Thin film transistors were fabricated using amorphous IZO (In2O3-10wt%ZnO) with low carrier concentration (∼3×1017/cm3) for the channel material and a-IZO with high carrier concentration (∼2×1020/cm3) for source-drain metallization. The performance of a-IZO channel materials processed entirely at room temperature was established using a simple gate-down thin film transistor device. The TFT test structures were fabricated on p-type Si substrates with a thermally grown SiO2 gate oxide. The channel and metallization layers were sputter deposited from a commercially available IZO target at room temperature in a gas atmosphere containing 10 vol.% and 0 vol.% oxygen, respectively. The TFT devices are depletion mode n-channel devices with a high saturation mobility (∼20cm2/Vs) and high on/off ratio (∼108) and, as such, appear to be well suited for active matrix TFT applications.

Delafossite-type CuAlO2 thin films have been deposited by radio frequency (RF) reactive sputtering on sapphire using a CuAlO2 ceramic target. A study of structural and optical properties was performed on films of varying deposition parameters such as substrate temperature and oxygen partial pressure and also post annealing. The crystalline phase in the films was identified to be the delafossite structure by x-ray diffraction. The optical properties, such as the wavelength dependence of the transmittance and the band gap, were determined. The average transmittance is 80% in the wavelength range of 400-1500 nm and the band gap is 3.81 eV.

High electron mobility thin films of In2−xWxO3+d (0 ≤ × ≤ 0.075) were prepared by pulsed laser deposition. The highest mobility polycrystalline and textured films show mobility >110 cm2/Vs on both amorphous SiO2 and single crystal yttria-stabilized zirconia substrates. The carrier density is in the range 1−3 × 1020 cm−3 at room temperature. The W dopant concentration for films with optimized electrical properties was x ∼ 0.03.

Laser induced insulator-to-metal phase transition in VO2 thin films was explored using femtosecond optical pump-probe spectroscopy. The transient reflection and relaxation processes in VO2 were observed during phase transition on 10-11 - 10-9 temporal-scale. Optical generation of carriers in VO2 initiates extremely fast changes in reflectivity which is strongly dependent on pump fluence. Analysis of transient optical properties allows suggesting the excitonic-controlled mechanism responsible for the light-induced phase transition in VO2.

Amorphous ZITO films were deposited by dc magnetron sputtering onto glass substrates from ceramic oxide targets containing Zn:In:Sn cation ratios of 1:2:1 and 1:2:1.5. The microstructure, carrier density, mobility, and resistivity of as-deposited and annealed samples were evaluated using x-ray diffraction and Hall effect measurements. The as-deposited films were amorphous and remained so after annealing at 200°C in air for up to five hours. Transmissivity of the films exceeded 80% in the visible spectral region. The minimum resistivity value (7.6×10−4 Ω-cm) was obtained from thin films deposited using the 1:2:1 composition target and a substrate temperature of 300°C.

Molybdenum doped indium oxide (IMO) thin films rf sputtered at room temperature were studied as a function of oxygen volume percentage (O2 vol. %) varied between 0 and 17.5. The as-deposited films were amorphous irrespective of O2 vol. %. The minimum transmittance (<10 %) of the films deposited without oxygen has been increased on introducing oxygen (3.5 O2 vol. %) to a maximum of 90 %. The optical band gap has been increased from 3.80 eV (without oxygen) to 3.92 eV (3.5 O2 vol. %). The films were highly resistive and the hall coefficients were detectable only for the films deposited without oxygen. In order to increase the electrical conductivity, the films were annealed in the range 100-500°C in open-air and N2/H2 gas for 1 hour. The annealed films become polycrystalline with enhanced electrical and optical properties. The effect of annealing conditions on these films will be presented and discussed in detail.

We have approximated the tail of the Gaussian distribution of states of organic semiconduc-tors with an exponential function. We have used this approach to calculate the carrier concentra-tion in organic materials, and subsequently the charge distribution in the accumulation region of a field effect device and the space-charge capacitance in accumulation mode. Small signal high frequency capacitance-voltage measurements performed at various temperatures show good agreement with this model and the characteristic temperature of the exponential function has been estimated from these measurements based on the theory developed.

Following our pervious works demonstrating all-organic memory devices based on a nanocomposite material consisting of C60 molecules dispersed in an insulating polymer. In this paper, we will report on conducting atomic force microscopy (c-AFM) measurements from nanosized regions on memory devices. The c-AFM nanoscale measurements show a hysteresis of high and low conductance states, in agreement with our previous reports on macroscopic memory devices. The c-AFM measurements were verified by 30nm gap cell devices fabricated via e-beam lithography, which also showed similar current values. Analysis of our data reveals that the conduction mechanism switches from direct tunneling to Fowler-Nordheim tunneling above a threshold voltage.

High quality single crystal diamond film is an excellent transparent semiconductor material. Combined with its good electrical, optical, thermal and chemical properties, diamond-based semiconductor devices offer the potential of operation at very high voltages (>10 kV), power levels, and temperatures (>400°C) and under extreme radiation conditions.

In this paper, we exploit the optical transparent property of MPCVD single crystal diamond films to correlate the quality of the epi-layers with the performance of Schottky barrier diodes fabricated on the layer. We used optical microscopy to observe stress induced birefringence caused by defects/dislocations in the material and micro- Raman/photoluminescence to detect relative amounts of non-diamond carbon and color centers (nitrogen and silicon atom complexes with lattice vacancies) in the material. High structural quality (low stress) is correlated with the properties of Schottky barrier diodes fabricated in the material. Vertical devices made from a 20 µm homo-epi-layer have been shown high breakdown fields of 1.85 MVcm-1 (BV = 3.7 kV) and conduction of 0.6 A/cm2 at 20V forward drop at 290 °C. Through device failure analysis, we can conclude that the 1.85 MVcm-1 field is only a lower limit for the material. Local stresses (dislocations) and point defects appear to be the main reasons for the high voltage failure of our single crystal diamond rectifiers.

We describe a process to grow ZnO nanowires in aqueous solution of Hexamine and Zinc Nitrate to obtain a network of nanowires 0.5-1.5μm long. The growth was initiated on ZnO nanoparticles spun-cast onto thermal SiO2. We demonstrate bottom-gate FET structures formed using these nanowire networks as channel layers with gold (Au) and aluminum (Al) source/drain pads. Resulting transistors are well-behaved with on-off ratios >104 and mobility >10-2 cm2/V-s, calculated without accounting for actual surface coverage of nanowires. Actual nanowire mobility is therefore substantially higher, attesting to the potential for this technique as a method for realizing low-cost, high-brightness displays.

We report on the insulator-charging-effects of poly-4-vinylphenol (PVP) gate dielectric on the reliabilities of pentacene thin-film transistors (TFTs). Our PVP films were prepared by spin coating and curing at various temperatures (155, 175, and 200 °C). Evaluated using Au/PVP/p+−Si structures, the dielectric strength of PVP films cured at 175 °C was superior to those of the other PVP films cured at different temperatures. Although saturation current and field mobility (∼0.13 cm2/Vs) obtained from a TFT with PVP film cured at 200 °C appeared higher than those (∼0.07 cm2/Vs) from the device with 175 °C-cured polymer film, the TFT prepared at 200 °C revealed a low on/off current ratio of less than 104 due to its high off-state current and also unreliable saturation behavior under repetitive gate voltage sweep. The unreliable behavior is due to the dielectric-charging caused by gate-electron-injection. We thus conclude that there are some optimal PVP-curing conditions to improve the reliability of pentacene TFT.

We have discovered new transparent conducting oxides (TCOs), anatase Ti1-xMxO2 (M=Nb,Ta), in thin film form. Both films with 0.03 ≤ × ≤ 0.06 showed resistivity of 2−3 × 10−4 Ωcm and internal transmittance of ∼95% in the visible light region (40 nm in thickness), at room temperature. These values are comparable to those of typical TCOs, such as In2−xSnxO3 (ITO).

The random, two-dimensional network formed of electrically conducting nanoscale wires, called carbon nanotubes, is a transparent electronic material that can be fabricated using room-temperature printing or spraying technologies. Depending on the network density, networks with both metallic- and semiconducting-like attributes can be fabricated. Both display high conductivity, high carrier mobility and optical transparency. The networks also have high mechanical flexibility, robustness and environmental resistance. Application opportunities range from lightweight, transparent conducting films, to electrically conducting fabrics, to active electronic devices and sensors.