Origin of band-A emission in diamond thin films

By means of scanning cathodoluminescence (CL) measurements, high-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS), we have studied the origin of the band-A emission in homoepitaxial diamond thin films grown using microwave-plasma chemical vapor deposition (CVD). A broad luminescence peak at around 2.9 eV, the band-A emission, was observed in homoepitaxial diamond films with nonepitaxial crystallites (NC's), but not in the high-quality films without NC's. The scanning CL measurements showed that the band-A emission appeared only at NC sites. TEM revealed that the NC's contained defects such as dislocations and several types of grain boundary (GB). Further, HRTEM indicated that several types of incoherent GB existed within the NC's including five-, six-, and seven-member carbon atom rings. These were the same GB's as those in polycrystalline CVD diamond films that had sp2-like structure of carbon atoms as indicated by the observation of the 1s-π signal in EELS. It is then reasonable to consider that, if sp2-like structures behave as defects in the network of sp3 structure of diamond, one possible origin of band-A emission might be the sp2 defects in the GB's and dislocations. The band-A emission behavior in homoepitaxial CVD diamond films is the same as that in polycrystalline diamond films. The origin of the band-A emission generally observed in many kinds of CVD diamond is discussed relative to these results

ANNEALING STUDIES ON LOW OPTICAL ABSORPTION OF GD a-Si:H USING PHOTOACOUSTIC SPECTROSCOPY

We have performed photoacoustic spectroscopy (PAS), ESR and ir absorption measurements on undoped GD a-Si:H film before and after isochronal annealings, from which absorption coefficient (down to α = 1 cm-1), spin density (Ns) and bonded H content (CH) were determined. It has been found out that the extraporated spectrum of spin-free a-Si:H shows a long exponential tail, and that additional broad absorption is strongly correlated with Ns. The origin of α below Eo is discussed

Deterministic Electrical Charge-State Initialization of Single Nitrogen-Vacancy Center in Diamond

Apart from applications in classical information-processing devices, the electrical control of atomic defects in solids at room temperature will have a tremendous impact on quantum devices that are based on such defects. In this study, we demonstrate the electrical manipulation of individual prominent representatives of such atomic solid-state defects, namely, the negative charge state of single nitrogen-vacancy defect centers (NV^{−}) in diamond. We experimentally demonstrate, deterministic, purely electrical charge-state initialization of individual NV centers. The NV centers are placed in the intrinsic region of a p-i-n diode structure that facilitates the delivery of charge carriers to the defect for charge-state switching. The charge-state dynamics of a single NV center were investigated by time-resolved measurements and a nondestructive single-shot readout of the charge state. Fast charge-state switching rates (from negative to neutrally charged defects), which are greater than 0.72 ± 0.10  μs^{−1}, were realized. Furthermore, in no-operation mode, the realized charge states were stable for presumably much more than 0.45 s. We believe that the results obtained are useful not only for ultrafast electrical control of qubits, long T_{2} quantum memory, and quantum sensors associated with single NV centers but also for classical memory devices based on single atomic storage bits working under ambient conditions