We report the preparation of arsenic doped p-type ZnO films using a Zn3As2∕ZnO target by pulsed laser deposition. Zn3As2 was used as a p-type dopant source material for arsenic doping in ZnO. The existence of As in the As-doped ZnO films was confirmed by the x-ray photoelectron spectroscopy study. The p-type behavior of the As-doped ZnO films was determined by the Hall and photoluminescence measurements. Room temperature Hall measurements revealed that the As-doped ZnO films exhibited p-type conductivity after being annealed at 200°C in N2 ambient for 2min with the hole concentrations varied between 2.48×1017 and 1.18×1018cm−3. The resistivity and carrier mobility of the As-doped p-type ZnO films were in the range of 2.2–6.7Ωcm and 0.83–11.4cm2∕Vs, respectively. The low temperature photoluminescence measurements confirmed the peak associated with the neutral-acceptor bound exciton (A0X) emission in the As-doped p-type ZnO films.

We report the preparation of p-type ZnO thin films on Al2O3(0001) substrates with phosphorus doping by pulsed laser deposition using Zn3P2 as the dopant source material. The results of the Hall effect measurements taken at room temperature indicate that the 3-mol% phosphorus-doped ZnO films thermally annealed at temperatures between 600 and 800°C under an O2 atmosphere exhibit p-type behavior with a hole concentration of 5.1×1014−1.5×1017cm−3, a hole mobility of 2.38−39.3cm2∕Vs, and a resistivity of 17−330Ωcm. The low-temperature (15K) photoluminescence results reveal that the peak related to the neutral-acceptor bound exciton (A0,X) emission at 3.358eV is only observed in the films showing p-type behavior. Our results not only demonstrate that there is a narrow temperature window for rapid thermal annealing in which phosphorus-doped p-type ZnO films can be obtained, but also suggest that the use of Zn3P2 can provide an effective approach to the preparation of p-type ZnO films.

The x-ray absorption near-edge structure (XANES) spectroscopy has been used as a “fingerprint” to address the unresolved issues related to the changes in the local structure around As and to identify its chemical state in the As-doped, p-type ZnO. The spectral features of both AsK- and OK-edge XANES spectra strongly suggest that in the p-type state As substitutionally replaces O in the ZnO lattice, thereby forming AsO, which is the acceptor responsible for p-type conduction in the As-doped, p-type ZnO.

We report the fabrication of a chlorophyll-layer-inserted poly(3-hexyl-thiophene) (P3HT) solar cell. A significant enhancement in the light-to-current conversion efficiency of up to 1.48% with a fill factor of 0.32 was achieved in a solar cell with a device structure of indium tin oxide anode/poly (3,4-ethylene dioxy-thiophene):poly(styrene sulfonate)/P3HT/chlorophyll/Al cathode under the standard air mass 1.5 irradiation (20mW∕cm2). These results suggest that the generation of an internal electric field is mainly due to a difference between the highest occupied molecular orbital of the P3HT (donor) and the lowest unoccupied molecular orbital of the chlorophyll (acceptor), which permits the transfer of photoinduced electrons from P3HT to chlorophyll.

New insights into understanding and controlling the intriguing phenomena of spontaneous merging (kissing) and the self-assembly of monolithic Y- and T-junctions is demonstrated in the metal-organic chemical vapor deposition growth of GaAs nanowires. High-resolution transmission electron microscopy for determining polar facets was coupled to electrostatic-mechanical modeling and position-controlled synthesis to identify nanowire diameter, length, and pitch, leading to junction formation. When nanowire patterns are designed so that the electrostatic energy resulting from the interaction of polar surfaces exceeds the mechanical energy required to bend the nanowires to the point of contact, their fusion can lead to the self-assembly of monolithic junctions. Understanding and controlling this phenomenon is a great asset for the realization of dense arrays of vertical nanowire devices and opens up new ways toward the large scale integration of nanowire quantum junctions or nanowire intracellular probes.

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ZnO thin films prepared by pulsed laser deposition were implanted with phosphorous (P) using dose levels of 1012–1014ions∕cm2 at room temperature. The P-implanted films were subsequently annealed between 500 and 700°C in oxygen ambient. The Hall effect measurements revealed a substantial reduction in the electron concentration of the P-implanted films without annealing, whereas the reduction was more pronounced with optimized rapid thermal annealing treatment. The photoluminescence spectra showed emissions associated with the shallow P-related acceptors at ∼3.179, ∼3.256, and ∼3.325eV as well as a strong red emission centered at ∼1.85eV originating from a donor-acceptor pair transition after annealing at 600 and 700°C. These results indicate that the P dose level during ion implantation and the annealing temperature are key processing parameters that should be optimized to produce p-type ZnO films.