Ionenstrahl-Modifikation von Diamant zur optimierten Farbzentrenbildung als Wegbereiter für skalierbare Quantentechnologien

Die vorliegende Dissertation ist eine Zusammenstellung einer Auswahl von drei Veröffentlichungen, welche vom Autor verfasst oder mit verfasst wurden. Sie beschäftigt sich mit der Ausheilung von Ionenstrahl-induzierten Gitterschäden sowie der Bildung von Farbzentren in Diamant.Das Stickstofffehlstellenzentrum als Farbzentrum im Diamant steht dabei im Fokus der Untersuchungen. Sein Elektronenspin lässt sich optisch bei Raumtemperatur initialisieren und auslesen. Dabei besitzt es eine lange Kohärenzzeit und die Kopplung zu umliegenden Spins machen es zu einem idealen Kandidaten als Qubit in der Quanteninformationsverarbeitung. Auch in der Einzelspinmagnetometrie hat es bereits seine Anwendung gefunden. Die effiziente Bildung von Farbzentren durch gezielte Implantation ist daher von großer Bedeutung. Im Ergebnis wurde eine Verzehnfachung der Bildungsrate sowie eine Verbesserung der Kohärenz und eine Stabilisierung des negativen Ladungszustands erreicht. Dadurch konnte ein mehr als zwanzig Jahre altes Problem gelöst werden. Mit Hilfe dieser wesentlichen Verbesserungen wird die skalierbare Festkörperquantencomputerarchitektur bei Raumtemperatur als zukünftige Alternative zu den Tieftemperaturansätzen mit Phosphor-Qubits in Silizium möglich. Untersucht wird in dieser Arbeit ein weites Spektrum von Ionenimplantationen in Diamant. Dies reicht von der vollständigen Zerstörung und Umwandlung des Diamanten zu graphitartigen Domäne durch Hochdosis-Implantationen bis hin zur Dotierung durch das gezielte Implantieren von Dotanten. Darüber hinaus wird die Bildung bekannten sowie auch neuer Farbzentren diskutiert.:Inhalt Bibliographische Beschreibung iii Referat iii Abstract iv 1. Einleitung. . .1 2. Thematischer Hintergrund. . .3 2.1. Ionenimplantation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Ionenstrahlinduzierte Gitterschäden . . . . . . . . . . . . . . . . . . . . . 7 2.3. Defekt-Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.4. Physikalische Klassifizierung und Typisierung von Diamanten . . . . . . . 10 2.5. Ladungszustand von Defekten . . . . . . . . . . . . . . . . . . . . . . . . 14 2.6. Farbzentren und Defekte in Diamant . . . . . . . . . . . . . . . . . . . . . 17 2.6.1. Die Leerstelle oder Vakanz GR1- und ND1-Zentrum . . . . . . . . 19 2.6.2. Das Kohlenstoff-”Zwischengitteratom” R2-Zentrum . . . . . . . . 22 2.6.3. Frenkel-Paar (I-V) . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.6.4. Vakanzaggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 2.6.5. Substitutioneller, vereinzelter Stickstoff im Diamanten . . . . . . . 28 2.6.6. Stickstofffehlstellenzentrum NV . . . . . . . . . . . . . . . . . . . 30 2.7. Thermische Behandlung von Diamanten . . . . . . . . . . . . . . . . . . . 34 2.7.1. Vakanz-Erzeugung . . . . . . . . . . . . . . . . . . . . . . . . . . 38 2.7.2. Kohlenstoff-Zwischengitteratom-Bildungsrate . . . . . . . . . . . . 40 2.7.3. Thermische Behandlung bis 600 °C nach der Bestrahlung . . . . . . 41 2.7.4. Thermische Behandlung oberhalb von 600 °C nach der Bestrahlung. . .47 3. Kumulativer Teil der Dissertation . . .55 3.1. Veröffentlichung Nr. 1 Investigation of the graphitization process of ionbeam irradiated diamond using ellipsometry, Raman spectroscopy and electrical transport measurements . . . . . . . . . . . . . . . . . . . . . . . . 55 3.1.1. Zusammenfassung und Diskussion Veröffentlichung Nr. 1 . . . . . 62 3.2. Veröffentlichung Nr. 2 Screening and engineering of colour centres in diamond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 3.2.1. Zusammenfassung und Diskussion Veröffentlichung Nr. 2 . . . . . 88 3.3. Veröffentlichung Nr. 3 Coulomb-driven single defect engineering for scalable qubits and spin sensors in diamond . . . . . . . . . . . . . . . . . . . 89 3.3.1. Zusammenfassung und Diskussion Veröffentlichung Nr. 3 . . . . . 109 4. Zusammenfassung und Ausblick . . .111 Literaturverzeichnis. . . 114 A. Eigenanteil der beigefügten Veröffentlichungen vii A.1. Veröffentlichung Nr. 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii A.2. Veröffentlichung Nr. 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii A.3. Veröffentlichung Nr. 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii B. Danksagung ix C. Lebenslauf xi D. Publikationen xiii E. Selbstständigkeitserklärung xv

Room-Temperature Solid-State Transformation of Na4 SnS4 ⋅ 14H2 O into Na4 Sn2 S6 ⋅ 5H2 O: An Unusual Epitaxial Reaction Including Bond Formation, Mass Transport, and Ionic Conductivity

A highly unusual solid-state epitaxy-induced phase transformation of Na4 SnS4  ⋅ 14H2 O (I) into Na4 Sn2 S6  ⋅ 5H2 O (II) occurs at room temperature. Ab initio molecular dynamics (AIMD) simulations indicate an internal acid-base reaction to form [SnS3 SH]3- which condensates to [Sn2 S6 ]4- . The reaction involves a complex sequence of O-H bond cleavage, S2- protonation, Sn-S bond formation and diffusion of various species while preserving the crystal morphology. In situ Raman and IR spectroscopy evidence the formation of [Sn2 S6 ]4- . DFT calculations allowed assignment of all bands appearing during the transformation. X-ray diffraction and in situ 1 H NMR demonstrate a transformation within several days and yield a reaction turnover of ≈0.38 %/h. AIMD and experimental ionic conductivity data closely follow a Vogel-Fulcher-Tammann type T dependence with D(Na)=6×10-14  m2  s-1 at T=300 K with values increasing by three orders of magnitude from -20 to +25 °C

Room‐Temperature Solid‐State Transformation of Na4_{4}SnS4_{4} ⋅ 14H2_{2}O into Na4_{4}Sn2_{2}S6_{6} ⋅ 5H2_{2}O: An Unusual Epitaxial Reaction Including Bond Formation, Mass Transport, and Ionic Conductivity

A highly unusual solid-state epitaxy-induced phase transformation of Na$_{4}$SnS$_{4}$ ⋅ 14H$_{2}$O (I) into Na$_{4}$Sn$_{2}$S$_{6}$ ⋅ 5H$_{2}$O (II) occurs at room temperature. Ab initio molecular dynamics (AIMD) simulations indicate an internal acid-base reaction to form [SnS$_{3}$SH]$^{3-}$ which condensates to [Sn$_{2}$S$_{6}$]$^{4–}$. The reaction involves a complex sequence of O−H bond cleavage, S$^{2–}$ protonation, Sn−S bond formation and diffusion of various species while preserving the crystal morphology. In situ Raman and IR spectroscopy evidence the formation of [Sn$_{2}$S$_{6}$]$^{4–}$. DFT calculations allowed assignment of all bands appearing during the transformation. X-ray diffraction and in situ $^{1}$H NMR demonstrate a transformation within several days and yield a reaction turnover of ≈0.38 %/h. AIMD and experimental ionic conductivity data closely follow a Vogel-Fulcher-Tammann type T dependence with D(Na)=6×10$^{-14}$ m$^{2}$ s$^{-1}$ at T=300 K with values increasing by three orders of magnitude from −20 to +25 °C

Weak electron irradiation suppresses the anomalous magnetization of N-doped diamond crystals

Several diamond bulk crystals with a concentration of electrically neutral single substitutional nitrogen atoms of ≲80 ppm, the so-called C or P1 centers, are irradiated with electrons at 10 MeV energy and low fluence. The results show a complete suppression of the irreversible behavior in field and temperature of the magnetization below 30 K, after a decrease in ≲40 ppm in the concentration of C centers produced by the electron irradiation. This result indicates that magnetic C centers are at the origin of the large hysteretic behavior found recently in nitrogen-doped diamond crystals. This is remarkable because of the relatively low density of C centers, stressing the extraordinary role of the C centers in triggering those phenomena in diamond at relatively high temperatures. After annealing the samples at high temperatures in vacuum, the hysteretic behavior is partially recovered

Spectral features of Pb-related color centers in diamond: a systematic photoluminescence characterization

We report on the systematic characterization of the optical properties of diamond color centers based on Pb impurities. An ensemble photoluminescence analysis of their spectral emission was performed at different excitation wavelengths in the 405–520 nm range and at different temperatures in the 4–300 K range. The series of observed spectral features consist of different emission lines associated with Pb-related defects. Finally, a room-temperature investigation of single-photon emitters under 490.5 nm laser excitation is reported, revealing different spectral signatures with respect to those already reported under 514 nm excitation. This work represents a substantial progress with respect to previous studies on Pb-related color centers, both in the attribution of an articulated series of spectral features and in the understanding of the formation process of this type of defect, thus clarifying the potential of this system for high-impact applications in quantum technologies

Spectral Emission Dependence of Tin‐Vacancy Centers in Diamond from Thermal Processing and Chemical Functionalization

We report a systematic photoluminescence (PL) investigation of the spectral emission properties of individual optical defects fabricated in diamond upon ion implantation and annealing. Three spectral lines at 620 nm, 631 nm, and 647 nm are identified and attributed to the SnV center due to their occurrence in the PL spectra of the very same single-photon emitting defects. We show that the relative occurrence of the three spectral features can be modified by oxidizing the sample surface following thermal annealing. We finally report the relevant emission properties of each class of individual emitters, including the excited state emission lifetime and the emission intensity saturation parameters.Comment: 12 pages, 6 figures, 1 tabl

Spectral features of Pb-related color centers in diamond – a systematic photoluminescence characterization

We report on the systematic characterization of the optical properties of diamond color centers based on Pb impurities. An ensemble photoluminescence analysis of their spectral emission was performed at different excitation wavelengths in the 405-520 nm range and at different temperatures in the 4-300 K range. The series of observed spectral features consist of different emission lines associated with Pb-related defects. Finally, a room-temperature investigation of single-photon emitters under 490.5 nm laser excitation is reported, revealing different spectral signatures with respect to those already reported under 514 nm excitation. This work represents a substantial progress with respect to previous studies on Pb-related color centers, both in the attribution of an articulated series of spectral features and in the understanding of the formation process of this type of defect, thus clarifying the potential of this system for high-impact applications in quantum technologies

Pathogen- and Host-Directed Antileishmanial Effects Mediated by Polyhexanide (PHMB)

BACKGROUND:Cutaneous leishmaniasis (CL) is a neglected tropical disease caused by protozoan parasites of the genus Leishmania. CL causes enormous suffering in many countries worldwide. There is no licensed vaccine against CL, and the chemotherapy options show limited efficacy and high toxicity. Localization of the parasites inside host cells is a barrier to most standard chemo- and immune-based interventions. Hence, novel drugs, which are safe, effective and readily accessible to third-world countries and/or drug delivery technologies for effective CL treatments are desperately needed. METHODOLOGY/PRINCIPAL FINDINGS:Here we evaluated the antileishmanial properties and delivery potential of polyhexamethylene biguanide (PHMB; polyhexanide), a widely used antimicrobial and wound antiseptic, in the Leishmania model. PHMB showed an inherent antileishmanial activity at submicromolar concentrations. Our data revealed that PHMB kills Leishmania major (L. major) via a dual mechanism involving disruption of membrane integrity and selective chromosome condensation and damage. PHMB's DNA binding and host cell entry properties were further exploited to improve the delivery and immunomodulatory activities of unmethylated cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODN). PHMB spontaneously bound CpG ODN, forming stable nanopolyplexes that enhanced uptake of CpG ODN, potentiated antimicrobial killing and reduced host cell toxicity of PHMB. CONCLUSIONS:Given its low cost and long history of safe topical use, PHMB holds promise as a drug for CL therapy and delivery vehicle for nucleic acid immunomodulators