Search

We extend the infrared thermography of thin materials for measurements of the full time response to homogeneous heating via illumination. We demonstrate that the thermal conductivity, the heat capacity, as well as the thermal diffusivity can be determined comparing the experimental data to finite difference simulations using a variety of test materials such as thin doped and undoped silicon wafers, sheets of steel, as well as gold and polymer films. We show how radiative cooling during calibration and measurement can be accounted for and that the effective emissivity of the material investigated can also be measured by the setup developed. [ABSTRACT FROM AUTHOR]

Introduces the Constant Degradation Method (CDM) as an experimental scheme to study the kinetics of metastable defect creation in amorphous hydrogenated silicon. Information on amorphous hydrogenated silicon; Kinetic theories for defect creation; Increase in light intensity needed to keep the photoconductivity constant during the CDM experiment.

Presents a study which described results for deuterium effusion from undoped and doped crystalline silicon treated in a D[sub2] plasma under different conditions. Measurement of effusion spectra; Characteristics of the form of effusion spectrum for the dopant concentration; Description of the effusion spectra of silicon.

We investigate the coupling of an ensemble of phosphorus donors in an isotopically purified 28Si host lattice interacting with a superconducting coplanar waveguide resonator. The microwave transmission spectrum of the resonator shows a normal mode splitting characteristic for high cooperativity. The evaluated collective coupling strength geff is of the same order as the loss rate of the spin system γ, indicating the onset of strong coupling. We develop a statistical model to describe the influence of temperature on the coupling strength from 50mK to 3:5K and find a scaling of the coupling strength with the square root of the number of thermally polarized spins. [ABSTRACT FROM AUTHOR]

Spin-dependent transport processes in thin near-surface doping regions created by low energy ion implantation of arsenic in silicon are detected by two methods, spin-dependent recombination using microwave photoconductivity and electrically detected magnetic resonance monitoring the direct current through the sample. The high sensitivity of these techniques allows the observation of the magnetic resonance, in particular, of As in weak magnetic fields and at low resonance frequencies (40–1200 MHz), where high-field-forbidden transitions between the magnetic sublevels can be observed due to the mixing of electron and nuclear spin states. Several implantation-induced defects are present in the samples studied and act as spin readout partner. We explicitly demonstrate this by electrically detected electron double resonance experiments and identify a pair recombination of close pairs formed by As donors and oxygen-vacancy centers in an excited triplet state (SL1) as the dominant spin-dependent process in As-implanted Czochralski-grown Si. [ABSTRACT FROM AUTHOR]

Charge transfer between silicon nanocrystals (Si-nc) and organic semiconductors has been investigated via light-induced electron spin resonance (LESR). Composites of Si-nc with the hole conductor poly(3-hexylthiophene) (P3HT) and with the electron acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) have been investigated. The LESR measurements allow one to quantify light-induced charge transfer between Si-nc and P3HT, which results in positive P3HT polarons. PCBM, in contrast, acts as an electron acceptor in composites with Si-nc, and after illumination, negative PCBM radicals are created. These results are discussed in terms of light-induced generation and separation of charge carriers in the hybrid composites. [ABSTRACT FROM AUTHOR]

We present a wet chemical process for nanoscale texturing of Si surfaces, which results in an almost complete suppression of the reflectivity in a broad spectral range, leading to black Si surfaces. The process affects only the topmost 200–300 nm of the material and is independent of the surface orientation and doping. Thus, it can be applied to various structural forms of bulk silicon (single, poly-, or multicrystalline) as well as to thin Si films (amorphous or microcrystalline). The optical properties of various black Si samples are presented and discussed in correlation with the surface morphology. [ABSTRACT FROM AUTHOR]

Studies excitonic states involved in light-induced degradation of amorphous hydrogenated silicon. Spin-dependent photoconductivity spectrum of low defect density undoped amorphous hydrogenated silicon; Change in conductivity at resonance for a given recombination channel; Creation of metastable defects resulting from excitonic states.

Group IV vacancy color centers in diamond are promising spin-photon interfaces with strong potential for applications in photonic quantum technologies. Reliable methods for controlling and stabilizing their charge state are urgently needed for scaling to multiqubit devices. Here, we manipulate the charge state of silicon vacancy (SiV) ensembles by combining luminescence and photocurrent spectroscopy. We controllably convert the charge state between the optically active SiV- and dark SiV2- with megahertz rates and >90% contrast by judiciously choosing the local potential applied to in-plane surface electrodes and the laser excitation wavelength. We observe intense SiV- photoluminescence under hole capture, measure the intrinsic conversion time from the dark SiV2- to the bright SiV- to be 36.4(67) ms, and demonstrate how it can be enhanced by a factor of 105 via optical pumping. Moreover, we obtain previously unknown information on the defects that contribute to photoconductivity, indicating the presence of substitutional nitrogen and divacancies. [ABSTRACT FROM AUTHOR]

We show that in pulsed electrically detected magnetic resonance (pEDMR) signal modulation in combination with a lock-in detection scheme can reduce the low-frequency noise level by one order of magnitude and in addition removes the microwave-induced non-resonant background. This is exemplarily demonstrated for spin-echo measurements in phosphorus-doped silicon. The modulation of the signal is achieved by cycling the phase of the projection pulse used in pEDMR for the readout of the spin state. [ABSTRACT FROM AUTHOR]

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 S11 = 1.5 × 1022 V/m2 and S44 = 6 × 1022 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. [ABSTRACT FROM AUTHOR]

Spin-dependent relaxation and recombination processes in γ-irradiated n-type Czochralski-grown silicon are studied using continuous wave (cw) and pulsed electrically detected magnetic resonance (EDMR). Two processes involving the SL1 center, the neutral excited triplet state of the oxygen-vacancy complex, are observed which can be separated by their different dynamics. One of the processes is the relaxation of the excited SL1 state to the ground state of the oxygen-vacancy complex, the other a charge transfer between 31P donors and SL1 centers forming close pairs, as indicated by electrically detected electron double resonance. For both processes, the recombination dynamics is studied with pulsed EDMR techniques. We demonstrate the feasibility of true zero-field cw and pulsed EDMR for spin-1 systems and use this to measure the lifetimes of the different spin states of SL1 also at vanishing external magnetic field. [ABSTRACT FROM AUTHOR]

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 29Si nuclear spins. [ABSTRACT FROM AUTHOR]

We present Auger-electron-detected magnetic resonance (AEDMR) experiments on phosphorus donors in silicon, where the selective optical generation of donor-bound excitons is used for the electrical detection of the electron spin state. Because of the long dephasing times of the electron spins in isotopically purified 28Si, weak microwave fields are sufficient, which allow one to realize broadband AEDMR in a commercial electron spin resonance resonator. Implementing Auger-electron-detected electron nuclear double resonance (ENDOR), we further demonstrate the optically assisted control of the nuclear spin under conditions where the hyperfine splitting is not resolved in the optical spectrum. Compared to previous studies, this significantly relaxes the requirements on the sample and the experimental setup, e.g., with respect to strain, isotopic purity, and temperature. We show AEDMR of phosphorus donors in silicon with natural isotope composition, and discuss the feasibility of ENDOR measurements also in this system. [ABSTRACT FROM AUTHOR]

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 wave function under strain. [ABSTRACT FROM AUTHOR]