]. The complexes [(BX3)2{MeTe(CH2)3TeMe}] (X = F, Cl, Br) have been identified in solution by multinuclear NMR spectroscopy, but decompose rapidly, whilst o-C6H4(TeMe)2 decomposes immediately on contact with BBr3 or BCl3. Dealkylation of some of the chalcogenoether ligands at room temperature by BI3, to yield complexes including [BI2{o-C6H4S(SMe)] and [BI2{o-C6H4Se(SeMe)], has been identified and the X-ray structure of [BI2{o-C6H4Se(SeMe)] determined. The trends in behaviour along the series of boron halides and with the various chalcogenoethers are described and compared with the behaviour of BX3 with neutral phosphorus and arsenic donor ligands (Burt et al., Inorg. Chem., 2016, 55, 8852) and with [BX3(EMe2)] (E = S, Se, Te) (Okio et al., J. Organometal. Chem., 2017, 848, 232).

Luminescence Spectroscopy of Bound Excitons in Diamond (Phys. Status Solidi A 11∕2017)

Since the research on diamond doping remains an issue for electronic applications, the luminescence spectroscopy of bound excitons appears essential to evaluate the properties of shallow dopants in diamond. In this paper (article No. 201700402), the formation and recombination processes of bound excitons in diamond are reviewed for boron acceptors, phosphorus, and arsenic donors. Pulsed and continuous excitations are considered, the latter being currently used for the measurement of donor and acceptor concentrations in diamond.

Luminescence Spectroscopy of Bound Excitons in Diamond

Since the research on diamond doping remains an issue for electronic applications, the luminescence spectroscopy of bound excitons appears essential to evaluate the properties of shallow dopants in diamond. In this paper, the formation and recombination processes of bound excitons in diamond are reviewed for boron acceptors, phosphorus, and arsenic donors. Pulsed and continuous excitations are considered, the latter being currently used for the measurement of donor and acceptor concentrations in diamond.

Multiple-Quantum Transitions and Charge-Induced Decoherence of Donor Nuclear Spins in Silicon.

We study single- and multiquantum transitions of the nuclear spins of an ensemble of ionized arsenic donors in silicon and find quadrupolar effects on the coherence times, which we link to fluctuating electrical field gradients present after the application of light and bias voltage pulses. To determine the coherence times of superpositions of all orders in the 4-dimensional Hilbert space, we use a phase-cycling technique and find that, when electrical effects were allowed to decay, these times scale as expected for a fieldlike decoherence mechanism such as the interaction with surrounding ^{29}Si nuclear spins.

ChemInform Abstract: Cyclononanes: The Extensive Chemistry of Fundamentally Simple Ligands

AbstractReview: 305 refs.

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.

Interaction of Strain and Nuclear Spins in Silicon: Quadrupolar Effects on Ionized Donors.

The nuclear spins of ionized donors in silicon have become an interesting quantum resource due to their very long coherence times. Their perfect isolation, however, comes at a price, since the absence of the donor electron makes the nuclear spin difficult to control. We demonstrate that the quadrupolar interaction allows us to effectively tune the nuclear magnetic resonance of ionized arsenic donors in silicon via strain and determine the two nonzero elements of the S tensor linking strain and electric field gradients in this material to S(11)=1.5×10(22) V/m2 and S(44)=6×10(22) V/m2. We find a stronger benefit of dynamical decoupling on the coherence properties of transitions subject to first-order quadrupole shifts than on those subject to only second-order shifts and discuss applications of quadrupole physics including mechanical driving of magnetic resonance, cooling of mechanical resonators, and strain-mediated spin coupling.

Donor hyperfine Stark shift and the role of central-cell corrections in tight-binding theory

Atomistic tight-binding (TB) simulations are performed to calculate the Stark shift of the hyperfine coupling for a single arsenic (As) donor in silicon (Si). The role of the central-cell correction is studied by implementing both the static and the non-static dielectric screenings of the donor potential, and by including the effect of the lattice strain close to the donor site. The dielectric screening of the donor potential tunes the value of the quadratic Stark shift parameter (η2) from −1.3 × 10−3 µm2 V−2 for the static dielectric screening to −1.72 × 10−3 µm2 V−2 for the non-static dielectric screening. The effect of lattice strain, implemented by a 3.2% change in the As–Si nearest-neighbour bond length, further shifts the value of η2 to −1.87 × 10−3 µm2 V−2, resulting in an excellent agreement of theory with the experimentally measured value of −1.9 ± 0.2 × 10−3 µm2 V−2. Based on our direct comparison of the calculations with the experiment, we conclude that the previously ignored non-static dielectric screening of the donor potential and the lattice strain significantly influence the donor wave function charge density and thereby leads to a better agreement with the available experimental data sets.

Random telegraph signal and spin characteristics of the gate-all-around poly-silicon nanowire

An arsenic (As)-doped poly-silicon nanowire gate-all-around transistor fabricated using standard semiconductor methods was used to measure the Coulomb blockade effect by applying a tunable gate voltage. Two-level trapping states due to the random telegraph signal of fluctuating drain current were observed in the silicon transport channel. Under high magnetic fields, the superposition points of differential conductance revealed weak 2-electron singlet-triplet splitting states of the arsenic magnetic impurity. The weak spin-orbital coupling suggests that the electron-spin-polarization in the As-doped silicon nanowire and the two-level trapping state coexisted in the Coulomb blockade oscillations. These characteristics indicate that a few arsenic donors strongly affect the quantum behavior of the poly-silicon material.