Oxygen Concentration Dependence of the Optical and Electrical Properties of Mn-Doped Tin Oxide Thin Films Deposited on a Polyethylene Terephthalate Substrate.

Mn (2.59 wt.%)-doped tin oxide (MTO) was deposited on a polyethylene terephthalate (PET) substrate using RF magnetron sputtering at room temperature. Oxygen was introduced during the sputtering process to prevent the reduction of transmittance and the formation of nonstoichiometric compositions. The dependence of the optical and electrical properties of MTO thin films on the O2/(Ar+O2) ratio was systematically investigated. The transmittance of the MTO single layer (24 nm) at 550 nm gradually increased from 85.9% to 88.2% with an increase of the O2/(Ar+O2) ratio from 0% to 7.9%. The optical band gap was also affected by the O2/(Ar+O2) ratio, varying from 3.30 to 3.64 eV. The MTO film deposited at an O2/(Ar+O2) ratio of 2.7% showed the minimum resistivity (0.03 Ω·cm). The XPS spectra indicated that the SnO2 thin films become almost stoichiometric as the O2/(Ar+O2) ratio increased. Thus, this sputtering process can be used to prepare flexible MTO films with a wider optical band gap, improved transmittance, and decreased resistivity.

Manganese-Doped Tin Oxide for Highly Flexible and Transparent Multilayer Electrodes with Index-Matching Layers.

We fabricated transparent Mn (2.59 wt.%)-doped tin oxide (MTO)/Ag/MTO films with refractive index-matching layers (IMLs) on a polyethylene terephthalate (PET) substrate. To reduce refractive index-mismatching, polydimethylsiloxane (PDMS) and MTO layers were inserted between the MTO/Ag/MTO multilayer film and the PET substrate. MTO and Ag were deposited by RF/DC magnetron sputtering at room temperature, whereas spin-coating was used to deposit PDMS at various dilution ratios in hexane. In this study, pattern visibility was examined by comparing the differences in the color and reflectance of oxide/metal/oxide multilayers before and after adding the PDMS and MTO IMLs. In addition, the effects of the PDMS dilution ratio on the electrical and optical characteristics were also investigated. The MTO/Ag/MTO/PDMS/MTO multilayer films showed high transmittance (>86% at 550 nm) except at the dilution ratio of 1:50. As the PDMS dilution ratio increased from 1:50 to 1:200, the reflectance difference (ΔR) increased from 0.08% to 0.35% and the color difference (Δb*) increased from 0.31 to 1.23. The maximum resistance changes of the multilayer films were 0.126% and 0.124% after outer and inner bending, respectively, for 10,000 cycles with a radius of curvature of 4 mm.

In-depth Investigation of Hg2Br2 Crystal Growth and Evolution.

Physical vapor transport (PVT) has frequently been adopted for the synthesis of mercurous bromide (Hg2Br2) single crystals for acousto-optic modulators. However, thus far, very few in-depth studies have been conducted that elucidate the growth process of the Hg2Br2 single crystal. This paper reports an in-depth investigation regarding the crystal growth and evolution behavior of the Hg2Br2 crystal with facet growth mode. Based on the experimental and simulation results, the temperature profile conditions concerning the seed generation and seed growth could be optimized. Next, the PVT-grown Hg2Br2 crystals (divided into single crystal and quasi-single crystal regions) were characterized using various analysis techniques. The single-crystal Hg2Br2 was found to possess a more uniform strain than that of the quasi-single crystal through a comparison of the X-ray diffraction data. Meanwhile, the binding energy states and electron backscatter diffraction images of the as-synthesized Hg2Br2 crystals were similar, regardless of the crystal type. Furthermore, Raman spectroscopy and transmission electron microscopy analyses provided information on the atomic vibration mode and atomic structures of the two kinds of samples. The synergistic combination of the simulation and experimental results used to verify the growth mechanism facilitates the synthesis of high-quality Hg2Br2 crystals for potential acousto-optic tunable filter device applications.

Effect of O2 Flow Rate on Properties of Mn-SnO2/Ag/Mn-SnO2 Multilayer Film.

Multilayer films with Mn-SnO2 (MTO)/Ag/Mn-SnO2 (MTO) hybrid structure were prepared on a flexible polyethylene terephthalate (PET) substrate using a DC/RF sputtering system at room temperature. The optical, electrical, and structural properties of the thus-synthesized multilayer films were systematically investigated as a function of the O2/(Ar+O2) flow rate. The transmittance of the MTO/Ag/MTO multilayer films at 550 nm increased gradually from 83.1% to 87.9% and the sheet resistance (Rs) of the multilayer films increased from 6.3 to 9.8 Ω/sq upon increasing the O2/(Ar+O2) flow rate. The highest figure of merit (φTC) of MTO/Ag/MTO multilayer film was 45.7×10-3 Ω-1 at an O2/(Ar+O2) flow rate of 2.8%. X-ray photoelectron spectra of multilayer films obtained with different O2/(Ar+O2) flow rates showed no noticeable variation.

Characterizations of Ga-doped ZnO nanowires depending on growth temperature and target-substrate distance in hot-walled pulsed laser deposition.

Using a hot-walled pulsed laser deposition (HW-PLD), nanowires (NWs) comprising 3 weight% Ga-doped ZnO (3GZO) have been successfully grown on a sapphire substrate. The structural and optical properties of 3GZO nanostructures have also been systematically investigated with respect to the target-substrate (T-S) distance and the growth temperature. The morphology transformations of nanostructures such as nano-horns, NWs, and clusters are strongly affected by growth temperatures due to different thermal energy. Also, the morphologies of nanostructures--including length, diameter, and density--are strongly affected by the T-S distance, illustrating a close correlation between the growth kinetics and the position in the plume formed by the particles from the GZO target. Also, the exciton that is bound to the neutral donor (D(0)X) peak of the 3GZO nanostructures is found at the low temperature PL spectra, indicating successful Ga-doping into ZnO NWs.

Effect of Ag/Al co-doping method on optically p-type ZnO nanowires synthesized by hot-walled pulsed laser deposition.

Silver and aluminum-co-doped zinc oxide (SAZO) nanowires (NWs) of 1, 3, and 5 at.% were grown on sapphire substrates. Low-temperature photoluminescence (PL) was studied experimentally to investigate the p-type behavior observed by the exciton bound to a neutral acceptor (A0X). The A0X was not observed in the 1 at.% SAZO NWs by low-temperature PL because 1 at.% SAZO NWs do not have a Ag-O chemical bonding as confirmed by XPS measurement. The activation energies (Ea) of the A0X were calculated to be about 18.14 and 19.77 meV for 3 and 5 at.% SAZO NWs, respectively, which are lower than the activation energy of single Ag-doped NW which is about 25 meV. These results indicate that Ag/Al co-doping method is a good candidate to make optically p-type ZnO NWs.

Superhydrophobic thin films with nanostructured surface prepared with Au nanoparticle masks.

The hydrophobicity of a perfluoropolyether bisurethane methacrylate polymer film was investigated along with the formation of nano-hairs on its surface through reactive ion etching using gold nanoparticles (Au NPs) as masks. It was found that the hydrophobicity of the polymer film was strongly dependent on the number density of the nano-hairs which was determined by that of the Au NPs. The superhydrophobic surface was obtained when the number density was higher than 250 microm(-2). The effects of surface functionalization, Au NP immobilization, and etching time on the hydrophobicity of the polymer film were also examined extensively and discussed based on the results of the contact angle measurements and the scanning electron microscopy.

Physically processed Ag-doped ZnO nanowires for all-ZnO p-n diodes.

We synthesize and analyze Ag-doped ZnO (SZO) nanowires (NWs) via a vapor-liquid-solid mechanism in a physical vapor deposition. The process condition for the SZO NW formation is optimized by adjusting the kinetic energy and the flux of the laser-ablated particles by hot-wall control. Electron microscopes ensure excellent morphologies of the doped NWs obtained. We confirm p-type doping effects, with low temperature photoluminescence used to trace the A(0)X peak. We realize diodes with all-ZnO-based p-n junctions of SZO NWs and Ga-doped ZnO thin films, resulting in asymmetric I-V characteristics with the turn on voltage of 3.8 V.