[Show abstract][Hide abstract] ABSTRACT: We demonstrate the controlled preparation of heteroepitaxial diamond nano-
and microstructures on silicon wafer based iridium films as hosts for single
color centers. Our approach uses electron beam lithography followed by reactive
ion etching to pattern the carbon layer formed by bias enhanced nucleation on
the iridium surface. In the subsequent chemical vapor deposition process, the
patterned areas evolve into regular arrays of (001) oriented diamond
nano-islands with diameters of <500nm and a height of approx. 60 nm. In the
islands, we identify single SiV color centers with narrow zero phonon lines
down to 1 nm at room temperature.
[Show abstract][Hide abstract] ABSTRACT: Threading dislocations in off-axis grown heteroepitaxial diamond films have been visualized by preferential etching of the surface. The lateral distributions of the etch pits display characteristic inhomogeneities. Patterns with fourfold symmetry consisting of a cell structure with dislocation poor cores and dislocation rich walls aligned along  and  appear on (001) samples with off-axis tilt toward . These patterns which developed after extended growth to a thickness of 1.5 mm are mainly attributed to intrinsic anisotropies in the mutual interaction between neighboring dislocations via their stress fields. In contrast, growth on (001) surfaces with off-axis direction toward  yielded patterns with twofold symmetry. Here, the etch pits are aligned exclusively along the  off-axis direction which is attributed to the additional impact of the local surface inclination on the dislocations, resulting in an effective lateral movement during growth. Dislocation tilting in the local step-flow direction away from the crystallographic  axis, which provides a reasonable mechanism explaining the lateral movement, is confirmed by transmission electron microscopy. Homoepitaxial growth experiments on (001) surfaces 8° off toward  reveal etch pit patterns around “V” shaped microstructures that suggest a similar interpretation in terms of an effective lateral movement of dislocations induced by high local surface inclination.
Physica Status Solidi (A) Applications and Materials 06/2015; DOI:10.1002/pssa.201532243 · 1.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The topographic surface features that develop during chemical vapour deposition of heteroepitaxial diamond on off-axis Ir/YSZ/Si(001) and their implications on the incorporation and modification of 0D and 1D defects have been studied. After growth with nitrogen in the gas phase, the surface has split into alternating stripes of opposite inclination. The terrace regions are tilted towards the crystallographic  axis, while the risers are tilted in the opposite direction. AFM measurements on the macroscopic terraces reveal a microscopic substructure consisting of terraces and risers on a smaller length scale. Cross-section SEM images display inclined dark and bright striations. In photoluminescence maps, the stripes ending at risers show a higher NV and SiV emission intensity thus indicating a stronger defect incorporation of colour centres. Relative growth rates on terrace and riser areas have been evaluated. In high resolution Raman measurements, the cross-section maps display bands of high line width embedded in a background of lower line width. Conversion of these data into dislocation density maps reveals local variations by one order of magnitude. The tilt angle of the threading dislocation bundles is attributed to an interaction induced by the lateral step flow on the off-axis growth surface.Scheme of the investigated diamond samples.
Physica Status Solidi (A) Applications and Materials 10/2014; 211(10). DOI:10.1002/pssa.201431210 · 1.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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
[Show abstract][Hide abstract] ABSTRACT: Deterministic coupling of a single emitter to a photonic crystal cavity is an important step towards the realization of integrated solid-state devices for quantum photonics. As single emitters, color centers in diamond, e.g. the Nitrogen-Vacancy (NV) center or the Silicon-Vacancy (SiV) center have attracted significant interest due to their extraordinary properties like long spin-coherence times or narrowband and bright single photon emission, respectively. For the realization of recent proposals like cavity-enhanced spin measurements or cavity-enhanced single photon sources, it is necessary to couple single color centers to a cavity with small mode volume and high quality factor. Photonic crystal cavities directly fabricated within a monocrystalline diamond membrane are well suited for this task, as they offer tiny mode volumes for efficient emitter-cavity coupling as well as scalable architectures for integrated photonic devices.
International Quantum Electronics Conference; 05/2013
[Show abstract][Hide abstract] ABSTRACT: We study single silicon vacancy (SiV) centres in chemical vapour deposition
(CVD) nanodiamonds on iridium as well as an ensemble of SiV centres in a high
quality, low stress CVD diamond film by using temperature dependent
luminescence spectroscopy in the temperature range 5-295 K. We investigate in
detail the temperature dependent fine structure of the zero-phonon-line (ZPL)
of the SiV centres. The ZPL transition is affected by inhomogeneous as well as
temperature dependent homogeneous broadening and blue shifts by about 20 cm-1
upon cooling from room temperature to 5 K. We employ excitation power dependent
g(2) measurements to explore the temperature dependent internal population
dynamics of single SiV centres and infer almost temperature independent
New Journal of Physics 10/2012; 15(4). DOI:10.1088/1367-2630/15/4/043005 · 3.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In situ boron doping of heteroepitaxial diamond films grown by microwave plasma chemical vapor deposition on Ir/YSZ/Si (001) is investigated. The study comprises the analysis of the gas phase by optical emission spectroscopy (OES) and measurements of B doped films by secondary ion mass spectroscopy (SIMS), cathodoluminescence (CL), and X-ray diffraction (XRD). The OE intensity of BH species scales linearly with the concentration of the boron precursor trimethylboron (TMB) in the feed gas. Addition of CO2 as an oxygen source causes a proportional reduction of the BH signal. At a ratio C:O = 1, a reduction factor of ∼50 is obtained. It is shown for two diamond samples that the boron incorporation drops nearly identical to the BH emission intensity. We conclude that the influence of oxygen on boron incorporation is a pure gas phase effect. In contrast, CN and BH emission indicate a negligible interaction between N2 and TMB added to the feed gas. At the same time, preliminary growth rate measurements show that the boron background pressure in the chamber after growth with TMB completely cancels the growth acceleration by nitrogen up to N2 concentrations of 100 ppm which points to the dominance of surface processes. Heteroepitaxial diamond films grown on Ir at 50 mbar between 720 and 900 °C contain high intrinsic stress that varies from −2.2 GPa compressive at the lowest to slightly tensile at the highest deposition temperature. The observed behavior is similar to former work at 200 mbar in which effective climb of dislocations was suggested as responsible mechanism. Addition of boron rather enhances the stress formation than causing a relaxation. The B concentration in the heteroepitaxial films is deduced by SIMS, CL, and XRD and correlated with the TMB concentration in the gas phase.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: We fabricate photonic crystal microcavities in a single crystal diamond membrane and actively tune the cavity modes into resonance with the emission line of color centers in diamond to enhance the emission rate.
Lasers and Electro-Optics (CLEO), 2012 Conference on; 01/2012
[Show abstract][Hide abstract] ABSTRACT: Diamond is an attractive material for photonic quantum technologies because its colour centres have a number of outstanding properties, including bright single photon emission and long spin coherence times. To take advantage of these properties it is favourable to directly fabricate optical microcavities in high-quality diamond samples. Such microcavities could be used to control the photons emitted by the colour centres or to couple widely separated spins. Here, we present a method for the fabrication of one- and two-dimensional photonic crystal microcavities with quality factors of up to 700 in single crystal diamond. Using a post-processing etching technique, we tune the cavity modes into resonance with the zero phonon line of an ensemble of silicon-vacancy colour centres, and we measure an intensity enhancement factor of 2.8. The controlled coupling of colour centres to photonic crystal microcavities could pave the way to larger-scale photonic quantum devices based on single crystal diamond.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: We present single photon sources based on Silicon-vacancy centres in CVD-nano-diamonds on iridium featuring high brightness up to 4.8 Mcps and narrowband emission predominantly into zero-phonon-lines as small as 0.7 nm at room temperature.
[Show abstract][Hide abstract] ABSTRACT: We introduce a process for the fabrication of high-quality, spatially isolated nano-diamonds on iridium via microwave-plasma-assisted chemical vapour deposition (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.
New Journal of Physics 02/2011; 13(2):025012. DOI:10.1088/1367-2630/13/2/025012 · 3.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: Quite comparable: A graphene monolayer is used as a substrate for the growth of two-dimensional hydrogen-bonded supramolecular structures (see STM image). The formation of these extended structures arises from a commensurability between their dimensions and a moiré pattern formed by the graphene.
[Show abstract][Hide abstract] ABSTRACT: The selective formation of large-scale graphene layers on a Rh-YSZ-Si(111) multilayer substrate by a surface-induced chemical growth mechanism is investigated using low-energy electron diffraction, X-ray photoelectron spectroscopy, X-ray photoelectron diffraction, and scanning tunneling microscopy. It is shown that well-ordered graphene layers can be grown using simple and controllable procedures. In addition, temperature-dependent experiments provide insight into the details of the growth mechanisms. A comparison of different precursors shows that a mobile dicarbon species (e.g., C(2)H(2) or C(2)) acts as a common intermediate for graphene formation. These new approaches offer scalable methods for the large-scale production of high-quality graphene layers on silicon-based multilayer substrates.
Small 10/2009; 5(20):2291-6. DOI:10.1002/smll.200900158 · 8.37 Impact Factor