| 1. |
- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 3. |
- Chen, Weimin, et al.
(author)
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How to Deactivate Harmful Defects and Active them for New Spin Functionalities in a Semiconductor?
- 2015
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In: Abstract Book. ; , s. FF3.02-
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Conference paper (peer-reviewed)abstract
- We demonstrate a general approach via spin engineering that is capable of not only deactivating defect-mediated efficient non-radiative carrier recombination channels in a semiconductor that are harmful to photonic and photovoltaic device performance, but also adding new room-temperature (RT) spin functionalities that are desirable for future spintronics and spin-photonics but so far unachievable otherwise. This approach exploits the Pauli Exclusion Principle that prohibits occupation of a non-degenerate defect level by two spin-parallel electrons, thereby providing spin blockade of carrier recombination via the defect level. The success of the approach is demonstrated in the dilute nitride of Ga(In)NAs, which holds promises for low-cost, highly efficient lasers for fiber-optic communications as well as for multi-band and multi-junction solar cell applications. First we identify that Gai self-interstitials and their complexes are the most common grown-in defects found in Ga(In)NAs grown by both molecular beam epitaxy (MBE) and metalorganic chemical vapour deposition (MOCVD). They provide a dominant non-radiative shunt path for non-equilibrium carriers, leading to low efficiencies of light-emitting and photon-charge carrier conversion. Spin blockade is shown to lead to a giant enhancement by up to 800% in light emission intensity at RT.Furthermore we show that via spin engineering these seemingly harmful defects can be turned into advantages by adding unconventional defect-enabled spin functionalities that are highly effective at RT, including some of the fundamental building blocks essential for future spintronics. We demonstrate efficient defect-engineered spin filtering in Ga(In)NAs, which is capable of generating a record-high degree (> 40%) of electron spin polarization at RT [Nature Materials 8, 198 (2009), Phys. Rev. B 89, 195412 (2014)]. We also provide the first experimental demonstration of an efficient RT spin amplifier based on defect engineered Ga(In)NAs with a spin gain up to 2700% [Adv. Materials 25, 738 (2013)]. Such a spin amplifier is shown to be capable of amplifying a fast-modulating input spin signal while truthfully maintaining its time variation of the spin-encoded information [7]. By taking advantage of the spin amplification effect, we show that Ga(In)NAs can be employed as efficient RT spin detectors, with spin detection efficiency well exceeding 100% [8,9]. By combining the spin-filtering effect and hyperfine coupling, we further achieve the first realization of RT nuclear spin hyperpolarization in semiconductors via conduction electrons [Nature Communications. 4, 1751 (2013)], relevant to nuclear spin qubits. We believe that such defect-enabled spin functionalities could potentially provide an attractive, alternative solution to the current and important issues on RT spin injection, spin amplification and spin detection in semiconductors for future spintronics.
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| 5. |
- Puttisong, Yuttapoom, et al.
(author)
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Defect-enabled Room-temperature Spin Functionality in Ga(In)NAs
- 2012
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Conference paper (other academic/artistic)abstract
- Efficient generation, maintaining, manipulation and detection of electron spin polarization and coherence at room-temperature (RT) in semiconductors is a prerequisite for the success of future semiconductor spintronics. Potential spintronic devices are expected to be based on fundamental building blocks such as spin filters (or spin injectors or spin aligners), spin amplifiers and spin detectors. During the past decade spin filters and spin detectors have been a main focal point of intense research efforts in the field of semiconductor spintronics that have led to many innovative approaches and encouraging developments. In contrast, experimental developments in spin amplifiers have been extremely limited. At present, realization of efficient RT spin functionality remains to be a great challenge and a hotly pursued research topic.In this work, we explore a new and unconventional approach of defect-enabled spin functionality in a non-magnetic semiconductor without requiring a magnetic layer or external magnetic fields. We demonstrated efficient defect-engineered spin filtering in Ga(In)NAs, which is capable of generating a remarkably high spin polarization degree (> 40%) of conduction electrons at RT. The highest spin polarization achieved to date by using this approach is up to 90 %. We also proposed a conceptually new spin amplifier by defect engineering and provided the first experimental demonstration of an efficient RT spin amplifier based on Ga(In)NAs with a spin gain up to 2700%! Such a spin amplifier is shown to be capable of amplifying a fast-modulating input spin signal while truthfully maintaining its time variation of the spin-encoded information, and is predicted to remain functional up to 1 GHz. By taking advantage of the spin amplification effect, we further showed that Ga(In)NAs can be employed as an efficient RT spin detector, with spin detection efficiency well exceeding 100%. Applications of such a spin-functional semiconductor material could potentially provide an attractive and viable solution to the current and important issues on RT spin injection, spin amplification and spin detection in semiconductors for future spintronics.
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| 8. |
- Puttisong, Yuttapoom, et al.
(author)
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Room-Temperature Electron Spin Amplifier Base on Ga(In)NAs Alloys
- 2013
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In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 25:5, s. 738-742
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Journal article (peer-reviewed)abstract
- The first experimental demonstration of a spin amplifier at room temperature is presented. An efficient, defect-enabled spin amplifier based on a non-magnetic semiconductor, Ga(In)NAs, is proposed and demonstrated, with a large spin gain (up to 2700% at zero field) for conduction electrons and a high cut-off frequency up to 1 GHz.
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| 9. |
- Wang, Xingjun, et al.
(author)
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Dominant recombination centers in Ga(In)NAs alloys: Ga interstitials
- 2009
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In: Applied Physics Letters. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 95, s. 241904-
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Journal article (peer-reviewed)abstract
- Opticallydetected magnetic resonance measurements are carried out to study formationof Ga interstitial-related defects in Ga(In)NAs alloys. The defects, whichare among dominant nonradiative recombination centers that control carrier lifetimein Ga(In)NAs, are unambiguously proven to be common grown-in defectsin these alloys independent of the employed growth methods. Thedefects formation is suggested to become thermodynamically favorable because ofthe presence of nitrogen, possibly due to local strain compensation.
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