Extrinsic Quantum Centers in Silicon for Nanophotonics and Quantum Applications

Quantenzentren in Kristallgittern spielen als sogenannte Festkörper-Qubits eine entscheidende Rolle für die Entwicklung der zweiten Quantenrevolution. Das G-Zentrum in Silizium kann hierfür einen wesentlichen Beitrag leisten, da es sich CMOS-kompatibel und damit skalierbar herstellen lässt, es eine scharfe Nullphononenlinie im Bereich der optischen Telekommunikation besitzt und ODMR-aktiv ist. Dies macht es zu einem geeigneten Kandidaten für die Entwicklung photonischer Mikrochips, auf denen Quantentechnologien und Lichtwellenleitung durch eine Spin-Photon-Schnittstelle miteinander verknüpft werden, um somit alle Kriterien zum Aufbau eines Quantennetzwerkes zu erfüllen. In der vorliegenden Arbeit werden G-Zentren durch niederenergetische und räumlich-selektive Ionen-Implantation hergestellt und mittels Photolumineszenz-Spektroskopie und Magnetresonanzmessungen auf ihre optischen und quantenphysikalischen Eigenschaften untersucht. Anhand umfangreicher temperaturabhängiger Ensemble-Messungen in reinem Silizium werden offene Fragen zum Sättigungsverhalten, der Rekombinationsdynamik und der Verschiebung bzw. Verbreiterung der Nullphononenlinie geklärt und die ersten Zerfallszeit-Messungen des angeregten Zustandes des Defektes vorgestellt. Durch die Verwendung von SOI-Proben in Kombination mit niederenergetischer Ionen-Implantation wird weiterhin die erste, jemals in Silizium isolierte Einzelphotonenquelle hergestellt und durch zahlreiche Polarisations- und Korrelationsmessungen als solche identifiziert. Durch die Einzelphotonenmessung erfolgt zusätzlich eine erste Abschätzung der Quanteneffizienz der G-Zentren und die Messung der Lebensdauer des isolierten angeregten Zustandes. Um den Quantenzustand der G-Zentren mittels Mikrowellenfeld manipulieren und sowohl optische als auch elektronisch auslesen zu können, wird ein experimenteller Aufbau beschrieben, mit dem die magnetische Resonanz der G-Zentren in einer SOI-Probe temperaturabhängig bis in den kryogenen Bereich detektiert werden kann. Nach den ersten manuellen Testmessungen wird der Versuchsaufbau durch neue Steuergeräte und eine Automatisierung weiter optimiert, um damit umfangreiche Messungen bei T = 40K und Raumtemperatur durchzuführen. Dabei wird eine mikrowellenabhängige Manipulation der Photolumineszenz der G-Zentren beobachtet, welche mit dem detektierten Photostrom korreliert ist. Die Manipulation der Photolumineszenz wird hauptsächlich auf eine Veränderung der Ladungsträgerdichte aufgrund anderer spinabhängiger Rekombinationszentren zurückgeführt, welche sich an den Grenzflächen des SOI-Schichtstapels bilden. Ideen, um den Einfluss der G-Zentren durch Unterdrückung der anderen Rekombinationszentren zu erhöhen, werden diskutiert.:Bibliografische Beschreibung Referat Abstract Zusammenfassung der Dissertation Contents List of Figures List of Tables Abbreviations 1 Introduction and motivation 1.1 Demand for silicon photonics and quantum technologies 1.2 Description and aim of the project 1.3 Outline 2 Solid-state and optical properties of silicon 2.1 Crystal properties 2.1.1 Structure 2.1.2 Lattice vibrations 2.1.3 Debye-Waller factor 2.1.4 Energy bands 2.2 Defects and doping in silicon 2.2.1 Intrinsic and extrinsic point defects 2.2.2 Line, area and volume defects 2.2.3 Doping 2.3 Luminescence from silicon 2.3.1 Optical properties of bulk silicon 2.3.2 Non-linear effects in silicon 2.3.3 Dislocation loops 2.3.4 Quantum confinement effects 2.3.5 Rare-Earth (Erbium) doping 2.3.6 Light emitting defects in silicon 2.4 G centers in silicon 2.4.1 Structural properties and creation of G centers 2.4.2 Optical properties and applications of G centers 3 Solid-state quantum technologies 3.1 Ion implantation for defect engineering 3.1.1 High-energy accelerator “Lipsion” 3.1.2 100 kV Microbeam 3.2 Quantum optics 3.2.1 Properties of single photons 3.2.2 Photoluminescence and single-photon measurements 3.2.3 Applications of single-photon sources - quantum key distribution 3.3 Quantum computing 3.3.1 Basic principle 3.3.2 Photonic qubits 3.3.3 Solid-state qubits 4 Optical properties of an ensemble of G centers in silicon 4.1 Experiment description and basic properties 4.1.1 Sample fabrication 4.1.2 Optical spectroscopy 4.1.3 PL response of different defect densities 4.1.4 Photoluminescence excitation measurement 4.1.5 Saturation behavior 4.2 Temperature-dependent photoluminescence spectroscopy 4.2.1 Thermal redshift 4.2.2 ZPL broadening 4.2.3 Temperature-dependent PL intensity 4.2.4 Temperature-dependent lifetime and decay rate 4.3 Recombination dynamics 4.3.1 Spectrally selective recombination dynamics 4.3.2 Lifetime and defect density 4.3.3 Phonon-assisted recombination model 5 G centers as single-photon sources in silicon 5.1 Experimental description 5.1.1 Sample fabrication 5.1.2 Optical spectroscopy 5.2 Evidence of a single-photon source 5.2.1 Autocorrelation study 5.2.2 Photodynamics 5.2.3 PL polarization 5.3 Properties of single photons from G centers 5.3.1 ZPL shift 5.3.2 Saturation and stability 5.3.3 Lifetime of an isolated G center 5.3.4 Estimation of the quantum efficiency 6 Optical and photoelectric readout of G centers in silicon 6.1 Setup 6.1.1 Sample preparation 6.1.2 Circuit board and cryostat 6.1.3 Measuring and control devices 6.1.4 PL spectroscopy 6.2 Manual ODMR and PDMR at cryogenic temperature 6.3 Automated PDMR measurements 6.3.1 Spectrum analysis 6.3.2 Etiology 6.3.3 Voltage dependence 6.3.4 Temperature dependence 6.3.5 Laser dependence 6.3.6 Magnetic field dependence 6.4 Automated PDMR and ODMR at cryogenic temperature 6.5 Discussion 6.5.1 Microwave dielectric heating in silicon 6.5.2 Spin-dependent recombination centers in Si and Si/SiO2 interfaces 6.6 Conclusion 7 Summary and outlook Bibliography Danksagung Wissenschaftlicher Werdegang Selbstständigkeitserklärung Erklärung für die BibliothekQuantum centers in crystal lattices can form so-called solid-state qubits that play a crucial role for the progress of the second quantum revolution. The G center in silicon can make a significant contribution to this, since it can be fabricated in a CMOS compatible and thus scalable way, it has a sharp zero-phonon line in the optical telecommunication range, and it is ODMR active. This makes it a suitable candidate for the development of photonic microchips, where quantum technologies and optical waveguides are linked by a spin-photon interface, thus fulfilling all the criteria to build a quantum network. In the present work, G centers are fabricated by low-energy and spatially-selective ion implantation and their optical and quantum physical properties are investigated by photoluminescence spectroscopy and magnetic resonance measurements. Using extensive temperature-dependent ensemble measurements in pure silicon, open questions on saturation behavior, recombination dynamics, and zero-phonon line shift as well as broadening are clarified, and the first decay time measurements of the excited state of this defect are presented. By using SOI samples in combination with low-energy ion implantation, the first single-photon source ever isolated in silicon is further fabricated and identified as such by extensive polarization and correlation measurements. The single-photon measurement additionally provides a first estimation of the quantum efficiency of the G centers and the measurement of the lifetime of the isolated excited state. In order to manipulate the quantum state of the G centers by means of a microwave field and to enable an optical as well as an electronical readout, an experimental setup is designed and assembled that allows the temperature-dependent detection of magnetic resonances of G centers in a SOI sample down to the cryogenic range. After the first manual test measurements, the experimental setup is further optimized by new control devices and process automation to allow extensive measurements at T = 40K and room temperature. A microwave-dependent manipulation of the photoluminescence of the G centers is observed, which is correlated with the detected photocurrent. The manipulation of the photoluminescence is mainly attributed to a change in the charge carrier density due to other spin-dependent recombination centers that form at the interfaces of the SOI layer stack. Ideas to increase the influence of the G centers by suppressing the other recombination centers are discussed.:Bibliografische Beschreibung Referat Abstract Zusammenfassung der Dissertation Contents List of Figures List of Tables Abbreviations 1 Introduction and motivation 1.1 Demand for silicon photonics and quantum technologies 1.2 Description and aim of the project 1.3 Outline 2 Solid-state and optical properties of silicon 2.1 Crystal properties 2.1.1 Structure 2.1.2 Lattice vibrations 2.1.3 Debye-Waller factor 2.1.4 Energy bands 2.2 Defects and doping in silicon 2.2.1 Intrinsic and extrinsic point defects 2.2.2 Line, area and volume defects 2.2.3 Doping 2.3 Luminescence from silicon 2.3.1 Optical properties of bulk silicon 2.3.2 Non-linear effects in silicon 2.3.3 Dislocation loops 2.3.4 Quantum confinement effects 2.3.5 Rare-Earth (Erbium) doping 2.3.6 Light emitting defects in silicon 2.4 G centers in silicon 2.4.1 Structural properties and creation of G centers 2.4.2 Optical properties and applications of G centers 3 Solid-state quantum technologies 3.1 Ion implantation for defect engineering 3.1.1 High-energy accelerator “Lipsion” 3.1.2 100 kV Microbeam 3.2 Quantum optics 3.2.1 Properties of single photons 3.2.2 Photoluminescence and single-photon measurements 3.2.3 Applications of single-photon sources - quantum key distribution 3.3 Quantum computing 3.3.1 Basic principle 3.3.2 Photonic qubits 3.3.3 Solid-state qubits 4 Optical properties of an ensemble of G centers in silicon 4.1 Experiment description and basic properties 4.1.1 Sample fabrication 4.1.2 Optical spectroscopy 4.1.3 PL response of different defect densities 4.1.4 Photoluminescence excitation measurement 4.1.5 Saturation behavior 4.2 Temperature-dependent photoluminescence spectroscopy 4.2.1 Thermal redshift 4.2.2 ZPL broadening 4.2.3 Temperature-dependent PL intensity 4.2.4 Temperature-dependent lifetime and decay rate 4.3 Recombination dynamics 4.3.1 Spectrally selective recombination dynamics 4.3.2 Lifetime and defect density 4.3.3 Phonon-assisted recombination model 5 G centers as single-photon sources in silicon 5.1 Experimental description 5.1.1 Sample fabrication 5.1.2 Optical spectroscopy 5.2 Evidence of a single-photon source 5.2.1 Autocorrelation study 5.2.2 Photodynamics 5.2.3 PL polarization 5.3 Properties of single photons from G centers 5.3.1 ZPL shift 5.3.2 Saturation and stability 5.3.3 Lifetime of an isolated G center 5.3.4 Estimation of the quantum efficiency 6 Optical and photoelectric readout of G centers in silicon 6.1 Setup 6.1.1 Sample preparation 6.1.2 Circuit board and cryostat 6.1.3 Measuring and control devices 6.1.4 PL spectroscopy 6.2 Manual ODMR and PDMR at cryogenic temperature 6.3 Automated PDMR measurements 6.3.1 Spectrum analysis 6.3.2 Etiology 6.3.3 Voltage dependence 6.3.4 Temperature dependence 6.3.5 Laser dependence 6.3.6 Magnetic field dependence 6.4 Automated PDMR and ODMR at cryogenic temperature 6.5 Discussion 6.5.1 Microwave dielectric heating in silicon 6.5.2 Spin-dependent recombination centers in Si and Si/SiO2 interfaces 6.6 Conclusion 7 Summary and outlook Bibliography Danksagung Wissenschaftlicher Werdegang Selbstständigkeitserklärung Erklärung für die Bibliothe

Highlights CNR 2009-2010

The 2009-2010 edition of CNR.it (the CNR Highlights) includes more than 200 scientific papers. Conceived and written in English to present to the international public the dynamic and multi-sided reality of the largest research organization in Italy, this review is a partial but significant collection of works carried out by CNR researchers and published on the main scientific journals. Articles have been selected on the basis of their impact factors among the 14.000 or so articles produced in the last two years, to present our best image to the world. The present one is only the second of the CNR Highlights, after a first one dedicated to the Italian public, but the series represent already a must for our researchers, to promote their works along best-practice lines followed in research organizations worldwide. In the present edition, with a more catchy new look, articles, images and scientific popularizations provide a broad outlook of the activities of CNR, reporting, side by side with research articles, about technology transfer and scientific support activities to national and local institutions. The 2009-2010 Highlights are divided into four sections, similarly to the previous edition. However, as the reader looks through the pages, the interdisciplinary nature of the works will not pass unnoticed, interdisciplinarity being the peculiar feature of CNR, an organization in which the different disciplines find a fertile breeding ground to communicate and share their different knowledge

Activity Report in “Highlights 2009/2010”

The 2009-2010 edition of CNR.it (the CNR Highlights) includes more than 200 scientific papers. Conceived and written in English to present to the international public the dynamic and multi-sided reality of the largest research organization in Italy, this review is a partial but significant collection of works carried out by CNR researchers and published on the main scientific journals. In the present edition, with a more catchy new look, articles, images and scientific popularizations provide a broad outlook of the activities of CNR, reporting, side by side with research articles, about technology transfer and scientific support activities to national and local institutions. The 2009-2010 Highlights are divided into four sections, similarly to the previous edition. However, as the reader looks through the pages, the interdisciplinary nature of the works will not pass unnoticed, interdisciplinarity being the peculiar feature of CNR, an organization in which the different disciplines find a fertile breeding ground to communicate and share their different knowledge