The nitrogen-vacancy centre (NV) has drawn much attention for over a decade, yet detailed knowledge of the photophysics needs to be established. Under typical conditions, the NV can have two stable charge states, negative (NV − ) or neutral (NV 0 ), with photo-induced interconversion of these two states. Here, we present detailed studies of the ionization dynamics of single NV centres in bulk diamond at room temperature during illumination and its dependence on the excitation wavelength and power. We apply a recent method which allows us to directly measure the charge state of a single NV centre, and observe its temporal evolution. We find that the steady-state NV − population is always 75% for 450-610 nm excitation wavelength. In combination with saturation measurements, we show that the optimal excitation wavelength is around 510-540 nm. Furthermore, the relative absorption cross-section of NV − is determined for 540-610 nm, revealing a double-peak structure. Finally, the energy of the NV − ground state of 2.6 eV below the conduction band is measured. These results reveal new insights into the charge state dynamics of the NV centre.

Nuclear magnetic resonance (NMR) spectroscopy is a key analytical technique in chemistry, biology, and medicine. However, conventional NMR spectroscopy requires an at least nanoliter-sized sample volume to achieve sufficient signal. We combined the use of a quantum memory and high magnetic fields with a dedicated quantum sensor based on nitrogen vacancy centers in diamond to achieve chemical shift resolution in H andF NMR spectroscopy of 20-zeptoliter sample volumes. We demonstrate the application of NMR pulse sequences to achieve homonuclear decoupling and spin diffusion measurements. The best measured NMR linewidth of a liquid sample was ~1 part per million, mainly limited by molecular diffusion. To mitigate the influence of diffusion, we performed high-resolution solid-state NMR by applying homonuclear decoupling and achieved a 20-fold narrowing of the NMR linewidth.

Emerging resistively switching devices are thought to enable ultradense passive nanocrossbar arrays for use as random access memories (ReRAM) by the end of the decade, both for embedded and mass storage applications. Moreover, ReRAMs offer inherent logic‐in‐memory (LIM) capabilities due to the nonvolatility of the devices and therefore great potential to reduce the communication between memory and calculation unit by alleviating the so‐called von Neumann bottleneck. A single bipolar resistive switching device is capable of performing 14 of 16 two input logic functions in the logic concept presented by Linn et al. (“CRS‐logic”). In this paper, five types of selectorless devices are considered to validate this CRS‐logic concept is experimentally by means of the IMP and AND logic operations. As reference device a TaO x ‐based ReRAM cell is considered, which is compared to three more advanced device configurations consisting either of a threshold supported resistive switch (TS‐ReRAM), a complementary switching device (CS), or a complementary resistive switch (CRS). It is shown that all of these devices offer the desired LIM behavior. Moreover, the feasibility of XOR and XNOR operations using a modified logic concept is applied for both CS and CRS devices and the pros and cons are discussed.

Volatile threshold switching devices have attracted great attention for use as selectors in passive crossbar arrays. These devices show an abrupt hysteretic jump in the current–voltage characteristic and thus offer very high selectivity. As this nonlinearity appears for either voltage polarity, threshold switches are an ideal selector for bipolar‐switching redox‐based resistive memories. To date, the predominant explanation of the threshold‐switching phenomenon in NbO2 and related materials is the insulator‐to‐metal transition that occurs at a certain temperature and is connected to a phase transition. However, some essential experimental findings are not satisfactorily explained. Here, a multidimensional simulation of the threshold switching in NbO2 is presented that overcomes these shortcomings. The model is based on an electric field‐induced thermal runaway that increases the amount of mobile charge carriers in the device. Applying this model in a simulation correctly predicts the experimentally observed threshold‐type current–voltage characteristic, inclusive of important features like the narrow opening of the hysteresis and the magnitude of the current jump. Furthermore, the simulation enables to discuss different influencing parameters independently at spatial resolution. The model is also applicable to a wider class of materials showing the threshold switching, but does not show a temperature‐induced insulator‐to‐metal transition.