Pulsed Laser Deposition of ITO: From Films to Nanostructures

Indium-tin oxide (ITO) films have been deposited by pulsed laser deposition (PLD) to achieve low resistivity and high transmittance in visible region. Important parameters governing the growth of ITO films, which include laser wavelength, substrate temperature, and the background gas pressure, are discussed. By utilizing the energetic plasma in laser ablation of an ITO target, relatively low substrate temperature growth has been demonstrated. Room temperature deposition enables ITO films to be deposited on the polymer substrate. In addition, deposition in different background gases promotes the catalyst-free growth of nanostructured ITO films. In particular, deposition in Ar or He at optimized pressures enables the growth of highly crystalline ITO nanostructures, which include nanorods and nanowires due to the self-catalyzed growth from the plasma plume. The conditions which allow the pulsed laser deposition of ITO thin films and the growth of nanostructured ITO are reviewed and discussed

Pulsed laser deposition of nanostructured indium-tin-oxide films

Effects of O2, N2, Ar and He on the formation of micro- and nanostructured indium tin oxide (ITO) thin films were investigated in pulsed Nd:YAG laser deposition on glass substrate. For O2 and Ar, ITO resistivity of ≤ 4 × 10-4 Ωcm and optical transmittance of \u3e 90% were obtained with substrate temperature of 250 °C. For N2 and He, low ITO resisitivity could be obtained but with poor optical transmittance. SEM images show nano-structured ITO thin films for all gases, where dense, larger and highly oriented, microcrystalline structures were obtained for deposition in O2 and He, as revealed from the XRD lines. EDX results indicated the inclusion of Ar and N2 at the expense of reduced tin (Sn) content. When the ITO films were applied for fabrication of organic light emitting devices (OLED), only those deposited in Ar and O2 produced comparable performance to single-layer OLED fabricated on the commercial ITO. © 2010 SPIE

Femtosecond and nanosecond pulsed laser deposition of silicon and germanium

150 fs Ti:Sapphire laser pulsed laser deposition of Si and Ge were compared to a nanosecond KrF laser (25 ns). The ablation thresholds for for ns lasers were about 2.5 Jcm−2 for Si and 2.1 Jcm−2 for Ge. The values were about 5-10 times lower when fs laser were used. The power densities were 108-109 Wcm−2 for ns but 1012 Wcm−2 for fs. By using an ion probe, the ions emission at different fluence were measured where the emitting ions achieving the velocity in the range of 7-40 kms−1 and kinetic energy in the range of 30-200 eV for ns laser. The ion produced by fs laser was measured to be highly energetic, 90-200 kms−1, 2-10 KeV. Two ion peaks were detected above specific laser fluence for both ns and fs laser ablation. Under fs laser ablation, the films were dominated by nano-sized crystalline particles, drastically different from nanosecond pulsed laser deposition where amorphous films were obtained. The ions characteristics and effects of pulse length on the properties of the deposited films were discussed

Laser Emissions from Disodium Fluorescein-Doped Poly(Vinyl Alcohol) Films

Superradiant-mode laser emissions were obtained from disodium fluorescein (DF)-doped poly(vinyl alcohol) (PVA) films which had been dip-coated on a microscope glass slide. When the film was transversely pumped using a nitrogen laser, superradiant emission was trapped and propagated in the supporting glass slide which acted as a waveguide. The trapped light underwent multiple internal reflections before it exited at both ends of the slide, producing a lasing effect. The laser beam profile varied with the edge condition of the glass slide; a circular beam was obtained with a frosted edge. An output conversion efficiency of 22% was obtained for a fresh sample while its lasing output energy at a localized excitation position, or operating lifetime, decreased at a rate of 0.015% per shot of nitrogen laser. Despite the decrease in output energy, the laser peak wavelength of DF was largely unchanged

Effects of electric field on polysilicon gettering of iron and copper in highly boron-doped silicon

The polysilicon gettering behavior of iron (Fe) and copper (Cu) in highly boron doped silicon was studied under isothermal annealing with and without the presence of an electric field. Depth profiles of Fe and Cu in the polysilicon were obtained by dynamic secondary ion mass spectrometry. Enhanced gettering as a result of the electric field can be attributed to the drift-behavior of Fe and Cu over thermal diffusion at elevated temperature. While the polysilicon-silicon interfacial segregation acted against the back-diffusion of Cu, the same was not observed for Fe. About 61% of Cu and 35% of Fe were trapped in polysilicon after 2 days owing to strong interfacial segregations

Lithium and sodium stearates as electron injection materials in organic light-emitting diodes

Despite being efficient electron injection for the organic light-emitting diode, sub-nanometer ultrathin layer of lithium fluoride requires deposition at high temperature and precise layer thickness. Nontoxic organometallic compounds such as lithium stearate and sodium stearate are tested for electron-injection alternatives, which can be deposited at lower temperatures. In this work, OLEDs with lithium or sodium stearates are found to perform better than the lithium fluoride as electron injection. These devices also manage to achieve 90% maximum luminance and power efficiencies over a broader range of 1.5 - 4.5 nm thick of lithium stearate and 2.5 – 4.0 nm thick of sodium stearate

Zinc oxide films deposited by radio frequency plasma magnetron sputtering technique

Zinc oxide (ZnO) is a wide band gap transparent conductive oxide (TCO) material with a lot of potential applications including transparent thin-film sensors, transistors (TFTs), solar cells, and window insulation systems. In this work, ZnO films were deposited on glass substrates by the radio frequency (RF) plasma magnetron sputtering deposition technique. The effects of the RF power on the properties of the ZnO films were elucidated. The influences of the RF power on the surface morphology, structural, and optical properties of the ZnO films were investigated by Mahr surface profilometer, Atomic Force Microscopy (AFM), X-ray diffractometer (XRD), and ultraviolet–visible (UV–VIS) spectrophotometer. To allow for accurate comparison of the power effects, ZnO films with similar thickness deposited at different RF powers were examined. The RF power effects on the properties of the ZnO films are revealed and discussed in this paper

Pulsed laser deposition of ITO nanorods in argon and OLED applications

Indium tin oxide (ITO) nanorods were deposited in argon gas environment on glass substrate at 250 °C by a pulsed Nd:YAG laser, with laser parameters of 10 Hz, 355 nm and 2–3 J/cm2. The formation of ITO nanorods was found to depend strongly on argon pressure and deposition duration, of (4–7) Pa and (30–60 min) respectively. At the initial growth stage, a large number of nucleation sites were first formed which eventually evolved into pin-needle types of nanorods. For extended period of deposition, oval-shaped lumps were seen to be formed among the nanorods. The growth of spherical tips in nanorods suggests the vapor–liquid–solid (VLS) mechanism. The XRD patterns show that ITO with In2O3 bixbyite structure is strongly orientated in direction. The presence of ITO nanorods, however, was found to improve the organic light emitting diodes (OLED) performance with higher brightness and lower turn-on voltage, as compared to OLED fabricated with commercial ITO. ITO samples were also deposited in N2 but nanorod was not observed and its OLED failed to operate