Thin films of ternary compounds CuxlnyN and CuxTiyN were grown by magnetron sputtering to improve the thermal stability of Cu3N, a material that decomposes below 300 ℃, and thus promises many interesting applications in directwriting. The effect of In or Ti incorporation in altering the structure and physical properties of copper nitride was evaluated by characterizing the film structure, surface morphology, and temperature dependence of electrical resistivity. More Ti than In can be accommodated by copper nitride without completely deteriorating the Cu3N lattice. A small amount of In or Ti can improve the crystallinity, and consequently the surface morphology. While the decomposition temperature is rarely influenced by In, the Ti-doped sample, Cu59.31Ti2.64N38.05, shows an X-ray diffraction pattern dominated by characteristic Cu3N peaks, even after annealing at 500 ℃. Both In and Ti reduce the bandgap of the original Cu3N phase, resulting in a smaller electrical resistivity at room temperature. The samples with more Ti content manifest metal-semiconductor transition when cooled from room temperature down to 50 K. These results can be useful in improving the applicability of copper-nitride-based thin films.
Motion control of a single molecule through a solid-state nanopore offers a new perspective on detecting and analyzing single biomolecules.Repeat recapture of a single DNA molecule reveals the dynamics in DNA translocation through a nanopore and may significantly increase the signal-to-noise ratio for DNA base distinguishing.However,the transient current at the moment of voltage reversal prevents the observation of instantly recaptured molecules and invalidates the continuous DNA ping-pong control.We performed and analyzed the DNA translocation and recapture experiment in a silicon nitride solid-state nanopore.Numerical calculation of molecular motion clearly shows the recapture dynamics with different delay times.The prohibited time when the data acquisition system is saturated by the transient current is derived by equivalent circuit analysis and finite element simulation.The COMSOL simulation reveals that the membrane capacitance plays an important role in determining the electric field distribution during the charging process.As a result of the transient charging process,a non-constant driving force pulls the DNA back to nanopores faster than theoretically predicted.The observed long time constant in the transient current trace is explained by the dielectric absorption of the membrane capacitor.
