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Simple laser irradiation of well-aligned multiwall carbon nanotubes (MWCNTs) was performed to intentionally modify structural defects and to ablate possible contamination of the MWCNTs. Scanning electron microscopy and transmission electron microscopy confirmed the clear presence of the MWCNTs with open tips. A Raman spectra exhibited a decrease in an intensity ratio (ID/IG) of 1352 cm−1 (D band) over 1583 cm−1 (G band) peaks by significantly reducing the amorphous carbon phases of D band peaks. The structural improvement in the MWCNTs after optimum laser exposure resulted in a reduction of the turn-on voltage from 1.0 to 0.6 V/μm and an increase in the emission current.

We propose a semiconductor metasurface that simultaneously performs two independent functions: focusing and polarization filtering. The wavefronts of the reflected and transmitted light distributions are precisely manipulated by spatial parametric variation of a subwavelength thin-film Si grating, which inherently possesses polarization filtering properties. We design a 12-μm-wide metasurface containing only nineteen Si grating ridges. Under a 10-μm-wide unpolarized Gaussian beam incidence at wavelength of 1.55 μm, the resulting device shows promising theoretical performance with high power efficiency exceeding 80% and polarization extinction ratio of ∼10 dB with focal spot diameters near 1–2 μm.

Using ultraviolet photoelectron spectroscopy (UPS), we have measured the energy level offset at the planar interface between poly(3-hexylthiophene) (P3HT) and C61-butyric acid methylester (PCBM). Gradual deposition of PCBM onto spin-coated P3HT in high vacuum was made possible by using electrospray vacuum deposition (EVD). The UPS measurement of EVD-prepared planar interface resulted in the energy level offset of 0.91 eV between P3HT HOMO and PCBM LUMO, which is considered as the upper limit of Voc of the organic photovoltaic cells.Using ultraviolet photoelectron spectroscopy (UPS), we have measured the energy level offset at the planar interface between poly(3-hexylthiophene) (P3HT) and C61-butyric acid methylester (PCBM). Gradual deposition of PCBM onto spin-coated P3HT in high vacuum was made possible by using electrospray vacuum deposition (EVD). The UPS measurement of EVD-prepared planar interface resulted in the energy level offset of 0.91 eV between P3HT HOMO and PCBM LUMO, which is considered as the upper limit of Voc of the organic photovoltaic cells.

A low resistive tungsten (W) Schottky contact to GaAs has been developed by plasma enhanced chemical vapor deposition. The resistivity of tungsten (W) films deposited on GaAs at 300 °C is about 18 μΩ cm and the film structure is (111) oriented α‐phase W coexisting with (200) and (211) oriented β‐phase tungsten. The resistivity of W films deposited above 350 °C is increased due to the diffusion of Ga and As atoms from GaAs into W films. This has been confirmed by secondary ion mass spectroscopy. I‐V characteristics of GaAs Schottky contacts formed at 300 °C show that the maximum barrier height is 0.81 eV and the ideality factor is 1.04. They are not degraded during rapid thermal annealing at temperatures ranging from 500 to 700 °C for 10 s without an arsenic overpressure.

Resistivities of tungsten thin films deposited by plasma enhanced chemical vapor deposition are very sensitive to the H2/WF6 partial pressure ratio, while the resistivities of tungsten films deposited by low pressure chemical vapor deposition are insensitive to the H2/WF6 ratio. The reason is investigated with x‐ray diffraction, transmission electron microscopy, Auger electron spectroscopy and optical emission spectroscopy. As a result, when the H2/WF6 partial pressure ratio is higher than 15, plasma deposited tungsten has a low resistive (11 μΩ cm) bcc structure without F impurities. However, if the H2/WF6 ratios are decreased, porous and β‐phase W films are formed due to the incomplete reduction of F concentrations.

Controlling the wafer temperatures from 200 to 500 °C at H2/WF6 flow ratio equal to 24, low‐resistive (about 11 μΩ cm) tungsten thin films are deposited by plasma‐enhanced chemical vapor deposition. The as‐deposited tungsten films have (110), (200), and (211) oriented bcc structures and Auger depth profile shows that fluorine and oxygen impurities are below the detection limit of Auger electron spectroscopy.

Label-free electrical detection of deoxyribonucleic acid (DNA) hybridization was demonstrated using an AlGaN/GaN high electron mobility transistor (HEMT) based transducer with a biofunctionalized gate. The HEMT DNA sensor employed the immobilization of amine-modified single strand DNA on the self-assembled monolayers of 11-mercaptoundecanoic acid. The sensor exhibited a substantial current drop upon introduction of complimentary DNA to the gate well, which is a clear indication of the hybridization. The application of 3 base-pair mismatched target DNA showed little change in output current characteristics of the transistor. Therefore, it can be concluded that our DNA sensor is highly specific to DNA sequences.

An organic floating-gate memory device using CdSe quantum dots (QDs) as a charge-trapping element was fabricated. CdSe QDs were localized beneath a pentacene without any tunneling insulator, and the QD layer played a role as hole-trapping sites. The band bending formed at the junction between pentacene and QD layers inhibited back-injection of holes trapped in CdSe into pentacene, which appeared as a hysteretic capacitance-voltage response during the operation of the device. Nearly, 60% of trapped charge was sustained even after 104 s in programmed state, and this long retention time can be potentially useful in practical applications of non-volatile memory.

A high efficiency blue fluorescent organic light-emitting diode without LiF electron injection layer was developed. Aluminum electrode was directly deposited on a phosphine oxide type electron transport layer and the observed quantum efficiency was as high as 6.13%. The ultraviolet photoemission spectroscopy data clearly indicated that the electron injection barrier (the offset between Al Fermi level and the lowest unoccupied molecular orbital of the organic layer) is less than 0.1 eV, which led us to believe that more efficient electron injection through the lower barrier is mainly responsible for the high efficiency.

The enhancement in light extraction efficiency from a periodic micron-scale rugged surface pattern on Si quantum dot light-emitting-diode (Si-QD LED) structures was investigated, both numerically and experimentally. Micron-scale rugged surface patterns were fabricated on the top layer of the Si-QD LED to increase the extraction of light from the active layer. The optimum light extraction condition for a Si-QD LED corresponded to a pattern size/period ratio of ∼0.7. In experiments, the luminescent powers of a Si-QD LED with/without micron-scale surface patterns increase linearly with current density, and the efficiency of light extraction was enhanced by a factor of 2.8.

The authors report on an alignment layerless (AL) flexible liquid crystal (LC) display fabricated at ambient temperature through an imprinting process. One-dimensional microgrooves and two-dimensional arrays of microstructures embossed on plastic substrates provide the spontaneous alignment of the LC molecules and spacers for the uniform cell gap in a flexible LC display, respectively. It is found that the azimuthal anchoring energy, generated from the microgrooves, is on the order of 10−5J∕m2 which is strong enough to uniformly align the LC over large area. Our AL flexible LC display shows symmetric viewing characteristics and stable electro-optic properties under a bent environment.

We report on a pixel-encapsulated flexible liquid crystal display (LCD) based on an elastomer substrate of self-aligning LC molecules. The elastomer substrate, fabricated by a replica molding technique, has pixel-encapsulating walls that serve as spacers and allow for mechanical stability and reproducibility against bending deformations. Our pixel-encapsulated LCD provides great flexibility, durability, and excellent electro-optic performances in a highly bent environment.