Impact of strain on electronic defects in (Mg,Zn)O thin films

We have investigated the impact of strain on the incorporation and the properties of extended and point defects in (Mg,Zn)O thin films by means of photoluminescence, X-ray diffraction, deep-level transient spectroscopy (DLTS), and deep-level optical spectroscopy. The recombination line Y2, previously detected in ZnO thin films grown on an Al-doped ZnO buffer layer and attributed to tensile strain, was exclusively found in (Mg,Zn)O samples being under tensile strain and is absent in relaxed or compressively strained thin films. Furthermore a structural defect E3′ can be detected via DLTS measurements and is only incorporated in tensile strained samples. Finally it is shown that the omnipresent deep-level E3 in ZnO can only be optically recharged in relaxed ZnO samples

Lasing in cuprous iodide microwires

We report on the observation of lasing in cuprous iodide (CuI) microwires. A vapor-phase transport growth procedure was used to synthesize CuI microwires with low defect concentration. The crystal structure of single microwires was determined to be of zincblende-type. The high optical quality of single microwires is indicated by the observed series of excitonic emission lines as well as by the formation of gain under optical excitation. Lasing of triangular whispering-gallery modes in single microwires is demonstrated for fs- and ns-excitation from cryogenic temperatures up to 200 K. Timeresolved micro-photoluminescence studies reveal the dynamics of the laser process on the time scale of several picoseconds

Supplementary Notes - Defect engineering of silicon with ion pulses from laser acceleration

14 pages. -- Supplementary Note 1. Time lapse movie showing evaporation of the aluminum foil mask during 100 shots. -- Supplementary Note 2. Photoluminescence (PL) and Secondary Ion Mass Spectrometry (SIMS) data correlation to PL data. -- Supplementary Note 3. Details on energy deposition and heat calculations. -- Supplementary Note 4. Details on Nuclear Reaction Analysis (NRA). -- Supplementary Note 5. Details on channeling Rutherford Backscattering (ch-RBS). -- Supplementary Note 6. Supplemental material on Density Functional Theory (DFT) calculations of G and W-centers in silicon.Peer reviewe

Defect engineering of silicon with ion pulses from laser acceleration

Defect engineering is foundational to classical electronic device development and for emerging quantum devices. Here, we report on defect engineering of silicon with ion pulses from a laser accelerator in the laser intensity range of 1019 W cm−2 and ion flux levels of up to 1022 ions cm−2 s−1, about five orders of magnitude higher than conventional ion implanters. Low energy ions from plasma expansion of the laser-foil target are implanted near the surface and then diffuse into silicon samples locally pre-heated by high energy ions from the same laser-ion pulse. Silicon crystals exfoliate in the areas of highest energy deposition. Color centers, predominantly W and G-centers, form directly in response to ion pulses without a subsequent annealing step. We find that the linewidth of G-centers increases with high ion flux faster than the linewidth of W-centers, consistent with density functional theory calculations of their electronic structure. Intense ion pulses from a laser-accelerator drive materials far from equilibrium and enable direct local defect engineering and high flux doping of semiconductors.This work was supported by the Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy, under Contract No. DE-AC02-05CH11231. Experiments at the BELLA Center were enabled through facilities developed by HEP and LaserNetUS. TS and JGL gratefully acknowledge support by the coordinated research project “F11020” of the International Atomic Energy Agency (IAEA). LZT and JS were supported by the Molecular Foundry, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231Peer reviewe

A sequence based SNP approach for non-culture strain characterisation of Neisseria meningitidis

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Donor-acceptor pair recombination in non-stoichiometric ZnO thin films

The stoichiometry of pulsed-laser deposited, nominally undoped ZnO thin films can be controlled via oxygen partial pressure during growth. Samples grown under zinc-rich conditions at pressures below 0.02 mbar show the formation of a donor-acceptor pair recombination at 3.104 eV. Temperature- and excitation-dependent photoluminescence studies revealed structural defects, namely zinc interstitials and zinc vacancies, with donor and acceptor binding energies of E(D) = 40 meV and E(A) = 320 meV, respectively, to be accountable for this recombination. The findings were confirmed via calculations within the quantum defect model. (C) 2009 Elsevier Ltd. All rights reserved.</p

Origin of the near-band-edge luminescence in MgxZn1-xO alloys

The carrier dynamics of donor-bound and free excitons, localized in the alloy disorder potential, were investigated for MgxZn1-xO (0.08 &lt;x &lt;0.33) thin films. The measured transients show a fast decrease in the luminescence intensity within the first nanoseconds, followed by a slow, strongly nonexponential decay. Shortly after the excitation pulse, the time-delayed spectra are dominated by the (D-0,X) recombination. With increasing time, the free exciton recombination becomes visible on the high-energy side, dominating the spectra at large times after the excitation pulse. By fitting the transients with nonexponential model decay functions, we can deconvolve the luminescence spectra. As expected, the mean decay time of the excitons localized in the alloy disorder potential significantly increases with increasing Mg content.</p

Donor-acceptor pair recombination in non-stoichiometric ZnO thin films

The stoichiometry of pulsed-laser deposited, nominally undoped ZnO thin films can be controlled via oxygen partial pressure during growth. Samples grown under zinc-rich conditions at pressures below 0.02 mbar show the formation of a donor-acceptor pair recombination at 3.104 eV. Temperature- and excitation-dependent photoluminescence studies revealed structural defects, namely zinc interstitials and zinc vacancies, with donor and acceptor binding energies of E(D) = 40 meV and E(A) = 320 meV, respectively, to be accountable for this recombination. The findings were confirmed via calculations within the quantum defect model. (C) 2009 Elsevier Ltd. All rights reserved.</p

Origin of the near-band-edge luminescence in MgxZn1-xO alloys

The carrier dynamics of donor-bound and free excitons, localized in the alloy disorder potential, were investigated for MgxZn1-xO (0.08 &lt;x &lt;0.33) thin films. The measured transients show a fast decrease in the luminescence intensity within the first nanoseconds, followed by a slow, strongly nonexponential decay. Shortly after the excitation pulse, the time-delayed spectra are dominated by the (D-0,X) recombination. With increasing time, the free exciton recombination becomes visible on the high-energy side, dominating the spectra at large times after the excitation pulse. By fitting the transients with nonexponential model decay functions, we can deconvolve the luminescence spectra. As expected, the mean decay time of the excitons localized in the alloy disorder potential significantly increases with increasing Mg content.</p

Impact of strain on electronic defects in (Mg,Zn)O thin films

We have investigated the impact of strain on the incorporation and the properties of extended and point defects in (Mg,Zn)O thin films by means of photoluminescence, X-ray diffraction, deep-level transient spectroscopy (DLTS), and deep-level optical spectroscopy. The recombination line Y2, previously detected in ZnO thin films grown on an Al-doped ZnO buffer layer and attributed to tensile strain, was exclusively found in (Mg,Zn)O samples being under tensile strain and is absent in relaxed or compressively strained thin films. Furthermore a structural defect E3′ can be detected via DLTS measurements and is only incorporated in tensile strained samples. Finally it is shown that the omnipresent deep-level E3 in ZnO can only be optically recharged in relaxed ZnO samples