Deterministic coupling of a single silicon-vacancy color center to a photonic crystal cavity in diamond

Deterministic coupling of single solid-state emitters to nanocavities is the key for integrated quantum information devices. We here fabricate a photonic crystal cavity around a preselected single silicon-vacancy color center in diamond and demonstrate modification of the emitters internal population dynamics and radiative quantum efficiency. The controlled, room-temperature cavity coupling gives rise to a resonant Purcell enhancement of the zero-phonon transition by a factor of 19, coming along with a 2.5-fold reduction of the emitter's lifetime

Fluorescence and polarization spectroscopy of single silicon vacancy centers in heteroepitaxial nanodiamonds on iridium

We introduce an advanced material system for the production and spectroscopy of single silicon vacancy (SiV) color centers in diamond. We use microwave plasma chemical vapor deposition to synthesize heteroepitaxial nanodiamonds of approx. 160 nm in lateral size with a thickness of approx. 75 nm. These oriented 'nanoislands' combine the enhanced fluorescence extraction from subwavelength sized nanodiamonds with defined crystal orientation. The investigated SiV centers display narrow zero-phonon-lines down to 0.7 nm in the wavelength range 730-750 nm. We investigate in detail the phonon-coupling and vibronic sidebands of single SiV centers, revealing significant inhomogeneous effects. Polarization measurements reveal polarized luminescence and preferential absorption of linearly polarized light.Comment: 9 pages, 9 figures, v3 slightly revised, accepted by Phys. Rev.

Electronic transitions of single silicon vacancy centers in the near-infrared spectral region

Photoluminescence (PL) spectra of single silicon vacancy (SiV) centers frequently feature very narrow room temperature PL lines in the near-infrared (NIR) spectral region, mostly between 820 nm and 840 nm, in addition to the well known zero-phonon-line (ZPL) at approx. 738 nm [E. Neu et al., Phys. Rev. B 84, 205211 (2011)]. We here exemplarily prove for a single SiV center that this NIR PL is due to an additional purely electronic transition (ZPL). For the NIR line at 822.7 nm, we find a room temperature linewidth of 1.4 nm (2.6 meV). The line saturates at similar excitation power as the ZPL. ZPL and NIR line exhibit identical polarization properties. Cross-correlation measurements between the ZPL and the NIR line reveal anti-correlated emission and prove that the lines originate from a single SiV center, furthermore indicating a fast switching between the transitions (0.7 ns). g(2) auto-correlation measurements exclude that the NIR line is a vibronic sideband or that it arises due to a transition from/to a meta-stable (shelving) state.Comment: 9 pages, 7 figures, v2 accepted for publication in Phys. Rev.

Toward wafer-scale diamond nano- and quantum technologies

We investigate native nitrogen vacancy (NV) and silicon vacancy (SiV) color centers in a commercially available, heteroepitaxial, wafer-sized, mm thick, single-crystal diamond. We observe single, native NV centers with a density of roughly 1 NV per µm3 and moderate coherence time (T2 = 5 µs) embedded in an ensemble of SiV centers. Using low temperature luminescence of SiV centers as a probe, we prove the high crystalline quality of the diamond especially close to the growth surface, consistent with a reduced dislocation density. Using ion implantation and plasma etching, we verify the possibility to fabricate nanostructures with shallow color centers rendering our material promising for fabrication of nanoscale sensing devices. As this diamond is available in wafer-sizes up to 100 mm, it offers the opportunity to up-scale diamond-based device fabrication

Single photon emission from silicon-vacancy centres in CVD-nano-diamonds on iridium

We introduce a process for the fabrication of high quality, spatially isolated nano-diamonds on iridium via microwave plasma assisted CVD-growth. We perform spectroscopy of single silicon-vacancy (SiV)-centres produced during the growth of the nano-diamonds. The colour centres exhibit extraordinary narrow zero-phonon-lines down to 0.7 nm at room temperature. Single photon count rates up to 4.8 Mcps at saturation make these SiV-centres the brightest diamond based single photon sources to date. We measure for the first time the fine structure of a single SiV-centre thus confirming the atomic composition of the investigated colour centres.Comment: 20 pages, 13 figures, accepted by New Journal of Physic

One- and two-dimensional photonic crystal micro-cavities in single crystal diamond

The development of solid-state photonic quantum technologies is of great interest for fundamental studies of light-matter interactions and quantum information science. Diamond has turned out to be an attractive material for integrated quantum information processing due to the extraordinary properties of its colour centres enabling e.g. bright single photon emission and spin quantum bits. To control emitted photons and to interconnect distant quantum bits, micro-cavities directly fabricated in the diamond material are desired. However, the production of photonic devices in high-quality diamond has been a challenge so far. Here we present a method to fabricate one- and two-dimensional photonic crystal micro-cavities in single-crystal diamond, yielding quality factors up to 700. Using a post-processing etching technique, we tune the cavity modes into resonance with the zero phonon line of an ensemble of silicon-vacancy centres and measure an intensity enhancement by a factor of 2.8. The controlled coupling to small mode volume photonic crystal cavities paves the way to larger scale photonic quantum devices based on single-crystal diamond

Deposition of large area single crystal diamond films via heteroepitaxy on silicon: Development of appropriate buffer layer systems and studies on the nucleation mechanisms

Diamant besitzt eine Vielzahl extremer Eigenschaften wie hohe mechanische Härte, Bruchfestigkeit, thermische Leitfähigkeit oder breitbandige optische Transparenz. Speziell für elektronische Anwendungen ist Diamant in einkristalliner Qualität erforderlich, wobei das für diesen Einsatz geeignete Material nur in begrenzter Größe ( 1°) aufweisen, präpariert werden. Es wird ein Modell zur Texturverbesserung vorgestellt, das auf der gegenseitigen Ausrichtung der Ir-Kristallite im Anfangsstadium des Wachstums beruht. Die Abscheidung einkristalliner Schichten konnte auch auf andere Metalle (Rhodium, Ruthenium und Platin) übertragen werden. Der kritischste Prozess bei der heteroepitaktischen Diamantabscheidung auf Iridium ist der Nukleationsschritt, der in dieser Arbeit mit dem sog. BEN-Prozess sowohl in einem Mikrowellenplasma als auch mit einer reinen Gleichspannungs-Entladung durchgeführt wurde. Die Phänomene, die man bei der Diamantnukleation auf Iridium beobachtet, widersprechen den Vorstellungen der klassischen Keimbildungsmodelle. So bilden sich die Diamantkeime innerhalb einer ultradünnen Kohlenstoffschicht auf der Ir-Oberfläche unter Bedingungen, unter denen die Volumenphase, d.h. makroskopische Diamantkristallite, durch den Ionenbeschuss bei angelegter Biasspannung geätzt werden. Zudem stellt man direkt nach der Nukleation eine charakteristische Musterbildung und nach einem kurzen Wachstumsschritt eine selbstorganisierte Struktur der Diamantkeime fest. In Kapitel 5.3 werden deshalb die Prozesse bei der Diamantnukleation eingehend untersucht und die Struktur und Verteilung der Diamantkeime aufgeklärt. Auf der Grundlage all dieser Ergebnisse konnte ein Keimbildungsmodell für die Diamantnukleation auf Ir(001) formuliert werden, das die außergewöhnlichen Phänomene bei der Nukleation schlüssig erklärt. Abschließend wird gezeigt, dass eine großflächige Diamantabscheidung auf dem Schichtpaket Ir/YSZ/Si möglich ist.Diamond combines a multitude of unique material properties (hardness, fracture toughness, thermal conductivity, optical transparency). For electronic applications like transistors or detectors a single crystal quality is inevitable. Diamond of this quality can be synthesized only in limited size (< 1 cm2). In this work we developed a method to deposit single crystal diamond over areas bigger than 10 cm2 via chemical vapour deposition (CVD) on foreign substrates. Up to now the noble metal iridium is the most promising substrate for the heteroepitaxial deposition of diamond. At the beginning of this work thin films were prepared on SrTiO3 crystals (1 cm2) via e-beam evaporation. The huge difference in thermal expansion coefficients constitutes a serious problem for the growth of several 100-µm-thick diamond films on SrTiO3 or other typically used substrates (problem of delamination). Therefore a multilayer buffer system was implemented in this work to overcome these problems. Concerning the thermal expansion silicon represents an ideal substrate for the deposition of diamond. In a first step the Ir(001) growth surface was integrated on silicon using oxidic buffer layers. The latter inhibits silicide formation at the interface. In chapter 5.1 the results of the deposition of yttria-stabilized zirconia (YSZ) on silicon are presented. By means of an annealing step films of unrivalled crystal quality are obtained. The subsequent chapter deals with the evaporation of epitaxial iridium films on YSZ via e-beam evaporation. The development of a two-step growth process is the decisive key to obtain single crystal iridium films on top of underlying oxide buffer layers (YSZ, SrTiO3, MgO) which exhibit a much higher mosaic spread. The underlying mechanism of this exceptional behaviour was elucidated: the iridium crystallites orient themselves in the stage of coalescence. Subsequently the growth of single crystal metal films on silicon could be extended to other metals (rhodium, ruthenium and platinum). The most critical step in heteroepitaxial diamond deposition is the nucleation step. In this work the so called BEN process in a microwave plasma and a pure direct current discharge were used. The observed phenomena contradict predictions of classical nucleation theory. The diamond nuclei are formed within an ultra thin carbon layer on the Ir surface during the ion bombardment. By contrast macroscopic diamond crystallites are etched under these conditions. Furthermore a characteristic pattern formation directly after BEN and a self-organized structure of the diamond crystallites after a short growth step are observed. In chapter 5.3 the processes of the diamond nucleation are examined in detail and the structure and distribution of the diamond nuclei is elucidated. Based on this multitude of experimental results a model for the nucleation of diamond on Ir(001) is proposed which explains the observed phenomena conclusively. Finally first results concerning the large area deposition of single crystal diamond on the multilayer stack Ir/YSZ/Si are presented

Ion bombardment induced buried lateral growth: the key mechanism for the synthesis of single crystal diamond wafers

A detailed mechanism for heteroepitaxial diamond nucleation under ion bombardment in a microwave plasma enhanced chemical vapour deposition setup on the single crystal surface of iridium is presented. The novel mechanism of Ion Bombardment Induced Buried Lateral Growth (IBI-BLG) is based on the ion bombardment induced formation and lateral spread of epitaxial diamond within a ~1 nm thick carbon layer. Starting from one single primary nucleation event the buried epitaxial island can expand laterally over distances of several microns. During this epitaxial lateral growth typically thousands of isolated secondary nuclei are generated continuously. The unique process is so far only observed on iridium surfaces. It is shown that a diamond single crystal with a diameter of ~90 mm and a weight of 155 carat can be grown from such a carbon film which initially consisted of 2 · 10(13) individual grains