We report an improvement of the optical power and thermal stability of GaN LEDs using a chemically doped graphene transparent conducting layer (TCL) and a low-resistance contact structure. In order to obtain low contact resistance between the TCL and p-GaN surface, a patterned graphene TCL with Cr/Au electrodes is suggested. A bi-layer patterning method of a graphene TCL was utilized to prevent the graphene from peeling off the p-GaN surface. To improve the work function and the sheet resistance of graphene, CVD (chemical vapor deposition) graphene was doped by a chemical treatment using a HNO(3) solution. The effect of the contact resistance on the power degradation of LEDs at a high injection current level was investigated. In addition, the enhancement of the optical power via an increase in the current spreading and a decrease in the potential barrier of the graphene TCL was investigated.

A gas sensor based on a hierarchical WS ₂ structure embedded with vertically aligned WS ₂ nanocrystallites was demonstrated. The three-dimensional (3D) hierarchical structure provides many edge sites of nanocrystallites and an extremely large gas contact volume, resulting in a high gas response. The decreased contact resistance between the 3D hierarchical WS ₂ fibers and sensor electrode resulted in improved NO ₂ response. We fabricated a one-dimensional (1D) conductive WS ₂ fiber using a two-step annealing process under sulfur flow (sulfurization). It delivers a continuous and conductive carrier path and lowers the potential barrier at the interface of the WS ₂ nanocrystallites (top) and electrospun WS ₂ fiber (bottom), resulting in an improved gas response. We developed 3D hierarchical WS ₂ fibers embedded with vertically aligned WS ₂ nanocrystallites to increase the gas adsorption site in comparison with that of 1D WS ₂ fibers without WS ₂ flakes. Vertically aligned WS ₂ nanocrystallites were formed after a two-step annealing treatment. Sensors based on the 3D hierarchical WS ₂ fibers embedded with WS ₂ flakes, showed higher response to NO ₂ gas in comparison to that of pure WS ₂ fibers without WS ₂ flakes.

In this letter, we report that vertically well-aligned ZnO nanowires were grown on GaN epilayers and c-plane sapphire via a vapor-liquid-solid process by introducing a 3 nm Au thin film as a catalyst. In our experiments, epitaxially grown ZnO nanowires on Au-coated GaN were vertically well-aligned, while nanowires normally tilted from the surface when grown on Au-coated c-Al₂O₃ substrates. However, pre-growth annealing of the Au thin layer on c-Al₂O₃ resulted in the growth of well-aligned nanowires in a normal surface direction. High-resolution transmission electron microscopy measurements showed that the grown nanowires have a hexagonal c-axis orientation with a single-crystalline structure.

Solution-processable organic semiconductors have been investigated not only for flexible and large-area electronics but also in the field of biotechnology. In this paper, we report the design and fabrication of biosensors based on completely organic thin-film transistors (OTFTs). The active material of the OTFTs is poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) polymer functionalized with biotin hydrazide. The relationship between the chemoresistive change and the binding of avidin-biotin moieties in the polymer is observed in the output and on/off characteristics of the OTFTs. The exposure of the OTFTs to avidin causes a lowering of ID at V_D = -40 V and V_G = -40 V of nearly five orders of magnitude.

This paper presents a method by which it is possible to control the align-angle arbitrarily from vertical to horizontal demonstrating a mechanical stretch of as much as 120%. Fibers are aligned directly onto the sample surface.