In quantum optical technologies, identical emitters of indistinguishable single photons are difficult to realize due to the inherent dissimilarity of each emitting device Here, Rogers et al demonstrate a solid-state uniform single-photon source, which does not require external tuning of optical properties

Multiple intrinsically identical single-photon emitters in the solid state

The characterisation of point defects in diamond by luminescence spectroscopy

Photoluminescence (PL) and Raman spectroscopy were employed to investigate the nature and sources of stress and the type and distribution of impurities and defects in thin diamond films grown on silicon substrates. The types of impurities and defects which were detected in the diamond films are the nitrogen, silicon, and the sp2‐type bonding of the graphitic phase. Our Raman analyses indicate that the diamond films exhibit a net compressive stress. After compensating for the thermal interfacial stress and for the stress due to grain boundaries it was found that the residual internal stress is compressive in nature. From Raman line‐shape analysis it was determined that the internal stress is due to the various impurities and defects present in the film. Moreover, the stress magnitude exhibits a strong correlation with the graphitic phase implying that the sp2 bonding produces a dominant compressive stress field. The PL analytical line‐shape investigation of the nitrogen band at 2.154 eV indicates that the ...

Raman and photoluminescence analysis of stress state and impurity distribution in diamond thin films

High quality homoepitaxial CVD diamond for electronic devices

Employing photoluminescence (PL) spectroscopy, we have carried out a detailed study of the characteristics and origin of the 1.681 eV luminescence center in chemical‐vapor‐deposited (CVD) diamond films. In addition to the zero‐phonon line (ZPL), the fine structure of the PL emission spectrum revealed vibronics corresponding to both phonon emission and phonon absorption. Most of the vibronics can be identified with known lattice phonons in a natural diamond, although a few of the peaks appear to be associated with a local vibrational mode. The emission intensity was found to be a strong function of the CH4/H2 ratio used to grow the diamond films. Decreasing the methane concentration from 2.0% to 0.25% resulted in an increase of about four orders of magnitude in the PL intensity. It has been found that residual stress on the order of 0.5 GPa in the diamond film quenches the PL emission intensity but has no measurable effects on the peak position and half‐width of the 1.681 eV ZPL. Temperature has a marked i...

Characteristics and origin of the 1.681 eV luminescence center in chemical‐vapor‐deposited diamond films

Absorption and cathodoluminescence spectra have been recorded for single crystals of diamond and polycrystalline films of diamond, grown by microwave-assisted chemical vapor deposition (CVD) using methane and hydrogen. The investigation has been carried out to see to what extent the properties of CVD diamond are similar to those of conventional diamond, and to what extent they are unique. Studies have been made of the as-grown material, which has not been intentionally doped, and also samples that have been subjected to radiation damage and thermal annealing. The single crystals grown using methane concentrations of 0.5 to 1.0% exhibit bright blue “band A” emission and also intense edge emission, similar to the cathodoluminescence spectra of some natural type IIa diamonds. This implies that the crystals are relatively free from structural and chemical defects, a conclusion which is reinforced by the absence of any zero-phonon lines in the absorption spectra of crystals which have been subjected to radiation damage and annealing at 800 °C. Before radiation damage the spectrum does, however, reveal an absorption which increases progressively to higher energies, and which may be associated with sp2-bonded carbon. The cathodoluminescence spectra after radiation damage indicate that the crystals contain some isolated nitrogen, and the detection of H3 luminescence, following thermal annealing at 800 °C, demonstrates for the first time that these samples contain small concentrations of nitrogen pairs. All of the polycrystalline films, grown using methane concentrations between 0.3 and 1.5%, have an absorption which increases progressively to higher energies, and which again is attributed to sp2-bonded carbon. This absorption is stronger in the films grown using higher methane concentrations. Films grown at a methane concentration of 0.3% also exhibit bright blue cathodoluminescence, although the edge emission is undetectably weak. The use of higher methane concentrations produces films with evidence in the cathodoluminescence spectra of nitrogen + vacancy and nitrogen + interstitial complexes, as well as optical centers unique to CVD diamond. One particular defect produces an emission and absorption line at 1.681 eV. By implanting conventional diamonds with 29Si ions it has been confirmed that this center involves silicon, and it has been shown that the 1.681 eV luminescence is relatively more intense in implanted diamonds which have a high concentration of isolated nitrogen.

A. T. Collins

Papers

A spectroscopic study of optical centers in diamond grown by microwave-assisted chemical vapor deposition