Sang Wuk Lee

Vertical ZnO nanorod/Si contact light-emitting diode

Blue-white light emission was obtained from glass/indium tin oxide (ITO)/n-ZnO nanorod array (NRA)/p+-Si vertical contact light emitting diodes (VCLEDs). The nanoscale p-n heterojunction VCLEDs were formed by direct engagement n−-tips of n-ZnO NRA grown vertically on an ITO/glass substrate with p+-Si wafer. Proposed configuration of the VCLED allows creating a high density (∼109 cm−2) of self-assembled ZnO/Si nanodiodes with point junctions of high quality due to structural perfection of the Si wafer and the tips of ZnO nanorods as well as providing a high injection current and light emission from the NRA VCLED required for solid state lighting.

Resistive Switching in Al/Graphene Oxide/Al Structure

We report resistive switching behaviors in an Al/graphene oxide/Al planar structure. Graphene oxide was synthesized by a modified Hummers method from graphite rods. The planar structures were fabricated on a Si/SiO2 substrate by spin-coating graphene oxide suspensions and patterning Al electrodes by photolithography. Both diode-like (rectifying) and resistor-like (nonrectifying) behaviors were observed in the device switching characteristics. Electrical characterization of the Al/graphene oxide interface using the induced current identified a potential barrier near the interface and its spatial modulation, caused by local changes of resistance at a bias voltage, which correlated well with the resistive switching of the whole structure. The mechanism of the observed local resistance changes near the electrode and the associated resistive switching of the entire structure is associated with the electrodiffusion of oxygen and the formation of sp2 graphene clusters in an sp3 insulating graphene oxide layer formed near the electrode by a pre-forming process.

Energy Level Structure of Amorphous Silicon Carbide

The photoluminescence spectra of amorphous SiC films have been studied. The films were fabricated by the plasma-enhanced chemical vapor deposition method. The energy scheme of amorphous SiC has been proposed. This scheme contains a donor state at 0.1 eV and two acceptor states at 0.27 eV and 0.34 eV. It is shown that acceptor electronic states are due to Si–H and C–H bonds. Experimental data confirming this energy scheme are given. Blue photoluminescence (λmax=5100 A) is observed in amorphous SiC films prepared at a high-frequency discharge power of more than 200 W. It is shown, that this is caused by the increase of carbon concentration.